Sun 5:10 PM —Forecast Review —Some very light showers have moved through western Chester/Montgomery counties and reached into Philadelphia. Closer to the RRFS forecast than the HRRR or ECMWF.
The dynamics are unfavorable right now over Philadelphia to support much in the way of rainfall. However, things change by about 10 PM to midnight where some heavy rain and storms may move in.
Sunday Forecast Update
Posted Sunday 08/02/26 @ 8:35 AM — Today’s forecast is mostly unchanged. The uncertainty centers around the timing of the onset of the showers and thundershowers expected to move in either mid to late this afternoon or this evening. The best match for the current radar is the ECMWF—
Current radar around 8 AM with water vapor image and RAP model Omega. Few models capture this breakout of showers. (Click on image for a larger view.)
If we were go all in on the ECMWF, it would imply that most of the daylight hours are precipitation free in the immediate Philadelphia area.
The latest REFS (combines the RRFS and the HRRR) shows some showers just west of Philadelphia in the late afternoon—
06z REFS rain plus standard deviation (contours) at 6 PM Sunday. (Click on image for a larger view.)
A mix of clouds with breaks of sun this morning with mostly cloudy skies for this afternoon. Despite my earlier forecasts of showers increasingly earlier this afternoon, if we take the ECMWF and REFS together, the earliest we’ll see showers (west of Philadelphia) will be 5-6 PM and more likely closer to 11 PM. The earlier start is a low confidence forecast, but the 07z NBM seems to support it—
07z NBM forecast 1 hour precipitation at 5 PM. (Click on image for a larger view.)
Forecast Update
Posted Saturday 08/01/26 @ 10:13 AM — I mentioned that Saturday would have sunshine through thin high clouds in the morning. That dimmed sunshine is also due to smoke throughout the atmosphere above us (not so much at ground level).
12z HRRR smoke model showing Vertically integrated smoke total at this time. (Click on image for a larger view.)
A flow of increasingly humid air will affect our weather over the coming days. A warm front associated with a low will slowly move towards us this weekend—
Water Vapor image at XX with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFSpotential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, I’ve drawn the approximate position of the warm front. (Click on image for a larger view.)
Saturday‘s forecast remains on track with increasing periods of sunshine through mid and high level clouds.
The trend I identified with Sunday‘s forecast continues with the rain and showers moving in earlier with each successive model run. The latest RRFS from 06z shows showers (and thunderstorms) possible as early as 3-4 PM. The 12z model (not yet completed) suggests it may even be earlier.
06z RRFS forecast for 4 PM Sunday- 1 hour rain plus simulated radar. The orange contour is the general location of the northern edge of the heat dome. (Click on image for a larger view.)
Saturday – Sunday Forecast
Posted Friday 07/31/26 @ 7:41 PM —
Saturday
Saturday looks to be mostly sunny in the morning with increasing thin high level cirrus clouds towards late morning as a warm front slowly approaches. Saturday afternoon looks to have variable amounts of sunshine through high and mid level clouds. A few areas, especially near Trenton, may have showers pop up late afternoon; most areas dry.
Highs (Model Blend): Blue Bell- 88º Philadelphia 88º ±2.0º Average sd and confidence.
Sunday
Considerable cloudiness. A few isolated showers possible during the early afternoon: most areas dry. The trend noted this morning continues. Warm air and associated showers/thunderstorms move in early evening on Sunday from the south. Arrival about 6-7 PM with a few areas seeing some isolated showers around 4-5 PM.
Highs (Model Blend): Blue Bell- 88 º Philadelphia 87º ± 2.3º Lower than average sd and higher confidence .
18z RRFS forecast for 7 PM Sunday. Rain and simulated radar. Orange contour is the edge of the heat dome. (Click on image for a larger view.)
Early Outlook Edition
Originally Posted Fri 9:42 AM —A warm front to our south will slowly push north towards us over the weekend.
Saturday will be sunny with some high cirrus clouds moving in during the early afternoon with some mid-level cloudiness at times towards late afternoon. A few highly isolated pop-up showers are possible, mostly in northern Delaware and parts of NJ. Most of the area will be dry.
As the warm front moves closer on Sunday, showers will break out but the majority of the models (ECMWF-AI and RRFS, CMC-RDPS) have these showers in Lancaster and Berks counties and westward. This morning’s 06z GFS does have a few showers in the immediately Philadelphia area late afternoon Sunday and early evening. This is supported by the AIGFS and the Hybrid AI GFS. Looking at the model trends, there is some indication that the system will advance somewhat faster, supporting the GFS forecast.
06z GFS forecast for Sunday at 7 PM. Rain and simulated Radar. Orange contour is the edge of the heat dome. (Click on image for a larger view.)
I’ll update later this afternoon or early evening.
Posted Thursday 07/30/26 @ 8:01 PM —The scattered showers forecast for this evening are moving through and should dissipate later tonight. Friday looks to be mostly sunny, although some periods of cloudiness will develop mid to late afternoon Friday, especially in NJ. Scattered showers are possible again, mostly at the Jersey shore.
For the weekend, Saturday will be mostly sunny through high thin cirrus clouds. Towards the late afternoon, an increase in cloudiness is expected as a warm front moves towards us.
For Sunday. there’s some uncertainty regarding cloud cover and the northern movement of the very warm humid air behind the warm front. Most models keep the rain to our far west (Lancaster and Berks counties) and some have some have a few showers near Cape May county in NJ. It will be noticeably warmer and certainly more humid.
18z RRFS forecast for Sunday at 2 PM. Radar/rain and clouds. Blue=low clouds, maroon=mid-level clouds, tan = high cirrus clouds The 576 line is the northern edge of the heat dome. Various models differ with the position of the northern extent of the heat dome (Click on image for a larger view.)
We’ll have to wait another day or so for the Sunday forecast to clarify.
Thursday Weather Update
Posted Thursday 07/30/26 @ 11:50 AM — The upper air low continues to rotate close enough to cause some cloudiness and showers. (Some areas saw late day showers yesterday; many areas did not.) Here’s the current water vapor image—
Water Vapor image at 11:30 AM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, The violet fine contours ( Potential vorticity) are labeled as the trigger for showers expected to develop ahead of them. It’s already happening in northern NY State. (Click on image for a larger view.)
This morning’s RRFS shows considerable shower coverage this evening about 6 PM. (Some isolated showers may develop earlier this afternoon as well.)
12z RRFS shows showers develop near Philadelphia by 6 PM. (Click on image for a larger view.)
Folks, my posts have been less frequent over recent days. A recent MacOS update decided that my model post-processing scripts (python-based) were malware and both quarantined and inactivated them., Apparently my python certificate had also expired. Diagnosing the issues and repairing them has taken the better part of almost 3 days. During that time, my model downloads were reduced significantly. I’m now back with 4 computers working again.
Wednesday Update
Posted Wednesday 07/29/26 @ 9:56 AM — The system has exited our area, but there is an upper low with cold air aloft in New York State may cause instability showers and thunderstorms to develop later today. The latest RRFS has scattered showers and thunderstorms north of our area during the afternoon and some of this activity may develop in the immediate Philadelphia area around 5 -8 PM—
11z RRFS forecast for 7 PM. 1 hour rainfall/radar. Showers develop as early as 5 PM and continue to 9 PM. (Click on image for a larger view.)
Here’s the rainfall totals, MRMS-based for Tuesday—
MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch) (Click on image for a larger view.)
Storm Review
Posted Tuesday 07/28/26 @ 8:35 PM — Today’s heavy rain has begun to enter the Philadelphia area. Very little with today’s weather has gone as forecast yesterday or even this morning. Much of the activity went to our north and west much of the day. Here’s the current radar—
Radar about 8 PM with superimposed RAP model vertical motion (Omega).
I don’t see much in the way of very severe weather. Nonetheless, the NWS has issued a tornado watch for some of the area. Additionally, much of the immediate Philadelphia area hasn’t received anywhere near the heavy rain that had been forecast.
The back end of the rain is already visible on radar and it should be ending around midnight. As for the forecast for Wednesday, it appears now that there won’t be as much in the way of shower activity as had been forecast. Wednesday may be a decent day weather-wise with just a few scattered storms.
Comparison Table- Severe Weather
Posted Tuesday 07/28/26 @ 11:58 AM — With the sun breaking out through clouds (and smoke) additional energy for storms is available.
Severity Parameter (HRRR)
Sept 1 , 2021 Tornado Outbreak (example of highly severe)
Severity Parameters Impact: ⚑ indicates favors Severity⚐ indicates Possible Severity ↓ indicates works against Severity ⇩ Significant, but less impact
Heavy Rain Update
Posted Tuesday 07/28/26 @ 11:32 AM —Many of the 12z models are in. There have been changes in the forecast with a later start and the current appearance of the precipitation on radar.
The HRRR differs somewhat from the RRFS with the HRRR having most of the rain and storms expected this afternoon storms move north of the immediate Philadelphia area. It delays the heavy rains near the city until about 10 PM. The RRFS has scattered activity near the city late afternoon and evening, again now with the heavy activity mid to late evening about 9 PM – 1 AM Wednesday.
Severe weather (tornadoes, hail,) is still not expected with these storms but wind gusts and heavy rain still in the picture.
None of the models capture the current radar at all. This suggests that this is a low confidence forecast in terms of timing.
Water Vapor image at 11:40 AM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, (Click on image for a larger view.)
I’ll be posting the severe weather comparison table over the next hour.
Heavy Rain
Posted Tuesday 07/28/26 @ 9:11 AM — The morning models (12z) haven’t been completed yet. But based on the 06z models (2 AM EDT), here’s the trends I’m seeing.
Heavy rain will be the primary concern with this system. Precipitable water (PWAT) is ‘only’ in the 2 inch range (last severe system we had had PWATs close to 2.5″. However, the expected longer duration of the system and development of a surface low (and upper air low) is expected to cause strong dynamics any precipitation accumulate and be significant.
The storms move in between 12 PM and 2 PM. Heaviest activity is between 4 PM and 10 PM .
Severe parameters are not overly impressive. I don’t expect tornadic activity with this system. Wind gusts may reach 30 mph in S. NJ.
First look suggests heaviest rain from just west of Philadelphia into NJ.
Water Vapor image at ~ 9 AM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, (Click on image for a larger view.)
I’m short on time right now. I’ll update with a severity table and new model data before noon today.
Tuesday Weather
Posted Monday 07/27/26 @ 7:57 PM — We had quite the rain-maker develop this afternoon. In addition to the triggered storms (see below), many other cells developed in-place and moved very little causing significant rainfall and flooding. Here’s the MRMS summary of rainfall through 5 PM; incredible totals considering the rain lasted not much more than 2-3 hours—
MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch) (Click on image for a larger view.)
For tonight (Monday), some additional widely scattered storms are still possible. The real action begins on Tuesday morning (10-11 AM) where showers and thunderstorms will develop and move in from the northwest. —
18z GFS forecast for Tuesday at 2 PM. Large area of heavy rain develops. The violet contours are potential vorticity (PVU) which will spawn surface low pressure. (Click on image for a larger view.)
Rain continues through Tuesday night and tapers early Wednesday. But an upper low associated with this system lingers and additional showers and storms are expected Wednesday afternoon.
As much as an additional 1-3 inches of rain is expected by Wednesday evening. I’ll update on expected severity parameters tomorrow morning.
A Quick Update
Posted Monday 07/27/26 @ 1:33 PM — As mentioned predicting these popups is an exercise in utility. But I’m trying. Current RRFS shows and area of thermal potential energy (theta-e) and an area of moisture convergence at the same level—
12z RRFS-based calculated 850 theta-E frontogenesis (orange-yellow) and 850 level moisture convergence. (small concentric circles inside this orange area. This has caused storms to form earlier than forecast and moving towards Philadelphia earlier than forecast. An area of downward motion )blue-green over Philadelphia may affect the storms triggered by these mechanisms. (Click on image for a larger view.)
The latest water vapor image with hourly RAP model data shows thunderstorms moving into an area that the RAP model feels is favorable for storm strengthening—
Water Vapor Channel 10 image at 1:15 PM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, The concentric yellow contours shows strong strengthening possible as they move into Philadelphia. We’ll see. (Click on image for a larger view.)
Monday Forecast Update
Posted Monday 07/27/26 @ 10:33 AM —This morning’s 12z HRRR just became available. Today’s weather will have some isolated to scattered showers and thunderstorms. The triggers for today’s weather will be weak upper air disturbances with some help from thermal/dew point gradients. Severity parameters are in the low to moderate range with shear values less than 15 and helicity less than 200.
The triggers for today’s storms are visible on water vapor imagery—
Water Vapor image about 10 AM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, Dark areas coincide with PVU (potential Vorticity). Their movement will approximately follow the 700mb wind flow. If you look closely, the blue patch in the upper left corner is the energy for Tuesday’s storms. (Click on image for a larger view.)
At 5 PM, the RRFS shows scattered storms with the triggers—
5 PM snapshot RRFS forecast triggers (500mb vorticity advection) and showers. RH at 700mb is maroon. Arrows are 700 mb winds. (Click on image for a larger view.)
That translates into moderate to low level storms where they pop up. That said, expect the NWS to issue some severe thunderstorm alerts.
Attempting to forecast today’s storms location is an exercise in futility, but that doesn’t keep me from trying. Based on this morning’s RRFS and the latest HRRR, storms will first form around 12-3 PM in NJ, along the coastal areas. Storms closer to the immediate Philadelphia area will likely form closer to 4-7 PM.
As shown in the water vapor image, there’s a strong impulse far northwest that will give us heavy storms on Tuesday. Stay tuned.
Originally Posted Sun 8:08 PM —With the weather so perfect over the past few days, I’ve taken a break from forecasting. With the coming week, we have some active weather expected from Monday through part of Wednesday.
Warm humid air is moving northward towards us as a disturbance riding over the heat dome will descend towards us —
Water Vapor image at 7 PM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, The area of energy will move towards us. (Click on image for a larger view.)
With the gradient in temperature moving in, showers and thunderstorms will develop during the afternoon and evening on Monday. The RRFS has most of the activity to our north by late afternoon, but several models are forecasting showers and thunderstorms as early as 2PM in our immediate area.
18z RRFS forecast for 6 PM on Monday with most of the widespread activity to our north. Many other models have scattered activity closer to Philadelphia and the shore as early as 2 PM and continuing. (Click on image for a larger view.)
The ensemble model, the REFS, captures this, perhaps better than the RRFS—
Today’s 18z REFS 1 hour rain forecast + sd at 3 PM Monday. (Click on image for a larger view.)
The Canadian GDPS with “AI spectral nudging” captures the forecast for Tuesday into Wednesday. A surface low forms over Pennsylvania with a nearby upper level low. Periods of rain and thunderstorms likely on Tuesday with additional showers developing again Wednesday.
12z CMC GDPS with AI forecast for midnight Tuesday. Low in Pennsylvania with upper low shows heavy showers and storms Tuesday. The upper low (purple L) will cause additional showers Wednesday afternoon. (Click on image for a larger view.)
The models have been predicting 1-3 inches of rain from this multi-day system. Exact placement can’t be predicted in advance and the total rainfall may change from the forecast.
Posted Thursday 07/23/26 @ 4:26 PM — High pressure will keep things comfortable and quiet probably through Sunday. The edge of the heat dome (576 thickness) is suppressed to our south—
Water Vapor image at 4:16 PM with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, The edge of the heat dome (576) is suppressed far to our south. (Click on image for a larger view.)
I’m keeping my eye on the edge of another system that moves in from the northwest late Sunday. Some scattered sprinkles may reach near us by 8 PM Sunday according to the AI models.
12z ECMWF-AI forecast for 8 PM Sunday. This model is a low resolution model, both spatially and temporally. The shading for precipitation will appear overblown. (Click on image for a larger view.)
Wednesday
Posted Wednesday 07/22/26 @ 9:33 AM —The skies are not blue this morning because of continued smoke throughout the atmosphere. Near ground level smoke is elevated slightly, enough for some people to smell. This is expected to reduce slightly during the day —
12z HRRR smoke model- full atmosphere integrated smoke level forecast at 10 AM (Click on image for a larger view.)
For Wednesday, some showers and storms are still forecast near the S Jersey shore and Cape May County this afternoon as a stalled front is still there to trigger some showers.
In the Philadelphia area, we’ll have mostly sunny skies with sunlight dimmed slightly by some smoke.
Mostly sunny skies Thursday, Friday and Saturday. An approaching warm front may bring some clouds and showers late Sunday, especially to western sections.
Tue 7:13 PM —Forecast Review — Updated Wed 9:30 AM— . As mentioned in my 4:58 PM update (below) this weather system did not unfold as forecast.
Yes, South Jersey and Delaware had plenty of severe weather and while my update from this morning indicated most of the severe weather would occur there, it didn’t mean that all the severe weather would occur there. Here’s the MRMS rain totals for Tuesday showing the storms developed to our south—
Big Forecast Change??
Posted Tuesday 07/21/26 @ 4:58 PM — This system is not evolving as had been forecast by the models. The line of storms that has just arrived (early) is heading into Southern NJ. The current radar and 18z models show additional storms near northwest PA will fall apart as they move towards us. That may have been it for the severe activity in and around the immediate Philadelphia area.
Current radar with Theta-E forecing (yellow contours). (Click on image for a larger view.)
The latest RRFS doesn’t show any more storms for us later this evening. The Phillies may be able to play.
RRFS at 8 PM Storms to our south. Nothing in the immediate PHL area. (Click on image for a larger view.)
Since it’s clear the models are not getting this right, I really don’t know what to expect for the rest of the night.
Stormy Tuesday Update
Posted Tuesday 07/21/26 @ 11:51 AM — The new HRRR and RRFS hae become available. Center City and other areas did have some showers/storms this morning as forecast. Here are the trends—
The system looks to move through Philadelphia somewhat faster, not lingering as had been previously forecast.
A mix of clouds and some sun in this afternoon. A few pop up storms, isolated or highly scattered.
The most severe storms are forecast to occur in areas from the city eastward and south of the city; mostly S Jersey and Delaware.Also near Allentown
Some renegade storms fire up early near the city and S. Jersey as early as 5 -6 PM
The main area of storms moves through 6-9 PM
Additional pop-up widely scattered storms before daybreak Wednesday morning.
The HRRR is forecasting another impulse moves through 5 PM Wednesday, with storms forming from the city moving eastward in the afternoon.
Severity Parameter (HRRR)
Sept 1 , 2021 Tornado Outbreak (example of highly severe)
Recent 4-1-23 Tornadoes (Example of severe)
Recent 08-07-23 18z HRRR Bow Echo
08-10-23 Today’s 06z HRRR & Impact
Today Updated 07-21-26 12z HRRR
CAPE Joules/kg
3500-4200 ⚑⚑⚑⚑
2100 ⚑⚑
2600 ⚑⚑
1200 ⚐ ⚐
3400 ⚑⚑⚑⚑
Helicity m^2/s^2
1350 ⚑⚑⚑⚑⚑
655 ⚑⚑
726 ⚑⚑
560 ⚑
612 ⚑⚑ far northwest
Vertical Shear 1/sec
40-46 ⚑⚑⚑
40-45 ⚑⚑⚑
30 ⚑
32 ⚑⚑
32 ⚑⚑
Precipitable Water
2.7″ ⚑⚑⚑⚑
0.83” ↓
2.1″ ⚑⚑
2.3″ ⚑⚑⚑
2.4″ ⚑⚑⚑⚑ NJ
Lifted Index º K
minus 6º ⚑⚑
minus 9.3º ⚑⚑⚑
minus 9.9º ⚑⚑⚑⚑
Minus 4.4º ⚐
Minus 9.5º ⚑⚑⚑⚑
HRRR Hail inches
1.9 ⚑⚑
1.4 ⚑
1.8 ⚑⚑
1.6 ⚑
2.1″ ⚑⚑⚑
Peak Wind Gusts mph
40-50 ⚑⚑⚑
40-50 ⚑⚑⚑
65mph ⚑⚑⚑⚑
32mph ⚐
62 mph ⚑⚑⚑
250 mb Jet Stream Wind mph
63 ⚑
135 ⚑⚑⚑⚑
74 ⚑⚑
95-104 ⚑⚑⚑
91 ⚑⚑⚑
CWASP (NBM Model 13z)
70 ⚑⚑⚑ in NJ
SWEAT Index (RRFS)
508 ⚑⚑⚑⚑ In NJ
K Index (RDPS)
43 ⚑⚑⚑⚑ (S. NJ)
Max Up Helicity (RRFS)
400 ⚑⚑⚑⚑ (S. NJ & shore)
Severity Parameters Impact: ⚑ indicates favors Severity⚐ indicates Possible Severity ↓ indicates works against Severity ⇩ Significant, but less impact
Stormy Tuesday Update
Posted Tuesday 07/21/26 @ 8:32 AM — No showers or thundershowers have developed in our immediate area as of this post in response to the warm front. Several models continue to show showers and thundershowers developing over Philadelphia around 9 AM through noon and tapering off by noon or so.
Additional storms possible during the afternoon with the Canadian HRDPS emphatic with that possibility at 2 PM. In fact, isolated/scattered storms may form almost anywhere in our region during the afternoon.
The major activity begins about 3-4 PM, mostly west of the immediate Delaware valley. Some severe storms/tornadoes possible with this first northwestern line of storms.
The line of storms moves through western Chester Montgomery and Bucks counties by about 6-7 PM and the immediate PHL area by 8 PM. Severe storms are expected at this time.
06z RRFS forecast simulated radar plus 1 hour accumulated rain at 6 PM (Click on image for a larger view.)
Showers and storms move through over night but there’s still a chance they may linger from I-95 eastward in NJ on Wednesday as the cold front stalls.
Here’s my severity table based on the latest 06z HRRR. (I’ll update before noon with this morning’s models.) —
Severity Parameter (HRRR)
Sept 1 , 2021 Tornado Outbreak (example of highly severe)
Recent 4-1-23 Tornadoes (Example of severe)
Recent 08-07-23 18z HRRR Bow Echo
08-10-23 Today’s 06z HRRR & Impact
Today 07-21-26 06z HRRR
CAPE Joules/kg
3500-4200 ⚑⚑⚑⚑
2100 ⚑⚑
2600 ⚑⚑
1200 ⚐ ⚐
3600 ⚑⚑⚑⚑
Helicity m^2/s^2
1350 ⚑⚑⚑⚑⚑
655 ⚑⚑
726 ⚑⚑
560 ⚑
469 ⚑
Vertical Shear 1/sec
40-46 ⚑⚑⚑
40-45 ⚑⚑⚑
30 ⚑
32 ⚑⚑
33 ⚑⚑
Precipitable Water
2.7″ ⚑⚑⚑⚑
0.83” ↓
2.1″ ⚑⚑
2.3″ ⚑⚑⚑
2.3″ ⚑⚑⚑
Lifted Index º K
minus 6º ⚑⚑
minus 9.3º ⚑⚑⚑
minus 9.9º ⚑⚑⚑⚑
Minus 4.4º ⚐
Minus 8,7 ⚑⚑⚑
HRRR Hail inches
1.9 ⚑⚑
1.4 ⚑
1.8 ⚑⚑
1.6 ⚑
1.8″ ⚑⚑
Peak Wind Gusts mph
40-50 ⚑⚑⚑
40-50 ⚑⚑⚑
65mph ⚑⚑⚑⚑
32mph ⚐
59 mph ⚑⚑⚑
Storm Motion Shear Vector Alignment
Aligned ⚑⚑⚑
Almost aligned ⚑⚑
Aligned ⚑⚑⚑
Somewhat aligned ⚐
Aligned ⚑⚑⚑
250 mb Jet Stream Wind mph
63 ⚑
135 ⚑⚑⚑⚑
74 ⚑⚑
95-104 ⚑⚑⚑
91 ⚑⚑⚑
CWASP (NBM Model)
75 ⚑⚑⚑⚑ far northwest
SWEAT Index (RRFS)
467 ⚑⚑⚑⚑
K Index (RDPS)
42 ⚑⚑⚑⚑ (S. NJ)
Severity Parameters Impact: ⚑ indicates favors Severity⚐ indicates Possible Severity ↓ indicates works against Severity ⇩ Significant, but less impact
Severe Weather Possible Tuesday & Early Wednesday.
Posted Monday 07/20/26 @ 5:28 PM — As shown in previous water vapor images, two distinct disturbances will converge over our area late Tuesday into Wednesday.A front moving through during the predawn hours on Wednesday may stall and may provide the focus for additional storms Wednesday morning just east of I-95 into the afternoon in NJ.
This system will present as two parts—
A warm front moves through Tuesday morning with showers and thunderstorms, as early as 6-7 AM with scattered activity lasting through noon or 1 PM These storms will move up from the south-southwest and will move northeastward. These storms will be scattered with a mix of clouds and sunshine through clouds….some strong storms possible, but not expected to be severe.
2. Increasing likelihood of more storms mid to late afternoon on Tuesdaythrough the night into Wednesday morning. Once again, different models have different peak times for storms. I did what I call a parameter match, comparing the 18z models to the current conditions on the RTMA. The RRFS was the best match so I’m going with its forecast.
The RRFS shows storms possible late afternoon, but a cluster of storms moves into western sections by 6-8PM with additional clusters of storms moving through between 10 and midnight. Scattered storms still after midnight into Wednesday, depending upon the model.
RRFS simulated radar at 9 PM (Click on image for a larger view.)
The storms may linger in NJ Wednesday morning.
Regarding severity, the usual parameters – CAPE, helicity, vertical shear are not particularly outstanding. They are capable of severe weather but are not all that impressive.
What does stand out – Some of the derived thermodynamic and frontogenic “forcing” parameters. Forcing is a general term for triggers and drivers of vertical motion. These are exceptionally elevated.
At 11 PM, the severe weather threat index has many areas with indices over 400. That is very high and concerning.
SWEAT index (Severe Weather Threat Index) shows many areas exceeding 400 at 11 PM which is concerning (Click on image for a larger view.)
Also of interest— the new Model Blend includes the “Craven-Wesenfield Aggregate Parameter index”, referred to as CWASP with extreme values here and in NJ early Wednesday morning. It’s not clear to me why these values are so high in our area Wednesday unless the front somehow stalls. I’ve been looking at the CWASP for well over two years; I’ve never seen it this high in this region.
Model Blend CWASP index at 8 AM Wednesday morning. Anything over 70 suggests dangerous weather. It’s not clear why it’s so elevated. (Click on image for a larger view.)
Monday Tuesday Wednesday
Posted Monday 07/20/26 @ 8:41 AM — The forecast appears on track for a beautiful Monday and a stormy Tuesday, especially Tuesday afternoon and evening.
Current water vapor image shows the setup—
Water Vapor image at XX with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, (Click on image for a larger view.)
The warm front will approach Monday night into Tuesday morning. Some showers and even some thundershowers are possible at daybreak Tuesday. Right now, following widely scattered showers, much of Tuesday will have dim sunshine through mid-level clouds, perhaps with some sunny breaks. The chance of thunderstorms increase from late afternoon into the evening, but the actual widespread severe storms and heavy rain begin between 7 PM and 9 PM and continue past midnight.
Anywhere from 1-3 inches of rain is currently forecast for our area. From the current models, severe storms look likely. Details about severity later today.
Originally Posted Sun 9:58 PM — This week’s weather will start with high pressure over our area and except for some smoke, the Monday should be delightful for July. (Monday morning should be smoke-free, but some smoke returns in the late afternoon and evening hours.)
Here’s the setup based on current water vapor image—
Water Vapor image at XX with superimposed RAP model MSL pressure (black contours), 500-1000mb Thickness (yellow contours) , GFS potential vorticity contours (violet fine contours) with MRMS Radar and surface wind barbs, (Click on image for a larger view.)
The above water vapor corresponds well to the current 18z GFS forecast map—
18z GFS forecast for NOW, Sunday evening. (Click on image for a larger view.)
Referencing the above GFS map above, the edge of the heat dome (576 thickness line) is to our south. On Tuesday, this will push northward again as a warm front with showers and thunderstorms. At the same time, a disturbance ( L above) moves over the top of the ridge and joins with the front over us with more showers and storms ahead of a cold front. Sound familiar?… it’s similar to what we had this past Saturday. Showers may linger into Wednesday morning followed by clearing.
Following the cold front very early Wednesday, things look tranquil Thursday and Friday at this time.
There’s a tropical system visible off of the western Florida coast. It’s forecast to move westward. I’ll keep an eye on it.
