Posted Friday 06/19/26 @ 7:34 PM — This afternoon’s models show some of Saturday’s scattered showers (depicted here earlier) make it into the Philadelphia area Saturday evening between 7 PM and 11 PM.
18zREFS total accumulated rainfall at 11 PM. Showers will be scattered during the evening. (Click on image for a larger view.)
Previously Posted Fri @ 4:27 PM — —The semi-tropical storm off the southeastern US coast will move away. High pressure builds in for Saturday and Sunday.
Saturday
12zCanadian GDPS with AI spectral nudging forecast at 2 PM Saturday. (Click on image for a larger view.)
High pressure will bring mostly sunny skies along with low humidity. A few disturbances in the upper air flow will bring a bit of cloudiness late in the afternoon. Continued windy—14-22 mph during the day.
Model Blend Highs: Blue Bell- 82º Philadelphia 84º ±1.8º
Sunday
12z Canadian GDPS with AI spectral nudging forecast for 5 PM Sunday. Tropical air over mid portion of the country will push up as low pressure intensifies over the Midwest and moves eastward to affect our weather on Monday (Click on image for a larger view.)
Sunshine and pleasant. Less windy. Highs (Model Blend): Blue Bell- 85 º Philadelphia 86º ±2.2º Average standard deviation and uncertainty.
Rain is expected sometime Monday morning, perhaps lasting into part of Tuesday.
Posted Thursday 06/18/26 @ 9:05 PM — A quick forecast. Low pressure that developed in the Carolinas with yesterday’s front will brush the NJ coastline early Friday morning. Depending on the model, some light showers are possible as far west as the I-95 corridor, but most models keep it just brushing parts of Southern NJ.
Here’s the northern extent of any rainfall early Friday morning—
18z REFS total accumulated rainfall by noontime Friday. (Click on image for a larger view.)
Sunshine and a beautiful weekend is expected.
Thursday Forecast Update
Posted Thursday 06/18/26 @ 10:58 AM — This morning’s RRFS (12z) just became available and it is also not capturing current conditions. Here’s current radar—
Current Radar (10AM) with superimposed RAP model parameters (RH at 700 mb, isentropic 305ºK wind streams,surface pressure) (Click on image for a larger view.)
I won’t post the 12z RRFS because it needs a reality check. The 12z HRRR currently best matches the current radar although it’s an hour too fast and the rain it forecasts for our area is too heavy—
12z HRRR forecast for 10 AM Thursday. This rain falls apart as it moves through. (Click on image for a larger view.)
Based on both models, I don’t expect much in the way of rain for the immediate PHL area and much of the afternoon will be windy and probably dry.
Thu 9:09 AM Forecast Review — A total change in the model forecast has occurred over the past 12 hours.
Here’s the 18z RRFS forecast I used yesterday—
Yesterday’s RRFS forecast for today at 8 AM. Little to no precipitation noted. (Click on image for a larger view.)
Twelve hours later, the 06z RRFS forecast has totally changed (and now more closely matches the actual conditions)—
Today’s 06z RRFS (available at 4:45 AM EDT) shows the area of rain has increased dramatically in size. (Click on image for a larger view.)
Here’s the current radar—
Today’s 8 AM MRMS radar with superimposed RAP model Theta-E based winds around 10,000 feet. (Click on image for a larger view.)
Folks, you can’t do anything about these major model changes. Review of the models suggests the change has occurred as a result of a slight change in the jet streak position and shape.
If the current administration keeps reducing the size of NOAA’s budget and reducing the number of upper air sampling stations, you can expect more of these poor forecasts.
I’m waiting for the latest 12z models to update today’s forecast. It still looks like most of the rain will miss Philadelphia and southern NJ.
Thursday Outlook
Posted Wednesday 06/17/26 @ 7:33 PM —
Wed 7:33 PM —Forecast Review — A few areas north and west of the city saw a few showers and storms today; most areas saw no rain.
Radar Image around 3 PM this afternoon. These scattered/isolated storms developed in western Montgomery county and move northeastward. (Click on image for a larger view.)
The RRFS was fairly good at this forecast. The Canadian HRDPS which I use to ‘balance’ the RRFS forecast had predicted much more rain near the city than actually developed. The REFS which includes ‘time-lagged’ RRFS model runs and the HRRR also over-predicted the rainfall.
On Thursday, hot humid air will make it into our region. While conditions may seem ideal for some strong to severe storms as a weak cold front approaches during the afternoon, a deeper inspection shows that the immediate PHL area lacks the vertical motions to produce and maintain these storms. Here’s the latest RRFS—
18z RRFS shows has some activity in far western suburbs as early as 11 AM. Most in the immediate PHL area won’t see much in the way of rain, as the storms develop and move towards our south and east. (Click on image for a larger view.)
Despite this tepid RRFS forecast, the same model shows highly elevated Severe Weather Threat Index (SWEAT) with a few areas approaching a formidable level of near 370. (Things can get interesting when the SWEAT index approaches and exceeds 400.)
It should be noted that the latest Model Blend (NBM) differs from the RRFS forecast and shows some rainfall (<0.30″) about 1-5 PM across much of the area. Yet is shows thunderstorm probability to be low.
High temperatures 90º-93º.
We’ll have to wait until tonight’s models to see if the how this falls into place.
Wednesday Forecast Update
Posted Wednesday 06/17/26 @ 8:31 AM — There hasn’t been much clarification regarding the showers for today. The forecast showers this morning are attempting to take shape, as shown on radar, but they so far haven’t really developed—
Current Radar/water vapor image at about 8:30 AM with some echoes increasing in intensity. The vertical motion support (yellow contours) is weak over the immediate PHL area and non-existent over South Jersey (Click on image for a larger view.)
There’s still a chance of a widely scattered sprinkle this morning.
The soon-to-be operational RRFS model has backed away from showers this afternoon, but the statistical ensemble REFS still shows scattered showers mid to late afternoon. (The REFS group of models (“ensemble”) includes the HRRR.)
I don’t see much evidence of heavy thunderstorms in our area this afternoon, despite what I just heard on the radio this morning. Nonetheless, the afternoon possible storms will be driven by an upper air jet-streak quickly moving over our area—
Today’s 11z RAP model 250 mb winds (jet level) at 1:30 PM . The Philadelphia area will briefly be in the right exit regionof the jet streak, which accounts for some models forecasting rain/thunderstorms mid afternoon. The jet streak is curved anticyclonically,, which works against any lift from being the right exit region. (Click on image for a larger view.)
The latest ECMW-AI model (which is low resolution) does show showers early to mid afternoon while the German ICON model shows little to none. The RRFS shows little to none. A good opportunity to evaluate the RRFS.
Wednesday Forecast
Posted Tuesday 06/16/26 @ 8:12 PM — Wednesday’s weather forecast is high uncertainty/low confidence. Several models are forecasting widely scattered showers between 8 AM and 10 AM with another round of widely scattered showers/thundershowers around 2-4 PM.
Other models have most of the showers far north and far south of Philadelphia, with the city and the immediate suburbs in the doughnut hole of little to no precipitation. (Yesterday, the city was in the bullseye of the precipitation.)
So we’re dealing with high uncertainty, but the trend has been for little to no precipitation in and around the city. The latest REFS captures this—
Today’s 18z REFS statistical forecast for total precipitation on Wednesday – local probability matched mean. (Click on image for a larger view.)
There will be periods of cloudiness but much of the day will have sunshine through high cirrus clouds.
The heat returns for Thursday.
Tuesday -Wednesday Forecast Update
Posted Monday 06/15/26 @ 7:50 PM — After reviewing some additional afternoon models, it appears that warm air returns before daybreak Wednesday with some showers. Another disturbance brings showers and possible thunderstorms Wednesday afternoon.
Posted Monday 06/15/26 @ 5:52 PM — Another beautiful day on tap for Tuesday. The latest RRFS has some light scattered shower activity developing early to mid afternoon on Wednesday as another disturbance moves in from the west.
18z RRFS forecast 1 hour rainfall for Wednesday at 2PM (Click on image for a larger view.)
Originally Posted Mon 9:54 AM —The rain came in as forecast late evening yesterday and banding areas of rain provided some impressive rain totals for parts of our area, still in a rainfall deficit—
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.)
While the word ‘pattern’ is often thrown around by the TV weather entertainers, the current weather pattern does somewhat reflect a general change from last year at this time. And the coming week continues to show almost 24-36 hour intervals for chances of rain/showers. The rain won’t be as heavy as we had Sunday night.
The graphic of the ECMWF-AI forecast for Wednesday captures the general expectation for this week, with the jet in a broad cyclonic dip across the continental US and several impulses lined up to bring a chance of rain—
Today’s 06z ECMWF-AI shows the approximate position of the jet stream and several areas of moisture and energy poised to move in during the week. Meanwhile, the tropical hot air will be mostly confined to the areas south of the orange 760 thickness line. l (Click on image for a larger view.)
For today, Monday, expect delightful sunny weather with some gusty winds. The next impulse approaches during the day Wednesday. Heat returns for Friday. The upcoming weekend looks quite good!
Posted Sunday 06/14/26 @ 9:10 AM — The forecast for today remains mostly unchanged. Despite a forecast heard on the radio last night for showers this afternoon, it appears that showers and thunderstorms will wait until 7-9 PM at the earliest, moving in from west to east.
Potentially strong storms are expected, especially by 10 PM to midnight, although no tornadic level activity is expected. Additional showers and storms may develop about 3 AM and these showers should be out of the Philadelphia area by 7-9 AM. Total rainfall about 0.60″ with amounts as high as >2.0″ where banding sets up.
06z REFS total rainfall (Local probability matched mean) (Click on image for a larger view.)
Weekend Forecast Update
Posted Saturday 06/13/26 @ 7:19 AM — Last night’s models have come into agreement regarding Sunday’s forecast. It appears that Sunday will be sunny (through some thin cirrus clouds) and it won’t become cloudy until late afternoon or early evening. Showers and thunderstorms develop about 9PM – midnight Sunday evening. Some of the showers and storms will result in rainfall amounts in the 0.5″ – 1.0″ range with even some locally higher amounts.
Today’s water vapor satellite image showing approximate position of cold front. The orange shading is warm dry air that is flowing into the region today—
Water Vapor image at 8 AM Satrurday 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 in the approximate position of the cold front that will affect us late Sunday evening. (Click on image for a larger view.)
Previously Posted Fri @ 7:53 PM — —High pressure on northwesterly winds will reduce the humidity and temperatures on Saturday. An approaching cold front on Sunday will spawn showers and thunderstorms as early as mid afternoon Sunday and especially Sunday evening.
12z ECMWF-AI forecast for Sunday at 8 AM. Cold front over the Great Lakes will push south towards us as weak low pressure develops over our area. (Click on image for a larger view.)
Saturday
High pressure builds in for fair skies and less humidity. Light winds. 6-11 mph Highs: Blue Bell- 86º Philadelphia 88º ±2.9º Above average sd and uncertainty.
Sunday
Sunshine through thin high cirrus clouds. Increasing cloudiness late afternoon. The humidity and dew point temp increase as well. The latest RRFS delays any showers until about 9-10 PM. Some models show scattered showers developing in the mid to late afternoon. Highs (Model Blend): Blue Bell- 88 º Philadelphia 90º ±3.8º Above average sd and uncertainty.
