Category Archives: Philadelphia Weather Outlook

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#weather #paweather #wx #pawx #philadelphia #phillywx

Friday Forecast Update

Update Fri 06/09 @ 9:20 AM — A disturbance rotating around the upper low over eastern Canada will bring a mix of cloudiness and sunshine late morning into the afternoon and evening. Most models keep any showers too far to our west, but the Canadian models have been consistently forecasting the possibility of light showers around here, most likely during the evening—

Canadian HRDPS accumulated rain forecast by 11 PM Friday. The Canadian models are on the high end of the spectrum in predicting shower activity near Philadelphia. Most areas will receive no rain. (Click on image for a larger view.)

Showers, if any, will be light and scattered. Update Fri 06/09 @ 9:47 AM — This morning’s RAP and HRRR are more similar to the above HRDPS. showing more shower activity in and near Philadelphia. The RAP shows a line of showers/thundershowers about 8-9 PM passing through Philadelphia.

As for smoke, here’s the very latest smoke level forecast at near-ground level for 4 PM Friday—

Today”s 12z HRRR. Some areas, mostly in Chester county and areas south of the city will have elevated smoke at near ground level. (Click on image for a larger view.)

The weekend is looking much warmer and currently, no rain is forecast. A change in the general weather pattern still on-track for next week.

Philadelphia Smoke & Friday Forecast Update

Update Thu 06/08 @ 5:58 PM —Smoke levels improved this afternoon, but it appears that more smoke and particulates will move through through this evening, before the end of the Phillies game.

This evening’s smoke levels—

18z HRRR smoke forecast for 10 PM this evening (Thursday) Shading is total column smoke concentration while white contours are areas of significant near ground level smoke. The worst areas will be far southwest of the city this evening.

For Friday evening, about 24 hours later, smoke levels improve significantly—

Friday — As for the weather, some scattered showers and thundershowers are possible Friday afternoon and evening. Most of the activity will be far west of the city and near the Jersey shore.

Philadelphia Smoke Forecast Update

Update Thu 06/08 @ 7:25 AM — Here’s the latest HRRR extended smoke forecast. This is the forecast for smoke at ground level to 8 meters above ground level (about 26 feet above ground)

06z HRRR forecast for NOW (7 AM) Thursday. Still very high smoke concentration. This is forecast smoke at 8 meters above ground height(26 feet) (Click on image for a larger view.)

By noon, the air quality at ground level is improved, especially west of Philadelphia—

06z HRRR smoke forecast at ground level at noon (Click on image for a larger view.)

The forecast above is for smoke levels 8 meters above ground. While the ground level smoke will be significantly reduced in some areas today, the sky will look quite hazy and smokey due to high levels of smoke still being present at mid and upper levels of the atmosphere.

Unfortunately, the HRRR shows low level smoke increasing during the second half of the Phillies game tonight at 9 PM—

06z HRRR smoke forecast at 9 PM Thursday evening. (Click on image for a larger view.)

Regarding rain on Thursday, while some areas far northwest and in Delaware/Maryland may get some showers this afternoon and evening, little to no rain is currently expected in the Philadelphia area today.

Philadelphia Smoke Forecast Update

Update Wed 6/07 @ 10:22 PM — The latest HRRR shows the Philadelphia area in the thick of smoke at 10 PM—

Tonight’s HRRR smoke at near ground level near maximum tonight. (Click on image for larger view.)A

The HRRR shows that things improve temporarily Thursday afternoon near ground level—

HRRR smoke forecast for 2 PM Thursday. The sky will still look smokey because upper levels will still have plenty of smoke. (Click on image for larger view.)

Update Wed 06/07 @ 8:35 PM — As I mentioned earlier, I never thought I’d be programming for HRRR smoke model downloads for Philadelphia. I’ve gotten a better handle on these specific parameters and I’ve updated the graphics.

This afternoon’s HRRR shows things improving at the surface during the early afternoon Thursday, but things get nasty again during the evening.

18z HRRR total smoke near ground at 1 PM Thursday. Things improve temporarily during the afternoon as somewhat cleaner air moves in from the west. (Click on image for a larger view.)

Most HRRR model runs only forecast out to 18 hours. The next HRRR model run that forecasts out to 48 hours will be available after 10 PM. I’ll update later this evening with the new HRRR regarding the smoke forecast for tomorrow.

As for the weather pattern change, it’s still on track. Some showers are possible later Friday and some rain later Monday, as the jet stream finally flattens and the blocked pattern breaks down by next Wednesday.

Philadelphia Smoke Forecast

Update Wed 06/07 @ 5:50 PM — I never thought I would have to download a smoke forecast parameter for the Philadelphia area. But the HRRR model has a separate model for smoke (particulate matter- fine) and I’ve spent a fair number of hours today leaning how to program the download and process this parameter.

It appears that the current HRRR model keeps the heavy smoke with us through most of Thursday, with some improvement early Thursday evening in southern areas as some cleaner air punches in from the west.

HRRR forecast Particulate Matter Fine (smoke) for Thursday evening at 7 PM. A tongue of somewhat cleaner air punches in from the southwest Thursday evening. I have no experience with this sort of forecast and I don’t know how accurate the HRRR is in forecasting smoke. (Click on image for a larger view.)
Where there’s smoke there’s fire

Update Wed 06/07 @ 9:42 AM — The current smoke situation here is a serious health risk. All the result of the incredible stretch of dry weather that has affected the local Philadelphia region but also areas in Canada.

One of the many capabilities of the HRRR is low level smoke concentration forecasts. Here’s the current HRRR analysis at 8 AM today—

HRRR smoke analysis shows the Philadelphia area in a relative maxima of smoke concentration. Each contour is increasing/decreasing smoke concentration. (Click on image for a larger view.)

Unfortunately, more smoke is on the way. Here’s the HRRR forecast for this afternoon and evening—

HRRR smoke near ground forecast for 6 PM Wednesday. (Click on image for a larger view.)

Update Tue 06/06 @ 5:40 PM — Despite some radar echos, most areas had little rain. Perhaps the RRFS will be a big improvement in forecasting when it’s released the end of this calendar year?

Radar image at 4:38 PM suggests that some areas were getting rain. Most of those echos were caused by rain evaporating before it reached the ground. Most areas had no rain, including areas with radar echos.

Wednesday looks to be sunny and continued cooler than average, with highs in the mid 70s.

Several models are now forecasting a large scale change in the stagnant jet pattern and are predicting rain for our area next Monday and Tuesday. A significant change in the jet stream pattern is expected by next Wednesday through Friday.

Update Tue 06/06 @ 7:23 AM — The uncertainty with the isolated/scattered showers this afternoon continues. Capturing this is a forecast comparison between the NAM-NEST (also shown below) and the new RRFS model (still experimental)—

The RRFS (Rapid Refresh Forecast System) and the NAM-NEST total precipitation forecast comparison for today, Tuesday. As mentioned last night, the NAM-NEST is in the high end of total precip forecast for today, Tuesday. (Click on image for a larger view.)

There’s another chance of showers this Thursday afternoon or evening.

As mentioned over the weekend, there are signs that the long-standing blocked pattern we’ve been in for over a month will be breaking down between Monday and Wednesday of next week. Expect a change to warmer and possibly wetter weather.

Update Mon 06/05 @ 5:32 PM — It’s been back and forth with the chance of showers on Tuesday. There’s a range from little to nothing with the GFS, while the NAM-NEST is forecasting the most shower coverage. Showers possible as early as 2 PM, but 4-6 PM is most the most likely time frame. Most areas will see no showers.

Here’s the NAM-NEST total accumulation forecast for Tuesday which is at the high end—

Today’s 18z NAM-NEST model forecast total precipitation for Tuesday afternoon and evening. (Click on image for a larger view.)

The Canadian HRDPS is probably the closest to the HREF and HRRR and is probably closer to the the likely actual amounts and coverage—

Today’s 12z Canadian HRDPS total rain forecast for Tuesday. (Most areas get nothing.) (Click on image for a larger view.)

The experimental RRFS has almost no shower activity.

Update Sun 06/04 @ 8:37 PM —I think l need to retract that ‘dry’ forecast for Tuesday. Several of this afternoon’s models (18z) are showing scattered shower/thundershowers, similar to what we had the other day.

Previously Posted Sun 5:08 PM —

The blocking pattern (Omega block Ω ) that’s been with us for weeks will maintain it’s hold over our weather through the coming week.

(There are finally signs that the block will break down between the 10th and the 15th of this month and we’ll see a change to a more typical summertime pattern likely next week —More heat, more humidity, maybe more thunderstorms.)

Monday looks to be mostly sunny to partly sunny/partly cloudy in the afternoon.

Tuesday: Regarding the current blocking pattern, a deep upper cyclonic flow currently over New England will rotate a disturbance around its center resulting in the formation of a surface trough moving through our area on Tuesday.

Sunday afternoon Satellite Water Vapor image shows upper low near coast of Maine. and the potential disturbance that will move through on Tuesday with what appears to be a low possibility of some showers. A similar scenario for Thursday. (Click on image for a larger view.)

For Tuesday, the latest GFS, ECMWF and today’s earlier NAM-NEST have some potential showers moving through, both earlier in the day and especially late afternoon Tuesday. We could use the rain.

Unfortunately, the latest NAM-NEST, Canadian GEM and the still-experimental RRFS have little in the way of showers for us from this system. (Little in the way of clouds too.) I’m leaning towards a fairly dry Tuesday for us.

After a sunny Wednesday, another disturbance may rotate through on Thursday with more clouds and maybe some sprinkles.

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#weather #paweather #wx #pawx #philadelphia #phillywx

Shower Forecast Update

Update Fri 06/02 @ 9:10 AM — Despite reasonably high CAPE and thermal instability, the lack of soil moisture feedback and marginal available precipitable water (PWAT= 1.3″) will result in a low degree of shower activity Friday afternoon.

Very widely isolated/scattered activity as early as 3-4 PM lasting until about 2 AM Saturday morning.

Here’s the HRRR total accumulation forecast—

HRRR total precipitation by 2 AM Saturday. Totals are in the range of 0.00- 0.16 inches (Click on image for a larger view.)

Outlook for Saturday— periods of clouds with periods of sunshine. Low probability of any showers. Cooler.

Friday Forecast Update

Update Thu 6/01 @ 10:38 PM —Tonight’s models just coming in show widely scattered showers and thunderstorms moving down from the north Friday afternoon. Peak time about 5-6 PM but possible as early as 3 PM. Widely scattered is the operative word. There’s enough CAPE and thermal instability, but not very high available moisture. Minimal shear and little jet stream support. Not a drought buster.

Update Thu 06/01 @ 4:30 PM — Most models are forecasting high temperatures around 92º-93º on Friday afternoon.

That said, the ECMWF, German ICON and Canadian HRDPS are showing some suburbs of Philadelphia reaching 95º-96º.

The NBM which is designed to iron out differences in the model forecasts is showing 92º but with a high standard deviation of ± 3.2º.

Interestingly, the dew point temperatures will be low, so the heat index (“apparent temperatures”) will likely be lower than the air temperature.

NBM Apparent Temperatures at 3 PM Friday (HEAT INDEX) (Click on image for a larger view.)

It appears that a lack of soil moisture and precipitable water may significantly reduce thunderstorm development and coverage Friday evening. Much needed rain doesn’t currently appear to be a likely possibility in many areas.

Possibly some thunderstorms early Friday evening?

Update Wed 05/31 @ 5:35 PM — The incredible weather we’ve been having is really quite perfect, BUT there’s been a significant deficit in rainfall in may areas, especially from Philadelphia and the suburbs immediately westward.

The backdoor cold front expected Saturday could produce some light showers.

Today’s higher resolution models are suggesting the possibility of some thunderstorms late Friday afternoon or early evening in advance of the front.

(There will be plenty of heat and CAPE available for thunderstorm formation on Friday. Precipitable water is expected to increase to 1.7″. Missing will be soil moisture, which tends to enhance convective activity.)

The NAM-NEST model is showing a few scattered storms early Friday evening, mostly to our far north and more later in the evening.

Just out of curiosity, I took a look at the experimental RRFS (Rapid Refresh Forecast System) model under development and scheduled for release the end of this year.

Here’s a comparison of the NAM-NEST and the experimental RRFS at 6 PM Friday—

The RRFS is showing a thunderstorm cluster over Philadelphia Friday at 6 PM. It will be interesting to see if this model forecast holds. (Click on image for a larger view.)
Ninety Degrees Plus on Friday. Light showers possible Saturday

Update Wed 05/31 @ 9:39 AM — The upper level ridge will move eastward enough on Friday to give us some true summer temperatures. There’s a range of forecast high temperatures, but here’s the latest ECMWF and NBM to give a sense of what’s expected—

Lastest ECMWF high temperatures forecast for Friday (Click on image for a larger view.)

Here’s the NBM model version 4.1 forecast which is a weighted average of over 40 models, weighted based on the model’s most recent 6 hour performance—

Today’s 12z NBM model high temperature forecast with standard deviation shown as ±. (Click on image for a larger view.)

Dew point temperatures will be relatively low (60º or less) so the actual “apparent temperature” (“heat index”) will not be that high (less than 90º in most areas.)

For Saturday, a back door cold front moves through. Most models are showing light showers mid-day with about 0.2-0.3″ of rain. Not very much, but we’ll take it. With soil moisture so low, we’ll see if we even get that much.

Blocking Pattern Retrogrades. Expect 90º on Friday

Update Tue 05/30 @ 11:50 AM — Not only is the blocking pattern expected to persist this week, but the latest GFS has joined the ECMWF in showing a deepening of the upper low over the Newfoundland and a retrograde of the entire block westward—

ECMWF jet stream forecast for Saturday shows a strengthening of the upper level low near Newfoundland over with it extending further southwestward (retrograde) with the entire block circulation retrograding westward.

Following 90+º temperatures here on Friday, the retrograde will cause a backdoor cold front to move across us Saturday. The last two days of the ECMWF model shows a bullseye of rain with this backdoor cold front over us on Saturday. The GFS has joined the ECMWF with this forecast, but has significantly less rain for us.

Following the backdoor cold front, we cool down significantly for Sunday.

Previously Posted Mon 9:24 AM —

Blocking Pattern Entrenches

It’s been over three weeks since the immediate Philadelphia area has had any significant rain.

While the term “pattern” is sometimes loosely used regarding weather changes, this is beginning to look like a true persistent pattern for our area, all the result of a relatively unchanged, blocked upper air configuration.

Over past weeks, I’ve used the terms Omega Block and Rex Block to describe the upper air configuration that is resistant to change.

The latest ICON ensemble (ICON-EPS) clearly shows we’re heading into a combined Rex block and large scale Omega block for the end of this week—

ICON-EPS (ensemble) mean 250 mb Heights (jet stream summer level winds) forecast for this Friday. (Click on image for a larger view.)

The GFS ensemble (GEFS) shows a similar Omega block configuration without the Rex Block—

GEFS 250 mb mean Wind forecast (summer jet stream level) (Click on image for a larger view.)

What does this all mean? Well, what we have weather-wise is essentially what we will be getting through at least the next week or so— Beautiful, cooler to near average weather with little-to-no chance of rain.

The center of the US will be in the very warm (hot) sector of the block, but we’ll be in the cooler part of the block, influenced by the upper low pressure system.

As I’ve expressed over the past week or two, I’m concerned that this may progress into a significant dry period (short term drought) for the immediate PHL region.

Patterns change, often without advance notice, but for now this is what we’ll see. The NAEFS suggests we may get some light rain the end of NEXT week (June 7-10th time frame.)