Category Archives: Philadelphia Weather Outlook

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

Perfect Weather

Update Thu 11/03 @ 5:47 PM — Not much happening since my last update. Just perfect weather! Expected to continue! High pressure remains in control off the coast—

Today’s 12z NAEFS Forecast for Thursday. High pressure off the coast. A strong upper ridge over us (as shown by the red 540 thickness line) and a sharp trough in the West. That cold trough never makes it into our area. (Click on image for a larger view.)

The push of colder air in the West never makes it into our area. A front falls apart as it approaches later Sunday—

NAEFS forecast for Sunday at 7 PM. High pressure remains stationary in the Atlantic. The weak cold front falls apart in central PA. A tropical like storm develops near Florida, that needs to be watched. .

Mild Weather— Little Chance of Rain

Update Tue 11/01 @ 5:25 PM — A strong ridge of high pressure will maintain a southwesterly flow of mild air through the weekend and perhaps well into next week.

My caption on the NAEFS graphic below explains—

12z NAEFS forecast for Friday morning. A Bermuda-like High (1) off the coast will maintain a southwesterly flow of mild air into our region. A cold front (2) will lose its punch as the push of cold air (3) diminishes. The front shears off to our north and east on Sunday. For next week, a flat zonal flow will continue generally mild dry conditions .

Updated Mon 10/31 6:55 PM — So game 3 is officially postponed. It’s not clear to me why MLB waited so long. By this afternoon, there wasn’t a single model that wasn’t forecasting rain, if not by the start, by 9-10 PM.

So which model, if any, did the best with this forecast? Well, the ECMWF would have been the clear winner, but this morning’s ECMWF had the rain starting early in the afternoon. Clearly not correct and the model run last night had very little falling right along I-95 and the stadium.

The high resolution HREF, HRRR and NAM-NEST all kept the heavier rain off to the west of the city until later this evening. Clearly not correct.

Last night’s new GFS had the rain starting about 9-10 PM at the stadium. A little slow with the start time, but the general axis of the rain right now is just as predicted. Still, not a winner.

The German ICON model from this morning wasn’t bad. Some rain at about 7PM and increasing afterwards. Axis of rain isn’t what we have on radar.

Yesterday’s Canadian HRDPS, as was this morning’s, was surprisingly good. It had the rain starting about 7-8 PM and the rain axis is pretty much what we have right now. Not sure that it’s a winner, but close.

The bottom line — models rarely capture reality exactly, especially with precipitation placement and timing. This is something we get reminded about each winter with snow storms.

Update Mon 10/31 @ 4:58 PM — The lastest HRRR still keeps the heavier rain to the west of the stadium at 9 PM, but the rain moves in and increases in intensity after that time—

The earlier forecast that Trick-Or-Treaters would be OK before 7:30 – 8:00 PM probably is too optimistic.

Current Radar (5:10 PM)—

Radar with RAP model jet stream wind streamlines (red) at 5:10 PM (Click on image for a larger view.)

A radar image with motion captures that the rain is moving in rapidly—

Latest HRRR model forecast total accumulated rain by 9 PM—

18z HRRR Total accumulated rain totals at 9 PM. the HRRR shows only light rain at Citizens Bank Park at 9 PM, but rain increases afterwards. If the Phllies play tonight, they will play in increasingly heavier rain. (Click on image for a larger view.)

The NAM-NEST cranks out more rain than the HRRR. Here’s the Total Accumulated Rain forecast by 10 PM—

18z NAM-NEST forecast Total Accumulated Rain by 10 PM. Significant rainfall by then. (Click on image for a larger view.)

Previously Posted Mon 9:49 AM —

First order of business this week is the forecast for Trick-Or-Treaters and the Phillies World Series game this evening. I’ve been waiting for the latest ECMWF and NBM to become available before posting this.

Those of you following the weekend postings will know that the ECMWF has consistently forecast some light rain during the Phillies game this evening.

Here’s the latest ECMWF accumulated rain forecast for 9 PM—

06z ECMWF showing very light precip at 9 PM. By 11 PM, it increases only slightly to 0.02- 0.03″ (Click on image for a larger view.)

However, many of our high resolution models (HRRR, RAP, HIRESW, NAM-NEST) have all kept light rain in the western suburbs during the evening hours while keeping the immediate PHL area mostly dry until after 11 PM.

The new GFS-v 16.3 continues to have light rain move in between 9 and 10 PM. The high resolution Canadian model is similar to the GFS.

New GFS for 10 PM—

06z GFS (new version 16.3) showing considerable rain near stadium (0.11″) accumulated by 10 PM tonight. (Click on image for a larger view.)

The latest model blend (NBM) just became available and it captures the majority consensus —

12z NBM shows similar ot the ECMWF at 8 PM but increases accumulated rain to 0.07-0.10 inches of rain by 11 PM. Not great for baseball. (Click on image for a larger view.)

Based on the NBM, Trick-Or-Treaters should be fine in most of the area before 7:30 to 8 PM.

For the World Series Game 3, some light rain expected by 9 PM which will increase by 11 PM which may require some decision-making by MLB.

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

Update Thu 10/27 @ 5:38 PM — The Friday through Sunday period is looking very nice. Sunday isn’t forecast to be as cloudy as previously thought.

Even the system expected to affect us on Monday (Halloween) doesn’t appear to be as wet as previously forecast. With the exception of the ECMWF model (which still forecasts some heavier showers), it may be relatively dry for Trick or Treaters Monday evening.

Update Wed 10/26 @ 5:17 PM — High pressure will build in for Thursday through Saturday. Very nice autumnal weather expected.

(The only thing to watch: the high will move off to our northeast. An easterly flow around the high may bring in some cloudiness on Saturday, but not currently forecast by the models.)

Low pressure in the Southwest will move towards us on Sunday with an increase in clouds. Rain associated with this system is currently forecast to move in during Sunday evening and linger into Halloween.

Wednesday afternoon’s Water Vapor image showing upper air disturbance that will spawn low pressure in Colorado and move towards us on Sunday. (Click on image for a larger view.)

GEFS forecast for Thursday. Large, sprawling high pressure moves in. Low pressure (white circle) will move towards us Sunday. (Click on image for a larger view.) and move

Updated Tue 10/25 10:46 PM — Several of tonight’s high resolution models show some scattered showers between 1 and 4 PM Wednesday afternoon with a weak frontal passage.

Update Tue 10/25 @ 11:09 AM — Today’s models continue forecasting the low clouds to hang tight through today (Tuesday). We are sandwiched between two low pressure systems that will move off to the northeast on Wednesday. We may get some break in the clouds for a time on Wednesday afternoon.

Tuesday’s 06z GEFS forecast for Wednesday at 2 PM. The current trough over us (1) will be swept away by the approaching cold front (2) as the systems shear off to our northwest. (clouds are black/grey) Click on image for a larger view.)

Thursday is looking good as are Friday and Saturday. There’s some question about another coastal low affecting us on Sunday. (high uncertainty.)

A low pressure system will shear off to the northwest of us on Wednesday with most of the rain with its associated cold front also moving off to the north and west.

Update Mon 10/24 @ 8:14 PM — This afternoon’s models suggest the low clouds may hang in tight through most of Tuesday afternoon, except in NJ.

Previously Posted Mon 4:41 PM —

A weak upper level trough and a high pressure system to our north have given us a damp easterly wind flow and light rain/drizzle.

NAESF shows strong trough over Colorado and weak trough over the eastern seaboard on Monday. These troughs will lift out by late Wednesday-Thursday.

The damp easterly flow will persist through much of Tuesday, but skies may brighten by mid to late Tuesday afternoon.

A weak front moves through Wednesday, with most of the energy to our far north. High pressure builds in for Thursday and Friday. Very nice weather expected Thursday and Friday and likely Saturday.