Category Archives: Philadelphia Weather Outlook

THIS WEEK’S WEATHER

Any snow on the horizon for us?

Update Fri 12/02 @ 8:24 AM — The latest NAEFS continues to show a warm front type snow situation, now for early NEXT Friday morning. Still a long ways off in the future, but it is potentially our first wintry possibility for this season.

This morning’s NAEFS forecast for NEXT Friday morning—

Today’s NAEFS forecast for next Friday 4 AM. Critical temperature 32º lines (blue, magenta) and surface 32º line (white). Red is 540 thickness line. This forecast suggests some snow will fall above the red thickness line, but too warm for any accumulation right around the city. (Click on image for a larger view.)

Update Thu 12/01 @ 8:10 PM — I’ve had my eye on the long-range forecasts. Over the past week, there has been a consistent signal for a warm-front type winter mix for NEXT Friday evening (12/9). I get a kick out of trying to spot these events. (Usually these extended range forecasts fall apart with time. )

Here’s the possibility as shown in the NAEFS—

Friday Dec 9th forecast— near freezing temperatures with warm front type snow possible west of the city, possibly also affecting our immediate area. White wavy line is 32º line. Red line is 540 thickness line. Way too early to really take this forecast literally, but the NAEFS has been showing this possibility for the past week. (Click on image for a larger view.)

Sunday now looking sunny

Update Thu 12/01 @ 8:02 PM — This afternoon’s models have backed away from the instability cloudiness previously forecast for Sunday. Sunday now looks to be mostly sunny but cold.


Weekend Weather Outlook

Update Thu 12/01 @ 11:41 AM — A strong cold front moved through as forecast yesterday. Another very strong cold front, associated with deep low pressure in Canada, will move through Saturday morning with additional rain and strong winds.

Saturday morning—

Thu 12z NAM forecast for 10 AM Saturday showing cold front, rain/snow. High winds expected again with this frontal passage. There may be clearing by afternoon. (Click on image for a larger view.)

Most models have the rain ending by 12PM -1 PM Saturday with gusty winds continuing into the afternoon and some clearing and sun possible by 3 PM. This morning’s GFS shows a secondary cold front moving through about 5 PM Saturday with a few sprinkles.

Sunday looks to have considerable instability cloudiness and windy conditions.

Another front expected Tuesday and the general trend is for cold weather the end of next week.


My 2022-2023 Winter Climate Snow Outlook

Wednesday Forecast Update

Update Wed 11/30 @ 8:04 AM — Last night’s models show little change in the forecast. The cold front comes through about 3 PM with strong wind gusts starting around noontime. Rain this morning precedes the frontal passage.

Latest RAP model (09z) meteogram for location Blue Bell, PA shows barometric change at 3 PM, indicating frontal passage. Wind gust near 45 mph at Blue Bell. Some higher gusts predicted in western suburbs. (Click on image for a larger view.)

With Twitter’s change in ownership, I am suspending auto-posting to the Twitter site and will continue to evaluate the situation. Those of you using Twitter can learn of theweatherguy.net updates by following me on Mastodon.    ( Read more here. )

Wednesday Forecast Update

Update Tue 11/29 @ 5:41 PM — We’re back to a frontal passage between 2 and 4 PM with rainfall about 0.5 inches. Rain starts in the morning Wednesday, about 8-9 AM.

Winds increase early afternoon with many models exceeding 40 mph wind gusts and with some approaching 50 mph.

Here’s the latest GFS (18z) wind gust forecast for 3 PM Wednesday—

18z GFS wind gusts and wind direction at 3 PM Wednesday. (color coding is wind gust speed) Notice the change in streamline direction (white dashed line) that occurs at 3 PM, indicating the winds are shifting from the SW to the WNW with the frontal passage. (Click on image for a larger view.)

Here’s the latest RAP model (21z) wind gust forecast for 3 PM—

21z RAP model Wind gust forecast for 3 PM Wednesday (Click on image for a larger view.)

Update Tue 11/29 12:22 PM — The latest models show the front moving through here somewhat earlier on Wednesday than previously forecast. Current timing for the frontal passage about 12-2 PM with the highest wind gusts (40-50 mph) around that time. Total precipitation in our immediate area is now forecast to be only about 0.40-0.50 inches.


Update Mon 11/28 @ 8:22 PM — Heavy rain and high winds Wednesday afternoon between 2 and 6 PM. The strong cold front mentioned in the “week overview” below looks like it might pack a punch as it moves through between 2 and 6 PM (peak probability 3-5 PM).

Rainfall 1.0 inches (CMC-GEM) to 1.4 inches (NBM) are possible in a few hour period. Wind gusts 40-50 mph possible.


Previously Posted Mon 5:52 PM —

Week Overview

Two weather events for this coming week, currently timed for Wednesday and Saturday. There’s good agreement in the models for Wednesday’s rain. There’s less agreement in the timing for Saturday’s rain.

The jet stream will be making some significant changes over the week as cold high pressure pushes the jet flow down into our area on Wednesday with milder temperatures becoming colder by Thursday as a strong cold front moves through—

NAEFS forecast (250 mb winds) for Wednesday 10 AM shows a dip in the jet flow in response to cold air moving down from Canada. (Click on image for a larger view.)
NAEFS forecast for Wednesday shows a cold front in western PA and rain in our area. (red line is the 540 thickness line ) (Click on image for a larger view.)

Here’s what the surface map is forecast to be Wednesday at 1 PM with the cold front approaching the Delaware Valley—

High pressure builds in for Thursday and Friday. Another dip in the jet flow will bring another cold front through on Saturday—

Split Jet flow on Friday 1 PM with a ridge trying to develop, but the split southern stream jet flow will bring rain by Saturday.

Surface forecast for Saturday—

NAEFS forecast for Saturday. Another cold front moves through. (red line is the 540 thickness line )

THIS WEEK’S WEATHER

Rain Totals and Cold Weather

Update Wed 11/16 @ 8:09 AM — The models did well with the forecast precipitation. Here’s the MRMS estimated totals; compare to the HREF forecast below—

MRMS measured rainfall totals from last night’s rain. (contours are in mm. 25.4mm =1 inch) (Click on image for a larger view.)

Below seasonable average temperatures expected for the weekend and remaining somewhat cold through much of next week.

Long Range Outlook- Thanksgiving day looks to become rainy into next Friday. Possibility of a coastal storm next weekend with snow or mix quite near our area.


Moderately Heavy Rain

Update Tue 11/15 @ 11:55 AM
No change in the forecast. Rain moves in from the southwest as early as 2-4 PM. Moderately heavy rain tonight. A generalized 1 to 1.4″ according to the HREF model—

This mornings’ HREF model total rainfall totals. (Click on image for a larger view.)

Rain ends around daybreak Wednesday. Some sun but mostly clouds until about 2 PM in the afternoon.

I took a quick look at the forecast for Thanksgiving day. Looks like some rain.


Update Mon 11/14 @ 11:14 AM
A quick update. The latest models have the rain coming in earlier on Tuesday and departing earlier on Wednesday. Rain begins as early as 3-4 PM Tuesday afternoon and ends around daybreak Wednesday. Some clearing expected during by the afternoon Wednesday. Total rainfall about 0.75 to 1.1″

Colder temperatures behind this system for Wednesday night through Thursday.


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Previously Posted Sun 9:12 PM —

This week’s weather will be influenced by a jet flow to our south, allowing cold air to move into our area. Additionally, a disturbance now near Arizona (not related to the election) will move east and spawn a coastal storm that will bring rain to our area late Tuesday.

Here’s the current jet flow and water vapor image—

Current Water Vapor image (with radar and jet flow) shows developing low pressure near the four corners area Sunday night. (Click on image for a larger view.)

Below is the latest GFS model for the same time period. Notice the Water Vapor image above (with Radar) shows some precipitation but the GFS below doesn’t—

GFS Forecast for the same time period as the water vapor image above. (Click on image for a larger view.)

The model forecasts for this system have been changing throughout the weekend, although they are coming together.

Rain is now expected to move in here as early as late afternoon Tuesday. (Previous model runs had it moving in on Wednesday and being further off the coast.)

Here’s the latest GFS v 16.3 forecast for Wednesday at 1AM—

18z GFS forecast for Wednesday at 1 AM. Coastal storm with rain for our area. Notice the red (540 thickness line) which is a general rain-snow dividing line in winter. (Click on image for a larger view.)

With the above satellite image not really matching the current GFS forecast, I expect to see some additional changes in the forecast. Stay tuned.