Category Archives: Philadelphia Weather Outlook

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#weather #paweather #wx #pawx #philadelphia

Snow Accumulation Tonight? Fuhgeddaboudit!

Update Mon 3/06 5:56 PM —This afternoon’s models have taken the trace snowfall predicted by last night’s models and have moved accumulations even closer to zero. The trend today has been for accumulating snowfall to be even further northward.

Here’s the very latest GFS snowfall accumulation for tonight—

Today’s 18z GFS shows accumulating snow from Allentown northward. The blue contours are every 0.5″ snow increments. (Click on image for a larger view.)

While some snow is expected to fall in our area, minimal accumulating snow expected due to temperatures being above freezing and “surface skin” temperatures also above freezing during the time of the precipitation.

While temperatures may fall close to 32º just outside the city by 7AM, it will occur after the precipitation has exited the area.

NBM showing exiting precip as 32º line drops south at 5AM Tuesday—

NBM foreast clouds (black) 32º line (white) precip (shades of green/blue) (Click on image for a larger view.)

Monday Forecast Update

Update Mon 3/06 9:05 AM —It appears that the fast moving weak storm for tonight will bring down enough cold air to allow the precipitation to fall as snow. The timing of the storm, occurring at night, helps with this colder thermal profile.

While the light precipitation in the immediate PHL area will fall as snow, surface temperatures will be above freezing in areas south of Doylestown. No accumulation on roadways and little accumulation on grassy surfaces expected in these areas.

Snow starts 11PM to midnight and ends before daybreak Tuesday.

North of Doylestown, accumulating snow is forecast by the models. There’s quite a range of accumulations forecast—

NBM:

NBM Snow accumulation forecast (Click on image for a larger view.)

NAM-NEST:

NAM-NEST snow accumulation (Click on image for a larger view.)

Previously Posted Sun 5:55 PM —

I don’t see much significant weather this coming week until next weekend, although a pattern change to colder weather is hinted at for us for the following week, according to the GEFS.

With the exception of a warmer Monday (53-54º), for the rest of the week, highs will be in the upper 40’s (Blue Bell), close to the seasonal average high of 49º (Blue Bell) and 50º (Philadelphia).

This Week’s Weather Highlights

Monday night—

A weak storm moves through Monday night with some rain. It continues to be windy, especially Tuesday through Wednesday. (Well, it IS early March).

GEFS forecast for Tuesday at 1 AM. Weak low pressure moves just to our south with rain. Clearing later Tuesday morning.

Friday Night into the Weekend—

Another storm approaches for next Saturday and a strong secondary low, a coastal storm, develops.

GEFS forecast for Saturday at 1 PM. Rain and wind due to a secondary low. (Click on image for a larger view.)
Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#weather #paweather #wx #pawx #philadelphia

Monday

Update Mon 02/20 @ 9:45 AM — No change in yesterday’s prediction of sun breaking out around noontime. The latest NBM supports this—

This morning’s 12z NBM showing cloud ceiling (shading) and cloud cover (contours) Movement to the southeast (arrows) Clear skies after the front moves through. (Click on image for a larger view.)

The weak cold front that is causing the clouds this morning will move back as a warm front tonight and Tuesday. Several periods of rain tonight and again Tuesday.

The weekend system is looking less impressive regarding any snow here.

Previously Posted Sun 5:51 PM —

Overview

This week’s weather will be influenced by an extremely strong jet stream flow (by Thursday into Friday, the jet streak winds approach 225 mph!) and generally southwest to northeast flat to upper ridge. The warm- cold boundary will be right near us and any movement of this frontal boundary will cause changes in the forecast. With such high jet stream winds, such waves in the frontal boundary are bound to occur.

NAEFS forecast for Thursday morning showing jet stream winds (at 250 mb height). Superimposed is the 540 thickness line (red line) captures the general position of the cold-warm boundary . (Click on image for a larger view.)

I think this week’s weather will turn out to be ‘interesting’, fast moving and probably difficult to forecast accurately.

(I’m still watching the system expected to approach us next Saturday. Timing differences have already developed between the various models that were strangely similar yesterday. A mixed precipitation event changing to all rain still possible Saturday or Saturday night.

With things so fast moving, I’m just going to look at Monday and Tuesday to start.

Monday

A cold front moves through late morning. Cloudy in the morning, then sunshine by the afternoon. High 58-60º

Tuesday

A warm front moves back through in the early morning with showers in the morning. Then sunshine by the afternoon. Very WINDY. High 58-60º