Monthly Archives: January 2024

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx

Wednesday

Posted Tuesday 01/30/24 @ 5:28 PM — Low pressure developing to our south will move off to the southeast. In the process, some colder air will move in for Wednesday in a narrow trough. We’ll have cloudiness on Wednesday for much of the day, the clouds breaking up towards evening.

By Thursday, high pressure and an upper air ridge to our west will move in and result in milder temperatures.

The ECMWF forecast for Wednesday afternoon captures the next two days—

ECMWF forecast for Wednesday at 4 PM. Coastal low moves off to the southeast . Milder air to our west is poised to move in for Thursday.
The Winter Outlook Page about potential future storms in the coming 10 days has been updated.
Tuesday -Wednesday

Posted Monday 01/29/24 @ 5:33 PM — The low pressure system expected to develop in West Virginia Tuesday evening is expected to move to our south.

Some models are forecasting some light snow showers and mixed light snow/light rain during the late Tuesday afternoon and evening into Tuesday night. There may be a dusting/coating in parts of Lehigh and Berks counties by Wednesday morning.

With temperatures expected to be above freezing, no accumulation is expected in our immediate area.

Here’s the NBM forecast for precipitation type at midnight—

01-29-24 18z NBM precipitation type. Blue- snow green=rain The lighter the shading, the less probable. The white contour at visible at the top is the 32º line. (Click on image for a larger view.)
updated my Winter Outlook Page about potential future storms in the coming 10 days.

Originally Posted Mon @ 9:49 AM — This week’s weather will be characterized by a very amplified upper ridge in the west and a persistent colder trough in the east that reloads with colder air by the weekend.

The main jet flow will keep any storms, both in the northern jet and southern jet, to our south. (The position of this trough is looking a lot like last year’s persistent eastern trough, in the ‘wrong’ position for snow in our area.)

The forecast image below for the NAEFS captures the setup, expected to persist through the weekend.

NAEFS statistical “mode” version model combined with GEFS “bias-corrected” precipitation model forecast for Wednesday. The cold air from eastern Canada will reload the positively tilted trough (dark blue line) over our area. Meanwhile storms developing around the bend in the jet (north Carolina) will move to our south and east, missing us. (Click on image for a larger view.)

Monday —Despite the some sunshine this morning (Monday), expect more cloudiness later this morning into this afternoon, but also with some breaks of sun possible at times. (an uncertain cloud forecast)

Energy dropping down (in central Canada) will cause a storm to form to our west Tuesday into early Wednesday, but light snow with this system should stay to our west and south—

Current satellite water vapor image Monday morning with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Disturbance (1) will drop down and develop into weak low pressure at (x) the bend in the jet. It’s expected to move off to our south and east. (Click on image for a larger view.)

So an interesting jet flow.

Colder over the weekend. Chance of possible snow next Monday.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx

Sunday Update

Posted Sunday 01/28/24 @ 10:54 AM — Light rain is expected to continue, perhaps with a slight lull in the action between 11 AM and 2 PM in areas south and east of city. Another batch of somewhat heavier rain expected between 3 PM and 6 PM, then tapering off by 8 or 9 PM.

So far, we’ve received about 1 inch of rain in many areas (through 10 AM) according the the MRMS summary. An additional quarter inch of rain is expected by the time it ends—

MRMS combined rain gauge & radar-based measurement of rainfall received through 10 AM. Color shading is in inches. Line contour numbers are in mm (25.4 mm= 1 inch) (Click on image for a larger view.)

That ending in snow showers looks increasingly unlikely in this area.

Sunday Forecast Update

Posted Saturday 01/27/24 @ 5:44 PM —Rain is still expected to move in tonight between 11 PM and 2 AM, somewhat later than forecast yesterday. The heaviest rain from 5 AM through about noontime, but showers and light rain continue into the evening. Rainfall totals look to be in the 0.80″ to 1.3″ inch range in our area. It will become quite WINDY and gusty. Wind gusts to 35 mph.

NBM wind meteogram for location Wings Field, Blue Bell, PA

Cold air rushes in aloft Sunday night, but the any change to snow showers will be very limited, (if it occurs at all) and no accumulation is expected anywhere around here. Temperatures near the ground expected to remain above freezing.

Sat 5:12 PM —Forecast Review — That was quite a bust of a forecast. Not surprising – my update this morning began with “The models have not been doing a stellar job.”

That poor track record continued into today with cloud cover much less than anybody (especially me, with my reference to this morning’s NBM) would have predicted.

At least from the city westward, we had quite a nice long stretch of sunshine. I always like to go back and see what model, if any, got this right. The HRRR 15z, available about 11:15 AM showed significant sunshine in the afternoon, but disappearing behind clouds about 2 PM. The Canadian HRDPS showed not a cloud in the sky west of the city. That was overdone. The experimental RRFS had significant clouds with a break for an hour or so, the clouds back about 2 PM. Looking back, the German ICON model had the best match in cloud cover. Go figure.

Saturday Forecast Update

Posted Saturday 01/27/24 @ 8:16 AM — The models have not been doing a stellar job.

The fog has lingered in some areas longer than forecast last night. Last night’s models continue to forecast a break in the clouds from the city westward with some sun by late morning lasting until about 1-2 PM. HOWEVER, the latest NBM (12z) just available keeps a layer of low clouds, no sun.

Here’s the latest NBM cloud ceiling forecast for 1 PM today—

01-27-24 12z NBM cloud cover/cloud ceiling forecast for 1 PM No sunshine around here if this is true. (Click on image for a larger view.)

Rain expected by 10-midnight this evening. Highs in the 48-50º range.

Previously Posted Fri 6:07 PM —

As of this posting, the stalled warm front remains to our south and we remain socked in with fog and light mist. The front will retreat southward with somewhat colder drier air moving in from the northwest tonight.

A system is developing over the Gulf States that will move in late Saturday night with rain for Sunday.

This developing system for Sunday is visible on this water vapor image from late Friday afternoon—

Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. (Click on image for a larger view.)

Saturday

Fog should dissipate after midnight Friday. We’ll have a break in the clouds by mid morning and we should see some sun Saturday around noontime before more clouds roll in early afternoon ahead of the next system.

Rain moves in from the southwest between 10-11 PM Saturday evening.

NBM high temperatures: Blue Bell, PA 50º Philadelphia, PA 52º
Uncertainty (based on standard deviation of 2.5º): slightly more than average

Sunday

Cloudy with rain. Heavy at times. About 1 inch total rainfall. Rain/snow showers tapers off about 10 PM.

Low pressure intensifies along the coast Sunday evening as colder air enters the system from the northwest—

NAEFS forecast for Sunday evening (Click on image for a larger view.)

Rain changes to snow showers during the evening from northwest to southeast. No accumulation in our area.

NBM high temperatures: Blue Bell, PA 40º Philadelphia, PA 41º
uncertainty (based on standard deviation ± 2.2º): more than average