Weather Updates

WEEKEND WEATHER UPDATE-Sunday

[su_note note_color=”#defcdc”]Update Sun 12 PM: So, the current radar shows precipitation moving in sooner than any models had predicted.  Rain may start as early as 1 PM.[/su_note]

Most of last night’s models continue with the idea that rain begins in the general Philadelphia area around 3-4 PM today, Sunday. A remaining exception is the high resolution Canadian (HRDPS) which waits until 7 PM for the rain to start.

Rain may be heavy overnight and into Monday morning, then more light and scattered.

A warm front will try to make its way into Philadelphia and areas on a line to its south on Monday morning.  If it does, temps will rise into the low 60s.

However, only the GFS has it making its way as far north as Willow Grove.  The NAM, NAMNEST and the Canadian HRDPS, GDPS  keep it further south.  Areas that remain north of the warm front will remain in the low 50s. (Warm fronts are not as distinct as cold fronts.) So it may not get as warm as previously though on Monday.

NAM warm front position 12 PM Monday.  (NAM Temp, wind streamlines)

Most models have a cold front moving through about 2-3 PM, dropping temperatures.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

[su_note note_color=”#defcdc”]Update Fri 11 PM: Tonight’s NAM and GFS have moved the rain start time to 3- 6 PM on Sunday.[/su_note]

An upper air ridge will continue to bring us mild temperatures. The upper ridge will break down as low pressure approaches and moves up through the Great Lakes from Sunday into Monday.  A secondary coastal low will develop on Monday

Saturday will be sunny in the morning, but throughout the day, high cirrus clouds will increase in sky coverage.  High 54.  Light winds.

Low pressure will gradually affect our weather on Sunday.  Sunday will be cloudy and increasingly windy.  As discussed in previous posts, rain should hold off until late afternoon and evening. (5-7 PM). High 52.

The rain should become heavy late Sunday night and continue into Monday. Monday was expected to be very warm with temps near 60º, but the models are suggesting a coastal low formation which may bring winds in from the northeast, lowering the high temperatures.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER UPDATE

As mentioned Thursday afternoon, the trend has been for rain to begin later in the day on Sunday.  The NAM and Canadian models have light rain starting very late afternoon or evening (~5 -7PM).

The GFS has trended later as well, about 4 PM.

Here’s the latest National Blend of Models (NMB v 3.2) precipitation forecast for 7 PM Sunday evening. Notice how light the rain is forecast to have fallen by that time.

NBM 3 hour rain totals for 7 PM Sunday Click for larger image

So, the trend is for a cloudy but mostly dry Sunday until later in the day.

It will be mild!  Here’s the EKDMOS high temps for Blue Bell, PA-

Ensemble Kernel Density Model Output Stats- Temp Blue Bell

I’ll update Fri evening.

Weather… and Other Things 'Up in the Air'