Update Sun 10/23 @ 10:23 AM — Optimism has its limits. This morning’s models are much more emphatic about some measurable rain moving in during the hours of 2-4 PM. Here’s the latest rainfall accumulation from the NAM-NEST—

Update Sun 10/23 @ 8:17 AM — Clearly, my forecast from last night (based on the HIRESW, GFS and NAM-NEST (and the Phillies win), was clearly overly optimistic about the cloud cover and maybe the lack of rain until later today.

As mentioned previously, this rain forecast has been as difficult as many past winter snow storm forecasts.

The GFS has consistently maintained clouds but has kept the rain from moving in until after 5-7 PM. The HRRR supported this forecast, as did the ECMWF. However, the Canadian and the ensemble forecasts (GEFS NAEFS) were consistently forecasting light rain inching in about 2-5 PM.

Last night’s 06z models began are suggesting that the light rain may move in sooner than “late afternoon”, as early as 2PM with more rain tonight.

Here’s the current situation—

Here’s the current NBM—

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Little to no Rain for Sunday afternoon

Updated Sat 10/22 11:24 PM —

Saturday afternoon’s HRRR continues with the rain from the coastal storm not reaching into Philadelphia. A few light sprinkles possible. —

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Little or no Rain for Sunday afternoon

Update Sat 10/22 @ 10:18 AM — The trend for the rain associated with the coastal storm to move east of us continues. This trend, first forecast by the GFS, is now supported by several models, including this morning’s HRRR and NAM-NEST.

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Forecast for Phillies Game Sunday

Update Fri 10/21 @ 6:25 PM — Just as I posted this forecast, the latest GFS model came in. It keeps the rain to our east on Sunday, off the coast. This scenario reminds me of several storms last winter with the GFS having an eastern track and it turned out to be correct. So expect cloudy, breezy conditions but little to no rain for Sunday afternoon.

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Previously Posted Fri 6:07 PM —

High pressure will give us another beautiful day on Saturday. It will move off the northeast Saturday night.

Impulses to our west are expected spawn a coastal low in the southeastern US coastline as a result of a sharp trough in the jet stream—

Sunday’s forecast depends upon a system that hasn’t formed yet and there are differences in the forecast track and speed of the expected secondary low.

Saturday

Sunny skies and warming temperatures.

High temperature 67.7º sd 0.8º NBM model (for Blue Bell, PA)

Sunday

Significant differences exist in the forecast track of the coastal low expected to form. For several model runs, the GFS has shown an eastern track for the storm with the rain missing us. Other models are not on-board with this. The latest NAM has rain moving in 2-4 PM. The latest ECMWF has the rain later in the afternoon or towards evening.

The ECMWF is trending towards the GFS with most of the precipitation off the coast—

Cloudy and increasingly breezy/windy. Currently, the models are forecasting very light rain or drizzle to move in about 3-5 PM (NAM, NBM, HIRESW-FV3) or after 5 PM (ECMWF). The GFS has the rain missing us entirely Too early to be sure. Stay tuned.

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Updated Sat 10/15 10:15 PM —As forecast on Friday, an upper air disturbance rotating around the upper low will bring mid-level cloudiness here on Sunday morning until about noon, then becoming sunny.  Clouds move back in early evening ahead of the next system.  

Previously Posted Fri 4:05 PM —

A fairly simple forecast. High pressure will bring sunny, mild weather to our area Saturday and Sunday while a somewhat stationary upper air low pressure system remains over the Great Lakes. (Seasonal average high temps for this weekend are 64º-66º.)

Saturday

Fair skies and mild temperatures. Some breezy conditions in early afternoon.

High temperature 70.5º sd 1.2º NBM model Blue Bell, PA

A weak front rotates through Saturday evening. Sunday will be a bit cooler.

Sunday

Some cloudiness possible in the morning, then mostly sunny. Increasing high clouds late afternoon.

High temperature 66.4º sd 2.0º NBM model— Blue Bell, PA

Update Sat 10/08 @ 5:43 PM — Latest NBM model shows low temperatures tonight to be the coldest so far this season—

While we’ll see moderating temperatures through Wednesday, a sharp dip in the jet flow expected Thursday-Friday with a cold front moving through probably before daybreak Friday—

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Previously Posted Fri 8:13 PM —

A cold front will pass through this evening (somewhat later than forecast yesterday) with a shift of winds to the north.  Cooler air will filter into the area.  Some light scattered sprinkles are showing on radar (as forecast by yesterday’s HRDPS) and this afternoon’s GFS is forecasting some additional sprinkles around midnight. Most areas dry.

The weekend will be sunny and cool.  (Seasonal average high temperature is 67-68º this week.)

Saturday

There’s still a chance of brief period of clouds early afternoon Saturday, but otherwise quite nice. 

High temperature 57.7º sd 1.9º NBM model Blue Bell, PA

Saturday night will feature fairly chilly temperatures, into the mid to upper 30s in some areas outside the city.

Sunday

Sunday will continue with fair skies and slightly warmer temperatures.

High temperature 61.7º sd 1.9º NBM model Blue Bell, PA

Outlook: Monday through Wednesday moderating temperatures. A strong cold front later in the week will bring much colder temperatures.

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