A low pressure system over the Great Lakes Friday night into Saturday is expected to slowly move to the east as a secondary coastal low develops north of us along the New England Coast.
The possibility of this setup has been showing in the models for almost a week and until today, was expected to start Friday night and quickly changeover to rain Saturday.
As is seemingly always the case, things have changed with the last two model runs of the GFS, Canadian and ECMWF.
Here’s this morning’s model forecast—
GFS PTYPE (precipitation type) forecast for Saturday noon. Violet-snow, pink-sleet, red-freezing rain, green- rain. White line is 32º degree surface temp line.
Snow starts before daybreak Saturday and changes to rain during the afternoon. Hard to believe, but the current GFS shows 4.7 inches of snow (Fort Washington) before a changeover to rain by 3 PM.
We all know that this is going to change by the time Saturday rolls around, but I think it’s useful to see what the current forecast trends are. Stay tuned.
Update Sun 04:34 PM — OK, it WAS a beautiful spring-like day, even though didn’t reach 70º.
Some interesting weather on tap for next Saturday, likely changing to all rain.
Today, I’m simply playing with a ‘live blogging’ type format. This may be a cleaner look for rapidly changing weather situations [su_note note_color=”#defcdc”]instead of the box format I’d been using previously.[/su_note]
Update Sun 12:37 PM – The temps are maintaining about 64-65 and the winds have diminished somewhat. Temps expected to remain in low 60s until 3-4 PM.
Update Sun 08:30 AM — The front moved through as forecast and the winds have picked up. Expect sunny skies for the rest of the day with winds gradually diminishing.
…Posted this morning—
As expected, we are NOT going to reach 70º today; all of the models had started to back off of that forecast on Friday evening and have continued with a forecast high of about 64º today, probably already reached.
Here’s the EKDMOS I posted on Friday–
Friday’s EKDMOS temp forecast for the upcoming days:
The EKDMOS, being an advanced statistical post-processing handling of 20 version variations (called “perturbations”) of the GFS model, shows the actual potential forecast temperature range being forecast was 63-70. The average was closer to 65 (red line). I was persuaded initially to go with the upper limit, but I began having my doubts as the the models rolled in Friday evening and posted my skepticism in a later update.
Temperatures will gradually fall into and through the 50s today. With the wind, the “spring like temperatures” predicted by the weather entertainers won’t make all that much sense.
Still no chance of any snow predicted in coming weeks, although a mixed-precipitation event is possible on Saturday before a change to rain.
Fri 10 PM Update – No significant changes. I want to emphasize the winds both Saturday and Sunday will be 15-20 mph with gusts.
The very warm temperatures predicted for this weekend have been well-advertised. The current EKDMOS (Ensemble Kernel Density Model Output Statistics) shows very warm temperatures: 67º for Saturday and 68º for Sunday (Blue Bell)—
O EKDMOS High Temp Forecast for Blue Bell, PA
A strong southwesterly flow of warm air ahead of an approaching cold front will bring the unseasonably mild air. But it won’t be a blue-sky day. With the warmth will be considerable cloudiness and some uncertainty about the amount and timing of sunshine (if any). It will be somewhat windy.
For Saturday, depending upon the model, we have sunny skies in the morning, becoming cloudy (NAM)
or clouds early breaking for sunny skies by noon (HIRESW-ARW) then cloudy later,
or mostly cloudy all day (GFS)!
For good measure, the NAM-NEST has some widely scattered showers in the morning (not supported by the other models).
So the warmth is a certainty, the cloud cover less so. I’m leaning toward the HIRES-ARW with clouds breaking for some sun mid-day, then clouds return.—
HIRESW-ARW-MEM2 Cloud cover forecast 1 PM Saturday. After 1 PM, clouds start move back in. Click for larger image.
The cold front moves through Saturday night. There may be a spotty shower early evening, then heavier rain after midnight.
For Sunday, all models have the front moving through about 7 AM with clearing afterwards. Mostly sunny skies but windy. High temps near 70, but that will be late morning. Temperatures slowly fall during the afternoon.
I don’t expect any changes, but I’ll do an update later if there are, based on the new model runs.
