#Philadelphia #weather #PAwx
Friday Quick Update
Posted Friday 03/01/24 @ 10:34 AM — The high layer clouds probably won’t move in until after 4-5 PM today, Friday.
Very rainy Saturday with latest models increasing the rainfall amounts to 0.6- 1″ of rain here.
There may be some periods of sun Sunday morning.
Friday and the Weekend Early Outlook
Posted Thursday 02/29/24 @ 5:10 PM — A complicated and split jet flow will result in a weak, slow moving coastal low near our area from Friday into the weekend—
Friday will start sunny, but very high clouds move in from southwest about 1-2 PM and cloudiness increases slowly during the late afternoon. Plenty of sunshine expected through these high clouds for much of the day. Highs 48º-51º
Saturday looks to be cloudy, damp with rain at times during the day. Despite the low clouds, temperatures will be in the low 50s.
Most models have our rainfall in the 0.3″-0.6″range, but the NAM has been consistently forecasting heavier rain on Saturday.
Sunday dries out but a significant cloud cover may remain. Very mild with highs in the low 60s.
Wednesday Evening Storm Update
Posted Wednesday 02/28/24 @ 5:32 PM — The winds are beginning to pick up and the latest HRRR from 4 PM (the HRRR model is run hourly and takes about 1:20 hours to complete) shows a line of very heavy rain moving through about 8 PM—
Wednesday Storm Update
Posted Wednesday 02/28/24 @ 11:22 AM — The cold front is entering northwestern Pennsylvania and several lines and areas of showers precede the front.
The trends from the latest HRRR- heaviest rain between 5:30 PM and 9 PM. Wind gust forecast is now in the 40-45mph range and continues behind the front.
Posted Wednesday 02/28/24 @ 8:46 AM — The forecast remains basically on track. Most areas received about 0.15- 0.20 inches of rain last night. As expected, greater amounts fell far northern Bucks County and northwestward into Allentown.
We may see some bright skies for a period later this morning. More showers will following.
The models are forecasting an additional 0.50- 0.80 inches of rain in our immediate area. This morning’s HRRR just available shows diminished shear and helicity values from last night’s extreme values.
The big impact will be the winds and the plummeting temperatures. The HRRR is still forecasting wind gusts in excess of 50 mph. The Canadian HRDPS interestingly, shows the high winds following the frontal passage, not so much with the rain and front.
The heaviest rain will be with the front, between 5:30 (western sections) and 8 PM.
More on Wednesday’s Storm
Posted Tuesday 02/27/24 @ 7:47 PM — We’ll have several periods of rain on Wednesday. With the cold front moving through between 7-9 PM, expect the possibility of strong, damaging winds especially between 5 PM and 9 PM.
A further review of this afternoon’s models suggests that despite a lack of CAPE, helicity and vertical shear values are predicted to be so high during these hours that strong thunderstorms can’t be ruled out.
Basically, the available high kinetic energy (helicity/shear) makes up for any lack of thermodynamic energy (CAPE) for spawning these storms.
Here’s the HRRR wind gust forecast for 9 PM—
Of greater interest is the severe weather parameters, vertical wind shear and helicity that peak in serious way about 6 PM. The last time I saw these values, we had some tornadic activity. With a lack of CAPE, I’m not really sure what to make of it—
I’ll update this evening if anything else shows up in tonight’s early models. I think we need to wait for tomorrow morning for the final call.
Stormy Wednesday
Posted Tuesday 02/27/24 @ 6:03 PM — While the wonderful mild temperatures have gotten most of the attention on the TV/radio, the real story will be the rather significant storminess on Wednesday afternoon and evening.
A sharp cold front will move through about 6-9 PM Wednesday evening. Plenty of dynamics has been expected but the latest models have increased the possibility of some wild weather here.
What had been expected to be a light rainfall is now in the heavy 1″- 1.5″ range with locally higher amounts.
Over the past several days, I’ve been talking about the high winds expected and the latest models are supporting sustained winds of over 25 mph with gusts 40-50 mph. While thunderstorms are not likely (according to the NBM) with low CAPE values, there’s plenty of wind shear and helicity to fuel some of the downpours. ( We’ll have to see if thunderstorms can form with such low expected CAPE).
Temperatures will plummet from the upper 50s to below freezing in about 6-8 hours after midnight Wednesday.
More details follow with tonight’s early models.
Tuesday- More Sunshine
Posted Tuesday 02/27/24 @ 8:54 AM — Last night’s models have pretty much converged on a later start for the showers instead of early afternoon. It appears that showers will hold off until about 4 PM (western areas) to 7 PM as forecast yesterday by the HRRR and Canadian models.
Regarding cloud cover, it appears that we’ll see an increase in cloudiness towards noon, but breaks of sun and clouds will remain with us through about 3 PM, at which time the lower level clouds move in.
Current Water Vapor image—
Tuesday Forecast Update
Posted Monday 02/26/24 @ 8:00 PM — This afternoon’s models show a change in the forecast for Tuesday. Some, but not all, models are now showing an earlier start to the showers.
Tuesday starts sunny, but clouds move in rapidly about noontime from the west. Several models (GFS, HREF, NBM, ECMWF and ICON) have light showers moving in as early as 1-3 PM. (The experimental RRFS shows showers 4-5 PM and the HRRR and Canadian models about 6-7 PM.)
I’m going with the earlier start time (1-3PM) for the showers since the GFS tends to be better with timing these things.
Despite the clouds, the NBM is still predicting fairly warm high temperatures—
As mentioned, a sharp cold front will move through Wednesday evening with rain and likely high winds. It doesn’t appear that thunderstorms will be part of the mix. Rainfall for the immediate Philadelphia area is running about 0.6-0.8″ of rain. Not the biggest rainstorm for us compared to recent others.
The big story will be the wind and wind gusts above 40 mph and sharp drop in temperatures Wednesday night behind the front. I realize that lately, some of the model forecasts for high winds just haven’t been materializing. This time around I think it’s a good bet.
Initially Posted Sun 5:28 PM —
A roller coaster experience of weather will unfold this week, beginning with the overnight period tonight (Sunday night). An upper air trough will move through along with a front before daybreak Monday with widely scattered showers, mostly north of the city. (It’s hard to believe since there isn’t a cloud in the sky as I write this. )
A well-advertised warm up is expected Monday through Wednesday. But an abrupt end to the warmup is expected later Wednesday as a strong cold front moves through and the temperatures drop almost 30 degrees after midnight into Thursday.
Here’s the current water vapor image on Sunday afternoon—
Here’s what unfolds later Wednesday—
The very warm temperatures have talked about, but there’s been little attention to the sharp front and possible stormy weather later Wednesday. I’ll have more coverage as the week progresses.
Monday — Following scattered showers before daybreak, clouds in the early morning becoming sunny by mid to late morning. Here are the NBM high temps—
For Tuesday—
By late Tuesday, some rain may move in. Wednesday will be warm, but with showers.
The interesting weather begins late afternoon Wednesday. Stay tuned for updates.
