Sun 5:23 PM —Forecast Review —We had less cloudiness than forecast on Saturday and even more surprising, we had more cloudiness than forecast on Sunday. Sunday’s cloudiness resulted from a weak front stalling with a band of clouds remaining from just north of Philadelphia and extending over the city into S. Jersey. Areas further north had blue skies!
Visible Satellite at 1:51 PM. (Click on image for a larger view.)
Originally Posted Fri 5:21 PM —Cold air is moving in on some very strong winds. Gusts are in the 45-50 mph range, according the RTMA, and I think there have been even a few stronger gusts to near 55-60 mph.
High pressure builds in for Saturday, but aloft, temperatures warm up a bit, and some mid level clouds form by afternoon with a southerly flow. Another cold front moves through Saturday night into Sunday, again with windy conditions and temperatures colder again.
The new model- the AIGFS forecast for 1 PM Saturday. Noted the red, lavender and yellow lines are north of our area, indicating a warmer lower half of the atmosphere. The white line is the 32º line (Click on image for a larger view.)
Our next chance of precipitation, likely rain (but briefly beginning as some wet snow or sleet) will be Monday night into Tuesday.
Saturday Forecast
Sunny in the morning, becoming cloudy by noon. Sunshine returns by 4 PM. Winds lighten up.
NBM high temperatures: Blue Bell, PA 38º Philadelphia, PA 40º Close to average uncertainty (based on standard deviation): ± 1.8º
Sunday Forecast
Clouds in the early morning, then mostly sunny. Windy again.
NBM high temperatures: Blue Bell, PA 44º Philadelphia, PA 46º Slightly Above Average uncertainty (based on standard deviation): ± 2.1º
Fri 4:42 PM —Forecast Review — We had quite a bit of rain last night and this morning. Here’s the final MRMS totals—
MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch) (Click on image for a larger view.)
Friday Forecast Update
Posted Friday 12/19/25 @ 7:24 AM — The rain has reached or is approaching its peak precipitation rate. The cold front is just west of Harrisburg and another line of rain and higher winds will move through about 10 -11 AM.
Water Vapor image at 7:15 AM with superimposed RAP model pressure (black). thickness (yellow) and potential vorticity contours (violet) (Click on image for a larger view.)
Rain tapers off around noontime, but widely scattered light instability showers may continue for a time during the afternoon. Temperatures near 60º this morning will drop to freezing by about 6 PM.
The cold air moving in will not be anywhere as cold as the last major front and temperatures aloft rise on Saturday before another cold front moves through.
My regular feature, the “Weekend Weather Forecast“, will be posted later this afternoon.
Thursday Friday Update
Updated Thursday 12/18/25 @ 8:33 AM — Following a warm-up late Thursday into early Friday, a strong cold front moving through will cause heavy rainfall and windy conditions for Friday. The actual front moves through late morning and temperatures will begin dropping from late morning through the rest of the afternoon. Wind gusts will exceed 40 mph.
NBM total rainfall (Click on image for larger view.)
Total rainfall will be 1.0” to 1.5”
A Warmup on Friday
Updated Tuesday 12/16/25 @ 4:20 PM — Despite the severe cold we’re experiencing right now, a warmup to above average temperatures is expected by late Thursday into Friday before a cold front moves through on Friday. Highs may approach 60°. This front will be accompanied by some moderate rainfall. Temperatures fall again for the weekend.
AIGFS forecast temperatures early Friday morning. (Click on image for larger view.)
No snow is currently seen for Christmas. Above average temperatures are possible for the last week in December.
Previously Posted Sun 9:59 PM —The cold front that moved through Sunday morning has brought very cold weather to our area for mid December that will last into Monday and Tuesday, with moderating temperatures for Wednesday.
Another weak front moves through Wednesday, but this will not be an arctic front. Another strong cold front moves through Friday, likely with rain, that may possibly change to snow before ending.
GFS forecast for Friday (Click on image for larger view.)
Just because the beginning of this winter season has started so cold here in the northeastern US does not mean that the entire winter season will be so cold. These persistent dips in the jet stream over our area have a tendency to change their position over the continental US and some very warm temperatures will likely surface, if not in December, in January.
Updated Sunday 12/14/25 @ 9:00 AM — The snow is tapering off and should be ending from west to east between 10 AM and noon.
For the Eagles game start at 1 PM, it will be windy and cold. Temperature at the Linc 29.5° wind chill 19°. Winds 12.5mph gusty 25-29 mph. At 4 PM, Temperature 23° Windchill 13°. Clouds early in the game break for periods of sunshine.
The NWS has a website which posts official snow totals reported by snow spotters. Not updated now, but updated throughout the day as reports are sent in.
Updated Saturday 12/13/25 @ 10:55 PM —Here’s the latest model blend (NBM) 01z with updated precipitation—
01z NBM model mean snowfall Saturday night into Sunday (Click on image for larger view.)
Updated Saturday 12/13/25 @ 5:43 PM —I’ve used the NBM for most of this snow event, so continuing with the latest 19z NBM run (the NBM updates its precipitation forecasts at 01, 07, 13, and 19z), it’s still showing higher snow totals despite temperatures not falling below freezing near the city until 3-4 AM. Here’s the latest forecast—
Today’s 19z model blend mean snowfall totals. (Click on image for larger view.)
The near ground temperatures somewhat challenge my confidence in these numbers, but they are consistent with the total water equivalent forecast. Additionally, the mean amounts shown are close to the median amounts predicted,
Updated Saturday 12/13/25 @ 3:26 PM — While we have the potential for over 5 inches of snow, this afternoon’s models have temperatures near the surface now remaining above freezing until 3AM. This will seriously cut into snow accumulation totals. So we’re back to the 3” to 4.5” range from this morning’s forecast.
Updated Saturday 12/13/25 @ 11:08 AM —The latest models are showing snowfall in the Philadelphia area in the 4-6 in range.
Updated Saturday 12/13/25 @ 9:18 AM —The latest models have the current forecast on track. Light snow moves in between 10 PM and midnight and tapers off early Sunday morning. I’ve been posting the NBM forecasts, so we’ll switch to the REFS which is in the same range—
06z REFS Snow totals. (Click on image for larger view.)
Low pressure over the Great Lakes will bring a cold front through our area early Sunday morning. The timing of the front during the period of the lowest temperatures of the day along with the upper levels of the atmosphere through18,000 feet being below freezing ensures that any precipitation will fall mostly as snow.
Low pressure expected to form along this front will enhance the precipitation rate, resulting in increased snow totals, now expected to occur in NJ.
Saturday Forecast
Cloudy in the morning, some breaks in the clouds and sunshine through clouds in the early afternoon, then cloudy again. Light snow moves in from west to east about 10 PM and continues through early morning Sunday.
NBM high temperatures: Blue Bell, PA 41º Philadelphia, PA 42º Low to average Uncertainty (based on standard deviation): ± 1.3°
Total snowfall –
18z NBM total snow accumulations (mean ) by noon Sunday (Click on image for larger view.)
Sunday Forecast
Snow ends from west to east between 6 AM and 10 AM. Temperatures drop through the day with high temperatures occurring in the morning. Windy!
NBM high temperatures: Blue Bell, PA 31°º Philadelphia, PA 29°º Above Average Uncertainty (based on standard deviation): ± 2.3°
