Posted Saturday 09/07/24 @ 3:51 PM — Radar shows an additional area of light rain behind this anafront that may move in between 4 PM and 7 PM. This additional area is showing in today’s models that became available late this morning.
Sat 3:39 PM —Forecast Review — The showers moved in on schedule and many areas received minimal rainfall while some received a decent amount, but hardly a drought buster.
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.)
The model forecast below did pretty good at capturing the area around Philadelphia that got minimal rainfall.
Saturday Update
Posted Saturday 09/07/24 @ 9:45 AM — The approaching cold front (classified asa frontal type “anafront” due to the precipitation lagging the actual surface front) will pass through here between 1 PM (western Montco/Bucks/Chester) and 2-3 PM (Philadelphia) and 4-5 PM (NJ).
Here’s the Water vapor/radar image—
“Anafront” type cold front with the precipitation lagging the surface front (blue cold front) (Click on image for a larger view.)
Expected total rainfall continues to lessen for our immediate area, with areas receiving 0.00″ to 0.15″—
00zREFS experimental total rainfall forecast. (Click on image for a larger view.)
Originally Posted Fri 5:34 PM —A cold front will move through our area between noon and 3PM Saturday. What had looked earlier this week to be a decent rain-maker has diminished to a chance of a few showers with precipitation totals of about 0.20″ or less. Our dry pattern continues and appears to be worsening.
Those of you who followed the discussion this past week about rain “skipping over” Philadelphia will recognize the rainfall pattern of the 06z experimental REFS forecast for Saturday—
06z REFS total rainfall The NBM model forecast is below. (Click on image for a larger view.)
The high pressure system that follows for Sunday will further suppress any possibility of rainfall far south of our area for much of the upcoming week.
Current satellite water vapor shows the current setup—
Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Cold front will bring light showers on Saturday. The moisture and rain is suppressed to the southern US. (Click on image for a larger view.)
Originally Posted Fri @ 5:34 PM —
Saturday Forecast
Cloudy. Showers move in to western Montco/Bucks/Chester counties about noon and through the city by 2 PM into NJ. Strong wind gusts with the frontal passage.
Total Rainfall (Model Blend)
NBM high temperatures: Blue Bell, PA 76º Philadelphia, PA 78º High Uncertainty (based on standard deviation): ± 2.3º
Sunday Forecast
Sunny and breezy.
NBM high temperatures: Blue Bell, PA 71º Philadelphia, PA 73º Low Uncertainty (based on standard deviation): ± 0.7º
Posted Sunday 09/01/24 @ 9:35 AM — The forecast continues to have cloudy skies (perhaps with some bright spots at times) and not much rainfall as a front is stalled over our area and small disturbance will move up towards us—
Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Stationary front over our area. (Click on image for a larger view.)
A few weak disturbances will move along the front with some light showers possible Sunday afternoon and again this evening as a secondary cold front is expected to move through late.
Increasing sunshine from northwest to southeast Monday. Cooler with lower humidity.
Unseasonably cool weather this week. Sunny with little chance of rainfall.
Sat 4:30 PM —Forecast Review — We had some sun and clouds, but the amount of sunshine was considerably less than forecast. As a result, high temperatures were lower than forecast, closer to 82º and dew points were only in the upper 60s instead of the low 70s. Current radar shows a line of storms and showers near Harrisburg, not forecast by the models.
Radar at 4:35 PM. The complex of storms near Hazelton is dissipateding as forecast. (Click on image for a larger view.)
So this weekend’s forecast is continuing with the lack of accuracy and low confidence that had been the situation of this past week.
Rain is forecast by the models to reach us about 11 PM and after midnight. It’s also expected to weaken considerably as it approaches, with heavier rain in northern Bucks county. There’s low confidence in this forecast, since the current situation isn’t being accurately modeled.
While the timing is uncertain, I do think there will be weakening of the storms as they approach our area.
Saturday Forecast Update
Posted Saturday 08/31/24 @ 8:24 AM — Last night’s 06z models show more sunshine for today than previously forecast in many, but not all, areas.
Here’s the latest RRFS cloud cover forecast for noon—
Experimental RRFS cloud- radar forecast for 12 PM Saturday. Blue=low clouds, maroon=mid-level clouds, tan = high cirrus clouds (Click on image for a larger view.)
Regarding showers, the showers associated with the approaching cold front move in late from the northwest, about midnight tonight (Saturday).
Heaviest showers appear to skip over the Philadelphia area, keeping many areas in a rainfall deficit.
RRFS cloud-simulated radar forecast for midnight. Blue=low clouds, maroon=mid-level clouds, tan = high cirrus clouds (Click on image for a larger view.)
For Sunday, low clouds break for sunshine through high cloudiness by early afternoon. Cloudy at the shore. Some scattered instability showers develop after 3 PM throughout the area.
Originally Posted Fri 5:19 PM — A warm front will pass north or our area Friday night into Saturday. An approaching cold front will bring showers and storms Saturday night into Sunday morning. The front will slow on Sunday.
Here’s the current water vapor image showing these features—
Current (4 PM Friday) satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. (Click on image for a larger view.)
The front will slowly sag south as weak low pressure develops along the front, causing clouds and showers to linger through Sunday.
Saturday Forecast
Some areas will see sunshine in the morning, some areas west will have more clouds and some spotty sprinkles. Overall, very changeable skies in many areas. The Jersey shore looks to have a fair amount of sunshiine.
Here’s the RRFS cloud/radar forecast for 2 PM—
RRFS experimental Clouds with simulated radar at 1 PM Saturday. Darker is cloudier. (Click on image for a larger view.)
Humid with dew points in the low 70s.
NBM high temperatures: Blue Bell, PA 85º Philadelphia, PA 86º Above Average Uncertainty (based on standard deviation): ± 2.3º
Sunday Forecast
Cloudy with lingering showers in the morning. Brighter skies at the west of the city in the afternoon with clouds and possible showers lingering in NJ and at the shore.
Here’s the latest experimental REFS depicting showers at 2 PM Sunday—
REFS forecast for 2 PM Sunday. (Click on image for a larger view.)
Increasingly breezy. Humid with dew points in the low 70s.
NBM high temperatures: Blue Bell, PA 85º Philadelphia, PA 86º Average Uncertainty (based on standard deviation): ± 1.8º
Monday Forecast
Sunny and breezy. Low humidity
NBM high temperatures: Blue Bell, PA 77º Philadelphia, PA 79º Low Uncertainty (based on standard deviation): ± 1.3º
