Posted Saturday 02/01/25 @ 3:48 PM — The rainfall we had Friday seemed more substantial than it was. Here’s the MRMS 24 hour rainfall totals based on rain gauges and radar calibrated to the rain gauges.—
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 forecast for Sunday is little changed. Cloudy for much of the day, except early morning and remaining slightly colder than seasonal averages with highs 37º-39º with higher than usual uncertainty (standard deviation).
Originally Posted Fri 5:04 PM —Following the rain Friday night, high pressure builds in for Saturday with cooler temperatures. On Sunday, low pressure to our north will bring clouds but no precipitation is expected here. Still seasonably cold.
Today’s 12z GFS forecast for 7 PM Saturday shows high pressure over us. Low pressure will move north of us on Sunday. (Click on image for a larger view.)
A seasonably cold day Sunday will be replaced by a mild day on Monday, followed by a cold front passing through Monday evening with colder weather returning for Tuesday.
By Monday—
GFS forecast for late Monday. Mild temperatures on Monday will be replaced by cold high pressure building in for Tuesday. (Click on image for a larger view.)
There’s still the possibility of rain on Thursday and another storm is again showing for Super Bowl weekend.
Saturday Forecast
Mostly sunny and somewhat seasonably cold. Windy in the morning, but winds gradually decrease during the afternoon.
NBM high temperatures: Blue Bell, PA 38º Philadelphia, PA 41º Higher than usual uncertainty (based on standard deviation): ± 2.1º
Sunday Forecast
Some bright areas through clouds early, then mostly cloudy late morning and during the afternoon. Less windy
NBM high temperatures: Blue Bell, PA 39º Philadelphia, PA 42º High then usual uncertainty (based on standard deviation): ± 2.4º
Posted Friday 01/31/25 @ 9:32 AM — A slight shift in the timing of the heavier rain today— late afternoon through this evening, ending after midnight. Total rainfall in the city and surrounding areas is now forecast to be less, closer to 0.30″-0.40″. Heavier rainfall in South Jersey.
NBM 12z Accumulated Rainfall for Friday into early Saturday. (Click on image for a larger view.)
The potential mixed precipitation storm I prematurely mentioned last evening has changed timing, from possibly next Saturday to possibly next Thursday. That’s a big change, suggesting the models, including the AI models, don’t yet have a good handle on things. Nonetheless, the setup ingredients appear to be there. Stay tuned.
Friday’s Rain Update
Posted Thursday 01/30/25 @ 6:01 PM — The rainy forecast for Friday hasn’t changed appreciably and rainfall totals are similar to the ECMWF forecast graphic posted yesterday. Rain begins about 3 AM Friday, earlier south and west and continues through about 9 PM Friday evening. It will be windy and gusty at times during the day, especially late afternoon when the heaviest rain is expected to fall.
The weekend looks as follows: Sunny on Saturday and cloudy on Sunday as a disturbance passes to our north.
No major storms until NEXT weekend, when things may get interesting, according to the AI models and the ECMWF—
The ECMWF forecast for Superbowl Weekend (NEXT Saturday) Very far off in the future, but the setup is for a mixed bag of very heavy precipitation here. (Click on image for a larger view.)
Friday’s Rain
Posted Wednesday 01/29/25 @ 7:42 PM — A storm bringing only rain to our area will move in several hours before daybreak on Friday. It will be rainy all day and the rain will taper off during the evening.
Continuing our ongoing trend towards lower than average rainfall, we’ll only see 0.50″ of rain in the immediate Philadelphia area according to the AI model. Areas not far to our south will receive over an inch, according to the latest models.
Staying with the AI model, here’s its forecast total rainfall for Friday—
Today’s 12z ECMWF-AIFS total accumulated rainfall by Saturday morning. (Click on image for a larger view.)
The NBM is forecasting heavier rainfall for Friday—
Today’s 18z NBM rainfall forecast (Click on image for a larger view.)
AI Model Looks Quite Good in Simple Experiment
Posted Wednesday 01/29/25 @ 5:47 PM — The temperature reached at Philadelphia airport today was 52º, 53º based on hourly records. ( If 53º was reached, it occurred off-hour and will be posted on the NWS site in a few hours.)
It’s very impressive that the AI model correctly forecast this range a week ago. Today’s NBM forecast was a still a degree so too cool.
Posted Wednesday 01/29/25 @ 9:39 AM —Over the past week, I’ve been conducting a simple observational experiment regarding today’s high temperature forecast. (Also see here.)
I chose to follow the AI model temperature forecast for today, because it was below freezing here at the time and the majority of the models, including my go-to model for temperatures (the NBM) were forecasting highs in the mid 40s for today, while the ECMWF-AIFS at that time was forecasting mid 50s! Quite a difference.
Incredibly, the regular model forecast have creeped upward towards the 50s and closer to the AI model while the ECMWF has shave off a few degrees to a high of near 53º.
Here’s the latest NBM —
Today’s NBM (12z) high temperature forecast for today. (Click on image for a larger view.)
Here’s the latest AI (ECMWF-AIFS) forecast for today—
Today’s ECMWF-AIFS high temperature forecast for today. (It should be noted that the ECMWF forecasts in 6 hour increments and the version I download does not include the day’s maximum temp. The only data is the actual temp at 1 PM as shown above. Since high temperatures typically occur around 3 PM, the actual max temp for today may be somewhat higher
What’s impressive is that the ECMWF-AIFS was forecasting this range of max temperatures almost a week ago! It took the computational models almost a week to approach its forecast.
Posted Tuesday 01/28/25 @ 10:53 AM — Radar shows some snow showers to our far northwest. Superimposed RAP model vertical motion (“omega”) shows strong downward motion, likely dissipating these snow showers greatly by the time they get to Philadelphia—
Radar shows some snow showers to our northwest. Superimposed RAP model vertical motion (“omega”- yellow dashed lines are negative) shows strong downward motion, likely dissipating these snow showers greatly by the time they get to Philadelphia (Click on image for a larger view.)
Posted Tuesday 01/28/25 @ 9:17 AM — When I went to bed last night, the forecast for Philadelphia on our news radio station called for “‘”snow showers, possibly reducing visibility” and clouds. Did I miss something with my update yesterday? What were they talking about?
We’ll have a mix of sun and clouds today. Several weak disturbances are in the pipeline for us over the next few days. Snow/rain showers are a slight possibility.
WV image with superimposed RAP model parameters. Disturbances 1-3 are in the pipeline to affect us. The upper level low (4) will bring rain on Friday. (Click on image for a larger view.)
There’s a chance that the storm on Friday may start as a bit of freezing rain or sleet here before a change to all rain. Not a certainty.
Posted Monday 01/27/25 @ 5:55 PM — A slight warmup for Tuesday and Wednesday. The ECMWF-AI model has us in the low 50s on Wednesday. The model blend (NBM), my go-to model for temperatures, now has a forecast high of 48º in Philadelphia with a rather large standard deviation of ± 2.8º.
A series of weak fronts and upper air disturbances come through over the next few days, specifically before daybreak Tuesday and Tuesday night. A rain maker is on the way for Friday, although the heaviest rain may move to our north and south.
The front and the system bringing rain on Friday are visible on water vapor imagery—
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. The closed low in the southwestern US will move into our area on Friday. (Click on image for a larger view.)
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Originally Posted Mon 10:45 AM —A split jet flow and a still somewhat chilly northwesterly flow will keep temperatures slightly above average through Wednesday, becoming somewhat colder Thursday, then warming again Friday with rain.
Today’s 06zNAEFS jet stream wind speed forecast for Wednesday morning. The upper closed Low (L) will eject towards us bringing rain by Friday. (Click on image for a larger view.)
Regular readers here know that over the past week, I’ve been watching the AI version of the ECMWF which has consistently forecast high temperatures on Wednesday to be in the low 50s! Every other model has us in the mid to upper 40s. So this is a little experiment to see if the AI model has any special insights into high temperatures—
Today’s 06z ECMWF-AIFS forecast temperatures on Wednesday. Much higher, and consistently so. then the regular models. (Click on image for a larger view.)
It appears we may have some rain on Friday into early Saturday. This feature has been in the forecast for several past days, with each model run moving it earlier. (It was originally forecast for this rain to move in Saturday into Sunday.)
Today’s 06z NAEFS forecast for Friday at 1 PM. The white contour is 32º, the red, yellow and magenta lines are critical thickness lines, indicating the average temperature of different lower levels of the atmosphere. With all of these lines to our north, we will have rain, not snow. (Click on image for a larger view.)
The weekend looks to be dry.
No significant snow storms are on the horizon for us. For that matter, we’re still running a rain/snow deficit and the dry conditions of last Fall have not shown signs of ameliorating to this point.
