THIS WEEK’S WEATHER

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NO RAIN for Philadelphia Area

Posted Thursday 10/17/24 @ 11:26 AM — The latest extended range models are in good agreement and currently show little to no rain (and certainly no meaningful rainfall ) through Oct 29th.

10-17-24 06z GEFS cloud (dark grey) and precip for next Friday, High Pressure dominates the US (Click on image for a larger view.)

The ECMWF-AIFS, which was impressive with its predictions of Helene and Milton, shows no tropical development to affect the mainland US within the next week or so.


Yet Another Pattern Change But NO Rain

Posted Tuesday 10/15/24 @ 5:09 PM — The cold upper air trough will dissipate by the end of the week. Troughs often spawn low pressure, and the current trough will spawn a low that will form off the coast, not giving us any rain.

The upper ridge in the central US will move over us by the weekend and the upper ridge will be with us through most if not all of next week. NO rain expected through at least the end of next week.

Here’s what we’re evolving into by next Monday. A broad ridge across the continental US and dry high pressure over us—

10-15-24 12z GEFS forecast for next Monday. This is stagnant through all of next week. Not a drop of rain!

A Pattern Change

Originally Posted Sun @ 4:21 PM — —The models are showing signs of an evolving pattern change beginning this week. Most obvious will be a developing trough in the the northeastern US giving us much cooler temperatures following a cold front passage tonight.

NAEFS for Wednesday. Cold upper air trough over the northeastern US. (Click on image for a larger view.)

Here’s the NBM temperatures through Wednesday—

10-13-24 12z NBM temperatures and dew points through Wednesday. Signficant drop in high and low temperatures (Click on image for a larger view.)

A cold front moves through tonight. Showers associated with this front will likely stay to our north. A few models vacillate on whether the Philadelphia area will see any showers or sprinkles with an upper air disturbance that moves through Monday morning. If we get anything, it will be scattered and very light.

The upper trough for the first part of this week may cause some instability cloudiness, perhaps more than the models are showing.

With the upper blocking ridge in the central US breaking down by the end of this week, we may finally see some systems by next week bring us some rain. although I don’t see any specific system yet in the extended range models.


WEEKEND WEATHER FORECAST

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Posted Saturday 10/12/24 @ 10:48 AM — Cancel those showers for Sunday night. Both the GFS and ECMWF now show less of an upper trough and weaker low pressure development. The very dry weather to continue.


Originally Posted Fri 5:36 PM —With a high pressure ridge and upper air trough seemingly unchanging in previous models runs, I’ve been taking a break from forecasts for the past two days. However, weather being what it is, things have changed and it seems there may actually be a chance for some rain late Sunday or Sunday night.

NAEFS forecast for Sunday at 11 PM Upper jet stream trough spawns low pressure over PA (Click on image for a larger view.)

We’re expected to be under the influence of an upper trough by Sunday and low pressure is expected to develop right over western Pennsylvania by Sunday evening.

While we’re still not located in the most favorable position for rain relative to the jet flow, the latest GFS is cranking out some rain Sunday night! Not a lot, about 1/4 of an inch, but we’ll take anything we can get.

10-11-24 12z GFS forecast for 2 AM Sunday. Low pressure with an area of rain. (Click on image for a larger view.)

Saturday Forecast

Sunny and quite nice. Some high thin cloudiness moves in late afternoon.

NBM high temperatures: Blue Bell, PA 74 º Philadelphia, PA 76º
Uncertainty (based on standard deviation): High confidence

Sunday Forecast

Considerable cloudiness far northern suburbs, mostly sunny closer to the city. Increasing cloudiness late afternoon. Cloud cover will affect high temperatures reached.

NBM high temperatures: Blue Bell, PA 77º Philadelphia, PA 79º, maybe 80º
Uncertainty (based on standard deviation): slightly below average confidence.