Category Archives: Weather Updates

Weather Updates

SUNDAY FORECAST UPDATE

Sun 09:10 AM Update — The optimistic sunshine forecast of the NBM looks to be correct for today.

Here’s the latest German Icosahedral “ICON” model which handles one of its cloud cover parameters a bit differently,  shows the sunny area sandwiched in directly over us today—

 

From Saturday…

As mentioned in yesterday’s posted weekend forecast, the Philadelphia area will be sandwiched between two areas of clouds and low pressure.   Clouds fill in by the end of the day.

The NBM (National Blend of Models) has the most optimistic forecast, with significant sunshine and some high/mid level clouds for most of Sunday.

NBM Cloud Ceiling forecast 4:45 PM Sunday  (Click on image for a larger view.)

The GFS and HIRESW-FV3 (experimental) are somewhat more pessimistic with their cloudiness forecasts, significant high and mid level clouds.  The models also predict a band of clear skies; the models are consistent about this band of clear skies, but differ regarding its exact location.

Here’s the HIRESW-FV3 cloud ceiling forecast, showing the clear sky band just west of Philadelphia—

HIRESW-FV3 (pre-release version) cloud ceiling 4:45 PM   (Click on image for a larger view.)

So,there’s a range of possibilities around the cloud cover for Sunday.  The GFS is often my preferred choice for cloud cover predictions, but but I can’t ignore the new NBM.  I guess we’ll see.

Weather Updates
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Tue 05:03 PM Update — This afternoon’s NAM-NEST, just available, has the heaviest “action” as the front moves into NJ between midnight and 3 AM.  Very heavy rain and high wind gusts possible.

Tue 12:10 PM Update — Heavy rain and gusty winds.  Reviewing this morning’s models, the rain will move in in two main waves.

The first round about 3-4 PM, with the possibility of some thunderstorms.  Available energy (CAPE) is in the low range, so thunderstorms should be not that impressive.

The second round will be between 9 and 1 AM.     The actual front moves through about midnight.  Helicity values very high (>300 J/Kg) with the frontal passage, especially in western suburbs.   High wind gusts (35-40mph) expected ahead of the actual front.  CAPE values low, so thunder not expected with this second round.

NAM NEST Helicity values at 11:30 PM Tuesday.   (Click on image for a larger view.)

Total amount of rain will be 1.25-1.5 inches with some locally heavier amounts possible.