Tag Archives: Philadelphia area Weather Forecast

Forecast Review, Updates

WEEKEND WEATHER REVIEW AND UPDATE

Yesterday’s cloud base did lift and thin, but we never saw the degree of clearing that was forecast by the HRRR or NAM-NEST models. Showers moved in, as expected, about 5 PM, but the northern-most extent and their duration into the evening hours was greater than predicted by any model.

For today, (similar to last Sunday), several upper air disturbances are causing the cloud deck right now.  Sun should break out later this morning, but another upper air disturbance is expected about 4 PM (not talking about the Eagles here.)  So, another period of cloudiness possible later.

The coastal storm for mid-week mentioned in last Friday’s post remains difficult to forecast.  The NAM and Canadian GDPS have 1-2 inches of snow (less in the city) late Tuesday afternoon into evening.  The GFS shows less development and a coating at most. The GFS has done the best this season with these storms.  This storm is still beyond the range of the shorter range models.  Stay tuned.

Updates

FORECAST UPDATE- CLEARING TODAY?

[su_note note_color=”#defcdc”] Update 10 AM: I just downloaded the new HIRESW NMMB2 and HIRESW ARW2  (yes, so many  models, so little time.)  They are a little less optimistic about clearing.  At best, patchy clearing with highly scattered sprinkles possible, increasing about 4-5 PM.

HIRESW NMMB2      2 PM Simulated Radar and cloud cover

Well, we’re going to get a bike ride in, I hope.

[/su_note]

…from earlier—

The low clouds and widely scattered showers were expected this morning.

I just downloaded the very latest NAMNEST, HRRR and RAP model data.

All models have winds shifting to the west about 11-12:30 PM, bringing in some drier air.  The HRRR is most optimistic about seeing some sun and bright skies by 12-2 PM.  The NAM NEST also has brightening skies by 2 PM, although not as clear as the HRRR.

I’m using the (sometimes unreliable) built-in cloud parameters, but clearing also supported by looking at the humidity fields.

HRRR cloud forecast 2 PM  (Arrow shows clearing skies)
NAMNEST Cloud Forecast 2 PM  Arrow points to few clouds.
NAM 3-D humidity below 70% (grey, not blue here!) shows areas of clearing.

The models maintain an increased chance of showers again about 4-7 PM as the main front moves through and again this evening.

We’ll see if the patchy clearing occurs as predicted.