Area forecast discussion...updated
National Weather Service Pittsburgh PA
937 PM EDT Friday may 24 2013
Synopsis...
dry and cool weather can be expected for the weekend.
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Near term /through Saturday/...
winds are weakening quickly as surface high builds in a bit faster
than models depicted. Subsidence and dry air continue to erode the
cloud cover from west to east. Still difficult to time exactly
will use latest rap model run as guidance.
Previous discussion...
The upper level trough will continue to pivot across the region
through the afternoon and evening as high pressure tries to build
overhead at the surface. Cold northwest flow continues to keep
cloud cover over much of the forecast area through this
afternoon...which is right in line with the latest RUC forecast.
With cloud cover still in place...continued a downward trend in
the high temperatures for the afternoon...with pit likely to be
very close to breaking it's low high temperatures record from
1877.
The most recent model runs continue to suggest that clouds will
eventually diminish over the entire region...lasting longest in
the ridges. How fast the clouds diminish will play a big role in
how quickly temperatures drop overnight. However...since
temperatures are already lower than originally forecast...clearing
skies should allow lows in the low to middle 30's to be realized
relatively quickly. For now...continued the frost/freeze as
is...although some counties may need to be upgraded to a freeze if
skies clear sooner and winds decouple.
High pressure will build overhead Saturday bringing a clear day
but northwest flow will keep temperatures 10 to 15 below seasonal
averages.
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Short term /Saturday night through Monday/...
high pressure will continue to dominate through the short term
period. Temperatures were kept 5 degrees below seasonal averages
Sunday...but moderated closer to normal by Monday. An approaching
warm front could bring the chance for a shower in the southern
portions of the forecast area late Monday but for now...left low
end probability of precipitation.
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Long term /Monday night through Friday/...
a warm front moving north across the district Tuesday will bring
a chance of showers and thunderstorms through Wednesday. As the warm
front moves north of the forecast area Thursday warm and more humid
conditions will return with high temperatures into the 80s through
Friday. There will be a slight chance of diurnal thunderstorms
Thursday and Friday.
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Aviation /02z Saturday through Wednesday/...
general strato-cumulus remains in place except at Zanesville where skies
have cleared. Cloud deck is thin and has a diurnal look on Sat
pictures. Breaks continue to develop and with deep drying moving into
region overnight still expect strato-cumulus to gradually dissipate
toward or just after midnight. Winds already beginning to weaken
as surface ridge builds east from Great Lakes. 18z soundings show
decoupling still occurring late tonight with a north to northwest
wind under 6 kts. By middle morning Saturday sunshine will mix down
northwest winds with gusts over 20 kts expected. Only scattered VFR cumulus
expected.
Outlook.../Saturday through Wednesday/... high pressure will
maintain general VFR through Monday. A warm front will bring a
chance of showers and thunderstorms for late Tuesday into Wednesday.
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Pbz watches/warnings/advisories...
Maryland...freeze warning from 3 am to 8 am EDT Saturday for mdz001.
Ohio...frost advisory from 3 am to 8 am EDT Saturday for ohz039>041-
048>050-057>059-068-069.
PA...frost advisory from 3 am to 8 am EDT Saturday for paz020-021-
029-031-073-075.
Freeze warning from 3 am to 8 am EDT Saturday for paz007>009-
013>016-022-023-074-076.
WV...frost advisory from 3 am to 8 am EDT Saturday for wvz001>004-
012-021-022.
Freeze warning from 3 am to 8 am EDT Saturday for wvz023-041.
&&
$$
