Area forecast discussion
National Weather Service State College PA
310 am EDT Sat may 25 2013
Synopsis...
a deep...slow moving upper low over southern New Jersey this morning
and associated cold air aloft will continue to bring unseasonably
chilly and quite breezy conditions today. Canadian high pressure
centered over the upper Great Lakes will build southeast over
Pennsylvania later Sunday into Memorial Day ensuring fair weather.
Temperatures will begin the weekend well below normal but moderate
by Memorial Day.
&&
Near term /until 6 am this morning/...
early morning infrared Sat loop shows widespread cold air strato cumulus
streaming southward across the County Warning Area. This cloud cover and a moderately tight
low level pressure gradient was helping to maintain a 7-12kt west to northwest
breeze...which was gusting at times into the middle teens.
The cloud cover and breeze will keep temperatures across the central mountains
and susq region in the 40-45 degree range through sunrise. A close call
for freezing temperatures across the alleghenies...where regional ASOS and
mesoscale observation showed most temperatures between 33-36f...with a few more degree of
cooling expected early today. A freeze warning is in effect for this
area until 9 am today.
Aside from a few sprinkles across the mountains this morning...it will
stay mostly cloudy and dry...as the western edge of a large scale rain
shield /associated with the upper low/S deformation zone/ will stay
across far eastern Penn today.
&&
Short term /6 am this morning through 6 PM Sunday/...
lg scale subsidence and anomalously dry air works over central PA
today in the wake of departing upper low...bringing mostly sunny skies to
much of the region. Temperatures may still be cold enough aloft to support
a more even mix of sun and cumulus across across the eastern
counties...especially Sullivan. However...will keep mention of rain showers out of
the forecast based on aforementioned low precipitable waters and lack of forcing.
Model soundings show mixing to 800 mb...which should translate to highs
from the m50s high terrain...to m60s susq valley...some 10-15f
warmer than today. As blyr depth increases...expect northwest winds to
become gusty again by late this morning. BUFKIT soundings support
gusts in the 25-30kt range by afternoon.
&&
Long term /Sunday night through Friday/...
we start the extended off dealing with the anomalousy deep upper
low that will be moving slowly through New England and the
coastal waters.
Sunday will be fair and dry...albeit on the chilly side. The dry
weather will continue through Monday as we benefit from the upper
ridge building in from the west. Those two days will start the
extended off in a rather uneventful fashion.
From Tuesday through at least midweek the forecast gets murky as
the building sub tropical ridge over the southern states shoves
the westerlies northward. With US being on the southern edge of
these westerlies/northern edge of the subtropical ridge...we will
become vulnerable to upstream mesoscale convective system development as the heat and
humidity begins to make inroads to the region once again.
Differences in the model timing of these convective complexes is
big with the operational GFS showing a wet day Tuesday...and the
European model (ecmwf) suggesting the convection stays mainly south of here at that
time. Gefs splashes a fair amount of diurnally favored precipitation
around just about every day starting Tuesday. The mean upper flow
and accompanying surface pattern suggest whatever semblance of a
warm front there is passes through on Wednesday...with the
remainder of the week firmly under the influence of the Bermuda
high and warm muggy southwest flow. With the operational
GFS/European model (ecmwf) both predicting a surge in middle level temperatures by later Wednesday
into Thursday...I am thinking we will spend much of the time after
middle week pretty capped leading to hazy hot and humid conditions
with fairly small chances for showers and thunderstorms. I like
our current forecast which downplays the chances for rain after
Wednesday...and will continue along those lines through Friday.
&&
Aviation /07z Saturday through Wednesday/...
generally VFR conditions over central PA...with the exception of
some patchy MVFR/IFR ceilings over kjst and kfig. Satellite trend
shows a gradual decrease in overcast deck over western and
northern mountains...but clearing rate not enough to break broken/overcast
ceilings until after daybreak.
Generally VFR conditions will prevail overnight...with again some
patchy exceptions over the western mountains.
Upper low will continue to pull east over the next few days as
high pressure at the surface builds into the region. Expect one
more day of brisk west-northwest winds today...gradually slackening for Sunday
and Monday. Otherwise...VFR conditions expected through Monday.
Warm advection on Tuesday could set off a few showers or storms...
mainly late. Warmer Wednesday...but still a chance of a shower or storm.
Outlook...
sun-Mon...VFR.
Tue-Wed...mainly VFR...but scattered thunderstorm impacts possible.
&&
Ctp watches/warnings/advisories...
freeze warning until 9 am EDT this morning for paz004>006-010-
011-017-024-033.
&&
$$
Synopsis...devoir/Fitzgerald
near term...Fitzgerald
short term...devoir/Fitzgerald
long term...la corte
aviation...jung/Martin
