Scientific Forecaster Discussion
fxus61 kctp 200619
Area forecast discussion
National Weather Service State College PA
219 am EDT Fri Sep 20 2019
anomalous upper level ridging will build east into the region
through the weekend. A cold front will likely push across the
area Monday, followed by high pressure building in from the
Great Lakes by the middle of next week.
Near term /through today/...
rather thick cirrus over the wrn half of the area right now, and
relative humidity progs have it going east slowly before thinning. This could
keep temps up just slightly from going mins. But, am shy to
change the mins much at all due to only high clouds. If they
were lower, say a mid deck, I would have more confidence in
upping mins. But, the possibility of them clearing away and the
early cooling we have had already makes ME think it is OK to
hold mins as-is. Thv tanked to 50f last hour, but caught a
little south wind in the last hour, but has gone back to calm.
Thv is back up to 56f. Expect them to drop off once again. Seg
not disappointing as the best radiational cooling site so far,
and they are down to 48f. Interesting returns seen on radar
over Chesapeake Bay over the last few hours - we figure that it
is likely chaff from flight Ops around Patuxent NAS.
mainly clear with just high clouds spilling over the ridge.
These clouds did make for a beautiful sunset. Some low stratus
is possible with/near the anticipated River Valley fog which
should form again overnight. But, not outside of the immediate
vicinity of the fog. Temps should fall into the 40s to lower
50s. Just the more sheltered places in the north could touch the
30s much like they did at bfd and in Kane and Coudersport last
night. While it seems cold - the upper 30s are just 5 or 6
degrees below normal for the day.
Short term /tonight through 6 PM Saturday/...
no changes to the going forecast on Friday as the strong surface
high slips south of the region. A return flow of warmer
southward flow will develop, and along with abundant sunshine,
temperatures should Jump Up to the mid to upper 70s north to the
lower 80s south/southeast.
Long term /Saturday night through Thursday/...
a building upper level ridge and surface high off of the East
Coast will bring a resurgence of summertime warmth across the
area this weekend. Max temperature departures of +10-15 degrees
are expected Sat-sun with peak readings in the mid to upper 80s
in the southeast. Max temperatures would have to reach or rise above
90f to challenge daily records in most locations.
The biggest forecast question in the mid range will be the
presence of a shortwave trough that will move through the mid
Atlantic region Saturday. This shortwave should flatten out the
ridge and bring in some mid to upper level instability. The only
reducing factors is that it will be very dry aloft and their
should be the presence of a low level cap. Temperatures will
have to get very warm for the air to be able to be lifted beyond
it. Latest soundings show this is possible but given the dry
air, less likely.
So have introduced slight chance to chance probability of precipitation to central PA
The models are coming into agreement on the tracking of a cold
front that will move through the area Monday. This system will
likely be accompanied by a round of showers. It should move
through the region quickly with a return to fair and seasonable
weather appears likely Tue/Wed. High pressure should build
southeast from the grt lks mid next week.
Aviation /06z Friday through Tuesday/...
valley fog/localized restrictions early this morning will give
way to widespread VFR shortly after sunrise. Persistence trends
favor northern tier airfields kbfd/kipt with brief IFR
conditions around daybreak.
A spotty/isolated shower is possible mainly across the western
1/2 of the airspace Saturday PM. There is a better chance for
showers/storms Monday PM, ahead of an approaching cold front.
Fri-sun...am valley fog. Isold shra possible wrn 1/2 Saturday
Mon...sct showers/isold T-storms as a cold front crosses the
autumn officially arrives at 3:50 a.M. EDT, on Monday, sept. 23.