Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 221935
Area Forecast Discussion
National Weather Service State College PA
335 PM EDT FRI JUL 22 2016
Pennsylvania will be on the northern edge of the subtropical
ridge into next week. A series of weakening cold fronts will bring
the mention of mainly afternoon or evening showers or
thunderstorms in the forecast, but most of the time it will be
fair, very warm and generally dry.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
The last of the MCS is moving through my far swrn zones while
continuing to dwindle.
Skies are clearing rapidly in the wake of the dying showers. Over
the far north there are signs of new cu formation while a more
general area of strato-cu advects off Lake erie over nwrn Pa.
The big question for the remainder of the day will be how much
new activity can fire with diurnal heating. RAP meso anal depicts
700mb temps of 9-10C already in place with continued warm
advection in progress. Local experience has associated 700mb temps
of 8C or higher with being a pretty effective cap in the absence
of strong forcing. For this reason I think any new convection, if
any, that develops will remain fairly isolated.
SPC has an area of MRGL risk for severe weather from Pa and
western NY west through the Ohio Valley and beyond. My far nern
zones are covered with a Slight risk as they are under slightly
cooler mid level temps and modestly better shear associated with
the parent shortwave that is sliding off to the north and east.
With region-wide CAPEs expected to be in the 1500-2000j range,
any storm that does manage to break the warm mid level cap will be
capable of producing a downpour and strong wind gusts.
8h temps rising to near 20C should translate to max temps ranging
from the m/80s over the Alleghenies, to between 90 and 95 elsewhere.
The heat, combined with rising dewpoints, should result in
widespread heat indices in the 90s.
A muggy night is in store over most of the region with any
convection that forms this afternoon expected to fade quickly
early this evening, leaving a mainly dry overnight. Overnight lows
will average around 10 deg above normal.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
3H weather, hazy-hot and humid, is in store for Saturday. With
the warm air aloft and a weak surface high in the low levels, it
will be a dry day with plenty of sunshine, a great day for the
pool or lake, but no relief for agricultural interests badly in
need of rain.
Highs will be well above normal, ranging from the mid 80s over the
NW to mid 90s over the SE.
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
-- Changed Discussion --Big story in the extended fcst is expected heat wave lasting into
early next week, as axis of subtropical ridge briefly shifts from
the plains to the northeast conus. Anomalous upper lvl ridging
building over PA should bring hot and mainly dry wx this weekend,
as warm temps aloft suppress convection. Next chance of shra/tsra
for most of the area comes Monday ahead of shortwave working
across the Great Lakes. However, any rainfall Monday is likely to
do little to stem the dry pattern we have been in. Latest GEFS
mean qpf is up to a half an inch at most.
12Z ECENS/NAEFS mean 8h temps are near 22C Saturday through
Monday, indicating the potential of several days in a row with
highs in the 90s in the valleys. The hottest temps look to be on
Saturday as latest GEFS gives high temperature anomalies in the
+4 standard deviation and have slightly backed off on Sunday. Have
adjusted Max temperatures accordingly. Heat indices around 100F
appear possible by Mon across the Susq Valley, as higher dewpoints
are advected into the area ahead of potential convection.
Overnight lows are also a concern as the area doesn`t cool off at
night through the weekend with Southern PA lows in the 70s with
highest readings Monday morning. Some modest cooling appears
likely by Tue/Wed of next week behind weak cold front. However,
temps still likely to remain somewhat abv normal within a
generally zonal flow.
Midweek weather looks dry again, with just low pops for isolated
tstms. Fri looks to be the next higher chance for tstm impacts
areawide as another cool front progged to move through.
-- End Changed Discussion --
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Some localized areas of fog will be possible late tonight and for
an hour or so around sunrise Saturday, but mainly VFR conditions
are expected to prevail into the weekend.
Localized restrictions will be also possible with scattered
showers and thunderstorms that will mainly favor the afternoon
into the early evening hours.
SAT-SUN...Early morning fog possible...otherwise no sig wx.
MON-TUE...Restrictions possible with a cold front bringing
scattered showers and thunderstorms.
WED...No sig wx.
Near Term...La Corte
Short Term...La Corte