Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 220729
Area Forecast Discussion
National Weather Service State College PA
329 AM EDT FRI JUL 22 2016
Pennsylvania will be on the northern edge of a subtropical ridge
into next week. An upper level disturbances and associated weak
cold front across the northern great lakes will move southeast
and cross Pennsylvania late today and tonight accompanied by
isolated to scattered, mainly afternoon and evening showers and
thunderstorms. Mostly sunny, very warm, and generally dry
conditions will follow for the upcoming weekend.
.NEAR TERM /UNTIL 8 AM THIS MORNING/...
Very warm temps aloft (around 8C at 700 mb) residing over the
state at 07Z, with even warmer mid-level temps upstream to our
northwest, will combine with only weak to mdt llvl positive
theta-e advection to bring just very minimal chances for a shower
or TSRA through the mid morning hours.
The rest of the overnight will stay mainly dry, with just a very
low (20 percent chc of less) POP painted across the NWS mtns of
Low temps around sunrise will vary from the lower 60s over the
Laurel highlands, to the mid and upper 60s elsewhere.
.SHORT TERM /8 AM THIS MORNING THROUGH 6 AM SATURDAY/...
Shortwave topping the ridge into the nw flow aloft will advect
increasing moisture/instability into the region today. Ensembles
point to an increase in the PWATs ahead of the shortwave and
associated weakening cold front (that should make it to the
the intersection with a developing lee trough somewhere across
north-central PA or the Susq Valley.
After the early day activity fades, diurnal heating and weak
convergence with the dying front will bring the chance for
additional showers/thunder mainly during the mid day and afternoon
hours and mainly over northern areas. Deterministic guidance shows
mid level temperatures on the order of 9-11C which will act as a
convective deterrent, limiting the extent of development and doing
little to break the recent extended period of widespread dry
conditions we have been experiencing.
00Z NCAR ensemble data indicates the best chance for late day
thunderstorms will be across northeast PA, closest to trailing
shortwave tracking across upstate NY. SPC has placed nearly all of
central Pa in a marginal risk area Friday, but with the expected
warm mid levels, thinking is that convective activity will be
widely scattered with the very far north being most susceptible to
a few strong storms.
8h temps rising to near 20C should translate to max temps this
afternoon ranging from the m/u80s over the Alleghenies, to 90-95F
elsewhere. The heat, combined with rising dewpoints, should result
in widespread heat indices in the 90s.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
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. 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.
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --VFR conditions should prevail through the majority of the period.
Area of showers/TS developing northwest of Lake Erie may reach the
BFD terminal area 12-15Z. Isolated to widely scattered thunderstorms
remain possible across the entire airspace this afternoon through
the early evening. Limited coverage/low confidence will preclude
TS mention for now and will reassess with the full suite of near
term meso guidance by the 12z scheduled issuance. The greatest
risk for strong to severe TS appears to be across the northeast
airspace in ZNY sector.
SAT-SUN...Early morning fog possible...otherwise no sig wx.
MON-TUE...Restrictions possible with a chance of SHRA/TSRA.
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SHORT TERM...La Corte/Lambert