Area Forecast Discussion
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FXUS61 KCTP 211128
Area Forecast Discussion
National Weather Service State College PA
728 AM EDT THU JUL 21 2016
Pennsylvania will be on the northern edge of a subtropical ridge
through next week with shortwave passages likely late Friday and
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure will move off the Mid Atl coast today...allowing
return sw flow to advect warmer and more humid air into the state.
Large scale subsidence and still low pwats should ensure another
dry day with abundant sunshine. GEFS mean 8h temps arnd 18C should
translate to max temps from the m80s ovr the high terrain, to near
90F in the valleys.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Shortwave and assoc swrly ll jet will advect increasing
moisture/instability into northwest Pa late tonight. 00Z NCAR
ensemble output supports the idea of a dying line of tsra working
into the nw mtns arnd dawn Friday, as parent shortwave and best lg
scale forcing pass well north of the state. A swrly breeze and
rising dwpts should result in a much warmer night than those
recently, with min temps in the m60s across much of the region.
After a lull in activity during late am/early aftn, a second
opportunity for sct tsra appears possible late in the day across
mainly northern Pa, as diurnal heating results in moderate CAPES
along axis of anomalous PWATs extending from the lower lakes into
southern New Eng. 00Z NCAR ensemble data indicates the best chc
of late day tsra 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 the mdl
thermodynamic/kinematic profiles suggest the northern tier is most
susceptible to a few strong storms.
8h temps rising to nr 20C should translate to max temps from the
m-u80s ovr the Alleghenies, to 90-95F elsewhere. The heat,
combined with rising humidity, should result in widespread heat
indices in the 90s.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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 ovr 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. Any rainfall Monday is likely to do little
to stem the dry pattern we have been in. Latest GEFS mean qpf is
only a couple tenths of an inch Monday.
00Z ECENS/NAEFS mean 8h temps are near 20C Saturday through
Monday, indicating the potential of several days in a row with
highs in the 90s in the valleys. 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. 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 /12Z THURSDAY THROUGH MONDAY/...
VFR expected through most of tonight. TS may cross Lake Erie and
impact the far northwest airspace between 06-12z Friday. Isolated
to widely scattered TS are possible across the entire airspace
Friday into Friday night.
SAT-SUN...A.M. fog possible...otherwise no sig wx.
MON...Restrictions possible with chance of TS.