Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
613 PM EDT Monday Aug 31 2015
a moderately high amount of moisture streaming east from the Ohio
Valley will extend across Penn through much of this week. The
close proximity of a nearly east- west frontal boundary across
Pennsylvania will lead to isolated showers today through Thursday.
High pressure off the East Coast will ridge northwest into
Pennsylvania and lead to temperatures well above normal this
entire week. It will feel more like the middle of Summer than
Near term /until 11 PM this evening/...
evening convection dwindling rapidly as mere remnants of what
earlier were locally heavy downpours linger over southern
portions of the Laurel Highlands and are just exiting southern
Schuylkill County as well. Not expecting any additional
development this evening...as per latest hrrr which had a good
handle on the explicit dissipation of diurnal activity this
evening. Dropped late evening probability of precipitation as a result.
Short term /11 PM this evening through 6 PM Tuesday/...
fog is not a slam-dunk tonight...but high moisture and clearing
sky should allow for the valleys to fog up as is usual in sept.
Yes...sept already. Will also mention some patchy fog in the southern
tier where it is raining. Mins should run in the muggy 60s and
l70s again. Tuesday looks like it should hold fewer showers...with
little forcing and only weak boundaries running about.
Thus...will keep probability of precipitation to 20s in the SW.
Long term /Tuesday night through Monday/...
anomalous upper level ridge is forecast to dominate the eastern
third to half of the United States trough the long term period.
This will lead to above- normal temperatures for much of the
period. The warmth and increasing humidity should allow for at
least a slight chance of diurnal convection each day...but warm middle-
levels will keep the probability of widespread rainfall quite low.
The hiest chances for precipitation will be during the middle-late week
period /Wed-Thu-Fri/ with a couple subtle features. First...a weak
upper level wave /best prognosticated on the European model (ecmwf)/ slips overhead on Wednesday
as the Bermuda high briefly recedes. At same time a weak backdoor
cold front slips southward off the East Coast. This could help
pool some low level moisture over the middle Atlantic and Ohio Valley
as middle levels cool just a bit...bringing potential for scattered thunderstorms.
Ridge builds back in for Friday...but another surface backdoor front
tries to slip across the state as surface high expands in from the
north. This boundary should bring scattered convection for Friday.
Extended models hint at potential for daily convection continuing
into the weekend along souther border...but overall conditions
will be mainly rain-free.
Temperatures peak midweek with readings approaching 90f in the southeast...and
even getting into the 80s else here...easily well above normal
for the first week of sept. Lows will also remain quite mild
middle/late week as high humidity air hangs around. Slightly cooler
but still above average temperatures will continue through the weekend.
Aviation /22z Monday through Saturday/...
isolated showers across southern PA should dissipate around sunset
as the atmosphere cools/stabilizes. Main focus tonight will be on
late night fog...which appears a near certainty in the deep valleys
of north central PA. Latest model output...combined with conditional
climatology...imply at least a 50 percent chance of a period of IFR
conds at kbfd/kipt/kaoo late tonight...only a slight chance at
kunv/klns and nearly no chance of sig reductions at kjst/kmdt.
Any am fog should burn off by between 12z-14z. Otherwise...high
pressure off the East Coast will ensure widespread VFR conds and
light winds on Tuesday. There is just a slight chance of a PM
rain showers/thunderstorms and rain in vicinity of kjst.
Wed-Sat...patchy am fog poss...mainly kipt/kbfd. Isolated PM thunderstorms and rain
impacts possible...mainly west.