Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
308 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
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/...
showers and isolated thunderstorms and rain over the southern mountains are drifting east-southeast. A few
other cells are sprinkled about the County Warning Area. In general...these are
not all that tall...but as we saw yesterday...the precipitable waters are
inching up and 1.5 to 1.75 inch values are not uncommon - mainly
in the south. Thus...a few may contain heavy downpours. The rap
and hrrr have all of the current showers dying a quick death very
early this evening - perhaps before sunst in the central cos
where instability is not so great and subsidence/drying is quite
evident. Will keep probability of precipitation under 20 there and north for the rest of
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 will dominate the Ohio Valley and
eastern United States much of the upcoming week...with latest
guidance remaining firm for an extended run of 850hpa temperatures
peaking daily around 16-18c. This will translate to well above-
normal surface temperatures. This warmth and increasing humidity should allow
for at least a slight chance for diurnal convection each day...but
warm middle-levels will keep the probability of widespread rainfall
Best 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
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 /19z Monday through Saturday/...
rain showers/thunderstorms and rain over the SC mountains will die off this aftn/evening. Most
will be gone before 22-23z. Fog is likely in the valleys and
perhaps aoo where it rained today.
High pressure off the East Coast will remain in place for a few
days. Return flow from the west/SW will make it very warm and
humid...but a ridge aloft will serve to suppress convection.
Thus...most of the time will be VFR with only early am fog in the
valleys as is normal for sept. Afternoon reductions in isolated sh/thunderstorms and rain
are poss through the next few days...but the majority of the time
will be VFR.
Wed-Sat...patchy am fog poss...mainly kipt/kbfd. Isolated PM thunderstorms and rain
impacts possible...mainly west.