Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
720 PM EDT Wednesday Jul 1 2015
a weak surface cold front is dissipating as it drops southward
across central Pennsylvania this evening. This boundary will
separate drier air to the north from moist and unstable air to the
south...and gradually lift back to the north as the week wears on.
Chances for showers and thunderstorms will increase across
southern Pennsylvania by Friday...and across the remainder of
central Pennsylvania on the Fourth of July. Drier air will return
southward on Sunday and Monday as an upper level ridge briefly
builds over the northeastern United States early next week.
Near term /until 6 am Thursday morning/...
6 PM update...
dry air winning out and showers are gone. Will hold a slight chance
in the far NE for another 2-3 hours. The convergence along the
boundary seems to have washed away. Models do hang onto low level
moisture in the alleghenies as the high pressure builds. So fog
and some low clouds are still expected to form through the night.
visible loop indicates frontal boundary extending from the endless
mountain region in northeast PA to the west central mountains...
denoted by a broken line of showers. Last few frames of regional
radar mosaic indicate a few heavier showers popping up along the
front west of the alleghenies...in a Richer moisture environment
where surface dewpoints are in the lower 60s. Hi res near term models
indicate remaining showers dying over the next few hours due to
dry air along and east of the alleghenies (sfc dewpoints in the
50s) and downsloping west-southwest boundary layer flow.
Weak 1017 mb ridge of high pressure builds across the Great Lakes
tonight...with lower deep layer moisture lying across the region
tonight. This will bring fair weather and decreasing to calm
winds...promoting fog developing late tonight and early Thursday
morning. Some could be locally dense in the deep northern valleys.
Short term /6 am Thursday morning through 6 PM Thursday/...
fair weather will continue on Thursday thanks to weak high
pressure traversing areas to our north. Moisture boundary along
and south of the Mason Dixon line will promote afternoon shower
and thunderstorm development over the higher terrain of northern
Maryland and WV...extending into the Laurel Highlands. Coverage will be
isolated to scattered.
Maximum temperatures should range from the lower 70s north to the lower 80s
Long term /Thursday night through Wednesday/...
the models remain in fair agreement with the drier...northwesterly
flow keeping the moisture south of the border Friday into
Saturday. Despite minor timing differences among medium range
models...the overall pattern appears fairly certain. Mean upper level
trough will remain centered west of PA...resulting in some
opportunities for rain. Ecens/gefs indicate the best chance for
showers will accompany passage of shortwaves Sat afternoon and
Tuesday. There is a chance on Friday afternoon as the trough digs down
as it propagates eastward. A strong ridge should remain itself
Gefs/ecens mean 800 mb temperatures imply temperatures fairly close to average for
early July. Sat is likely to be a bit cool due to clouds/showers
and low level easterly flow. However...SW flow in advance of an
approaching cold front is likely to push temperatures a bit above average
by Tuesday of next week.
Aviation /23z Wednesday through Monday/...
00z tafs going out in a few minutes.
Mainly a scattered-broken area of cumulus across central PA. Still hazy
out...but bulk of smoke south of our area now...can see it
from central Canada southeast to southern Ohio...on the observation and visible
satellite pics. Yesterday it was further north across our area.
Earlier discussion below.
Not much on radar for a change.
21z tafs sent.
Made some changes...which I will use on the 00z package.
Expect the gusty west to northwest flow to weaken by sunset.
Given the wet conditions of recent times...and that temperatures
are expected to drop to the dewpoint...cross over
temperature...expect some fog and low ceilings to form late.
Also the high will be nearly overhead late tonight.
Expect conditions to improve Thursday morning...given the strong
early July sun.
Thursday...mainly VFR. Isolated thunderstorms and rain mainly south of I-80.
Sat-Mon...mainly VFR...but a chance shra/tsra...mainly across