Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
623 PM EDT Wednesday Oct 22 2014
a slow moving low pressure system off the middle Atlantic coast will
continue to bring mostly cloudy and cool weather to central PA
along with intermittent rain through the end of the week.
Improving conditions are forecast over the weekend as the low
moves north through the Canadian Maritimes. High pressure should
migrate across the Appalachians to the East Coast by early next
week which should result in fair weather and warmer temperatures.
Near term /until 6 am Thursday morning/...
slowly deepening offshore coastal low will wobble northeastward
towards southeast New England overnight. Strong and moist low level NE
flow around the low center will persist across central and eastern
PA through Thursday...keeping persistent cloudy and damp
conditions in place across most of central and eastern PA.
Water vapor loop continues to show next wave of enhanced moisture
swinging westward into eastern/northeastern PA on the northwest
side of the upper low centered east of the Delaware-Maryland-Virginia coast. This
will keep 50/60 probability of precipitation over my far northeast counties later tonight
with low chance extending into the Central Mountain region.
Current shower activity will continue to increase across the east
through middle to late evening before fading again overnight as the
upper support pulls away.
Short term /6 am Thursday morning through 6 PM Thursday/...
the deep-layer cyclone will move little on day 2 off the northeast
U.S. Coast as shortwave energy crossing the upper Midwest weakens
and splits through the MS valley. The models show the southern branch wave
approaching the Appalachians by 12z Friday with the GFS being flatter
and more progressive than the ec. The main wrap-around precipitation area
should shift into northestern PA on backside of the slowly departing
coastal storm system. Thursday will be another raw day with brisk
northerly winds and highs about 5f below late October normals.
Probability of precipitation should continue to trend lower into tomorrow night with
portions of southern/southwestern PA starting to see some breaks in the cloud
Long term /Thursday night through Wednesday/...
by Thursday evening...coastal low will be drifting into the Gulf of Maine
which should end precipitation chances for central PA. After weak ridging
Thursday night into early Friday...the next feature up will be a
splitting wave over the Great Lakes that will send a piece of
energy across PA Friday night with minimal impact. A stronger system
following behind the initial splitting wave will drop across the
lakes for late weekend...with the ec trending faster than the GFS
initially /though the GFS catches up in placement over New England
by Sunday/. This system will bring a glancing blow of cooler air
into PA poss as early as Sat night...but more likely sun into Monday
as core of upper jet swings a moisture-starved cold front through.
Any light precipitation from this will the bulk of precipitation likely occur
behind the front in the colder northwest flow in the form of lake effect
and upslope rain showers.
This regime will be replaced quickly by a large ridge sliding in
from the central U.S. This ridge will amplify over the East Coast
as a wave drops into The Rockies...bringing a noticeable warmup
later Monday and especially Tuesday -when temperatures should be in the 60s areawide
and should touch 70f in the southern tier.
The western system will progress eastward for midweek...with
models diverging on timing/strength. But overall model guidance
implies a potential showery period with temperatures falling back to
Aviation /22z Wednesday through Monday/...
surface low off the middle Atlantic coast will move slowly to the
NE...keeping the region in a moist cyclonic flow. The
circulation around the storm will continue to spin rain showers
back into eastern PA.
Widespread MVFR/IFR will continue through much of the taf period
as north-nerly flow is slow to abate.
Thu-Fri...low ceilings poss northern mountains...mainly at night/early am. Rain showers
poss eastern third.
Sat-Mon...no sig weather expected.