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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 210845

Area Forecast Discussion
National Weather Service State College PA
445 AM EDT Sat Sep 21 2019

Anomalous upper level ridge over the eastern U.S. will
break down temporarily over the next few days as an upper level
trough moves across the northern Plains and Upper Great Lakes
region. Temperatures will peak some 12 to 15 degrees above
normal on Sunday. A cold front will likely push across the area
on Monday, followed by notably cooler temperatures Tuesday and
Wednesday as an area of high pressure builds in from the Great 
Lakes. Another weak cold front should push across the state on
Thursday with a few showers or brief thunderstorm. 


Surface high pressure (1024 mb) was centered over Central and 
Eastern PA early today, providing clear, cool and calm 
conditions with temps in the 40s to low 50s. Temps in our CWA were
warmest over the Laurel Highlands and across far NW Warren 
county where a light southerly breeze and moderately higher sfc 
dewpoints in the 50s were advecting into the region. 

Place your bets on PWAT values this weekend as they'll likely 
double in value in most places between early today (around 0.75 
inch) and late tonight (1.25 to 1.50 inches). PWAT values will
peak Sunday afternoon and evening between 1.5 and 1.75 inches
(with a few spots near 2 inches across the Mid and Lower Susq

The mostly clear skies and a calm wind had led once again 
to patchy valley fog across central and northern Pa. 

Look for temps to reach the upper 70s across the Northern and 
Western mtns for afternoon highs today, while the Lower Susq 
Valley peaks in the mid 80s. These temps will be 12 to 15 deg F
above normal for late September, but will fall well short of
the 94 deg record highs at both Williamsport and Harrisburg.

The warmth and increasingly moist air will lead to SFC Based
Cape of 1500-2000 j/kg across our SW zones this afteroon and
early evening. This instability will support isolated - sct
showers and perhaps a few TSRA near and to the SW of a line from
KFIG to KAOO and KHGR. 20-35 POPs look in good shape for our
western zones this afternoon.


Heights and temps aloft will rise again tonight and Sunday, 
leading to a fair conditions at night and mostly sunny and a 
pleasantly warm early Autumn day with temps well into the 70s 
across the northern and western mtns, and at least the mid 80s 
in the SE zones. it will feel more humid as sfc dewpoints rise
to the 60-65F range on Sunday. High temps will stay anomalously
warm tonight through Sunday with mins in the low 60s running
about 10 deg F warmer than normal in most of Central and Ern PA
but as much as 15 deg F or so across the western mtns of PA. 

The models are coming into agreement on the tracking of a cold 
front that will move through the area Monday. This system will 
likely be accompanied by a round of generally light showers. It 
should move through the region quickly with a return to fair and
slightly warmer than seasonable weather Tue/Wed. High pressure 
should build southeast from the Grt Lks mid next week.


Localized valley fog restrictions early this morning will give
way to VFR. An increase in low level moisture should result in
scattered cumulus this afternoon with a spotty/isolated shower 
possible across the western 1/2 of the airspace. Valley fog is
likely to redevelop tonight with local restrictions into early 
Sunday morning.


Sun...AM fog. VFR. 

Mon...Sct showers/isold t-storms as a cold front crosses the 

Tue...MVFR cigs possible north/west.

Wed...VFR/no sig wx.


Autumn officially arrives at 3:50 a.m. EDT, on Monday, Sept. 23.




NEAR TERM...Lambert
SHORT TERM...Fitzgerald/Lambert