Tuesday, July 17, 2018, 1:30 AM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 170156
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
956 PM EDT Mon Jul 16 2018

.SYNOPSIS...
Very warm and humid weather will persist overnight and into 
Tuesday. Showers and thunderstorms will precede a cold front 
which will move through during the day on Tuesday. Canadian high
pressure will follow and bring a refreshing change back to much
lower humidity and near to slightly below normal temperatures 
for the second half of the week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A very active late afternoon and evening occurred across a few
locations in northern and western PA. The most significant
weather, in the form of very heavy rain and Flash Flooding 
occurred across northern Potter County where rainfall estimates 
of up to 4 to 5 inches were substantiated by spotter reports.

Elsewhere, a line of strong to severe TSRA with a few damage
reports of downed trees moved NE across Warren County over the 
past few hours, and an isolated TSRA and associated microburst 
blew down a few trees in northern Cambria County early on.

An approaching cold front, increasing diffluence aloft, and a
NE/SW 925-850 mb theta-e ridge extending across NW PA through
much of tonight should support additional TSRA with expanding
coverage across the NW Mtns as the night wears on. Warm temps 
aloft (about 8-9C at 700 mb) and the lack of significant 
forcing further SE will keep POPs fairly minimal until the 
predawn hours of Tuesday.

We'll have to deal with one last muggy night in this latest
anomalous warm spell. Given the high sfc dewpoints in the upper
60s to low 70s, and extensive cloud cover, min temps early 
Tuesday will once again vary from the upper 60s to low 70s. 

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
A cold front will reach the northwest mountains around or very
shortly after sunrise Tuesday morning and take much of the
daylight hours to get past Lancaster Co. However, about half of
the area will be dry after 18Z. High PWAT air, increasing deep 
layer shear (20-30 kt) and the cold front may lead to strong 
thunderstorms depending on the amount of sunshine. SPC has 
a portion of east Central PA in a marginal risk for severe. Most
likely timing for the strongest storms would be generally 
during the afternoon hours when heating meets up with the front, 
forcing and modest shear. Maxes will be highest in the SE, but
most places won't be more than 3-4F away from their normals.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Drier air and building pressure behind the cold front Tuesday 
night into Wednesday helps clear things out and drop high 
temperatures Wednesday about 5 degrees over Tuesday - but
biggest change will be that lowering dewpoints will make humidity
levels become notably more comfortable. 

High pressure over PA Wednesday night will bring the coolest
morning of the week before it slided east off the coast on
Thursday. Flow aloft will shift from northwest to southwest and
surface winds will turn southeast. GFS hints at a marine layer 
moving into lower Susq Thursday night and a return of higher dew
points may bring some patchy morning fog. 

Next system slowly approaches by late Friday but stalls over the
Great Lakes as inverted trough develops on top of it. This
system will slowly work eastward into the Northeast over the
weekend bringing a return of unsettled weather. A weak low 
center trying to form on the coastal front off the Carolinas 
Saturday progged to move north to just of the Delmarva for 
Sun/Mon, enhancing shower/tstm threat for eastern half of CWA.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
The approach of a cold front will keep isold-sct thunderstorms 
going through much of the night, mainly in the NW. Not much fog 
is expected tonight with mild temps and at least 50pct cloud 
cover in most places. However,showers and thunderstorms will be
capable of producing heavy rain leading to temporary mvfr/ifr 
vsbys.

The cold front may reach KERI around sunrise and then slow a 
little as it should take most of the day to get thru KLNS. But, 
BFD should be dry aft 15Z and UNV/JST/AOO may be dry by 18Z. 
Some storms with gusty winds and heavy rain are expected, mainly
in IPT, MDT and LNS where peak heating will meet up with 
CFROPA. IFR is poss in any of the storms. 

Drier and less humid conditions start Tues morning in the NW and
evening in the SE and last for the rest of the week. 

.Outlook... 

Wed-Fri...AM valley fog N, otherwise, no sig wx expected.

Sat...SHRA/TSRA poss vcty warm front.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Dangelo/Lambert
NEAR TERM...Dangelo/Lambert
SHORT TERM...Dangelo
LONG TERM...RXR
AVIATION...Dangelo/Gartner

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