Monday, August 21, 2017, 8:08 AM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 211137
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
737 AM EDT Mon Aug 21 2017

.SYNOPSIS...
High pressure moving off the Mid Atlantic coast will bring a 
warm and increasingly humid southerly flow to the region into 
Tuesday. A strong cold front will move through the region late 
Tuesday and Tuesday night. Cooler and drier conditions will 
return for the second half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Radar shows scattered showers and thunderstorms moving mainly
through southern NY with a few trailing smaller cells in McKean
county. The HRRR weakens this activity by mid morning as it 
moves away from the instability.

High pressure will slide off the coast and a warm and more humid
airmass will return to the region. The shortwave will drift
across the area this afternoon providing weak large scale 
ascent. Models agree in developing a fair amount of CAPE and 
eastern areas are also expected to see some moderate deep layer 
shear develop as well. SPC has outlooked our eastern zones with 
a Marginal Risk which looks entirely reasonable. Convection 
will tend to decrease quickly after sunset with a warm and muggy
night in store ahead of an approaching cold front.

The amount of cloudiness today could hamper eclipse viewing as
clouds and showers begin to pop up this afternoon. As it stands
now, it looks like my SWRN zones will enjoy the least amount of
cloudcover.

&&

.SHORT TERM /TUESDAY/...
The big weather maker still looks to be a potent late summer 
cold front that will pass through the region Tuesday evening 
into early Wednesday. 

Consensus model timing shows the front just entering NWRN PA by
8PM Tuesday/00Z Wednesday. Models develop just some modest CAPE
east of the front over much of central and western PA. The 
exception is over eastern PA in what appears to be a lee side 
surface trough feature. The ECMWF/GFS and the ensembles all 
develop a finger of moderate to strong instability over SERN
areas along the coastal plain. Deep level shear is also progged
to increase and exceed 35kt. 

Interesting to note that the GEFS shows very little unstable 
air from the cold front into central PA and the SREF which 
paints more CAPE overall, has a distinct minimum of instability
over our area during the day into the evening. This suggests 
there could be a fair amount of pre-frontal cloudiness hindering
heating. The whole region is painted under a Slight Risk which 
seems based more on expected impressive wind fields than model 
generated instability. 

Highs are still expected to rise into the 80s, to around 90 
over southern areas before the clouds increase ahead of the 
front. A very humid airmass will make it feel warmer.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
After our surge of heat and humidity, the strong front will 
bring a noticeably cooler and drier airmass to the region 
starting midweek and lasting through the end of the week into
the weekend. Interesting to note that the deterministic models 
show 850 temps as cold as 2-3C just north of the Canadian 
border behind the cold front, a reminder the change in seasons 
is not all that far away. Chilliest readings look to be the 
mornings of Fri/Sat/Sun with high centered overhead, dipping 
lows into the 40s over the Northern Mountains (and deeper 
valleys of the Central Mountains) and solidly into the 50s 
elsewhere.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Cluster of showers and storms over southwest NY state
lifting northeast.

Some adjustment made to the 12Z TAFS.

Earlier discussion below.

Less weight on fog now, given clouds moving in.

Some storms near Lake Erie now. Mid level wind fields
may support some strong storms today.

Yesterday I was thinking today would be dry. However, 
strong warm advection may result in some showers and
storms later today and early this evening.

.OUTLOOK...

Tue...Patchy AM fog poss. Late day/evening tsra impacts poss. 

Wed...Early AM low cigs poss BFD/JST. 

Thu-Fri...No sig wx expected.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...La Corte
AVIATION...Martin

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