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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 161041
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
641 AM EDT Sun Jun 16 2019

.SYNOPSIS...
An unsettled and stormy weather pattern is expected across 
central Pennsylvania this week. There will be multiple rounds 
of heavy downpours with the potential for localized flooding 
and isolated severe storms. Temperatures and humidity levels are
forecast to remain near average for mid to late June.

&&

.NEAR TERM /THROUGH TONIGHT/...
A noticeably warmer and more humid overnight period and start 
to Father's Day with 24-hour temperature change of +5 to +15 
degrees.

MCV/shortwave will track from east central OH across north 
central PA this morning. A batch of rain/showers will accompany 
this feature with the heaviest QPF /0.50 to 1 inch/ forecast 
across the norther tier counties. Radar estimated rain rates 
have been on the decline so feel the treat of localized minor 
flooding is trending lower early this morning across the
northwest Alleghenies. 

Showers will likely continue over the northern tier into the
early afternoon as the MCV shortwave moves through the area. A 
trailing, lower amplitude shortwave trough will push east from 
the OH valley toward PA this afternoon/evening. Hires model 
guidance likes the idea of developing PM T-storms within moist 
and conditionally unstable airmass along and to the south a
nearly stationary frontal boundary near the I-80 corridor.
Combination of sufficient instability and deep shear supports
risk of isolated to scattered severe storms capable of producing
hail and localized strong wind gusts. The SPC Day1 outlook 
increased severe probs/categorical risk level from 1 to 2 out of
5 in a small area centered along the Mason Dixon line to the 
east of I-70 and south of the PA Turnpike. Heavy downpours will
accompany any t-storms with an isolated flash flood threat
mainly over areas of lowest FFG in southwest PA. Showers will
likely linger into early tonight with fading coverage and
intensity after midnight.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Convectively active period continues into early next week. The 
majority of model guidance is targeting south-central/southern 
PA with the greatest risk of isolated/scattered severe storms 
and potential flash flooding. 

The pattern remains largely unchanged (slight southward shift
with time?) as series of small shortwave troughs/vort maxes 
shift downstream from the OH Valley into a moist/unstable 
airmass residing to the south of an elongated stationary front.
Confidence in the axis of heaviest QPF is lower than average, 
as it is very dependent on the placement of the main frontal 
boundary and any additional mesoscale boundaries established 
from preceding convective complexes. The general trend is for 
excessive rain and severe weather risk/threat areas to shift 
southward from Monday into Tuesday but remain focused over the 
southern 1/2 to 1/3 of the area. Model spread in the QPF is 
also contributing to lower confidence, but there are plenty of 
ingredients to support rounds of heavy rain and isolated to 
scattered flash flooding. Like on day 1, SPC increased risk
level to slight on Monday over virtually the same area and
introduced a marginal risk along the southern tier on Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Models hint at a drier period toward the end of the week into 
first half of the weekend, which translates to just isolated 
showers focused on the NW half. But precip chances increase 
again with another storm system by Sunday.

Though elevated dewpoints will keep muggy conditions in place
with above average low temps, highs will top out a bit below
normal each day.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
For the 12Z TAF package, a few more adjustments.

Area of showers to the north and west continues to
weaken.

More in the way of convection across the Ohio Valley is 
looking more and more like it will stay south of our TAF sites.

Earlier discussion below.

More in the way of showers and storms later today, mainly
southern PA, if not further south. This based on current 
radar trends.

.Outlook...

Mon...AM low cigs/fog poss N and W Mtns. Scattered PM tsra 
poss, mainly south.

Tue...AM low cigs/fog possible. Scattered PM tsra impacts
possible south.

Wed...Patchy AM fog possible. Isold PM tsra impacts possible
western half of Pa. 

Thu...AM rain/low cigs possible. Scattered PM tsra impacts
possible.

&&

.CLIMATE...
Astronomical summer (solstice) begins Friday, June 21st at
1154AM EDT (1554 UTC).

&&

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

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...RXR/Steinbugl
AVIATION...Martin
CLIMATE...Steinbugl