Scientific Forecaster Discussion
fxus61 kctp 161211
Area forecast discussion
National Weather Service State College PA
811 am EDT Tue Jul 16 2019
---mid Summer heat and humidity on the way---
Humidity will be on the increase through Thursday as the much
weakened remnants of what was once Hurricane Barry, migrates
slowly northeast out of the Mississippi and Ohio River valleys.
Near term /until 6 PM this evening/...
mid and high clouds slowly starting to increase over southwest
PA this morning ahead of approaching warm front over the Ohio
Valley. Deep layer moisture will continue to slowly increase
throughout the day, with precipitable water increasing to between 1.5" to 2.0".
A warm front lifts across the region allowing sfc dewpoints to
steadily rise as well. Along with the humidity, the chances for
showers will be on the increase. Models develop a fair amount of
cape by afternoon as the warm front passes. Blended MOS pops
show the first small chances for a shower in the far western
counties early in the morning, but the best chance for
thunderstorms will be from mid day Onward, as pwats in excess of
1.75"/2-3 sigma accompany the warm front.
Lapse rates are not going to be especially high and wind shear
will be weak, so the threat for severe storms should be minimal.
However, local downpours producing spot 2+ inch amounts seem
possible in the tropical airmass. A good deal of cloudiness
should hold temperatures down across the Allegheny plateau,
where maxes are likely to be in the low 80s. More sunshine
further east could push readings to around 90f across the susq
valley before late day convection forms.
Short term /6 PM this evening through 6 PM Wednesday/...
evening convection will die out after sunset setting the stage
for a warm and muggy night with areas of valley fog. Still
chances for shra/tsra mainly west where boundary layer
convergence could maintain cells into the overnight. Mins will
range from the upper 60s north to the lower to mid 70s south.
Long term /Wednesday night through Monday/...
*heavy downpours possible Wed-Thu with remnants of tc Barry
*excessive heat risk Fri-Sat
Tropical moisture will stream into the region through Wednesday
from the remnants of tc Barry. There continues to be a marginal
risk on day 3 for excessive rainfall.
Model guidance continues to signal the potential for excessive
heat around the end of the week and into the weekend. Maximum
heat index values peak in the 100-105 range Friday and Saturday.
Heat headlines appear likely during this time and will continue
to highlight heat risk via hwo, social media and dss briefings.
Very warm mid-level temperatures may act to limit/cap T-storms
Fri-sun. That said, models hint at the potential for mesoscale convective system
activity propagating along wavy frontal zone on the northern
periphery of summertime upper ridge/heat dome. Plenty of
uncertainty with exact timing and placement of pcpn so opted to
stay close to blended model guidance.
Aviation /12z Tuesday through Saturday/...
VFR prevailing most of Tuesday. Scattered thunderstorms may
result in brief airfield restrictions this afternoon and
evening. Shower activity is most likely to continue across the
far northwest airspace late tonight into Wednesday morning.
Wed...scattered to numerous showers/thunderstorms with heavy
Thu-Sat...isolated PM thunderstorms possible.