Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
656 am EDT Friday Jul 31 2015
high pressure over the central U.S. Will nose into the region this
weekend. A persistent trough aloft will sit over the Great Lakes
and northeast at the same time. Weak fronts with little moisture
moving down on the northwest flow over the Great Lakes will try
to break down the high pressure.
Near term /until 6 PM this evening/...
sunshine already strong. No real tweaks to forecast necessary.
dry air and subsidence will provide a dry day for the area.
However...daytime instability and a short wave crossing the upper
Great Lakes this afternoon and evening could trigger isolated
showers or thunderstorms. These should stay confined to mainly
western New York state but could sneak into the far northern mountains
toward sunset. The northwest flow will provide moderate speed shear.
Little surface convergence...mid-level cap...weak instability and
unidirectional hodographs will keep the threat of severe storms
pretty much Bay. Marginal risk does not quite get into the County Warning Area.
Temperatures should rise nicely after the slightly cooler than normal
start to the day. The dry air should also make it fairly easy to
ramp the temperatures up to normal or warmer-than-normal afternoon temperatures.
Short term /6 PM this evening through 6 PM Saturday/...
upstream convection will try to get into the northwest this
evening and will probably succeed is making isolated to scattered
showers/storms for the northern third to half of the County Warning Area tonight. But
the loss of instability and the storms running into drier air and
a good cap will likely cause them to die out as they get to PA.
Nighttime lows 55-65f.
Dewpoints Don/T move much into Saturday...but better dynamics
aloft and slightly lowered heights will allow for a few more
storms to form on Sat afternoon/evening - but again confined to the northern
half of the area due to strong inversion in the southern half. 800 mb temperatures
a little cooler on Sat vs Friday...so maximum temperatures will likely be
slightly cooler as well - especially in the northwest.
Long term /Saturday night through Thursday/...
little change is anticipated in what should be a stable large
scale flow pattern across the Continental U.S. During the first week of
August. Upper ridge will continue to dominate out west while a
broad upper trough extends southward from eastern Canada across the eastern
U.S. Temperatures should average near normal into early next week
before trending cooler later in the week. Confidence is low on
timing of precipitation chances associated with northern stream frontal systems.
Did not change a lot. Did back off clouds some and have the
highest probability of precipitation during the daytime hours. Main thing going for
showers and storms will be heating with cold air aloft and
weak shortwaves moving across.
Aviation /12z Friday through Tuesday/...
surface high pressure over the region will support VFR conditions
through at least early Saturday morning.
Sat...mainly VFR...scattered showers/thunderstorms.
Mon-Tue...mainly VFR...scattered showers/thunderstorms.