Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 261545
Area Forecast Discussion
National Weather Service State College PA
1145 AM EDT THU MAY 26 2016
A ridge of high pressure will set up shop over the western
Atlantic for the next several days bringing warm and increasingly
humid conditions to the region into the holiday weekend.
Cooler and showery weather may arrive for Memorial Day.
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
-- Changed Discussion --Mid cloud deck has eroded to a large degree across much of the
central mtns and susq valley late this morning...and mdt cu are
developing across the ridges as sfc-based...and lowest 100mb ml
cape increases to a few hundred j/kg.
ml cape should ramp up further to 700-1000 j/kg during the mid to
late afternoon hours as a weak sfc/upper trough (currently moving
through central ohio) drifts across the Allegheny Front and
Central Mtns of the state.
this is where the last few runs of of the HRRR and WRF ARW paint
the greatest chc for showers and isolated to scattered TSRA. The
coverage and intensity of the convection should diminish this
evening as this disturbance and sfc trough approaches the Lower
Susq Valley. Will maintain high chc to low likely pops across the
central and western part of the CWA...with slightly lower chcs for
convection across the far east...as a result of the later arrival
of the theta-e ridge and aforementioned trigger mechanism in the
form of the sfc/upper trough.
SPC does not even put us in the marginal risk. PWATs will be in
the 1.25-1.5 inch range and the warm-cloud layer more than 10kft
deep today. There could be some heavy small rainers since they
will be moving slowly - but at least they will be moving today.
That being said. rainfall is still expected to "average" one
tenth of an inch or less in most places. However, locations
seeing a briefly heavier few showers (or a TSRA) could see a quick
one-quarter of an inch of rain.
High temps should be a few degrees lower than Wednesday for most
places. The NW mountains may struggle to climb out of the upper
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.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Precip chances get much lower after sunset, but a few cells may
survive until close to midnight. Then the light wind overnight
could allow for fog to form as the moisture/dewpoints will be much
higher than the last few nights - especially after many places
have some rain on Thursday.
While there should be a lull in the showers later tonight and
Friday morning, the CAPE gets high again in the afternoon -
possibly much higher (maybe twice) than Thursday. However, even
with CAPEs in the 2000J/kg range, the models generate only
scattered convection. This may have more to do with a lack of
forcing as there is no short wave to help convection along. Will
hold the course with 30-40 POPs at this point with the better
chance for a shower over the ridges. Once again, the showers
should pop up over the mountains first - but may just rain
themselves out of existence with almost no shear at all. What rain
does fall could be heavy with almost zero storm motion and PWATs
will still be above 1 inch.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The large scale pattern has a decidedly summertime look and feel
to it through the Memorial Day weekend and into next week with
light winds aloft and a prevailing ridge across the northeast
CONUS. Temperatures will average above normal with the core of the
`hot` weather front-loaded Friday-Sunday before trending modestly
toward late May/early June climatology. Precipitation risk early
in the period should be characterized by diurnal convection with
the highest probs occurring during peak afternoon heating,
augmented at times perhaps by weak disturbances drifting through
aloft. Max POP may be centered on or around Memorial Day as a weak
shortwave suppresses heights as it passes by to the north and some
interaction takes place with `tropical` system migrating toward
the southeast U.S. coast. Latest NHC forecast says this area of
disturbed weather has a 30% chance of cyclone formation in the
next 48 hours.
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --High pressure over the region will result in widespread vfr conds
with just a 6-10 kt southwesterly breeze developing and continuing
through late this afternoon.
An approaching weak upper lvl disturbance and subtle sfc trough,
combined with an increasingly moist ssw flow, will produce sct
shra/tsra during the aftn and early evening. Although vfr conds
will predominate, a brief vis reduction is possible associated
with a passing shra/tsra.
Sct evening shra/tsra should become confined to taf sites kmdt and
klns this evening before tapering off, as the disturbance passes
east of the region.
The focus will then shift to the potential of patchy late night
fog under light and variable wind...especially in spots that
receive rain this aftn/evening. A moist swrly flow ascending the
mtns could also result in ifr cigs at KBFD late tonight, as latest
mdl soundings and SREF prob data suggest.
Fri...Early am low cigs possible. Isold pm tsra impacts possible.
Sat-Mon...Isold pm tsra impacts possible.
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