Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
805 PM EDT Monday Jul 6 2015
a weakening upper low will track east across the region tonight.
A cold front will approach Tuesday night...and stall along just
south of the Mason Dixon line for midweek.
Near term /until 6 am Tuesday morning/...
23z regional radar loop showing convection decreasing in coverage...as
blyr begins to cool/stabilize. Weak shear and non-existent dcapes
imply a very low chance of severe weather. Main concern through this evening
continues to be isolated flooding from any training thunderstorms and rain. Wet
ground/low ffg values make the area abnormally susceptible to
flash flooding. Latest hrrr indicates the potential of isolated
amts over 1 inch between 00z-06z. Will continue to highlight flood
potential in the severe weather potential statement and hold off on a flash Flood Advisory due to isolated nature of
Expect rain showers to dwindle west/loss of heating after sunset. Focus of
remaining convection overnight should be focused along remnant ll
jet and plume of greatest moisture/instability. Near term models
move this feature from the central mountains early this evening to
the susq valley by 03z...then east of the County Warning Area after 06z. Given
abundant low level moisture...temperatures will not fall much overnight.
This will leave the region muggy with lows running several degree
Partial clearing...combined with wet ground and a nearly calm wind
should result in at least patchy fog overnight.
Short term /6 am Tuesday morning through 6 PM Tuesday/...
remnant upper low will be pushing east of the area Tuesday...resulting
in a mainly rain-free day. Will maintain just a slight chance of
showers across the eastern counties through early PM. Warming temperatures
in the middle levels will help limit showers and storms across much
of central PA during the PM hours. The exception will be the northwest
mountains...where an approaching cold front will likely push a line of
thunderstorms and rain into the area by early evening. This region is currently outlooked
for a marginal risk Tuesday evening.
High Tuesday will likely be the warmest this week...and about 3-4
degree above normal. 800 mb temperatures temperatures near 17c should translate to maximum
temperatures well into the 80s over most of central PA.
Long term /Tuesday night through Monday/...
the 07/00z model and ensemble guidance is providing a fairly
consistent signal that the area will remain in a low amplitude
quasi-zonal middle/upper flow pattern within the northern stream
westerlies. As might be expected in this pattern...there is low
predictability/confidence given degree of spread and meaningful
differences associated with shortwave details. This largely
unsettled and recently persistent weather pattern for the local
area will be modulated to some extent by retrogression of
unseasonably strong upper trough/ridge couplet off the West Coast
and over the southeast and scentrl U.S. There is broad support for
another mean trough to develop over the northeast/Middle Atlantic
States by next week/July 13th as energy ejecting from California upper low
evolves downstream in the westerlies and teams with vortex over
In terms of sensible weather...a well-defined cold front enters
central PA early Wednesday accompanied by showers/tstms...then
becomes wavy as it stalls out from near the Ohio River/Mason Dixon
line. Expect one or more episodes of precipitation through late week most likely
due to mesoscale convective system remnants or convectively induced lows tracking eastward from
the middle MS/Ohio Valley...but too difficult to Pin Point timing/location
at this point. Fwiw the model bias is usually too far north with
mesoscale convective system activity. Precipitation risk should eventually be enhanced toward the
end of the period into early next week as California low energy and
associated surface system reaches the Great Lakes.
What we can say with relative certainty is that we do not expect
any heat waves or extended periods of dry weather over the next 7+
Aviation /00z Tuesday through Saturday/...
sent 00z taf package.
Adjusted tafs based on current and expected condtions the
next few hours. Still some showers and isolated thunderstorms
with heavy downpours. Largest storms southeast of unv.
Earlier discussion below.
Conditions over the still mainly rain free lower susq
valley...with reduced conditions continuing over the Laurel
Highlands where showers are more numerous.
Expect shower activity to increase in coverage and spread from
south to north through the afternoon. Showers will tend to be
slow-moving and could produce heavy downpours and local IFR
conditions. The upper low will weaken as it enters central PA
overnight...but we should maintain a risk for scattered showers.
Expect ceilings/visibilities to trend gradually lower overnight given
diurnal cooling...very humid airmass and light winds...with at
least marginal restrictions likely at many sites into Tuesday
Lower conditions Tuesday morning will improve by middle morning to
middle day. A cold front will approach the airspace from the lower
lakes/Ohio Valley by late in the day and shift slowly southeastward into the
airspace Tuesday night/Wednesday before stalling out near PA/Maryland border
Thursday into Friday.
Wed-Sat...VFR/MVFR with periods of rain showers/afternoon thunderstorms.
short term...Fitzgerald/la corte