Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1114 am EDT Tuesday Jun 2 2015
an upper level low will nearly stall over the Ohio and Tennessee
valleys through Thursday...with rainfall chances mainly south and
east of Pittsburgh. Temperatures will rise to more seasonable
levels as the week progresses.
Near term /until 6 PM this evening/...
cloud shield is slowly starting to break up across far northern PA
as NE winds funnel in drier air. Its still a tough call how far
partial clearing gets this afternoon. Latest hrrr has it reaching
the I-80 vicinity. This agings well with the ongoing forecast.
Farther south...soundings illustrate deeper moisture and dewpoints
staying within a few degrees of their current readings...so mostly
cloudy/cloudy works. With the overcast sky temperatures will be 15 to 20
degrees below normal...however most locations should see at least
60f. The record low high for Pittsburgh is 51 and we are already
at 57 which means its safe for another year.
As for measurable precipitation...baroclinic zone remains draped along
The Spine of Appalachians and with weak pockets of DCVA riding
northeast coupled with a saturated column yields isolated showers
for the afternoon over the mountains of northern WV and western Maryland.
Short term /6 PM this evening through Friday/...
strong consensus exists on a closed upper cyclone traversing the
Tennessee Valley early in the period with the lower half of the
troposphere at least featuring easterly flow over the County Warning Area. This
should allow for moisture creep into at least the southern half of
the County Warning Area...as well as allow for some interesting wind features for
Wednesday. Model solutions favor fairly strong easterly flow at
the ridgetops...with strong lapse rates below the ridgetops and a
stable layer near the ridgetops. This seems as though it would be
conducive to downslope wind gusts on Wednesday. There does not
seem to be enough momentum in the column for them to be of much
concern...however easterly gusts of 20-30 kts would seem plausible
in Westmoreland and Fayette counties.
In general...the pattern evolves very slowly through the remainder
of the week as the upper low over the southeast slowly migrates
toward the coast and eventually weakens. This slowly turns our low
level flow from the east to the northwest by late in the week.
This flow change will allow for a bit of colder air aloft to run
into the area...increasing lapse rates by Friday...which should
allow for a chance of showers and thunderstorms.
Temperatures through the short term indicate a warming trend as
stratus finally gives way to better mixing and more insolation as
the upper low loses its definition. Fries
Long term /Friday night through Monday/...
model and ensemble guidance continues to favor the passage of a
northwesterly cold front on Saturday...which should finally bring
a drier period with ample sunshine behind it. However...the
improved conditions will likely be short-lived as the consensus
favors cyclonic flow reestablishing itself over the County Warning Area by early
next week...meaning a southerly dropping of the jet axis and
a better chance the strong track would favor wet conditions again
by early next week. Fries
Aviation /15z Tuesday through Saturday/...
improvement to low MVFR is occurring almost everywhere this
morning. However...with the upper low remaining situated over the
south...and ridging aloft...we may be in a stratus deck for most
of the day. Will offer an optimistic forecast which brings most
sites to VFR this afternoon...but confidence is low.
Outlook.../Tuesday through Saturday/...
conditional restrictions are expected into late week as upper
trough remains entrenched over the eastern U.S.