Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
713 PM EDT Tuesday Jul 7 2015
a cold front will approach tonight and stall near the Mason-Dixon
line by Wednesday morning...keeping rain chances in the forecast.
Near term /until 6 am Wednesday morning/...
a front is currently sagging southward into Northern Ohio at this
hour...with abundant moisture streaming up ahead of it. Model precipitable water
values are in excess of 2 inches over much of the County Warning Area...and given
that the upper flow is fairly zonal over the area...while the
middle-level wave pushing it southward this evening will likely
continue to do some for the next several hours...upper flow does
not favor a substantial southward push of the front through the
area over the next 48 hours. As such...deep moisture will become
more relegated to the southern fringes of the area briefly by
tomorrow...however a strong air mass change is not really
expected. Thus...with the frontal boundary likely to linger over
the southern tier of the County Warning Area...the heavy rain threat will continue
into the overnight hours.
Abundant moisture and a slow frontal movement seem likely to hold
temperatures up across the southeastern portions of the area.
Elsewhere...a bit of a lowering of dewpoints may allow for some
cooling relative to last night across the northwestern portions
of the area. Fries
Short term /6 am Wednesday morning through Friday/...
tonight's cold front will essentially stall out along the
Pennsylvania-Maryland border on Wednesday...with low pressure then
riding along the front. Majority of rain should be done by
Wednesday morning...with bulk of rain contained to the ridges by
the afternoon. Although a slight chance of thunder was kept in the
forecast during the morning...conditions should stabilize by the
afternoon and have pulled thunder from the forecast for that time
period. With the low off to the east...the chances for rain from
that system should diminish as the next low pressure system moves
to northeastern Indiana by Thursday morning and races to eastern
Pennsylvania by Thursday evening. This will bring another round of
showers to all locations...although models have not come into
agreement on where the axis of heaviest rainfall may occur. High
pressure will build into the region Thursday night...and may
persist long enough to keep Friday dry. In fact...Friday may be
the only dry day through the next 7 days. Temperatures will remain
below normal through the period.
Long term /Friday night through Tuesday/...
very little change to previous forecast as frontal boundary will
waver across the region through the period...with hard to time
shortwaves moving east in generally zonal flow. Daily chance probability of precipitation
continued with temperatures close to wpc forecasts.
Aviation /23z Tuesday through Sunday/...
mostly VFR this afternoon with gusty SW winds from 10-20 knots.
Spotty rain showers and a couple thunderstorms and rain may briefly impact a terminal...but
chances/duration too low to include in taf at this time. More
general rain chances arrive ahead of a front after 23z or so near
zzv...to around 01z at pit...and 04z at mgw. Expecting generalized
MVFR when the rain arrives this evening...and tried to time some
IFR tempo conditions in heavier rain as well. Expecting most
terminals to drop to IFR or even LIFR overnight with abundant
moisture and frontal passage. Precipitation coverage decreases by 12z as front
hangs up near the Mason/Dixon line...but expect only very slow
improvement to MVFR by midday.
Outlook.../Wednesday through Saturday/...
front will waver across region through the period with periodic
Maryland...Flash Flood Watch through Wednesday morning for mdz001.
Ohio...Flash Flood Watch through Wednesday morning for ohz059-068-069.
PA...Flash Flood Watch through Wednesday morning for paz021-029-031-
WV...Flash Flood Watch through Wednesday morning for wvz003-004-012-