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FXUS61 KPBZ 191749
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
149 PM EDT Tue Jun 19 2018

.SYNOPSIS...
A meandering front hangs around through Wednesday. Downpours are
possible over northern West Virginia today and farther north
into southwestern Pennsylvania and eastern Ohio Wednesday.
Temperatures will be above normal through the weekend, but there
will be an active weather pattern.

&&

.NEAR TERM /THROUGH TONIGHT/...
Minimal changes were made with the early afternoon update,
primarily updating temperatures behind the frontal passage.

A surface boundary splayed out near I-80 will continue to
trigger showers sagging southward through midday. None of these
showers are expected to amount to much, although we can't rule
out an isolated rumble of thunder.

A humid air mass remains in place today. Surface dewpoints will be
again well into the 60s and nearing 70 over northern West Virginia.
One reprieve we will get is with daytime high temperatures as they
will be almost 10F cooler than Monday. With a baroclinic zone
dropping south of I-70 during the peak heating hours. Showers and
thunderstorms will be most numerous over these aforementioned
locations. Column remains tropical evident by warm cloud depths
exceeding 13KFT and PWATS pushing 1.7". Storm motion will be less
than 20kts so any storm that develops will produce efficient
rainfall. Flash flooding is a threat and confidence is high enough
to maintain verbiage in the hazardous weather outlook. As atmosphere
warms with daytime heating look for convection to pop around noon
when temps climb into the lower 80s. Highest coverage will be along
and south of the baroclinic zone, while locations north of I-80 will
be far enough removed from the front that a dry day is forecast with
lower humidity.

Surface convergence coupled with residual boundaries from evening
convection will keep a trigger in place Tuesday night. It won't
take much for a shower to pop up especially south of I-70 where low
level moisture remains rich. Continued with pops for the better
part of the evening for southern locations per reasoning just
stated.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
Broken record of showers and storms in and around the surface
baroclinic zone continues Wednesday. With H5 anti-cyclone
strengthening the boundary retreats north. This spreads the threat
of high water into the I-70 corridor and perhaps into the Pittsburgh
urban region. Atmosphere will be ripe for heavy rain with PWATS
above 2.0" over much of the forecast area.

Mid level height falls Thursday will create another day with showers
and storms capable of producing heavy downpours. The region under
the gun is once again northern West Virginia. If the same areas get
impacted later Today and tonight then a flash flood watch may be
needed. Nearly all of the 00Z NCEP chain places an axis of 2.5" of
rainfall across the mountain state through 48 hours.

Placement of mid level anticyclone Friday which has shifted farther
northeast than previous runs will allow most of the day to be dry
especially toward the PA mountains and northwest sections of
Pennsylvania.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Highlights:
- Above normal temperatures
- Active pattern
- No heat waves forthcoming

H5 ridge yields to a fairly strong mid level wave traversing through
Saturday. The associated cooling aloft and modest lapse rates will
support showers and thunderstorms most numerous over northwestern
Pennsylvania close to the center of the mid level cyclone. The dry
slot moves across during the morning which could allow the
atmosphere to destabilize ahead of the shortwave trough. This
scenario would yield numerous showers and thunderstorms. A cold
front passes Sunday night, so until it clear the region, look for
chance pops to continue as any weak mesoscale feature will be enough
to ignite a shower. Likely pops work most of the weekend with the
combination of the two weather systems. Right now, no severe
weather nor flooding is forecast at this juncture. H8 temps drop 2-
4C behind the front for Monday so daytime highs will fall back to
more seasonal readings of the upper 70s to lower 80s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR conditions are expected this evening with only the possible
disruption by thunderstorm activity for MGW/ZZV.

Tonight, the cold front will push back to the north spreading
MVFR and possible high IFR from S-N through dawn on Wednesday.
Showers and isolated thunderstorms are possible near dawn
Wednesday, but confidence in thunderstorm coverage is not great
enough for inclusion at this time. Expecting MVFR conditions to
persist well into Wednesday as the surface low slides along the
boundary overhead.

Primarily north-northwest winds will diminish overnight and
transition to light and variable for the remainder of the TAF
period.

OUTLOOK...
Periodic restrictions are possible through Fri as the front
stalls and wavers across the OH Valley region.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

&&

$$
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