Area Forecast Discussion
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FXUS61 KPBZ 170602

Area Forecast Discussion
National Weather Service Pittsburgh PA
1253 AM EST Sun Dec 17 2017

Another upper level disturbance will result in scattered light
precipitation developing later this afternoon. Warmer
temperatures, cloudy skies, and light drizzle can be expected
Monday and Tuesday.



Overall...benign weather is expected overnight with patchy fog
development north of Pittsburgh where small dewpoint
depressions, minimal cloud coverage, and light winds will
support patchy fog development.
changes were needed for that portion of the forecast.
Lows will end up a few degrees above the seasonal averages.

An upper shortwave will approach Sunday afternoon and increase
light precipitation chances, but warm advection is expected to
support rain, possibly a mix for counties north of Pittsburgh.
Surface temperature is expected to be warm enough that no
problems are anticipated.


Shortwave will depart quickly to the east Sunday night, leaving
nearly zonal flow aloft and some uncertainty to boundary
placement through the period as additional weak shortwaves pass.
With no considerable lift apparent in the guidance but plenty of
moisture, expect mostly cloudy conditions and very light
precipitation. At this point, profiles are not even well
saturated above the boundary layer which suggests little more
than drizzle through this time frame. Made only modest
adjustments to the PoPs through the short term to reflect some
of the newer guidance but generally think chance is appropriate
given the likelihood of drizzle versus measurable rain.

Despite expected cloud cover, warm advection should lead to
temperatures at least near seasonal averages.


A broad trough will drop into the central CONUS Tuesday night
sweeping a cold front through the area. This could re-invigorate
showers Tuesday night into Wednesday, but will help drive
temperatures back to near-normal values. Upper-level flow
returns to zonal behind the front, bringing a drier and warmer
trend until the latter part of the week. Models still have
another system/cold front for Friday, but strength and
placement of the low have changed with newest guidance. Will
hold close to the SuperBlend for precipitation details, and look
for clarity in the coming guidance packages.


Mostly clear skies and broad dewpoint depressions will mean VFR
conditions will persist through the morning for most terminals.
However, valley fog spreading north to south through NW PA will
continue to impact FKL and DUJ through daybreak. In addition to this
fog, the low stratus entering southwest NY could creep back
southward and over these two northern ports.

VFR is expected after mid-morning Sunday areawide through the
afternoon. Condition deterioration can be expected by Sunday evening
as another disturbance spreads light precipitation over area

Restrictions are likely through Tuesday, as abundant low-level
moisture may become trapped underneath an inversion for an
extended period. IFR conditions are possible at times.




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