Area Forecast Discussion
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FXUS61 KPBZ 181842

Area Forecast Discussion
National Weather Service Pittsburgh PA
242 PM EDT Sun Mar 18 2018

High pressure will maintain dry weather and seasonal temperature
into Monday. Low pressure then is likely to bring a wintry
precipitation mix to the region Monday night and Tuesday.


A few high clouds are possible tonight as high pressure moves
ewd and flow aloft becomes more zonal. Given the lack of clouds
and expected light wind, radiational cooling will support a
rapid drop in temp post-sunset.


A generally-sunny morning will be supplanted by increasing
clouds through the day as low pressure from the Plains crosses
srn IL/IN. The response to the approaching sfc reflection of
this wave will be nely sfc wind and attendant reinforcement of
a cold sfc airmass.

Models remain in general agreement on a swd focus for
precipitation Mon night and Tue, echoing the earlier swd
deviation noted by the previous forecast. The reasoning noted
by the previous shift seems in line with current model
depictions, so little deviation from their wx process was made.

Some combination of FZRA and snow will affect the higher
elevations amid stronger warm-air advection aloft, while rain
(and eventually snow) will affect the lowlands as cooler air
advects swd into the trough. Where snow does occur, snow ratios
will be limited owing to warm air aloft approaching 32F---
especially in the ridges--- which ought to preclude need for
anything more significant than an advisory.

Where headlines are concerned, snow totals or FZRA presence are
likely to warrant a Winter Weather Advisory in the ridge zones.
Added Indiana County to the Hazardous Weather Outlook map, as
the higher terrain in the ern section of the county could be
affected by such wx.

For at least a portion of Tue, shortwave ridging in advance of
a digging Lower Ohio storm system should diminish PoPs, while
temperature rises into the 40s amid warm advection ahead of low
pressure encroaching upon the Lower Ohio.


The ECM, GFS and ensembles are in general agreement on
formation of an Eastern CONUS-to-coastal, southern-stream
trough for the mid- to late-week period. This pattern suggests
periodic, active wx for the remainder of the extended timeframe.

Given the projected weakness of the upper- and mid-level wind
field, a damp, light snow/snow showery period is envisioned for
Wednesday as cold advection in the low levels is intensified on
the wrn flank of coastal low pressure. Thereafter, a dry, but
cool, period is expected to close the work week as surface high
pressure builds under nwly flow aloft.

A wet and cloudy Saturday appears probable as the upper-air
pattern amplifies, and waves in the nrn and srn streams
interact as they approach the region.


VFR conditions will continue through the TAF period under high
pressure. High clouds will begin to appear overnight and thicken
somewhat on Mon. West to northwest wind of around 10 knots will
become light and variable tonight, and become light out of the
northeast on Mon.

Restriction potential returns with low pressure Mon night
through Wed.





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