Area Forecast Discussion
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FXUS61 KPBZ 192250
Area Forecast Discussion
National Weather Service Pittsburgh PA
550 PM EST Thu Jan 19 2017
Rain will return to the region late tonight and Friday as the
next upper level system moves through. The mild pattern continues
through the weekend.
.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --Hi-res and synoptic models have largely come into agreement with
regard to the overspread of rainfall through the night tonight
into Friday morning. This favors a timing for the start of
rainfall around Pittsburgh likely just before 12z/7am.
Even while dewpoint depressions are rather wide off the ground
this evening, warm advection working in tandem with moisture
transport keep the thermal profiles way, way, way above freezing
off the deck. When you combine this with the fact that boundary
layer wet bulb temperatures are already above freezing, this means
all areas should experience purely liquid precipitation.
Rain will continue to the northeast on Friday as the negatively-
tilted mid-level trough axis shifts northeastward. Rain will end
behind the axis from southwest to northeast in the latter half of
the day as both lift and layer moisture wane. Fries
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.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Although different models show isolated showers through this
period, have decided to go with a dry forecast Friday night and
Saturday, and chance pops Saturday night since there should not be
much to provide any sort of organized lift. This should be the
warmest stretch of the forecast, with lows only dropping into the
40s and many locations reaching the 60s on Saturday.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
A strong upper low will develop over the Southern Plains Sunday and
track eastward into early Monday, before turning toward the
northeast Monday night and Tuesday. While the GFS and ECMWF keep
the surface low moving along the Atlantic coastline, the NAM keeps
the surface low as far west as Kentucky, and have not used the NAM
during the early part of the extended forecast. The GFS and ECMWF
are trending farther east with the track of the system, and while
they are in good agreement, this track may result in the
widespread precipitation shield also being farther to the east.
Nevertheless, have still kept likely pops in the forecast for now
from Sunday through Monday night. After a brief break in
precipitation Tuesday, GFS and ECMWF are in good agreement showing
low pressure moving across the Great Lakes Wednesday and Thursday,
and have gone with chance pops. Although temperatures will be
lower with multiple storm systems, the forecast remains well above
.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
IFR cigs will persist as low level moisture remains trapped under
building high pressure. A brief break is possible overnight
shortly before the next disturbance returns rain and IFR/LIFR
Restrictions are likely with low pressure Friday, and again on