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FXUS61 KPBZ 211207

Area Forecast Discussion
National Weather Service Pittsburgh PA
807 AM EDT Mon Oct 21 2019

One more warm afternoon then a cold front brings rain and breezy 
weather tonight and Tuesday. Near average temperature with dry 
weather are expected the remainder of the week.


No changes to the ongoing forecast outside tweaking current
temperature trends. Previous discussion below...

Light wind and limited cloud cover overnight has resulted in patchy 
fog development overnight across the region, in addition to steam fog
along area rivers. Fog will begin to lift/dissipate mid-morning as 
lower levels begin to mix. Dry conditions are expected today with 
daytime highs 10-15 degrees above normal, increased southeasterly 
flow, and increasing cloud coverage as a deepening closed upper low 
advances toward the Upper MS Valley.

Low levels will remain mixed tonight as the associated frontal
boundary approaches and sfc pressure gradient increases, resulting in
relatively mild temperatures. Latest guidance has trended back onset
of precipitation and do not anticipate rain to begin entering eastern
Ohio zones until early Tuesday morning.


Rain coverage will expand from west to east Tuesday morning. Strong 
forcing for ascent of precipitable water in excess of 1.40" (+ 90% 
climatological average) should support periods of moderate rainfall 
through Tuesday morning as the cold front quickly advances through 
the forecast area. In general, expect 0.5 and 0.75" of total
precipitation with the majority of that occuring between daybreak and

Dry conditions will then resume as high pressure quickly builds back
in behind the front during the afternoon support a drying trend 
Tuesday behind the cold front. Gusty winds and persistent cloud
coverage expected behind the front with strong CAA. Clearing is
overnight, but gusty winds will continue through Wednesday. Latest
guidance agrees well with analogs which support max gusts around
30kts across the region.


Model consensus suggests return flow ahead of a deepening Plains 
trough which supports seasonable temperature in the long term. 
Precipitation chances will be dictated by shortwave activity in SWly 
flow aloft ahead of the aforementioned trough. At this time best
chances for precipitation look to be later in the weekend.


Medium confidence forecast as several sites teeter with river valley
fog. Any fog will dissipate by 14Z as wind will start to pick up 
with sustain speeds between 10-14kts and gusts exceeding 20kts. 
Highest speeds will be at LBE and HLG this afternoon. VFR weather can
be expected the balance of the day with scattered to broken cirrus. 
As a cold front gets closer cigs around 6-7KFT arrive by late 

Low level wind shear will be a concern given strong winds just above
the ground overnight. Did not include it in the terminals yet,
however the time window for the greatest threat resides between 4Z- 

As the front gets closer widespread rain arrives after midnight. 
Rain will start at ZZV after 4Z then reach western PA terminals
around 9Z. The trend continues for a later onset of rain and would 
not be surprised for a later time /1-3 hours/ than what is currently
forecast. Eastward progression of precipitation is slow from Ohio to
Pennsylvania since the larger time gap in onset time between ZZV and
PIT than normal. 

Widespread MVFR restrictions are expected Tuesday afternoon as the
cold front crosses. Wind gusts perhaps over 30kts are possible 
Tuesday afternoon through much of Wednesday.




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