Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
620 PM EST Friday Dec 19 2014
building high pressure is expected through the weekend.
Near term /until 6 am Saturday morning/...
with 615pm update...have made only minor changes to sky and
hourly temperature forecasts. Stratus has not shown any signs of
scattering out yet...and will continue mostly cloudy forecast at
this point. Previous discussion follows.
The upper trough will depart east and be replaced by ridging
tonight. Model profiles suggest that some moisture will remain
trapped under the building upper ridge...preventing US from
clearing out this evening. This isn't completely clear cut...but
will opt to keep mostly cloudy wording unless satellite
observations show otherwise. Did drop temperatures for the rest of the
afternoon as cloud cover should keep temperatures from warming
much above current values. Lows tonight were kept near met
Short term /6 am Saturday morning through Monday/...
high pressure ridge will settle over the northeastern Continental U.S. For
much of the weekend. A fast moving system will be suppressed to
the south Saturday but some middle-High Deck may replace the low
deck...maintaining mostly cloudy skies through much of the day.
With nearly stagnant 850hpa temperatures and minimal sun
tomorrow...expect highs will not surpass the low to middle 30's.
However...southerly flow and warm advection will return for Sunday
and Monday bringing temperatures to near or just above normal
On Monday...we will be in The Squeeze between two systems. One low
will be developing along the Gulf Coast...while another low and
deepening upper trough will sink southward over the central US.
This low over the Central Plains will help to amplify the upper
pattern...ejecting the southern system northward. At this point
the bulk of the moisture with the southern system should remain
east...just brushing our eastern mountains of WV/Maryland until the cold
front with the deepening low approaches. Maintained chance probability of precipitation
for the ridges with lower probability of precipitation further north and west through
Monday. While the middle levels will be warming...cannot rule out a
rain/snow mix initially Monday morning over the ridges before
changing to all rain. Some freezing rain could also be of concern
in any sheltered valleys...but for now will leave this out.
Long term /Monday night through Friday/...
models are in general agreement on deepening upper level closed low
over the Great Lakes Tuesday through Thursday with periods of rain
into Wednesday until cold front will change precipitation over to snow
showers later Wednesday and Thursday. Winds will be on the
increase Thursday as surface low wraps up north of the region. Quantitative precipitation forecast
on the front side of system will be near an inch...which should
not produce any significant problems. Backlash snow Wednesday
night into Thursday will be light with only minor accumulations
expected. Flow behind cold front looks to stay southwesterly which
looks to limit lake enhanced amounts along I-80 and the ridges.
Colder temperatures will then moderate Friday as middle level flow
quickly becomes zonal.
Aviation /23z Friday through Wednesday/...
pervasive stratus covers all sites this evening...while boundary
layer moisture has dropped off from earlier today. Given strong
inversions...stratus seems likely to continue for the next day at
least...however given a bit wider dewpoint depressions...light
precipitation chances seem very low. MVFR conditions seem likely
to continue. Fries
Outlook.../Saturday night through Wednesday/...
stratus and restrictions may persist into the weekend. Next storm
system will bring restrictions Tuesday and Wednesday.