Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
1209 am EST Monday Dec 22 2014
midwestern low pressure will bring warmer temperatures and rain to
the region for the first half of the week. Snow shower chances will
come with the passage of that systems cold front on Christmas.
Near term /through Monday/...
clouds are expd to gradually increase lt tonight into Monday in warm advection. A weak
surface low advancing up the East Coast could bring some precipitation as far west as
Garrett and Tucker counties this afternoon...though evening upper air charts
and mesoscale analysis indicate much if not all of this precipitation should remain
east of our area. If precipitation does reach these locations...a brief period of
freezing rain is possible as temperatures there remain below freezing in cold air damming.
Outside of the higher terrain...temperatures should reach just above seasonal
Short term /Monday night through Wednesday night/...
upper trough will amplify and slowly pivot eastward during this time
frame...becoming more negatively tilted with the help of a
strengthening upper level jet by late Wednesday. Early on...there
still remains some uncertainty in regard to the amount of precipitation
that we will see on Tuesday...as we will be parked in between the
better moisture from the weak coastal system...and the deepening
moisture associated with the cold front to our west. In
addition...S-se wind should help provide some downsloping and drying
just east of the ridges in PA/WV. With this in mind...opted to stay
with the chance probability of precipitation for the day Tuesday. Will increase probability of precipitation
overnight as the low level jet strengths and helps to pull moisture
from the Gulf northward. With the nearly northward progression of
the developing surface low...both the European model (ecmwf) and GFS suggest the bulk
of the heaviest rain will stay just west of the forecast area...with
the best chance for moderate rain to be as the cold front crosses
Wednesday night. This should limit any flood threat for the period.
Strong warm advection will be ongoing through the entire time
period. Even with cloud cover...high temperatures on both Tuesday
and Wednesday should be well above seasonal values with highs
likely to reach the middle 50's.
Long term /Thursday through Monday/...
cold front passage will initiate snow shower chances on Christmas...but
lack of depth to the cold layer...dry advection in the middle levels on the
southern perimeter of northward digging upper low...and rapidly ensuing warm
advection will ensure a lack of snow cover for Christmas.
The remainder of the long term period is prognosticated to feature seasonal temperatures
with a late week cooling trend as models forecast a reamplifying flow
portion with eastern Continental U.S. Troffg.
Aviation /05z Monday through Friday/...
genl improvement to VFR for all taf sites can be expected for the
taf period as southerly flow aloft intensifies over linger surface high pressure.
Outlook.../Monday night through Friday/...
midwrn low pressure will spread rain and restrictions over area ports on
Tuesday and Wednesday. Improvements are expected to be initiated
later on Thursday with dry shortwave ridging.