Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Pittsburgh PA
1243 am EST Sat Dec 27 2014
dry and mild conditions today. A cold front will bring the next
chance of rain tonight and Sunday.
Near term /through today/...
overnight in good shape. Just minor adjustments to clouds and
Upper level ridge will swing through today as surface high
pressure heads off the East Coast. Wind direction will be
conducive to warm air advection...shoving what's left of the cold pool aloft well
to the northeast this afternoon. Still some timing issues between
models with the speed of the surface front and how much shower
activity will accompany the boundary. Will lean toward a bit
slower of a solution...as the upper level support is well to the
northwest. This will provide a dry forecast today.
Short term /tonight through Monday/...
timing and location of front and precipitation shield become an
issue tonight and Sunday. Feel confident that most areas will see
showers tonight with the passage of the boundary...however
confidence decreases Sunday on location of the precipitation shield and
how fast the colder air moves in. The bulk of the precipitation should
remain in the warmer air mass...meaning mostly showers. But by
Sunday afternoon...as the colder air begins to dive southward...
models are hinting that some precipitation may linger to the north of
the boundary. This would mean that any precipitation behind the front
will change to snow. Any snow that falls will be light and it will
take time for surface temperatures to react to the colder air aloft...so
any snowfall should be negligible...but it does make for a
On Sunday night...shortwave trough will swing through the upper
Midwest and Great Lakes and surface high will move southward
through the western Great Lakes. This will shove the clouds and
precipitation further south...again differences in model solutions here
make for a difficult forecast. Will lean toward the drier solution
but with low confidence.
On Monday...high pressure moves through the Great Lakes. Sunday's
front will have stalled over the middle-Atlantic and a surface wave
will move through the southeastern US. A large portion of the
cloud cover should be confined to the far south Monday. The wrench
in the forecast will arrive Monday afternoon as a jet streak will
move through the far south increasing the lift and moisture. Models
are spitting out some light precipitation...mainly over the southeastern
ridges...Monday afternoon. This is when temperatures aloft and at the
surface will become crucial. Will use a blend of model solutions
here and leave in chance/schc probability of precipitation with this feature.
Long term /Monday night through Friday/...
the extended will largely be dry with a decreasing trend in
temperatures as a broad trough in the longwave pattern slowly sags
south across the eastern Continental U.S..
Aviation /06z Saturday through Wednesday/...
crossing shortwave is expected to have sufficient relative moisture to
spawn some stratocu early this morning. Low end VFR...MVFR ceilings
forecast will thus be retained for several hours with dominant VFR
quickly rtng by late morning.
Condition deterioration to genl MVFR can be expected aftr dark as
cold front draws near the region.
Outlook.../Saturday night through Wednesday/...
periodic restrictions can be expected for the first half of the
week with...and in the wake of a cold front passage.