Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1015 am EST Friday Nov 27 2015
high pressure will gradually relax its grip on the area and yield
to an approaching cold front which will cross the area slowly
between tonight and Saturday evening. The front is expected to
become nearly stationary just to the south of the region over the
weekend as high pressure builds to our north. The front will move
back north early next week and is likely to bring a return of
unsettled conditions that will continue through middle week.
Near term /through tonight/...
830 am update...
lots of high clouds but no precipitation. Front still back over Southern
Lower Michigan and moving slowly this way. Timing of first showers
still looks like afternoon or early evening in the northwestern mountains
initially cool temperatures in the valleys should pop up drastically
when/if they mix out this morning. Have counted on that for the
near term temperature trend. But the high clouds may have something to
say about that.
6 am update...
Satellite continues to show high clouds approaching from the west
ahead of a frontal system that currently extends from Lake
Michigan down into central Illinois and Missouri.
The approach of the front and The Retreat of the high off the
coast will continue the mild west-southwest flow into the forecast area for
one more day. Highs will range from the middle 50s over the northwest to middle
Short range high res guidance suggests the first of the rain
begins to reach my northwestern zones between middle to late afternoon.
The rain will continue to spread south and east
overnight...leading to a forecast with relatively high probability of precipitation but
relatively minor quantitative precipitation forecast. The parent upper shortwave will be getting
absorbed in the upper confluence zone over the northestern US and
Canadian Maritimes...resulting in the feature shearing out
quickly north of the area.
Short term /Saturday/...
the upper flow is made to become parallel to the surface front
overnight and Saturday resulting in it slowing as it moves just
south of the Mason-Dixon line. I leaned closer to sref probability of precipitation which
emphasize the best chance of getting wet Saturday being over the
southwestern half of the forecast area...before the rain settles south of
the border for at least a short time.
Highs Saturday will be noticeably cooler than today...varying
from around 40 over the northwest to middle to upper 50s over the southeast.
Long term /Saturday night through Thursday/...
the medium range starts off with fast quasi-zonal flow over the
northestern US and a weakening Rex block over The Rockies up into Canada.
The upper low under The Block is made to advance steadily east
and eventually up through the eastern gr lakes by middle week. The
end result will be for a cold front/occlusion to swing through and
bring a shot of cooler air for the end of the week.
Until then we will be wrestling with how much if any precipitation from
the quasi stationary front will affect my southern zones later in
the weekend into early next week. Short range operational GFS
shows the precipitation shield settling south of the border Sun afternoon
into Sunday night. The European model (ecmwf) keeps light quantitative precipitation forecast over my Maryland border
counties while the NAM is a blend of the drier GFS and wetter
European model (ecmwf).
As it stands right now...confidence for a period of dry weather
Sunday into Monday is highest for the northern half or so of the
forecast area...with lesser confidence the closer to the southern PA
border one gets.
Near normal high temperatures Sunday and Monday will nose just above
normal for Tuesday...before trending back below normal for middle to
After the middle week frontal passage...we will see a couple of days
of pretty typical cool season Post frontal cold advection flow
with the best chance for rain/snow showers over the western and
northern higher elevations...with probability of precipitation dropping off fast over
central and eastern areas.
Aviation /15z Friday through Tuesday/...
just some MVFR fog left in the eastern sites. Will hold it there for
another hour or two. But some mixing should help them get back to
6sm or better. Otherwise...mainly VFR conditions today and early
tonight with lots of high clouds but little middle/low level
moisture. Cold front moves slowly across the area from northwest
to southeast tonight and Saturday. Rain showers should begin around kbfd
around sunset. They may not affect the southeastern terminals until
sunrise. Rain will be light...but dewpoints rising may create
areas of lower clouds and fog. Showers and lower ceilings and fog
could linger into Sat...especially for the southern half of the area.
Sun...mainly VFR - rain possible extreme south.
Monday...no sig weather.
Tuesday...showers west...VFR east.
near term...dangelo/la corte
short term...la corte
long term...la corte