Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1115 am EDT Monday Oct 20 2014
low pressure moving across the lower Great Lakes will fill in as
it moves overhead or just to the north of the state before re-
forming off the coast. A new low will form off the middle Atlantic
coast Tuesday night and keep breezy and wet conditions across the
area into Wednesday. Conditions will slowly improve during the
latter part of the week...as the storm slowly moves away from the
Near term /until 10 PM this evening/...
surface low or Lake Huron and even some thunder back under the upper
trough/low in northern Indiana. Locally...lots of virga on the radar
but nothing reaching the ground per latest observation and webcams. Temperatures
may be held down just a degree or two from curr maxes. Will continue
to put the measurable precipitation off for another hour or two.
Short term /10 PM this evening through 6 PM Tuesday/...
a parent surface low will slowly translate southeastward into the
eastern glaks tonight as secondary development starts taking place
off the coast by late Tuesday. The result will be continued
extensive cloudiness and increasing chances for showers from west
to east across the state. However...highest probability of precipitation will remain over
the west and especially northwest through the day Tuesday as
deepest moisture and best lift are juxtaposed west of the
alleghenies into the eastern Ohio Valley. High temperatures Tuesday will be a
tad milder across the lower susq...and a tad cooler over the
northwest mountains...with little change in between.
Long term /Tuesday night through Sunday/...
an unusually high degree of model/ensemble agreement is leading
to a high confidence forecast for much of the long term period.
The overwhelmingly dominant main feature to affect the local area
during this period will be a cut-off...meandering upper low and
it/S reflection/mini-ME at the surface. The development takes place on
Monday night as a cold front pushes through and secondary low
deepens over the Middle-Atlantic States/coast. The system will only
slowly slide to the east and northeast through the period.
The position of the storm will keep lots of maritime air flowing
in from the North/East and keep probability of precipitation pretty high from Tuesday into
Wednesday...and perhaps Thursday. The highest probability of precipitation will generally be in
the northern half - especially the NE. But the moisture will wrap around the
storm completely at times. Thus...a moist upslope in the western mountains
will keep shower chances high there as well during mid-week. With all
the clouds and wind...the prospects for any snow are dim. 800 mb
temperatures generally stay well above zero. But Tuesday night/Wednesday am may be
cold enough over The Laurels to have some snow mix in with the
showers on the highest elevs. Have chosen to leave out mentions
of any mix at this point. The core of the cold air is shunted to
our south with help from the circulation of the upper low...which
keeps that maritime air wrapping in to the area.
Eventually...surface high pressure and concurrent upper ridging
should lead to a dry weekend with mild temperatures on Sat. There
could be a weak and dry front drop across the Great Lakes and
middle-Atlantic on Sunday...which may produce widely scattered
showers...but it is not Worth a pop at this point. Temperatures may then
dip a few degrees from Sat-sun.
Aviation /15z Monday through Friday/...
VFR conditions are expected today with middle and high clouds
thickening up in response to an approaching frontal system.
Scattered showers ahead of this front should spread into the
western mountains late in the day. However...widespread VFR
conditions will persist through dusk. MVFR with occasional IFR
conditions /especially in the western mountains/ are expected
Monday night as showers overspread the region.
Tue-Fri...low ceilings poss NE and West Mountains...mainly at night/early am.
Scattered rain showers through much of the period.