Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
357 PM EDT Sat Sep 20 2014
fair weather is expected through this evening as high pressure
moves east of the New England coast. A frontal system will bring
scattered showers and a few thunderstorms to the region on Sunday.
A large area of high pressure and a blocking upper- level ridge
over central Canada will lead to generally fair and cool weather
for most of next week.
Near term /until midnight tonight/...
visible satellite imagery and surface observation Show Low clouds continuing to thin
over the east and increasing high clouds to the west as high
pressure slips east of the New England coast. Fair and much
warmer temperatures than recent day will persist through the afternoon
Save for the high clouds to the west...skies should clear tonight
with min temperatures also much milder than recent days. Any threat of
precipitation should hold off until after midnight.
With the moistening of the lower air mass of the srly flow...expect
areas of fog to develop tonight.
Short term /midnight tonight through Monday/...
digging trough to the west will pull moisture up from the Midwest
and an advance trough will try to make showers in the northwestern cos by
daybreak on Sunday. The main low and upper trough will be offset
enough that the pattern should remain progressive and the main
cold front will pass through Sunday evening. The deep layer shear
and some decent instability in the low levels could produce a few
stronger storms as the front moves through. Quantitative precipitation forecast seems rather
paltry with precipitable waters briefly peaking around 1.5 inches. All the
showers/storms should be moving along steadily. The NAM Cranks up
more showers in the Post- frontal air...and have extended scattered probability of precipitation
through the night and into Monday morning for the western
Highlands. The 800 mb temperatures dip into the +1-2c range for a brief time
on Monday over the northwest. Maximum temperatures will therefore take a tumble rom
the mid70s-l80s on Sunday to the m50s- 70f on Monday.
The long wave trough will deepen as it moves eastward...bringing
in unstable northwesterly flow...which given the flow across the
lake could allow for showers to continue across the northwest mountains
into Monday morning. The limiting factor on Monday is the overall
lack of moisture...which will allow for clearing skies.
Long term /Monday night through Saturday/...
High pressure builds in as the long term is beginning and it sort
of Parks itself over New York and New England with +2 to +3 sigma
above normal mslp anomalies by Wednesday-Thursday. The models seem
to be in fair agreement showing a blocking 500 hpa anticyclone to
the northwest as a massive 500 hpa positive height anomaly of +2
to +3 sigma develops over central Canada by Thursday and into
The models and efs do well forecasting anticyclones so there seems
to be more of a consensus. On the fair weather forecast next
week. Expect diurnal valley fog and low clouds likely to affect
the region each morning once the big high takes hold....and
continuing daily into next weekend. That massive high should
continue the dry fair weather through next weekend. Temperatures
on Monday and Monday evening will be below normal...however
outside of Monday...temperatures there will be a period of near
Aviation /20z Saturday through Thursday/...
surface high pressure exiting well east of the New England
coast...and a cold front moving across the upper glakes today will
create a light to moderate southerly breeze of 8-10 kts with some
gusts up into the upper teens and lower 20 knots range this
Areas of MVFR-IFR ceilings /and MVFR visibilities in light fog/ will likely
form after 07z Sunday...similar to conds earlier this morning.
Aforementioned cold front will move through the state on Sunday
producing isolated to scattered showers and possibly a few thunderstorms and rain.
Period of MVFR to IFR conds will accompany the precipitation starting in
the northwest late morning and spreading east into the afternoon. Highest
chance of impacts will be across the western mountains
Monday...am low ceilings poss West Mountains
Tuesday- Thursday...no sig weather expected.