FXUS61 KCTP 271147
Area Forecast Discussion
National Weather Service State College PA
747 AM EDT Sat May 27 2017
Low pressure will ride to the south of PA this morning and
keep a warm front just south of the state today and tonight. The
warm front will try to work to the north as a cold front
approaches the region on Sunday. The cold front will pass
through on Monday morning. Low pressure will stall over
northern Ontario mid-week and create a slightly cooler than
normal and unsettled stretch of weather.
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
Lightning passing close enough to include a mention for the next
hour or two.
Cirrus and lowering cloud cover are moving in from the west. The
convection which has been producing these clouds has just about
dissipated as it slides to the SE just north of a warm front. The
residual showers/anvil rain will pass through the SW portion of
the CWA this morning. Dewpoints overhead and over MD/WV are
only in the lower to mid 50s, and stability here argues against
mentioning the T word for the morning despite the lingering
presence of T in Central OH. Sprinkles will fall in the Laurels
through 6 or 7 AM before the more-likely time for rain which is
between 7 and 10 AM.
The rain should slink to the SE and dissipate through the
morning. It will be either gone or off to the east of the area
by noon. Places N of FIG-UNV-SEG will likely stay dry, and POPs
will be held below 30pct there. But, we will still mention some
as the flow could still make some sprinkles up that-a-way.
The afternoon looks nice with lots of sunshine in the northwest,
but a bit of a struggle will be had to get sun through the
clouds in the south and east. The proximity of the warm front
just south of the state will mean some cloudiness is expected to
linger across the S. Will keep just a 20-30 POP S of the
Turnpike for the aftn. The chc for thunder does exist along the
MD border, so we will just mention it only there for now, as SPC
does just nick us with MRGL risk mention for any aftn
convection. Maxes will be within a deg or two of 70F. So, take a
break from heating/cooling the house today. Get out and enjoy
an afternoon picnic.
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Clearing across the north this afternoon and evening will not
last too long as the northerly flow from NY will bring some
lake-related clouds in from the north. The low level flow will
be more from the SE in southern PA (north of the warm front).
This could allow crud (a.k.a. low stratus clouds) to creep in
from the south/east. The more-likely places to see the low
clouds will be right along the MD border and up into the Laurels
where upglide due to the elevation change will help aid in
cooling and condensation. Mins will be in the u50s S and l-m50s
Will start to mention a little DZ possible in the SW, but keep
POPs almost nil tonight and Sun AM. As the flow becomes more
southerly in advance of the storm approaching from the west, the
chance for storms increases on Sunday afternoon. The
destabilization will be easiest in the east where less low
clouds are expected, but the deeper moisture is off to the west
and the dynamics are even farther to the west. PWAT goes above
1.5 inches in the west by the end of the day Sunday. Will ramp
POPs up in the west through the aftn, leaving the east in chc or
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A quick transition to increasing deep layer moisture and higher
PWAT air of 1-1.25 inches will occur late Sunday.
A large-scale trough and increasing upper level divergence
(associated with a lead upper shortwave in the west/SW flow)
will lead to a fairly large area of moderately strong uvvel and
a widespread moderate rainfall along and ahead of a cold front.
GEFS Probs for GE 0.50 inch of rain/24 hours ranges from 50-80
percent across the wrn mtns of PA...to generally less than 50
percent across the eastern half of the state. This translates
into very high POPs for measurable rain (90 percent or more)
across the western half of the CWA, to between 70 and 90 percent
across the south-central mtns and Susq Valley.
12Z EC and 12z GEFS are in very good agreement on the
timing/location of the north/south sfc cold front during the
afternoon hours Monday across the eastern half of the state with
weak deep- layer ridging and drying for Monday afternoon and
night. Dry conditions expected Tuesday morning before
significant cooling aloft accompanies a pair of short waves late
Tuesday and later Wednesday.
POPs during this midweek period will be painted as chc -
translating to scattered showers with preference for the
majority of the QPF (albeit quite light at that)to be across the
typical west-nwrly flow upslope prone areas of the Laurel
highlands and NW mtns. The chance for any thunder will be very
minimal Tuesday through Thursday.
Generally dry NW flow occurs late in the week into next weekend as
a 1020 sfc high over the upper midwest Friday evening builds SE twd
the region. Pops Thur night through Fri night will be 30 percent or
After our bout of coolish weather with temps several Deg F below
normal Sunday and Monday, GEFS mean temps rebound back to near or
slightly above normal (even under slightly cooling 850 mb temps)
for Tuesday through at least Thursday. ECENS mean temps are several
deg warmer than the GEFS and Nat'l Blend of Models temps. leaned
closer to the cooler solutions based on the few-svrl deg C of
cooling aloft with near to slightly below 850 mb temps.
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Area of showers should continue to weaken as they move over the
southern 1/2 of the airspace this morning. MVFR restrictions
are likely at JST and may briefly impact AOO. Most of the pcpn
will end around midday with just a slight chance for an isolated
shower to tstm across the southern 1/2 of the airspace this
afternoon. Fog may become a concern later tonight into Sunday
morning based on guidance blend and have added VCFG to all TAFs
Sun...AM fog. Sub-VFR possible in showers/Tstorms Sunday night
Mon...AM showers/low cigs possible.
Tue...No sig wx expected.
Wed...Slight chance of showers/reduced cigs.
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