Area Forecast Discussion
Issued by NWS State College, PA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 252317
Area Forecast Discussion
National Weather Service State College PA
717 PM EDT Sat Mar 25 2017
A cold front will sag south of Pennsylvania this
evening, then return north as a warm front late Sunday and
Sunday night. Unsettled conditions will continue through the
middle of next week before high pressure returns with drier air.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Backdoor cold front just pushing through KUNV last hour,
accompanied by a wind shift to the northeast and a 1-hour temp
drop from 72F to 54F. Near term model output indicates the front
will clear even Somerset County by around 02Z. Parent shortwave
and associated large scale forcing is passing by to the north of
Pa early this evening, so expect any remaining showers across
the eastern counties to dissipate by around 00Z. Later tonight,
expect some patchy drizzle to form over the higher terrain, as
moist easterly flow overspreads the region behind cold front.
Overnight lows will range from the mid 30s over the NE to mid
40s over the SW. These numbers are some 10-20 deg above normal.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The light showers...with areas of drizzle/ridge top fog
are likely to continue through much of the day Sunday.
Local experience suggests we lean away from blended model
guidance for max temps in such low level cold air damming
situations. As such, I lowered tomorrrow`s highs by a few
degrees counting on a day not nearly as nice as today,
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
This period starts out with above normal heights over the
eastern US. Several lows weaken as they move into this blocked
flow and are forced to move to our west.
The first wave is comes overnight Sunday into early Monday. It
has a good surge of moisture and a boundary related to the
cooler weather on Sunday. Thus nearly all guidance shows a very
high probability of rain overnight Sunday into Monday. Most of
the NCEP guidance shows the peak chance of rain from 0000-1200
UTC Monday. Then things improve during the day Monday.
Our POPS Monday may be too high but they are consistent with
nearby offices. GEFS implies little or no rain in our CWA much
after 1800 UTC. Most rain before than would be in the east. Our
850 hPa temperatures are above normal too so should be a warm
later afteroon and evening.
The second wave moving up to our west comes in overnight Monday
into Tuesday. Clearly the uncertainty with this and the longer
forecast length introduces more uncertainty. But at this time
peak rain probabilities are during the day Tuesday but lower
probabilities than the first event.
The second event will push the warm moist air to our south
Tuesday night into Wednesday. Chance of rain should drop
overnight Tuesday into Wednesday. Wednesday should be a
relatively good day as high pressure builds in from the
northwest. The dry air and high pressure are in all the guidance
implying Wednesday and Thursday should be relatively nice days.
High pressure, dry air, and normal to slightly below normal 850
hPa and 925 hPa temperatures imply near normal daytime highs.
The storm track shifts to our south and some models show a
southern stream wave Thursday night and Friday. This could bring
clouds to our region. GEFS and CMCE imply we could be on the
northern edge of an expanding precipitation shield Friday and
Saturday as the southern stream wave slides to our south and
east. Thus POPS increase Friday and Saturday. Could be a cold
rain across south-central PA Friday and Friday night.
.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --Can see the cold front on the radar earlier, just south and
west of the office.
CIGS not real low, even at BFD. For 00Z TAF package, did slow
down how fast conditions go downhill.
Overall expect a wide range of conditions later tonight into
Sunday, as colder air just to the north trys to work southward.
Conditions could improve some late Sunday afternoon, before a
band of showers moves eastward from the Ohio Vly.
Things could improve some on Monday, as some models bring the
warm front back north of the area.
The cold front could sag southward of the area on Tuesday, but
perhaps not by much.
Mon-Tue...Sub-VFR with periods of rain.
Wed...Chance of showers across the south early. Becoming VFR.
Thu...No sig wx.
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NEAR TERM...Fitzgerald/La Corte
SHORT TERM...La Corte