Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 210525

Area Forecast Discussion
National Weather Service State College PA
125 AM EDT Fri Oct 21 2016

A storm system will move into Western Pennsylvania later today and
this evening. The associated cold front will move slowly across
the state tonight and Friday. Windy and much colder weather will
move in for the weekend with the first bout of lake effect and
upslope rain and snow showers Saturday into Saturday night.


Serious flooding ongoing from southern Centre County ENE through
southern Clinton County as a stripe of 4 to 6"+ of rain has fallen
since 900 PM Thursday evening. Water rescues are ongoing in Howard
and customers are trapped in the Milesburg McDonalds where Dual
Pol estimates of 7.2" have been indicated. Now hearing 911 traffic
of rock slide in Lewis Township/Lycoming County as of 115 AM EDT.

Training persists and heavy rain threat is concentrated from
eastern Centre County through central Clinton/Lycoming Counties
through 3 AM and beyond...with an additional 2"+ expected in many
areas. FLood Warnings continue in a stripe from central Centre
County to the Sullivan/Lycoming/Bradford County border.

Additional heavy rain...but much lighter than the flooding rains
which have occurred across the central mountains...will be
targeting the NW Mountains in the pre dawn hours...thanks to
strengthening upper jet entrance region which will support strong
deep layer frontogenetic forcing moving slowly across the forecast
area, through the first half of Friday.

The front and area of rain will progress slowly eastward
overnight by morning.


There`s good consensus that the wavy front will have cleared at
least the western half of the forecast area by mid day to be east
of the entire forecast area by nightfall. Showers along the front
will transition onto a steady moderate to heavy soaking rain as
the front passes. The wind will shift to the NW and become gusty
along with steady or falling temperatures after the frontal

By late day we should see the rain finally starting to taper off
and become more showery.


A major change in the weather pattern is expected to occur early
in the period which could yield the first taste of snow over parts
of Central Pennsylvania. An anomalous upper level trough will
close off and take on a negative tilt, with a deepening coastal
surface low tracking from southern New England north and west into
eastern Quebec. Strong cold advection on the backside of the low
along with 100-150m height falls and dynamic cooling within a
pivoting deformation axis could result in a rain/snow transition
Friday night into Saturday morning. The 20/12Z operational
EC/GFS/NAM/CMC generate a coating to 1 inch of snow over parts of
the Alleghenies and Laurel Highlands. Confidence in accumulation
is still low but odds would seem to be increasing. For now will
continue to mention rain/snow in the wx grids with no accums.

A seasonably cold and brisk northwest flow will grip the area
into the weekend with lake effect and orographic rain and snow
showers likely over the Northwest Mtns and Laurel Highlands on
Saturday. There is still a low risk for coating into Saturday
night with accums very hard to come by during the daylight hours
this early in the season. 25-35 mph wind gusts will add an
additional blustery chill to below normal temps.

GFS/EC/CMC all show a fast-moving low diving through the Great
Lakes and Northeast into early next week. There is better
agreement with this system embedded in the WNW flow aloft passing
to the north of the area with max POPs over the far northern
tier. This feature will reinforce the cold air aloft at least into
Tuesday before strong warm advection commences through midweek.
The models show a low near the Great Lakes by the end of the
period with some hints a at a cold air damming pattern at low
levels with high pressure retreating into New England. Overall
not much pcpn expected Mon-Wed.

Temperatures will be noticeably colder by the weekend with highs
in the low 40s to mid 50s on Saturday. Expect some moderation on
Sunday followed by a steady to cooling trend with readings
averaging near to below normal through next Wednesday.


Adjusted 06Z TAF package for current radar. UNV and IPT
near the back edge of the heavier showers and storms. Another
hour or so for heavy storms.

Next batch of rain later tonight into Friday will be in the
form of more of the way of rain, instead of showers and storms.

Rain could linger into Friday evening, so did not try to end
rain too fast in 06Z TAFS.

The convective type of rain we had so far will give way to
widespread showers and lower ceilings and visibilities later
tonight into Friday, as a cold front moves into the area.

Front will be slow to move east of the area before late Friday.


Sat...Scattered showers with restrictions NW. Brisk NW wind.

Sun...No sig wx.

Mon...Mainly VFR. MVFR with rain showers possible NW.

Tue...No Sig Wx.


Flash Flood Watch through this afternoon for PAZ004>006-010-


NEAR TERM...DeVoir/La Corte/Tyburski
LONG TERM...Steinbugl
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