Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 231955
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
355 PM EDT Mon Oct 23 2017

.SYNOPSIS...
A strong frontal system will push colder air into the region
overnight Monday into Tuesday. A second shot of cold air is
expected this weekend. Overall most of the coming 6-8 days the
region will be in a mean trough thus cooler weather will be the
norm for awhile.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A strong upper-level low to our west is headed our way. Most
mesoscale guidance keeps the more organized rain out of the
region through about 8 PM.

The GEFS 3-hour data and the HRRR suggest most of the rain will
come in a north-south band between about 9 PM in the west and by
5 AM in the east. Meso models imply renegade shower potential
could affect NW areas this afternoon and evening.

But most of the rain will be overnight with showers and perhaps
some isolated thunderstorms. The winds along this line are about
50 to 60kts at 850 hPa so it will be breezy and any strong
convective cores could easily bring 35 to 50 mph winds to the
surface. The v-winds are about 4 to 5 sigma above normal ahead
and along the frontal boundary.

Most areas will have a good 1-3 hour window with the rain. In
the HRRR and the GEFS winds this has a classic NCFRB look so
most of the rain will be close to the frontal boundary.

Rapidly improving west to east behind the line.

Most of the rain should be to our east by 8 AM. Some areas patch
fog in east and a few isolated showers.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Improving day weatherwise as the front pushes farther to our
east. After 15Z the GEFS has no QPF in our CWA.

It will be a cold advection day with potential for some self-
destruct cumulus in the mountains. Strong westerly winds at 850
hPa should easily mix down behind the front. So gusty winds
likely.

The coldest air does not filter in until Wednesday but Tuesday
will be the start of a cooler period. Enjoy would could be one
of the warmest day for some time to come.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Surface ridging indicated over central Pa by med range guidance
late Tuesday through Friday, indicating dry weather for most of
the forecast area. The exception will be late Wed, when passage
of shortwave could produce a few showers across the northwest
mountains. Ensemble mean 925/850 temps are slightly below
normal Wed/Thu, likely translating to max temps from the upper
40s over the Alleghenies, to the upper 50s across the southeast
counties.

This cooler stretch will be short lived as heights and 850
temps rise quickly into next weekend.

Another chance for precipitation will arrive at the end of the
period when a cold front is anticipated next Sunday, bringing
rain to much of the CWA, while colder air and a few waves of low
pressure riding NNW along the front brings the chance of a light
to moderate, and elevation dependent snow event.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Lots of low clouds around today and gusty winds. The strong flow
will produce some low-level windshear issues this afternoon and
evening with winds a few thousand feet aloft in the 35 to 60kt
range. Around 4kft winds will be 50-60kts. Mainly VFR with
areas MVFR this afternoon and evening. A few isolated showers in
far west.

A a line of showers with embedded thunderstorms should move west
to east across our flying area between about 0000 and 1000 UTC
Tuesday which is mainly overnight. Gusty winds are likely and
there could be the rubble of thunder. Widespread MVFR areas of
IFR in rain/showers.

Tuesday will be windy day behind the cold front but this should
improve the CIG/VSBY issues for us. Mainly isolated showers in
mountains in the afternoon. Mainly VFR day after about 14-16Z.

Should be good start to the night Tuesday too.

Outlook...

Wed-Thu...Sct showers/low cigs possible especially KBFD/KJST.

Fri...Mainly VFR with chance of showers wrn 1/2 Fri night.

&&

.CLIMATE...
Through 10/22/17, the average monthly temperatures at
Harrisburg and Williamsport are 63.8F and 61.8F. When compared
to the maximum 1-month mean avg. temperature for previous
Octobers, both would rank as the warmest on record. Computing
a daily avg. temperature when only taking into account the first
22 days of the month and comparing to the previous Octobers,
the rankings are #2 at IPT and #3 at MDT.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Fitzgerald/Lambert
NEAR TERM...Grumm
SHORT TERM...Grumm
LONG TERM...Lambert/Gartner
AVIATION...Grumm
CLIMATE...



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