---

Maps

Surface Map at 7:00 AM EST	NWS Snow Squall Warning for I-287, I-476, and I-280	CTP Special Weather Statement	NWS Snow Squall Update

---

Photos & Video

NWS Update Tweet	NWS Snow Squall Awareness Tweet	NWS Snow Squall Update Tweet	CTP Special Weather Statement

---

Storm Reports

 

437 

FXUS61 KCTP 210944

AFDCTP

 

Area Forecast Discussion

National Weather Service State College PA

444 AM EST Wed Nov 21 2018

 

.SYNOPSIS...

An arctic cold front will push through the area today ushering 

in fair weather, but also near-record cold temperatures for 

Thanksgiving Day and Friday morning. Temperatures will moderate

over the holiday weekend with a new storm system likely to move

into the region for Saturday into Sunday.

 

&&

 

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Wind already gusty over the west even before the front. The wind

will get a little stronger through the day with sustained

10-20mph and gusts near or above 30mph, esp on the ridges and

along the front/in squalls. 09Z radar mosaic shows a batch of

light returns over wrn PA much like yesterday. The clouds from

this patch of lift will pass rather quickly, unlike yesterday 

where the lift was broader and lasted longer. This trough aloft 

is moving quickly and is rather small. Therefore, there could be

some better sfc heating/llvl instability with those higher 

clouds moving out of the way. The 8H temps drop even further 

today, with the -8C contour corresponding to about when the 

front is expected to pass. Interestingly, the snow squall 

parameter is not as strong as it was yesterday with this 06Z run

of the NAM. This could be an indication that the ferocity of 

the expected squalls will not be as bad as previously thought. 

However, it is not enough to back off the mentions of sct SQSN. 

The most likely timing is still pretty solid with the front 

going thru BFD around 17-18Z and FIG/UNV/IPT around 20-21Z. The 

west wind ahead of the front will be a negative for the stronger

snow showers/squalls making it into the Lower Susq Valley. Many

hi-res models/HREF members drop all QPF and any CAPE by around 

the time the front gets to an AOO-SEG line. As with yesterday, 

the moisture is meager, and it even drier with dewpoints about 

5F lower than matching times from Tues, and mixed layer not as 

tall/deep today. However, the models do hold onto the 

indications of precip farther to the south on the whole. The 

lift from the Laurels should keep the stronger/gusty snow 

showers going into the early evening.

 

Since SPSs for snow squalls and perhaps even an SQW is possible

today, we will not issue the all-day type SPS at this point.

Will continue to mention the possibility of squalls in the HWO,

since SQWs are possible today. 

 

Maxes in the downslope could get in the m-u40s in Lanc/York cos.

The rest of the area will range from near freezing in the

highest elevs to the lower 40s. These >32F temps could cause 

problems if the roads are above freezing as a strong squall and

the front were to move through, and rapid cooling/snow accum 

was to then take place.

 

&&

 

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...

Any SH/SQSN should be all but done by sunset, as CAPE will be 

gone, and the lift from the front will be balanced by the

downslope SE of Blue Mtn. There could be a few SHSN survive over

the Laurels through 00Z, but the flow then becomes NNW, and

yields a fetch off LM. This could produce a brief period of a

few hours where there could be 1-2" accumulate on the west-

facing slopes of the Laurels. Otherwise, the cross-lake fetch is

very short to make any appreciable snow in the nrn mtns. The

fetch off LO could actually push a few LES bands into the far NE

(Tioga/Sullivan Cos) later tonight. The cold and very dry air 

mass, lowering subsidence inversion, and non-favorable fetch 

will kill off the SHSN later tonight. Mins will be very much

below normal for this date, and could make record mins. The

more-likely places to set records would be the nrn half of the

area in protected valleys. The wind never really quits, so the 

mixing could keep temps just above record lows. Wind chills do

drop below zero on the hills late tonight and in the morning.

 

The sunshine promised for Thanksgiving Day these past few days

is still on tap for the SE, but the sun will at first be hidden

by a few clouds in the NErn counties. Then, a patch of lift

aloft will spread some higher clouds over the west/north through

the day. Overall, mostly sunny will be a good call. Maxes could

stay down below guidance if the clouds do get thick. But, the

going maxes look fine. See the climo section below for a listing

of record temps. The coldest period and most likely to drop some

records might actually be Friday morning. The sky should be

mainly clear and widespread single digits are expected across

the nrn half of the area. It is not out of the question to see a

0F min or two in the nrn mtns, esp the NE where the wind should

be calm most of the night.

 

&&

 

.LONG TERM /FRIDAY THROUGH TUESDAY/...

Friday looks cold and mainly sunny. High pressure overhead in

the morning will slide east, and a southeast flow will start up.

Temps should be in the black compared to Thurs, though, rising

some 5-10F higher in the aftn. 

 

Expect precipitation to return to the area on Saturday. The

retreating cold airmass sets up the potential for precipitation

to start as snow or a wintry mix before transitioning to rain.

Any wintry precip would be a high impact given the holiday

weekend and increased travel. Rainfall could reach an inch in

many places across the southern half of the region. This system

should pull out early Saturday night with only a brief respite 

until the next system arrives by next Monday. Colder air 

wrapping in behind this system should eventually lead to snow 

showers downwind of lake Erie with accumulation possible in the 

favored snowbelts and upslope locations.

 

&&

 

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...

06Z TAFS sent.

 

Main change was to edge winds up overnight.

 

MVFR to VFR conditions will continue overnight, with the 

best conditions across the east and south. 

 

Main push of colder air will be after sunset today. Gusty

winds will prevail today into this evening.

 

Models hinting at potential for a stronger snow band dropping 

southward across the mountains, impacting the northern mountains

late morning/midday and slipping toward I-80 in the afternoon 

before washing out over the central mountains. Placed a general 

MVFR reduction in visibility in snow timed with the arctic front

Wed. afternoon. The cold air push will be accompanied by wind 

gusts that could reach 25-35kts on the ridges and 15-25kts in 

the valleys.

 

Widespread VFR conditions develop for Thu/Fri with high 

pressure in control. 

 

.Outlook... 

 

Thu-Fri...No sig wx expected.

 

Sat...Wintry mix poss early, then restrictions in mainly rain.

 

Sun...Restrictions likely in rain showers.

 

&&

 

.CLIMATE...

Record-challenging cold is forecast for Thanksgiving Day. Both 

record low-maximum (daytime) and record low minimum (nighttime) 

temperatures are in jeopardy. *State College COOP records for

STCP1 taken between 7am-7am and coordinated with PSU Meteo 

Dept.

 

Record low-min (11/22)

------------------------- 

Williamsport: 13 in 2014

Harrisburg: 16 in 1964

Altoona: 13 in 1964

State College: 10 in 1984*

Bradford: 6 in 2008

 

Record low-max (11/22)

-------------------------

Williamsport: 30 in 2000

Harrisburg: 31 in 1989

Altoona: 27 in 2008

State College: 25 in 1956

Bradford: 20 in 2008

 

Record low-min (11/23)

-------------------------

Williamsport: 14 in 1964

Harrisburg: 14 in 1964

Altoona: 12 in 2000

State College: 12 in 1984

Bradford: -1 in 1971

 

&&

 

.CTP WATCHES/WARNINGS/ADVISORIES...

None.

 

&&

 

$$

SYNOPSIS...Dangelo

NEAR TERM...Dangelo

SHORT TERM...Dangelo

LONG TERM...Steinbugl

AVIATION...Martin/RXR/Tyburski

CLIMATE...

---