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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 181223
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
723 AM EST Mon Feb 18 2019

.SYNOPSIS...
A fast flow aloft will keep the weather active through the week.
Patchy freezing drizzle will end this morning. A strong storm
with a potentially significant amount of snow, sleet and 
freezing rain will approach for Wednesday. Another storm is 
possible next Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Clouds remain very thick and low, with few or no seeder 
crystals to make snow. The hill tops around there may still be 
AOB freezing as Camp David (KRSP) on South Mountain is currently
32F. Temps just above freezing in the SErn valley cities. Just 
can't see canx the advy before mid-morning in most places. 
Everywhere else is sub- freezing and the advy will continue for 
all areas. It is possible that we might cancel the advy if the 
temps consistently stay above freezing in the SE. 

Temps will stay nearly steady for the morning, but should rise
in the E as the wind picks up in the wake of the low pressure
system. The downslope and loss of clouds in the aftn should help
the temps rise into the l40s in the far SE. The NW will have an
opposite temperature trend, as the cold air is already being drawn
in behind the low. Temps could slip all day long in the NW, but
will likely level off in the m20s. A couple of flurries or brief
light SHSN are possible in the NW this morning, and the Laurels
may also keep some FZDZ or flurries for a few hours this
morning.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
Clearing will work to the NW and much of the area will be clear
by Tuesday morning. Sprawling high pressure will cover the NErn
half of the CONUS Tuesday. However, low pressure will gather
over the lower MS valley and the strong WAA will bring copious
moisture up from the GOMEX. The precipitation from this storm
will move quickly up the OH valley and precip should start in
the Laurels before sunrise Wednesday. It will likely start off
as snow.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Uncertainty is very high at this point as to the evolution of 
precip type and the QPF over PA on Wed. GEFS and SREF plumes
play out a QPF range from just a tenth or so to many inches.  
The temps also range wildly. The GFS warms everyone in Central
PA up to plain rain during the day, while the NAM and EC keep it
much colder. Will keep mentioning the storm in the HWO, but not
enough confidence in many aspects to post a watch. Most likely
place to get the worst impacts will be along and S of the PA
Turnpike. 

Prev... 
For Wed, low pressure lifting northeast across the Great Lakes 
will result in some snow, given warm advection. By late morning 
and early afternoon, looks like sleet and freezing rain would 
mix with the snow. This based on thickness coming up fast, as 
the system is weaker and faster than the one we had last week. 
Thus did not hit the snow real hard, and did not want to go too 
high on ice. This in part due to QPF on NAM across the far south
was looking too high. Other models have the .25 inch line just 
brushing the far south. Hard to see much more than .25 in any 6 
hour period. The NAM had .75 inches across the south in a 6 hour
window.

This event looks like the event last week, most of the precipitation
would be east of the area by Midnight.

For most of the period from Thursday into at least early Saturday,
not a lot going on. I did cut back on POPS and weather where I 
could. Temperatures borderline, so used a mix of rain and snow.

Main question is if a deep low will form and lift across the
lower Great Lakes on Sunday. For now, went close to the
superblend. EC and GFS runs not close. GFS has much weaker 
systems. If EC was to verify, Monday would be the first real
windy day of the late Winter, early Spring season.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Precipitation ending across airspace from west to east. Expect 
rapid improvement between post sunrise as drier westerly flow 
takes over. Model soundings indicate there will be lingering 
MVFR stratocu across the mountains of central Pa, while 
downsloping flow yields a return to VFR conditions in the 
Susquehanna Valley from KIPT south through KMDT/KLNS.

A tight pressure gradient behind the departing storm will 
produce gusty west-northwest winds for much of today. Bufkit 
soundings support gusts ranging from around 20kts over the 
northwest mountains (KBFD) to between 30-35kts over southeast Pa
(KMDT/KLNS).

Outlook...

Tue...No sig wx expected.

Wed...Wintry mix likely. 

Thu...AM wintry mix/low cigs possible.

Fri...No sig wx expected.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 PM EST this afternoon for 
PAZ004>006-010>012-037-041-042.
Winter Weather Advisory until 10 AM EST this morning for 
PAZ017>019-024>028-033>036-045-046-049>053-056>059-063>066.

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Dangelo/Martin
AVIATION...Fitzgerald/Gartner