textproduct: State College

WHAT HAS CHANGED

* Precip arrival pushed later Mon night; maybe even dry most of the night * Freezing rain threat for all the area Tues

KEY MESSAGES

1) Wintry mix with light freezing rain accumulations likely Tuesday

2) Periods of rain with temperatures very much above normal Wed onward

DISCUSSION

KEY MESSAGE 1: Wintry mix with light freezing rain accumulations likely Tuesday

Large 1040hPa high pressure dome slides over the NErn US Monday, pressing very dry air into the state. The W-E frontal boundary will be very far to the south of the state Monday, but warm/moist air will overrun the dome. Precip is expected to get right up to the Mason-Dixon Line on Monday, and bubble north into the CWA later Monday night. There could be a small patch of --SN slide thru the Laurels and South-Central Mtns on Monday. But, there is a near-consensus for the timing of precip onset to be a few hours slower on these latest runs. NAM having troubles staying with the pack; as it is bringing light precip up well north/faster then any other model on Mon night. We'll follow with the bigger group for now, and expect precip to arrive in the S around sunrise Tues. Temps will be very close to freezing at that time in the S and a few degs colder over the central and northern 2/3rds of the CWA. While current wind dir progs have it mainly srly on Tuesday, the big high may keep the dry/cooler air wedged up against the mtns, and keep the wind light and more from the E/SE. That would result in cold air damming and raise the risk of temps staying below freezing longer into the day, esp for the NErn third of the CWA. With the strong WAA aloft, the light mix of precip will turn to all liquid fairly quickly (before noon) in the SW half of the CWA, with the rest of the CWA becoming all liquid by 21Z. With the sfc temps cold to start, there is a 3-6hr window of possible ZR and ice accretions. Again, the current QPF thru noon Tues is pretty light (0.10-0.20"). So, any ice accretions should be below warning criteria (0.25" S, 0.50" N). As it looks now, this could eventually necessitate an advy for the ZR, and all of the CWA is at risk for a thin glaze. But, at this range, we'll just advertise it here in the discussion. Sfc temps are the most challenging thing for this situation, and will be the most likely thing to bust/change the forecast. Without a high certainty in the temps and the changing timing of the precip onset, confidence is too low to do more than just mention it here in the discussion and in the HWO (which we have been for a couple of days). It should turn to all plain rain before sunset Tues, even in the NE. Those areas that do get ice in the AM won't have any left in the aftn as temps rise and melt it.

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KEY MESSAGE 2: Periods of rain with temperatures very much above normal Wed onward

Big sfc high parks off the East Coast and directs plenty of warm and moist air up into the state for the rest of the week and weekend. Temps are slated to be very much above normal. The W-E frontal boundary does become pretty stationary, but wavy, over the CWA for that time frame, though. There is a possibility of a small surge of cooler air sliding down from the NE (backdoor cold front) Friday-ish. But, by then, the temps will be so warm that no threat exists for any wintry precip. It should all be plain rain. The wavy front will be the pathway for repeated shot of forcing and consistent lift. So...it should be a wet time. But, that's not so bad, considering some of the area is still in drought.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Light rain and snow will continue to move off to the east this morning and should be east of all TAF sites by 14Z. MVFR ceilings are likely at BFD and JST this morning and may briefly reach AOO, UNV, and IPT.

Skies clear out from northwest to southeast during the day as high pressure builds in from the north. VFR conditions are expected for all of Central PA after 18Z and will continue through the rest of the 12Z TAF period. Northerly winds will be sustained around 10 knots today with a few gusts to 20 knots possible during the afternoon.

A few low clouds may try to develop after 00Z near BFD and IPT, but the very dry airmass moving into the region should limit their extent.

Outlook...

Mon...VFR likely.

Tue...Restrictions likely in wintry mix changing to rain.

Wed-Thu...Restrictions possible in periods of rain.

CTP WATCHES/WARNINGS/ADVISORIES

None.