textproduct: State College

WHAT HAS CHANGED

* Additional details about Sunday-Sunday night system.

KEY MESSAGES

1) Light snow tapers off tonight as high pressure builds in.

2) Accumulating snow possible in southeast PA Sunday night; uncertainty remains, but the range of possible solutions is narrowing.

3) Trending warmer next week with a couple chances for rain and/or wintry mix.

DISCUSSION

KEY MESSAGE 1: Light snow tapers off tonight as high pressure builds in.

Northwesterly flow has continued to generate lake effect snow showers into the late evening with visibilities dropping below 1 mile along I-80 in Clearfield County under one of the stronger bands. Recent radar trends indicate showers are losing steam and should taper off into the wee hours of Friday morning. Stratocumulus will also fall apart east of the Allegheny Front overnight, as is typical in these types of patterns. Light winds and clearing skies will support one last chilly night with lows in the single digits across the northwest mountains and upper teens in the southeast.

High pressure will build in on Friday, resulting in decreasing clouds and no precipitation. Continued northwest flow will keep temperatures below average on Friday afternoon, ranging from the upper 20s to middle 30s, but abundant sunshine and light winds will feel pretty good. As high pressure moves south of the area this weekend, westerly winds will promote some warm advection and moderating temperatures on Saturday and Sunday.

-------------------------- KEY MESSAGE 2: Accumulating snow possible in southeast PA Sunday night; uncertainty remains, but the range of possible solutions is narrowing.

Here's what we know about Sunday's system: - Significant impacts are unlikely. - The best chance of plowable snow is southeast of I-81 - A total miss is possible, in which rain/snow would stay south of PA. - Motorists should prepare for minor travel impacts anywhere south of I-80, but continue to monitor the forecast for changes.

A fast-moving low pressure system is still expected to move W-E across the southern half of the CONUS this weekend. Ensembles continue to be clustered around a Sun- Sun night timeframe when precip might make it as far north as central PA. So, confidence is the same to a little higher that Monday will be generally dry. NBM PoPs look fine for this range, and have decreased very slightly on the whole due to the trend southward and faster/flatter. The ECMWF has waggled northward and now paints 0.10-0.20" QPF along the MD border. Temps are still marginal for any frozen precip in the S (best signal is for rain there) but more north of the PA Turnpike, the temp profile would suggest a rain/snow mix or snow. Of course, it should be highlighted that we only have chc PoPs at this point. So, there isn't a 40 pct chc of accumulating snow - just a 40pct chc that any measurable precipitation will occur.

If any of the (potential) precip arrives during the daylight, as currently hinted by the preponderance of models/ensemble members, temps will be more favorable for rain. Progged temp spread on Sunday is still wider than allows for high confidence in any precip type. Middle of the road maxes are around 40F N for most of the CTP CWA, and 40-45F in the valleys of the south- central mtns where the PoPs are actually the highest. Current thinking is that an inch or two of slushy snow could fall across southeast PA with little to no accumulation north of I-80. ECENS guidance is still bullish on the potential for snow, but recent performance has been suspect and a lower-impact solution appears more likely at this time.

-------------------------- KEY MESSAGE 3: Trending warmer next week with a couple chances for rain and/or wintry mix.

Temps still on track to warm for early-mid next week as heights rise on the eastern periphery of upper ridging migrating from the Intermountain West into the central U.S. Many towns in the srn third of the CWA could rise into the 50s for maxes each day mid-week. Precip chances look very low to nil Mon & Tue as warm advection occurs with PA devoid of sufficient deeper layer moisture. Min temperatures Tue night may stay above freezing for most. Medium confidence exists in a low pressure area or two rolling W-E into the OH Valley and Mid-Atlantic along a front dropping down into PA in the midweek timeframe. Confidence in the equatorward progress that the front makes before waggling north again is low. Even if the front drops in, temps should remain above normal on Thursday.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

High pressure building eastward into central PA will bring an end to the lower CIGS at BFD, JST, and at times UNV and AOO this morning.

A few flurries still possible at JST and BFD overnight. Otherwise dry today.

CIGS could come back down toward late Friday evening, with a few flurries, but main chance for this would be at BFD.

Outlook...

Sat...Low ceilings early north of KUNV along with a few snow showers. VFR for the afternoon.

Sun-Tue...Monitoring potential for winter weather on Sunday and Monday. Most likely restrictions are in southern PA at this time. Tuesday looks dry and VFR.

CTP WATCHES/WARNINGS/ADVISORIES

None.