textproduct: State College

WHAT HAS CHANGED

* Forecast highly similar to prior forecast packages.

KEY MESSAGES

1) Light snow accumulations N/W today and early tonight.

2) Winter weather threat for Sun-Sun night timeframe continues, with very minor changes. Medium chance PoPs southern PA, but still a 20 PoP all the way to the NY border.

3) Warmup in store for next week.

DISCUSSION

KEY MESSAGE 1: Light snow accumulations N/W today and early tonight.

8H temps remain in the -10 to -14C range today, and sfc-8H flow remains out of the NW. These parameters remain favorable for LES. Vorticity is going to be channeled in the NW flow - expecting little advection/change today. There will be little upper support for intensification. At this point, bands are weakly organized with more of a general/broad snowfall. Of course, the constant flow of moisture uphill into the Allegheny Plateau and the highest peaks of the Commonwealth will make snowfall. But, accumulations will be minor. Clouds are lasting quite a bit farther downstream than the blend of models suggests, and have nudged them upward throughout the next 24 hrs. The cloud cover and cold air in place will keep maxes down in the 20s to lower 30s.

-------------------------- KEY MESSAGE 2: Winter weather threat for Sun-Sun night timeframe continues, with very minor changes. Medium chance PoPs southern PA, but still a 20 PoP all the way to the NY border.

A fast-moving storm is still expected to move W-E across the srn half of the CONUS this weekend. The ensembles continue to be clustered around a Sun-Sun night timeframe when precip might sneak into southern PA. So, confidence is the same to a little higher that Mon will be generally dry. NBM PoPs look fine for this range, and have decreased very slightly on the whole. The 70 PoPs of 2 nights ago have entirely disappeared (or, really, have moved to the S of PA) due to the trend southward and faster/flatter. 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 move north of the PA Turnpike, and the temp profile would make 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.

In the end, we've made only small tweaks to this part of the forecast vs the straight-up NBM output.

-------------------------- KEY MESSAGE 3: Warmup in store for next week.

Temps still on track to rise nicely for Monday, and get warmer Tues-Wed-Thurs. Many towns in the srn third of the CWA could rise into the 50s for maxes each day mid-week. Precip chances (and clouds) look very low to nil Mon & Tues as the warm advection happens with PA devoid of moisture. Mins Tues night may stay above freezing everywhere but the But, PoPs still look a little optimistic at this range.nrn mtns - well above normal mins for mid-Feb. 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 Wed- Thurs timeframe. But, 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 Thurs (Day8).

AVIATION /12Z THURSDAY THROUGH MONDAY/

Scattered lake effect and upslope snow showers are lingering across the northern and western terminals of central Pennsylvania this morning (all but MDT/LNS) with reductions in visibility over the next couple of hours. General rule of thumb will remain MVFR in these snow showers based off of recent observations at BFD/JST/UNV; however, model guidance has indicated brief drops to IFR cannot be entirely ruled out at BFD/JST through 12/15Z. Probabilities outline BFD as the most likely candidate for reaching IFR thresholds based on visibility in locally heavier snow showers. Snow shower coverage is expected to decrease through 12/18Z with moderate-to-high (60-70%) confidence in no snow shower mentions.

Despite no shower mentions after 12/18Z, all model guidance continues to indicate low-level clouds continuing at BFD/JST through 13/12Z, thus giving high confidence in MVFR ceilings in this timeframe. Recent NBM/GLAMP model guidance has trended towards IFR conditions after 13/06Z, especially at BFD which is backed by increased low-level moisture in recent RAP model soundings. Elsewhere, ceilings at AOO/UNV will rise quickly as snow showers diminish after 12/15Z. Model guidance does indicate some increased low-level moisture at UNV/IPT which could allow for MVFR ceilings to work their way back into the airfield after 13/00Z, with more uncertainty after 13/06Z and into the end of the 12Z TAF period.

Outlook...

Fri-Sat...Improving conditions late week into the weekend

Sun-Mon...Monitoring potential for winter weather on Sunday and Monday. Most likely restrictions are in southern PA at this time.

CTP WATCHES/WARNINGS/ADVISORIES

None.