textproduct: State College

WHAT HAS CHANGED

* Winter Weather Advisory for Somerset County for Sunday into early Sunday night. * Wind Advisory for Laurel Highlands and southern Alleghenies for Sunday into early Sunday night. * 7-day forecast variables (snowfall, winds, temperatures, etc.) updated.

KEY MESSAGES

1) Periods of rain continue today into this evening, with 0.25-0.75" expected areawide.

2) Trending colder tonight and becoming windy on Sunday, with max gusts 35-50 mph pushing advisory level thresholds.

3) Snow accumulation /and possibly a few squalls/ expected across the western highlands Sunday into Sunday night, and could impact travel. A few localized heavy snow showers/squalls are also possible over the western half of PA. A few snow showers could even make it into eastern Pennsylvania Sunday afternoon.

DISCUSSION

KEY MESSAGE 1... Rain is on track, as it continues to spread northward across the region early this afternoon. It will be a damp and raw afternoon, with most places seeing steady temperatures in the 30s to low 40s.

The rainfall combined with snowmelt from the ongoing/early January thaw will cause rises on rivers and streams; we will continue to monitor for ice jams.

KEY MESSAGE 2...

A cold front will cross the commonwealth overnight, ushering in colder temperatures. It will turn blustery on Sunday, with wind gusts of 40-50 mph expected. A Wind Advisory has been posted for the Laurel Highlands and southern Alleghenies.

KEY MESSAGE 3...

A secondary cold front will will drive lake-effect and upslope snow showers Sunday into Sunday night. Guidance suggests that the ridges of Somerset County could receive up to 5 inches of snow, with lesser amounts in the valleys. Therefore, have posted a Winter Weather Advisory for Somerset County.

Elsewhere across the western highlands, a coating up to 3 inches of snow is possible.

Model SNSQ parameters indicate that a few heavier snow showers or squalls are possible as well, mainly across the western part of the state. Travel may be impacted particularly over the western highlands Sunday into Sunday night due to a combination of blustery winds, slippery roads and reduced visibility.

A few snow showers could even make it into the Susq Valley Sunday aftn.

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Look for improving conditions early next week, with little if any precip and moderating temperatures Monday & Tuesday.

Precipitation chances will increase into the middle to later part of next week in response to an amplifying upper trough carving out over the Eastern US. Moderating/above normal temps into Wednesday are forecast to trend colder to more typical levels for mid January by Thursday and Friday.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

IFR/LIFR conditions remain the rule of central Pennsylvania as of 00Z Sunday, with rainfall mainly stationed across the northern and western halves of the forecast area, with rainfall observed at all TAF sites outside of MDT/LNS. Ample low-level moisture remains in place across the southeast; however, so cannot rule out an hour-two of light drizzle/rain before limited precipitation mentions are expected. Some signal for clearing across the eastern half of the forecast area does promote some potential for fog formation at IPT/MDT/LNS with the threat lower (but still notable) at UNV given light/calm winds in the near- term. The 00Z TAF package hits eastern airfields with fog formation, leaning towards a blended GLAMP/RAP model solution that outlines ample low-level moisture that is trending well with current observations. Lower probability solution trends towards no fog mentions at any of the airfields; however, IFR conditions are expected (> 80%) confidence at all airfields through ~06Z Sunday.

Winds begin to pick up west-to-east near the 04Z-06Z Sunday timeframe, which will allow for lower confidence in IFR conditions prevailing area wide. Recent GLAMP/HREF model guidance does indicate improvement overnight towards MVFR ceilings and potentially VFR conditions should the low-level deck scour out completely. Highest uncertainty remains at BFD/JST, where low-level moisture remains present in most recent RAP model guidance, so have trended slightly towards the RAP solution in this timeframe with lower (30-40%) confidence. Elsewhere, a period of VFR conditions are virtually certain (~90-100% confidence) with the most uncertainty coming with respect to timing and duration of VFR flight categories.

Secondary cold front (see Key Message #3) will allow for lake effect and upslope snow showers across the western highlands of Pennsylvania, with BFD/JST (higher confidence, 60-80%) and AOO/UNV/IPT (lower confidence, 20-40%) having the potential for snow showers. The 00Z TAF package introduces mentions based on a RAP/HREF model blend, that tracks fairly well with recent GLAMP guidance; however, there remains some uncertainty with respect to a faster arrival time, so could realistically see onset of precipitation/restrictions moving up one-two hours in the next couple of TAF cycles. IFR conditions within snow showers are increasingly likely based on visibility restrictions; however, based on the lower confidence further east have trended back mentions towards MVFR. Some LLWS concerns begin to come towards the end of the TAF package; however, given time horizon and lower confidence based on NBM/NAM model guidance, have kept mentions out this cycle with low (~20%) confidence.

Outlook...

Mon...A few lingering lake effect snow showers early, giving way to mainly VFR conditions.

Tue-Wed...Mainly VFR.

Thu...Ceiling restrictions poss NW, VFR SE.

CTP WATCHES/WARNINGS/ADVISORIES

Wind Advisory from 10 AM Sunday to 1 AM EST Monday for PAZ024- 025-033-034. Winter Weather Advisory from 8 AM Sunday to 1 AM EST Monday for PAZ033.