Marine Weather and Tide Forecast for Whitaker, PA

NEAR TERM /UNTIL 6 AM THIS MORNING/
KEY MESSAGES:

- Light snow possible tonight with minimal accumulation.
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Snow showers and flurries continue to move across Ohio ahead of a surface cold front and digging shortwave trough. Most of the snow is light and expect it to remain that way as the boundary crosses. Have updated overnight PoPs using a blend of CAM/hires guidance as ensembles are not picking up on these mesoscale snow showers very well. Snow accumulations were also updated as well as overnight lows.

Previous discussion...

The best chances for snow showers locally will likely come tonight along and ahead of a weak boundary as opposed to the impulse.

Latest guidance still offsets the passage of the wave and the boundary, so the overlap of forcing will be displaced. Better moisture return will come just ahead of the boundary with a more saturated DGZ, but the 12z CAMs all suggest different flavors of moisture depth. The NAM seems to be the most bullish with saturation through -18C and producing efficient snow showers. Other CAMs are less interested in total boundary layer moisture content. The current snow squall parameter is elevated across Indiana with reductions to visibility dipping down to 1-2 miles and putting a quick coating on surfaces, but the RAP/NAM weaken the parameter as it progresses east to ~1; with loss of daytime heating, low level lapse rates likely weaken by the time it reaches here. At this point, HRRR hourly probabilities for measurable snowfall reach 30-60%, highest in the higher elevations. The more persistent snow will be across the ridges with orographic ascent, but the moisture issue will still remain. Bumping up to the HRRR 90th percentile accumulated QPF, totals outside of the ridges don't eclipse about 0.05", so assuming an 18-20:1 SLR, highest totals within the snow showers should be an inch or less with potentially up to 1-1.5" or so in the ridges. Timing looks to be after the evening rush, so peak travel shouldn't see a notable impact, but with road temperatures at or below freezing, a quick burst of snow within scattered showers will easily accumulate on surfaces.

SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/
KEY MESSAGES:

- Widely scattered light snow showers Friday with slightly colder temperatures.
- Light snow north of I-80 Saturday with moderating temperatures.
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A weak shortwave will slide through on Friday as surface high pressure progged across the Carolinas extends ridging locally. Can't entirely rule out very low-end snow shower chances in the afternoon as low-level lapse rates steepen to near dry adiabatic, but dew point depressions are anywhere from 7-12 degrees, so it may be a struggle to reach the ground. HRRR probability for reaching a half an inch is <10% in our area. Highs will take a hit back down a few degrees as some colder air works in in west-northwest flow. The steepening lapse rates with cold advection at the 850 mb level will allow us to tap into elevated flow aloft. Momentum transfer isn't all that impressive with only 15-20 knot flow, so wind may take on more of a 8-12 mph sustained nature with sporadic gusts. Depending on the amount of clearing we can get overnight, lows may have a good shot (currently 50-70%) at dropping into the single digits again across most of the area. Rising heights and intruding dry air looks to erode the clouds, and despite still noted spread within the NBM 25th/75th cloud coverage, the upper end of the distribution indicates clearing, so once confidence becomes higher, lows may need nudged down a bit.

Heights will rise a bit on Saturday behind the departing wave as the surface high expands across the Carolinas with ridging still in place locally. Temperatures will rebound in southwest flow aloft which will pump 850 mb temps to -7 to -9C, but heating will be stunted by lingering cloud coverage. A trough may spark off some snow showers north of I-80 in the afternoon, but the chance for >0.5" is ~20% with weak forcing available. Highs will reach the low 30s with better confidence across the board which is still a few degrees below average.

LONG TERM /SUNDAY THROUGH THURSDAY/
KEY MESSAGES:

- Below average temps are expected to linger through early next week.
- Rounds of weak disturbances will produce scattered snow chances.
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The better snow chance, albeit with low accumulation potential, will come on Sunday. Ensembles have come into better agreement on another flat shortwave making a quick fly by during the morning hours as surface low pressure drags a weak front through. All clusters hug the best chances (~20%) for >1" of snow to I-80 and north with lake enhancement, though boundary layer flow is progged to be more westerly than northwesterly, so said enhancement may stay north out of our area. Chances for >0.5" extend a bit further south down the ridges with favorable flow for orographic ascent, so the highest accumulations will be found in these locations, but still looks to be low impact. The primary issue will be available moisture as the lack of amplification with westerly mid-level flow isn't pulling from a great moisture source region.

Sunday's highs will be very similar to those of Saturday in the upper 20s/low 30s; probabilities to eclipse the freezing mark sit around a 50-70% chance as far north as Pittsburgh but are trending cooler.

Ensembles eject yet another shortwave late on Monday through the Great Lakes. Noted disagreement still comes into play with the latest ensembles regarding the progression of the upper levels; two clusters, with which has the most evenly distributed membership, exhibit a slower and deeper trough ~10 dam below the mean. Two others suggest a less amplified solution. Better moisture return, both low and mid level, comes from the more amplified solutions as expected with a slight enhancement in 24 hour QPF. The latest ensembles have trended toward a more amplified solution, but weaker ones are still in play. Total QPF is distributed anywhere between minimal on the low end to a quarter of an inch on the higher end.
Accordingly, the chance for >1" of snow is highest along the PA ridges and north of I-80 around 30-50%, but will have to wait for better agreement to hone down more details as overall confidence is low.

AVIATION /05Z FRIDAY THROUGH TUESDAY/
Snow showers with MVFR to IFR restrictions are expected to continue overnight with a crossing cold front. The best upper level ascent/vorticity max will be exiting the region after 06Z, with a gradual diminishing trend in the snow showers expected.

Otherwise, mainly MVFR cigs are expected to continue behind the front for much of the area, though an area of clearing across Ohio could briefly work in across portions of Wrn PA, including PIT. Any improvement should be temporary, as additional MVFR stratocu develops Friday morning as convective temperatures are reached. Some improvement to low VFR is expected by mid to late afternoon with mixing.

Outlook...
VFR is expected Friday night through early Saturday under high pressure. Restrictions and snow showers are then possible through Sunday with a crossing cold front, and subsequent upper troughing and NW flow. VFR returns Monday under high pressure.
Restrictions and snow shower potential is expected with a Tuesday cold front.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...None.