Marine Weather and Tide Forecast for Indiana, PA

KEY MESSAGES
1) Widespread snow ongoing this afternoon, with Advisories and Warnings in the ridges. Snow squall threat this evening.

2) Dangerously cold Wind Chill values this weekend.

3) Potential warm-up next week brings flooding concerns.

DISCUSSION
KEY MESSAGE 1...

Light to occasionally moderate snow is ongoing across the area this afternoon as an upper shortwave trough dives from the Great Lakes into the Mid Atlantic CONUS. While precipitation this morning started as a mix of freezing drizzle and snow, moisture profiles have since become more saturated into the DGZ leading to ptype transitioning to a drier, fluffy snow.

Latest radar and surface observations upstream over northern OH and southern MI confirm that the lull in snow that was anticipated late this afternoon is still on track to occur.
Therefore, expect accumulating snow to reduce to flurries or stop completely generally in the 4-7pm timeframe before scattered snow bands/squalls with locally heavy rates develop this evening along and behind an advancing cold front. Another quick coating to possibly an inch of snow will be possible with those evening showers.

Regarding snowfall amounts, the current forecast appears to remain on track as ensemble guidance has held remarkably stable for totals across the lowlands in the 1-3 inch range. Snow totals remain higher across the PA/WV ridges where upsloping is encouraging higher rates and more steady snow throughout the day. Generally 2-5 inches is expected for the PA ridges, locally near 6 inches on the peaks. Meanwhile for the WV ridges higher totals to 5-8 inches is forecast and localized areas may see near 9 inches. While all lowland areas remain below Advisory criteria, a Winter Storm Warning remains in effect for the WV ridges and a Winter Weather Advisory remains in effect for the PA ridges. Blowing snow may also be an issue in the higher terrain, especially in eastern Tucker County, where a High Wind Warning remains in effect tonight through Saturday night for gusts up to 60 mph.

KEY MESSAGE 2....

Winds will quickly pick up behind the front tonight as temperatures rapidly fall into the single to negative single digits by sunrise Saturday. With prevailing wind gusts of 25-30mph near the surface, wind chill values will drop to well below zero. Most of the area will see wind chill values of -10 or colder, with -20 to -25 possible north of Pittsburgh and in the higher elevations. An Extreme Cold Warning is in effect for these areas beginning tonight, and a Cold Weather Advisory is in effect elsewhere. Wind chill values will likely remain below zero through Sunday morning.

Saturday's very cold forecasted maximum temperatures may break daily records for a few climate sites. For example, Zanesville is currently forecasted to top out at 16F (record coldest is 17F from 2014), and Wheeling is forecast at 14F (the record coldest is 17F from 2007).

KEY MESSAGE 3....

A very welcome shift in the pattern is expected next week, finally returning above-freezing temperatures to the region at least through the middle part of the week. However, this may come at a cost, as it also introduces a potential flooding risk.
Milder conditions will help melt snowpack across the region, which currently holds a liquid equivalent ranging from around 1.4" around the Pittsburgh Metro to 2.3" for areas north of Pittsburgh. If temperatures end up trending on the higher end of guidance (e.g. NBM 90th percentile Tuesday is near 50 degrees in Pittsburgh), a more rapid melt of this snowpack could occur and affect local mainstem river levels, which remain ice covered at a depth of 3 to 8 inches thanks to the recent cold snap. Additionally, rain chances may accompany the warmer weather and further exacerbate conditions, leading to the risk for localized flooding. This will need to be be carefully monitored as we head through the upcoming weekend.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
KEY MESSAGES...

1) Snow tapers off through 00Z.

2) Brief, heavy snow with gusty winds possible from 01Z to 04Z.

3) Scattering possible Saturday morning, with MVFR cigs possible again Saturday afternoon.

------------------------------------------------------------

The aforementioned clipper system will continue its trek through the area, continuing light snow that has generally maintained borderline MVFR/IFR cigs and mostly IFR vis. Steady light snow is favored to depart in the 18Z to 20Z window as more dry air arrives in wake of generalized ascent. Maintained some tempo MVFR vis snow with efficient snow production in shallow moisture irrespective of the environment. Cigs are expected to remain at least MVFR with >75% confidence through the evening.

Areal separation between the mid-level jet driving the daytime snow and the arrival of the surface cold front favors a period of subdued snowfall rates between roughly 20z-00z (varying NW to SE). Then, the strong arctic front provides another shot of localized heavy snow squall showers btwn 01z-04z with rates that could briefly touch 1"/hr along with wind gusts around 30kts. Visibility could drop to 1/4mile in the high-end scenario of these showers. This mention was expanded at the 18Z update to most ports save DUJ and FKL with higher confidence in timing and presence of brief, heavy snow.

Cold, dry advection in NW flow in the post-frontal environment generally would lend to widespread MVFR into Saturday morning.
But with Lake Erie generally frozen, limited boundary layer moisture may create periods of scattered stratocumulus. There also remains a low probability for a Lake Huron lake effect fetch to sit around DUJ after 06z, but uncertainty still remains high at this point.

Into Saturday, cloud may fill in more with mixing into the afternoon, with a broken MVFR deck most likely for now. Gusty winds also remain likely with gusts topping out to 25kt to 35kts at times, out of the northwest.

Outlook... A low probability exists for a mid-level jet inducing a narrow band of snow Sunday that returns MVFR restrictions.
Otherwise, high pressure and subsidence will favor VFR until a mid- week weather system.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...Cold Weather Advisory from 1 AM Saturday to 10 AM EST Sunday for PAZ013-020-021-029-031-073-075.
Extreme Cold Warning from 1 AM Saturday to 10 AM EST Sunday for PAZ007>009-014>016-022-074-076>078.
Winter Weather Advisory until 6 AM EST Saturday for PAZ074-076- 078.
OH...Cold Weather Advisory from 1 AM Saturday to 10 AM EST Sunday for OHZ039>041-048>050-057>059-068-069.
WV...Cold Weather Advisory from 1 AM Saturday to 10 AM EST Sunday for WVZ001>004-012-021-509>511-513.
Extreme Cold Warning from 1 AM Saturday to 10 AM EST Sunday for WVZ512-514.
Winter Weather Advisory until 6 AM EST Saturday for WVZ510-511.
Winter Storm Warning until 6 AM EST Saturday for WVZ512>514.
High Wind Warning from 10 PM this evening to 10 PM EST Saturday for WVZ514.