Marine Weather and Tide Forecast for Washington Boro, PA

NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/
A broad area of ascent associated with PVA ahead of an upstream shortwave continues to produce light snow/flurries across Central PA this evening. Orographic enhancement is producing some very light accumulations over the Allegheny Plateau, while mainly just flurries observed downwind of the mountains.

Large scale subsidence behind the shortwave should cause the light snow/flurries to taper off late this evening. However, a slight veering of the boundary layer flow will draw lake effect snow southward into the northern tier of PA. Latest hi-res model qpf supports an additional 1-2 inches overnight across Warren/Mckean counties.

The core of coldest air aloft, which currently resides over Ohio, will push over Central PA around 06Z then shift east.
Thus, expect falling temps late this evening, with steady readings after 06Z. Min temps in the upper single digits, combined with gusty winds, should push wchills close to -10F over the Laurel Highlands. Elsewhere, expect min temps in the teens, with daybreaks wchills generally within a few degrees of zero.

SHORT TERM /7 AM WEDNESDAY MORNING THROUGH FRIDAY/
A Lk Huron connection, combined with the passage of another shortwave, will target the N Mtns for additional lake effect snow showers Wednesday. Elsewhere, upslope flow may generate a few light snow showers/flurries across the Laurel Highlands, but generally dry weather is anticipated across the southern half of the state. Latest model qpf supports an additional inch or so of accumulation Wed across the NW Mtns and a fresh dusting across the mountains north of Lock Haven and Williamsport.

Have increased wgusts Wednesday a bit above NBM guidance based on Bufkit soundings. Mixing down progged 900mb temps yields expected highs Wed ranging from just the upper teens over the Laurel Highlands, to around 30F in the Susq Valley.

BL flow backs to the southwest Wed night, which should spell an end to the lake enhanced snow showers, but approaching shortwave from the Great Lakes should bring light WAA snow on Thursday. The pattern shifts back to brisk NW flow and more lake enhanced snow showers Thu night into early Friday.

Expect a brief warmup to end the week as a milder southwest flow pushes max temps into the 30-40F range on Friday. Sfc ridge of high pressure migrating through CPA will end snow showers and provide dry wx for the balance of the day Friday with more sunshine favored over the southeastern part of the CWA

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
Dry conditions will continue Friday night under upper-level ridging, with relatively mild MinTs into Saturday morning. By early Saturday morning, a deepening area of surface low pressure stationed across northern Ontario/Quebec will allow for a cold frontal passage to push towards central Pennsylvania. The bulk of model guidance outlines precipitation begins overnight, with the majority of the area experiencing precipitation by sunrise, although model guidance has tracked the cold front approaching central PA slightly slower, thus dropping PoPs slightly later at onset. Marginal surface temperatures are expected at onset although there remains some added uncertainty with the cloud cover forecast. Clear skies across southern PA Friday night into Saturday morning could allow for surface temperatures to cool slightly more than forecast allowing for some radiational cooling. A wintry mix is expected at onset, especially across higher elevations of central Pennsylvania with non-zero freezing rain potential. Warming temperatures on Saturday will allow for a slow transition to rain across the Lower Susquehanna Valley with a wet snow/rain mix remaining possible across the Laurel Highlands and NW PA.

Lingering snow showers on Sunday and into Monday remain possible with localized enhancement across the Laurels/NW PA allowing for slightly higher PoPs. Enhanced westerly flow will bring about continued lake-effect and orographically enhanced snowfall in through Tuesday morning. The bulk of model guidance suggest dry conditions prevailing later in the day on Tuesday and continuing through Tuesday night.

Another aspect of the long-term will be relatively mild temperatures on Friday trending colder, with 850mb temperatures ranging between 0-4C Friday night into Saturday morning decreasing sharply after the cold frontal passage towards -20C Monday morning. These colder temperatures coupled with gusty winds will allow for another return to bitterly cold wind chills towards the end of the long-term period. Wind chills Sunday night into Monday morning will remain marginal with the highest elevations of the Laurels pushing close to Cold Weather Advisory. The coldest wind chills are expected to occur Monday night into Tuesday; however, with moderate (50-60%) confidence on the entire forecast area experiencing sub-zero winds chills by Tuesday morning with the most plausible solution for areas west of the Allegheny Front trending closer to the -10F to -20F range with locally lower wind chills in the cards, pushing close to Extreme Cold criteria. Given some uncertainty with regards to cloud cover/temperature interactions (clear skies could allow for some radiational cooling) and wind speeds (gusty winds = lower wind chills), have stuck closer to NBM in this timeframe.

AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
The area of stratiform light snow across central and western Pennsylvania will continue to shrink in coverage and pull off to the east between 00z and 06z Wed. As this occurs, the stratus deck will scatter out across much of the area. However, new lower cigs will begin to develop across the northwest and expand southeastward through the overnight, bringing IFR to MVFR cigs for BFD and JST. These low clouds will likely bring another round of light snow that can bring vsby down to IFR levels through 14-18z Wed, after which the chance for IFR conditions drops below 30 pct.

Diurnal heating during the day Wed, along with continued cold advection over the Great Lakes, will promote expansion of the MVFR deck towards AOO and UNV, with each of those airfields carrying a 50% chc of MVFR cigs during the afternoon. The chc for MVFR cigs is in the 80-100 pct range for BFD and JST.
Upslope and lake effect snow showers are likely at JST and especially BFD through the day.

Outlook...

Thu...Light snow with MVFR cigs and brief vsby reductions possible across the central & western mountains.

Fri...Restrictions continue across the N/W.

Sat...Morning wintry mix possible, transitioning to rain/snow in the afternoon. Reductions to IFR possible.

Sun...Lingering snow showers N/W, some potential for RA/SN mix southeast.

CTP WATCHES/WARNINGS/ADVISORIES
Winter Weather Advisory until 7 PM EST Wednesday for PAZ004- 005.
Cold Weather Advisory until 10 AM EST Wednesday for PAZ024-033.