textproduct: Wakefield

WHAT HAS CHANGED

The continued depiction of a strong low pressure off the SE and mid Atlantic coast this weekend by all major models and ensembles gives a slight increase in confidence for seeing significant impacts locally, and PoPs Fri night-Sat night have been raised 5-10% from the last forecast cycle for all but the NW (where the probs for moderate level snow impacts have decreased slightly). Also, the chance for some accumulating snow overnight Friday into Sat AM has increased over southern portions of the FA. Winds were increased slightly along the coast for the weekend.

KEY MESSAGES

1) A Cold Weather Advisory remains in effect through 10 AM for the northern tier of counties, the Peninsulas, and the Eastern Shore. Additional headlines are likely at times through the weekend given a prolonged period of very cold temperatures. Lingering localized impacts from the winter storm this past Sunday will continue in some areas with little to no melting of the snow/ice.

2) A weak clipper and arctic cold front will move across the area tonight and early Thursday morning, potentially bringing a few snow showers to NE portions of the area. This will also bring additional cold air to the region late this week.

3) While details remain uncertain regarding the weekend system, strong low pressure is very likely to develop off the SE/mid Atlantic coasts, bringing strong winds along the coast and the potential for significant winter weather impacts to the region.

DISCUSSION

As of 330 AM EST Wednesday...

KEY MESSAGE 1...A weak/dry frontal boundary has dropped south of most of the area early this morning, bringing gusty N winds along the coast. Temperatures range through the teens north and are in the 20s south, with wind chills values as low as the single digits above zero across the north. As temperatures fall another 5-10 degrees through sunrise, expect lows into the single digits over the NW, and mainly in the teens elsewhere. The Cold Weather Advisory remains in effect through 10 AM this morning for the the northern tier of counties, the Peninsulas, and the Eastern Shore where local thresholds for wind chills are expected to be reached.

Today's high temperatures will again be well below normal, ranging from the mid-upper 20s N to the mid 30s S (the areas getting above freezing are locations that already have minimal, if any, lingering snow/ice). High clouds prevail this morning, followed by increasing aftn clouds from the N as the next shortwave trough dives SE from Canada.

KEY MESSAGE 2...A weak clipper system and associated arctic cold front will move across the area tonight. This front will be mostly dry, though can't rule out a few snow showers or flurries mainly across the northern Neck and Eastern Shore as this system moves through. Have slight chc PoPs from 7 PM/00Z through 1 AM/06Z in these areas. At this time, no mentionable accumulation is expected, though if any snow shower overperforms a light dusting is possible on the already very cold ground. In the wake of the front, temperatures will quickly plummet into the single digits to teens across the entire area, though again the NBM continues to be several degrees colder than the numerical guidance (with the NBM verifying too low the past 2 nights). Still, additional Cold Weather Advisories may be needed with wind chills dropping into the single digits and localized areas where winds are highest likely seeing below zero apparent temperatures. Wind chills will struggle to rise above the mid teens to mid 20s during the day Thursday and Friday.

KEY MESSAGE 3...There remains a lot of model and ensemble spread regarding the details of the weekend system, particularly with respect to QPF and location. The pattern remains similar to what has been advertised over the past several forecast cycles: high confidence that there will be a digging upper trough over the Great Lakes, with a strong high dropping southward over the Plains towards the western Gulf Coast Sat. The trough is forecast to become a closed upper level low over the TN Valley Sat morning, shifting SE to a position along the SC/GA coast Sat night, though the exact placement of this remains somewhat uncertain and will play an important part in the the exact evolution of this system. The combination of these features will result in surface cyclogenesis somewhere off the Southeast Coast. Ensembles have a few different scenarios painted as to where this low develops, which will have a major impact on the sensible weather for the local area over the upcoming weekend. Pretty much everything depicts a significant deepening of the low along or off the mid-Atlantic coast into early Sunday, which could present a plethora of issues concerning impacts to the region including, but not limited to moderate to heavy snowfall, high winds, coastal flooding, and hazardous marine conditions. Latest models and ensembles generally have the GFS/GEFS as the farther inland/closest to the coast with the GEM/GEPS and ECMWF/EPS farther south and offshore. Probs for 3" and 6"+ pf snowfall remain fairly similar to the 12Z cycle from yesterday, with the GFS/GEFS being much higher inland and NW than the other solutions. There is one caveat to these probabilities is that they are using a 10:1 SLR, but with the very cold airmass already in place (and no warm nose aloft), these will likely be much higher especially father inland, probably from 15:1 to 18:1. Any subtle differences in the track of this low will ultimately dictate where the highest snow will be observed. As of now, our forecast has increased PoPs to chc/likely overnight Fri into early Saturday along the initial inland sfc trough progged over the southern Appalachians. This could bring accumulating snow to mainly southern VA and NE NC as the coastal system is just starting to organize. Still, the highest PoPs will be later Sat through early Sunday as the coastal system rapidly intensifies and makes its closest approach to the area. PoPs have been raised to 70-90% along the coast with likely PoPs from most of the remainder of the CWA (kept PoPs in the chc range NW). In contrast from this past weekend's storm, p-types will likely be pretty straightforward, likely all to predominately snow unless the track of the low deviates farther west. If this occurs, areas closer to coast may see a rain/snow mix. Again, there remains lower confidence in the specifics of this forecast, so stay tuned for updates regarding this potentially impactful winter storm. Additionally, some guidance is showing some very bullish snow totals, so ensure you are getting your information from trusted sources.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

As of 100 AM EST Wednesday...

VFR conditions will prevail through the 06z/28 TAF period, the only exception could be over the northern Neck and eastern shore NE this evening/tonight with a few passing snow showers possible at SBY from 00-06Z. Northerly winds will briefly be elevated and gusty along the coast through ~12Z this morning, otherwise, winds become WSW at 5-10 kt for most of the day. High clouds this morning, followed by increasing clouds and some BKN CIGs around 5-10 k ft over the N and central sites later in the aftn, shifting S tonight. Winds turn back to the NW late in the TAF period as the next cold front drops through.

Dry/VFR Thursday and most of Friday, with a chance for snow possible as early as Friday night. As the coastal low strengthens Saturday and Saturday night, widespread flight restrictions are likely closer to the coast and possible farther inland. Strong winds are likely over coastal terminals with elevated winds inland, but details remain uncertain.

MARINE

As of 125 AM EST Wednesday...

Key Messages:

- Small Craft Advisories in effect for the Chesapeake Bay, coastal waters, Lower James River, and Currituck Sound through early this morning due to elevated winds ahead of and behind a cold front.

- Confidence is increasing in high-end Gale or Storm conditions this weekend as a strong coastal low develops.

- Freezing spray will continue to be possible through the weekend with the best chance this weekend. Additional Freezing Spray Advisories may be needed.

A dry cold front is pushing SE over the local waters early this morning. Winds behind the front are out of the NNW at 15-25kt. SCAs are in effect for the bay and the coastal waters this morning. After this brief surge behind the front, winds will gradually diminish through the morning as high pressure fills in from the west. By this afternoon, WNW winds will be down to 5-10kt. NW winds increase again late tonight with a secondary push of CAA. Another round of SCAs will likely be needed late tonight into tomorrow morning for the bay for 15-20kt winds with gusts to 25kt. Could see some 5ft seas out near 20nm with this surge, but thinking the coastal waters should largely remain sub-SCA. Breezy, but sub-SCA conditions are then expected Thurs evening through Friday evening.

Attention then turns to the potential for a significant coastal storm over the weekend. There is high confidence in a strong surface low forming along and traveling up the coast early Saturday through Sunday. What remains uncertain is the exact track and timing, which will dictate just how strong winds will be. Confidence continues to increase in at least gale, if not storm-force, winds. Current guidance suggests winds increasing Saturday-Sat night and peaking at 35-45kt with gusts upwards of 50kt Sunday morning (25-35kt in the rivers). Seas during this period will largely depend on wind direction, but currently forecasting 8-12ft seas and 5-7ft waves in the bay.

Lastly, periods of light freezing spray are expected through the end of the week due to cold water and air temperatures and gusty winds. Moderate freezing spray over the weekend will likely require Freezing Spray Advisories.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Cold Weather Advisory until 10 AM EST this morning for MDZ021>025. NC...None. VA...Cold Weather Advisory until 10 AM EST this morning for VAZ048- 062-064-075>078-083>086-090-099-100-509>512-517>525. MARINE...Small Craft Advisory until 10 AM EST this morning for ANZ630- 631. Small Craft Advisory until 7 AM EST this morning for ANZ632- 634-650-652-654. Small Craft Advisory until 4 AM EST early this morning for ANZ633-638-656-658.