textproduct: Wakefield

WHAT HAS CHANGED

Increasing confidence for a potentially significant to severe winter storm and very cold temps this weekend, though uncertainties remain regarding coverage, timing, and precip type.

KEY MESSAGES

1) Cold and dry weather prevails through Wednesday, with today being the coldest of the days. Temperatures moderate on Thursday ahead of the next system.

2) Chances for a significant to potentially severe winter storm continue to increase this weekend. Exact details remain unclear at this time, but users should keep a close eye on the forecast this week.

DISCUSSION

As of 225 AM EST Tuesday...

KEY MESSAGE 1...Cold and dry weather prevails through Wednesday, with today being the coldest of the days. Temperatures moderate on Thursday ahead of the next system.

A deep-layer trough will remain situated over the eastern CONUS today. At the surface, cold Canadian high pressure gradually builds down from the northern Plains into the MS Valley, eventually settling over the area Wednesday. A reinforcing cold front is currently crossing the area with another round of cold and very dry air filtering in from the NW. Highs struggle to get above freezing across our northern and northwest counties today, and 30s elsewhere outside of far SE VA/NE NC where lower 40s are forecast. It will be cold tonight as high pressure moves overhead. Temperatures drop back into the teens for much of the area away from the coast with even some upper single digits possible at the typically colder locations.

The upper flow turns more zonal for the middle of the week. This should allow temps to moderate into the 40s Wednesday and then 50s by Thursday. A series of weak cold fronts will move through Wednesday night and again Thursday night. While these will be mainly dry (as the best forcing remains N and NW of us), cannot completely rule out a light rain shower on Thursday. Cooler temps return for Friday behind these fronts, but the coldest air doesn't arrive until the weekend.

KEY MESSAGE 2...Chances for a significant to potentially severe winter storm continue to increase this weekend. Exact details remain unclear at this time, but users should keep a close eye on the forecast this week.

There remains a very impressive medium range signal for a potentially significant to severe winter storm from the latest deterministic/ensemble guidance. Models have trended slightly slower with the onset of winter weather, though precipitation could still begin as early as Saturday AM. However, uncertainties still remain in regards to exact precipitation evolution. Details below:

There will be a very strong push of low-level CAA Saturday, with 850- 925mb temperatures dropping to -10 to -15 C across much of the area as 1045+mb Arctic high pressure builds into the midwest. This will translate to temperatures dropping into at least the teens (potentially single digits) for much of the area Friday night/Saturday AM. Temperatures will then struggle to to get out of the 20s on Saturday outside of far SE VA/NE NC where lower 30s are possible. The cold air likely lingers throughout the weekend and even into early next week, with the NBM showing below freezing high temperatures for much of the area through at least Monday. Regarding moisture, the upper pattern appears quite favorable for an active storm track and a significant winter event, with a strong Alaskan ridge, an active/amplified southern stream over the S/SW CONUS, and the aforementioned troughing to our N. There is increasing agreement among most model guidance and ensembles on an expansive precip shield blossoming in the central/southern Plains on Friday, expanding ENE into the Deep South and TN Valley by Saturday as a strong subtropical jet expands NE and strengthens. This precip will overrun the very cold airmass, likely leading to a large area of wintry precip across the central and southern CONUS.

For us locally, there still remains several uncertainties with respect to timing and specific precip types (especially S/SE), though the deterministic and ensemble guidance remains consistent in showing an impactful winter weather event for our area. As mentioned above, precip could begin as early as Saturday AM, though 00z model guidance has started to trend a bit slower, with precip starting Saturday afternoon or even Saturday evening. The most likely time for snow/sleet/freezing rain looks to be from late Saturday through Sunday (potentially lasting into early Monday AM). Both deterministic models and ensemble guidance have ticked up a bit in regards to QPF, now showing a moderate-high likelihood for 1.0-1.5+" of liquid equivalent precip with this event. The main question still remains whether we see snow, sleet, freezing rain, or some combination. With the strong high/impressive Arctic airmass building in, think p-type would be freezing or frozen everywhere except for maybe southside Hampton Roads and NE NC (and it could very well be mostly snow here as well depending on storm track).

Snow probabilities off the 00z suite of models are probably about as impressive as we have seen in some time. Both the EPS (ECMWF Ensemble) and EPS AI show 60-80%+ probs of total snowfall >= 6" (using 10:1 ratios), with 30-60%+ probs of >=12". There are even some low probs for higher amounts (18" and 24"). The GEFS (GFS Ensemble) tells a similar story with very high probs (at this time range) for >= 6" and >= 12". The CMCE (Canadian Ensemble) has the highest probs focused towards the northern half of the area, with higher sleet and freezing rain potential elsewhere as warmer air moves into the mid levels. These chances are likely to waver back and forth some over the next few days as the finer details become clearer. In summary, there is continued, increasing confidence in a significant to severe winter weather event for our area. Exact details regarding precip timing, coverage, and type remain uncertain and should be resolved over the next few days. Stay tuned!

Wintry precip aside, there is high confidence in very cold air spilling into the region for the weekend into early next week. Could certainly see widespread lows in the single digits Monday AM. Should any snow cover be present, some areas could see 0F readings!

AVIATION /07Z TUESDAY THROUGH SATURDAY/

As of 1245 AM EST Tuesday...

VFR conditions prevail today with just some passing mid-high clouds early this morning as a cold front moves through the region. Light W-SW winds shift to the NW early this morning as the boundary pushes through. WNW winds around 10 kt are expected this afternoon with occasional gusts to 20 kt. SKC skies and calm winds tonight.

Outlook: Mostly dry/VFR through Thursday. A cold front potentially crosses the area Thursday with only a 20% chance of showers at this time. Low-end precip chances continue into Friday. Winter weather is possible at all terminals this weekend, but it is too early for specifics.

MARINE

As of 225 AM EST Tuesday...

Key Messages:

- Sub-SCA conditions are expected through mid week.

- Increasing potential for a stronger system to impact the waters this weekend.

Marginal SCA conditions early this morning should improve as high pressure builds into the region behind a cold front. Winds have been very slow to increase so far this morning but hi-res guidance suggests a modest uptick prior to sunrise. Current headlines are set to expire at 4am/09z but may need to be extended by a few hours if observations trend toward the guidance. Thereafter, NW winds decrease through the day with generally benign marine expected through mid week. High pressure moves offshore Wednesday with flow becoming SW ahead of the next front. The chance for SCA conditions ahead of this feature has decreased with marginal winds and only limited potential for 4-5 ft seas across the northern coastal waters (well offshore). The late week period will feature another cold front dropping southward Thursday night as very strong (1050+mb) high pressure dives southeast from the Canadian Prairies. This will usher in an extended period of N and NE winds through the weekend as low pressure forms along the stalled front south of the local waters. Strong SCAs or gale conditions are on the table during this period depending on where the low forms and tracks. Very cold air will move into the region this weekend through the first half of next week, bringing at least some potential for freezing spray to the area waters.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 4 AM EST early this morning for ANZ630>634-650-652-654-656-658.