textproduct: Wakefield

WHAT HAS CHANGED

Increasing potential for impactful severe weather across the region ahead of a strong cold front. The Storm Prediction Center has most of the area in an Enhanced Risk (level 3/5) on Monday. All severe hazards (wind, hail, and tornadoes) are possible.

KEY MESSAGES

1) Warmer and not as windy today and Sunday. Chances for showers and a few thunderstorms increase Sunday evening into the overnight.

2) Another strong cold front approaches early next week, bringing the potential for strong to severe storms Monday, with below normal temperatures to follow.

DISCUSSION

As of 340 AM EDT Saturday...

KEY MESSAGE 1...Warmer and not as windy today and Sunday. Chances for showers and a few thunderstorms increase Sunday evening into the overnight.

Occluded low pressure is centered north of Lake Ontario early this morning. The steep pressure gradient that resulted in very gusty winds on Friday has finally started to relax. Continued mixing early this morning has kept temperatures from falling off with most locations still in the low to mid 50s. Temps may be able to drop a few more degrees prior to sunrise as winds continue to decrease. Mostly sunny to start the day today with increasing high level clouds into the afternoon, mainly across the northern half of the area. Highs today rise into the 60s for inland areas but stay stuck in the the mid to upper 50s for the Eastern Shore. Flow turns onshore tonight with lows falling back into the upper 30s to low/mid 40s. Warming trend continues Sunday with highs in the 60s to low 70s inland and around 60 degrees for the Eastern Shore. Moisture increases through the day Sunday with a chance for showers across the southern third of the area by late afternoon, spreading northward Sunday evening into the overnight. Forecast soundings show little in the way of instability overnight but a few rumbles of thunder are possible. Temperatures will be quite mild Sunday night with lows only falling into the 50s across the area.

KEY MESSAGE 2...Another strong cold front approaches early next week, bringing the potential for strong to severe storms Monday, with below normal temperatures to follow.

All attention turns to Monday and the potential for severe weather well ahead of and along a very strong cold front that is forecast to cross the region. The latest guidance continues to be in excellent agreement showing an extremely robust mid and upper level trough deepening substantially to our west on Sunday and moving toward the Mid-Atlantic on Monday. A strong surface low will move over the Midwest Sunday before occluding over the Great Lakes Sunday evening. A strong cold front/surface trough will extend to the south of the surface low with potential for secondary/weaker cyclogenesis along this trough axis on Monday.

Ahead of the trough/cold front, robust moisture transport will bring 60s dew points northward into the region. Very strong winds aloft (on the order 120-150 kts) will overspread the region on Monday in tandem with a 60-80 kt low level jet. Deep layer shear will be at or above 50 kts which is more than sufficient for strong to severe thunderstorms. The strengthening surface trough to the west will promote some backing of the low level flow which will augment the already impressive deep layer shear. Forecast soundings/hodographs show very favorable curvature in the low levels with 0-1 SRH generally on the order of 200-500 m2/s2.

The local area will be squarely in the right entrance region of the mid and upper level jet on Monday which will provide forcing for ascent even well ahead of the surface cold front. Accordingly, hi-res guidance has trended toward greater coverage of showers and storms in the open warm sector on Monday. The degree of destabilization remains somewhat in question with widespread cloud cover and scattered precipitation. However, most guidance now shows 750-1000 J/kg of MLCAPE which will be more than enough instability given the extreme kinematic environment in place. Low level confluence bands well ahead of the front and favorable jet forcing should prove sufficient for prefrontal convection/supercells on Monday. If this convection can maintain a discrete or semi-discrete storm mode, all severe hazards are on the table, including the potential for tornadoes, some of which would have the potential to be strong. SPC has outlined a broad Enhanced Risk (level 3/5) for all but the Eastern Shore, where a Slight Risk (level 2/5) is forecast.

The cold front moves into the area from the west by mid to late afternoon with an increasing threat for damaging straight line winds and embedded QLCS tornadoes. The front should translate offshore during the mid to late evening hours with severe threat ending from west to east.

The airmass behind this system will be much cooler (actually trending to well below normal Tue-Wed) as well as significantly drier. Highs mainly in the 40s Tue-Wed. Most of the area can expect a hard freeze Tue night/Wed AM as strong >1030mb sfc high builds overhead, with diminishing winds and lows ranging through the 20s. Even the coast will likely see at least a light freeze with lows in the upper 20s to lower 30s, the possible exception being the NC OBX. Gradually trending warmer by late in the week, and remaing dry.

AVIATION /07Z SATURDAY THROUGH WEDNESDAY/

As of 145 AM EDT Saturday...

VFR conditions are in place across the region this morning. SW winds remain fairly robust for this time of day, mainly 10-15 kt with gusts ~20 kt. Expect gusts to trail off over the next hour or two as the gradient slackens. LLWS remains in the forecast but will come to an end from NW to SE. WNW winds 5-10 kt will prevail at RIC, PHF, ORF, and ECG today. Stronger winds linger at SBY through mid to late afternoon.

Outlook: VFR conditions persist into Sunday. Shower chances increase late Sunday/Sunday night, with flight restrictions possible into early Monday. A strong cold front will bring the potential for additional flight restrictions and potentially strong to severe TSRA Monday. Even outside of any storms, strong, gusty southerly winds prevail into Mon evening. Dry/VFR Tue with breezy WNW winds, remaining dry Wed with less wind.

MARINE

As of 310 AM EDT Saturday...

Key Messages:

- A strong cold front approaches from the west Monday and crosses the coast Monday night. Small Craft Advisory conditions are likely with gale conditions possible. Additionally, there is a risk for strong thunderstorm wind gusts.

999mb low pressure is centered N of Lake Ontario early this morning with a cold front trailing to the SSW across the Appalachians. The pressure gradient is gradually relaxing across the Mid-Atlantic coast and the wind is generally 15-20kt with gusts up to 25 kt for the Ches. Bay and coastal waters N of the VA/NC border, and 10-15kt with gusts up to 20kt elsewhere. Seas are mainly 3-4ft, with 2-3ft waves in the Ches. Bay. The trailing cold front crosses the coast later this morning into the aftn. There is minimal CAA in the wake of the cold front and sub-SCA conditions are expected today into tonight. An ESE, then SE wind increases Sunday into Sunday night with 1030+mb high pressure off the New England coast and strong low pressure well to the W. SCA conditions are possible in the Ches. Bay for wind, and potentially for seas in the coastal waters by Sunday night.

Deepening low pressure lifts NE through the Great Lakes Monday with a strong cold front approaching from the W, which then crosses the Mid-Atlantic coast Monday night. High-end SCA conditions are likely, with a period of gale conditions possible late Monday aftn/evening in southerly flow ahead of the front, and also briefly in WNW flow immediately behind the front during the early overnight hours. Modestly strong pressure falls, a tight pressure gradient, and a 60- 75kt LLJ favor a 3-6hr period of southerly gales (primarily for the northern coastal waters). However, the limiting factor will be very stable low-level lapse rates with a mild and moist airmass overspreading cold ocean water. Local wind probs depict the greatest probability of 34kt gusts over the coastal waters N of the VA/NC border, and even a 30-50% chc of 43kt gusts N of Chincoteague. Additionally, there is a risk for strong tstm wind gusts ahead of the front. Seas build to 5-8ft S to 9-12ft N Monday into Monday night, with 3-5ft waves in the Ches. Bay and locally higher at the mouth of the Bay. More benign marine conditions are expected by the middle of next week as high pressure settles across the region.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ630>632-634-650-652. Small Craft Advisory until 4 AM EDT early this morning for ANZ638-654-656.