textproduct: Wakefield

WHAT HAS CHANGED

Increasing potential for impactful severe weather across the region ahead of a strong cold front. The Storm Prediction Center maintains an Enhanced Risk (level 3/5) on Monday, but has increased the probs to 45% for much of the area. All severe hazards (wind, hail, and tornadoes) are possible.

A Gale Watch has been issued for the coastal waters north of Cape Charles late Monday morning through early Tuesday.

KEY MESSAGES

1)...Showers and storms prevail Monday, following increasing moisture and shower chances late Sunday as a warm front lifts north. The greatest threat for severe storms will be Monday, from late morning through the afternoon or early evening hours. SPC maintains an Enhanced Risk (level 3/5) for most of the CWA Monday.

2) Cold and breezy Tuesday, with a hard freeze likely for most of the area Tuesday night/early Wed morning. It remains dry, with seasonable temperatures returning late in the week.

DISCUSSION

As of 330 PM EDT Saturday...

KEY MESSAGE 1...Showers and storms prevail Monday, following increasing moisture and shower chances late Sunday as a warm front lifts north. The greatest threat for severe storms will be Monday, from late morning through the afternoon or early evening hours. SPC maintains an Enhanced Risk (level 3/5) for most of the CWA Monday.

A cold front has pushed S of the area, with very dry air in its wake this aftn. Temperatures are mostly in the 60s under a thick batch of high clouds, which will shift north with time later this evening and tonight. High pressure settles in from the N tonight, with the flow turning onshore. Lows range from the upper 30s to low/mid 40s. Will quickly see increasing clouds Sunday with strengthening easterly flow on the cool side of a warm front lifting north. Enough moisture convergence and lift makes it into far southern VA and NE NC by mid-late afternoon for some low-end shower chances. Highs Sunday will mostly be in the 60s, but will range from the 50s at the immediate coast and on the eastern shore due to the onshore flow off the cold waters, with a few locations across interior NE NC potentially near 70F if the rain holds off until late. Shower chances increase more significantly in the evening as the deeper moisture lifts north. Forecast soundings show little in the way sfc-based instability until after ~09Z/5AM Monday which will be confined to the far S. Instability aloft does increase earlier, and MU CAPE of 200-400 J/Kg spread north after midnight which could lead to a few rumbles of thunder. Temperatures will be quite mild Sunday night with lows only falling into the 50s across the area, and probably rising overnight in many areas as the southerly low level flow increases.

The setup on Monday continues to be favorable for strong to severe thunderstorms, with all modes of severe possible (wind, hail, tornadoes). The latest guidance continues to be in excellent agreement showing an extremely robust mid and upper level trough amplifying well to our west late Sunday, while taking on a negative tilt, and eventually becoming nearly cutoff over the western Great Lakes Monday. At the sfc, intense low pressure is forecast to lift NE from the mid MS Valley to the western Great Lakes late Sun night/early Mon, with all of the forecast models depicting this feature deepening to 980mb or lower and then occluding as the surface and upper level features stack vertically. The 12Z/14 GFS/ECMWF/GEM are still in very good agreement with the timing Monday, showing a secondary, deepening sfc trough along the Appalachians Monday morning, shifting east to the coast by early evening. The only model that differs significantly is the NAM, which is slower (and often verifies too slow).

Ahead of the trough/cold front, robust moisture transport will bring 60s dew points northward into the entire region. Very strong winds aloft (on the order 120-150 kts) will overspread the region on Monday in tandem with a 60-70 kt low level jet. Deep layer shear will likely be in excess of 50 kts which is more than sufficient for strong to severe thunderstorms, and potential supercells. The deepening sfc trough will enhance what will already be impressive shear, and potentially allow the sfc to 1 km winds to back to the SSE ahead of the cold front. Forecast soundings/hodographs show very favorable curvature in the low levels with 0-1 SRH generally on the order of 200-400 m2/s2, and 0-3km SRH even higher.

The local area will be 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. The degree of destabilization remains somewhat in question with widespread cloud cover and scattered precipitation leftover from early monday morning. 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, during the late morning/midday hrs through much of the aftn, all severe hazards will be a concern, particularly the potential for tornadoes, some of which would have the potential to be strong. SPC has maintained a broad Day 3 Enhanced Risk (level 3/5) for all but the Eastern Shore, where a Slight Risk (level 2/5) is forecast., but the probs have been increased to 45% for much of the area W of the Bay.

The cold front moves into the area from the west by mid to late afternoon with the a probable shift to more of a quasi- linear mode, with an increasing threat for damaging straight line winds and embedded QLCS tornadoes. The front should translate offshore during the evening hours with severe threat ending from west to east.

KEY MESSAGE 2...Cold and breezy Tuesday, with a hard freeze likely for most of the area Tuesday night/early Wed morning. It remains dry, with seasonable temperatures returning late in the week.

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 with highs back into the 50s and 60s.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

As of 155 AM EDT Sunday...

VFR conditions are in place this morning with mostly clear skies. SE winds mainly 5-10 kt through sunrise, increasing to 10-15 kt with gusts ~20 kt as mixing gets underway. Clouds will gradually thicken and lower through the day and MVFR CIGs possible by the mid-late afternoon at ECG, ORF, PHF, and RIC. A few showers are also possible near ECG after 20z but will be scattered in nature. Showers become more prevalent after 00z Monday as well as IFR CIGs. Some restricted VSBY is also possible in showers and fog. A period of LIFR CIGs is possible late in the period as a warm front lifts northward. LLWS will also increase this evening, mainly SE at 45 kt.

Outlook: LLWS is also possible for most of the overnight hours Sunday. A strong cold front will bring the potential for additional flight restrictions and strong to severe TSRA Monday. Even outside of any storms, strong, gusty southerly winds prevail into Mon evening with gusts to 25-35 kt expected. Dry/VFR Tue with breezy WNW winds, remaining dry Wed-Thu with less wind.

MARINE

As of 300 PM EDT Saturday...

Key Messages:

- A strong cold front approaches from the west Monday and crosses the coast Monday night. Small Craft Advisories have been issued for tomorrow over the Bay, Sound and southern coastal zones south of Cape Charles. SCA are likely on Monday, with gale conditions possible. A Gale Watch has been issued for the coastal waters north of Cape Charles late Monday morning through early Tuesday.

- There is a risk for strong thunderstorm wind gusts, and potentially a few waterspouts on Monday, as the front moves through.

High pressure is situated across the Great Lakes region, with a low pressure system lifting northeastward away from Atlantic Canada. The gradient has relaxed early this evening, allowing winds to veer around to the E this evening in the wake of a weak cold front. Marine- based observations are measuring winds of ~5-10 kts across the Bay and coastal waters with seas of 2-3 ft, waves 1 ft or less. Winds will continue to trend down through late this evening, as high pressure slides eastward across the Mid- Atlantic and with no notable CAA with the aforementioned front expected. This high will shift off the New England coast and strengthen to ~1033mb during the day on Sunday, and SCA have been issued for E-SE winds ~20 kt in the Ches Bay and lower James. A bit more marginal over the rest of the rivers, so have held off there for now. SCA runs through Sun night, with more notable SCA conditions likely late Sun night and especially on Monday.

On Monday, a deepening low pressure system will move across the Great Lakes region, dragging an associated cold front through the local waters in the afternoon/evening hours. High end-SCA conditions are likely ahead of the front, with low end gale conditions possible, especially in the coastal waters north of Cape Charles. This will be a more marginal gale due to the cooler water temps, but modestly strong pressure falls, a tight pressure gradient, and a 60- 5kt LLJ do favor a period of southerly gales. Have gone ahead and issued a gale watch for these coastal waters as this is where confidence is highest that a more prolonged period of gale force gusts will be realized, though the southern coastal waters could see a brief period of low-end gusts. Additionally, along and potentially ahead of the front, there is a risk for strong thunderstorm wind gusts and possibly a few waterspouts across the local waters, which will be handled with Special Marine Warnings. Seas build to 5-8 ft S to 9-12 ft N Monday into Monday night, with 3-5 ft 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 from 1 PM this afternoon to 6 AM EDT Monday for ANZ630-631-656-658. Small Craft Advisory from 10 AM this morning to 6 AM EDT Monday for ANZ632-634. Small Craft Advisory from 7 PM this evening to 6 AM EDT Monday for ANZ633. Small Craft Advisory from 10 AM this morning to 7 PM EDT this evening for ANZ638. Gale Watch from Monday morning through late Monday night for ANZ650-652-654.