textproduct: Wakefield

WHAT HAS CHANGED

- Updated Discussion

- A SLight Risk Severe Weather Outlook now in place for much of the area, with the exception of far SE VA and NE NC. A Sligh Risk Excessive Rainfall Outlook remains in place for coastal VA and the Eastern Shore (VA/MD).

KEY MESSAGES

1) An active weather pattern begins today and lasts through Saturday. The severe weather threat peaks today, with all modes of severe weather possible late this afternoon through this evening. The threat from periodic locally heavy rainfall begins this evening and continues into the upcoming weekend.

2) Mainly dry with seasonable temperatures Sunday through Tuesday.

DISCUSSION

As of 255 AM EDT Thursday...

KEY MESSAGE 1...An active weather pattern begins today and lasts through Saturday. The severe weather threat peaks today, with all modes of severe weather possible late this afternoon through this evening. The threat from periodic locally heavy rainfall begins this evening and continues into the upcoming weekend.

Latest analysis reveals the well-advertised cold front extending from the Eastern Great Lakes back into central IN/IL as of this writing. The front will reach the Mason-Dixon Line by the early afternoon.

An upper-level low pivoting across SE Canada will amplify a broad trough over the Eastern CONUS. Multiple shortwaves tracking through the base of the trough from the Ohio Valley into the Mid-Atlantic tonight through Saturday will drive a strong cold front toward the region. Increasing clouds and some showers will be possible over far northern portions of our area from the Northern Neck to the Eastern Shore by late morning. How far south these clouds can push will be a crucial piece regarding afternoon destabilization potential.

The severe weather threat will be fairly short-lived, but could evolve rapidly late this afternoon and evening. A weak surface low is progged to develop along a lee trough just north of Richmond, tracking across the Northern Neck and MD Eastern Shore. Storms should initiate along the lee trough in the Piedmont before moving east into higher instability (MLCAPE 15002000 J/kg east of I-95) and strong 3040 kt deep-layer shear. Initial discrete to semi-discrete cells will quickly consolidate into more of a QLCS/bowing line segment storm mode as outflow interacts with line-parallel flow focused along the boundary. This initial transition to a more linear mode poses the highest brief tornado threat, particularly from north of RIC to Tappahannock and Salisbury, a narrow corridor where boundary-relative 01 km SRH is maximized. Thereafter, cold-pool dominant processes will take over, with the main hazard transitioning to straight-line damaging winds and heavy rainfall as forcing pushes the front east. It will be during this time frame that a transition to more protracted hydro concern begins. In terms of severe weather outlook, the SPC has expanded their D1 Slight Risk to cover most of our area, with the exception of far SE VA and NE NC, which remains in a Marginal Risk area.

Regarding heavy rainfall potential, slow frontal progression increases confidence in several waves of heavy rain Thursday through Saturday. PWATs rebound to 2.0-2.3", supporting efficient rainfall rates along the stalled boundary. Broad forcing for ascent increases this afternoon and evening with the initial shortwave, expanding thunderstorm coverage. While localized 3"/3hr HREF probabilities have pushed a bit farther north, away from the local area, there is nevertheless a very consistent QPF footprint from the past several runs of CAMS showing localized flash flooding potential along the coast of eastern VA and over the Eastern shore, coincident with convection and a developing theta-e ridge. Slow moving storms producing locally heavy rainfall will likely produce at least localized issues tonight into Friday morning, most likely in urban and poor-drainage areas.

The front lingers over the region Friday before pushing offshore Saturday. Once again, the local area will be downstream of the slow-moving trough axis on Friday, with at least a couple of rounds of convection persisting along coastal areas. CAMs have remained remarkably consistent with their heavy rain signal over the local area, with the greatest heavy rain threat shifting into the Carolinas, including south central/SE VA and NE NC locally, as the upper trough axis digs farther SE into the mid-south by Friday evening, diving another front toward the local area. Meanwhile, the initial front will still be draped along the coast Saturday morning. The approaching front and the stalled front to the SE will each be the focus for additional rounds of scattered showers and storms inland, and numerous to widespread convection along the coast through Sat evening.

WPC Excessive Rainfall Outlooks continue to outlook the entire area today, with a Marginal risk along and west of I-95 and into NC, with a Slight Risk over the VA coast and Eastern Shore. A Slight Risk is in place for much of the area tomorrow, with the exception of a Marginal Risk far NW counties. And a Marginal Risk is in place for most of the area east of I-95 on Saturday.

KEY MESSAGE 2...Mainly dry with seasonable temperatures Sunday through Tuesday.

Model ensembles remain in good agreement that the main upper trough axis shifts offshore by Sunday, driving the cold front south and east of the region. In its wake, surface high pressure builds over the Mid-Atlantic, introducing a drier air mass and seasonable temperatures through early next week.

AVIATION /06Z THURSDAY THROUGH MONDAY/

As of 145 AM EDT Thursday...

VFR conditions prevail to begin the 06z TAF period with light winds and a mostly clear sky. Could see some patchy fog over interior southern VA overnight/early Thursday morning, but this should mostly stay away from the terminals. S-SW winds increase to around later this morning and this afternoon with increasing mid to high level SCT- BKN clouds. Have maintained PROB30 groups for TSRA late this afternoon (after 20/21Z). Storms will be capable of producing brief strong wind gusts as well as flight restrictions from heavy rain/reduced VSBYs.

Outlook: Remaining unsettled Thursday night through Saturday ahead of a slow-moving frontal boundary that will likely bring additional rounds of showers and storms and sub-VFR conditions. Guidance has trended toward IFR/MVFR CIGs lingering at PHF/ORF Friday morning. Eventually drying out later Saturday night and Sunday, with VFR conditions returning Sunday morning through Monday.

MARINE

As of 255 AM EDT Thursday...

Key Messages:

- Generally benign marine conditions expected through the weekend, outside of afternoon/evening thunderstorms. Some storms may become strong to severe this afternoon and evening.

Prevailing sub-SCA marine conditions are expected to continue through the end of the week and weekend. Winds have shifted out of the south around 10-12 kt with a few gusts to 15 kt early this morning. A weak frontal boundary will approach the waters later today, stalling over the area Friday. Despite the boundary nearby, not expecting much of an increase in wind speeds outside of convection (15-20 kt), although winds may become more variable. The main hazard through the period will be strong to severe thunderstorms. Scattered to numerous storms are expected late this afternoon through late evening (most likely timing between 5 PM-12 AM over the waters). Wind gusts to 50 kt are possible, and SMWs are likely. Scattered showers/tstms are expected on Friday and Saturday as well. While severe wx is less likely when compared to Thursday, a few SMWs are possible.

There remains a low risk of rip currents at all beaches over the next few days.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...None.