textproduct: Wakefield

WHAT HAS CHANGED

- Updated Aviation Discussion for 12z

- A Slight Risk Excessive Rainfall Outlook area has been introduced for areas along and east of I-95 for both Thursday and Friday. Marginal Risk areas have been added for much of the area on Saturday.

KEY MESSAGES

1) Seasonably warm and noticeably less humid today.

2) Rain and storm chances increase Thurs-Sat.

3) Cooler and drier air briefly moves back in early next week

DISCUSSION

As of 330 AM EDT Wednesday...

KEY MESSAGE 1...Seasonably warm and noticeably less humid today.

Latest analysis reveals low pressure just south of Atlantic Canada, with a frontal boundary extending down the offshore waters of the eastern seaboard and across the Coastal Carolinas. To the west, weak 1016mb sfc high pressure centered over the OH/TN Valleys continues to slowly build east early this morning. Aloft, quasi-zonal flow was in place over the eastern half of the CONUS downstream of a sprawling upper ridge over the Desert Southwest and Intermountain West.

For today, a brief respite is in store as weak high pressure builds over the region from the Mid-South. More efficient mixing should allow drier air to finally move into the area, with dewpoint values falling into the mid-to-upper 60s inland, and upper 60s to mid-70s along the coast. Highs will be 1-2 degrees warmer than yesterday on average, mainly in the upper 80s to low 90s across the area. These temperatures mixed with lower dewpoints will yield heat indices close to actual air temperatures. Showers or storms are unlikely today, with PWs falling back closer to typical mid-to-late August values (1.25-1.4"). A very low rain chance remains along the Albemarle Sound with this afternoon's sea breeze, mainly between Edenton and Elizabeth City. Otherwise, partly to mostly sunny conditions will prevail today, followed by mostly clear and seasonable conditions tonight with lows in the upper 60s to low 70s. Today's break in active weather will be short-lived.

KEY MESSAGE 2...Rain and storm chances increase Thurs-Sat.

An active pattern is looking more likely by late week into the weekend. An upper low will pivot across SE Canada through late week, with a broad upper trough building over the Eastern CONUS. A series of shortwaves will pivot through the base of that trough, moving from the Ohio Valley into the mid-Atlantic Thu- Sat. These shortwaves will gradually drive a seasonally strong cold front toward our area starting Thursday, though frontal progression will likely slow in upcoming model cycles.

Models continue to differ on timing, with the ECMWF on the faster end of guidance and the GFS/CMC lagging by 12-24 hours. Given the expected slow frontal progression, concern for several waves of locally heavy rainfall Thursday through the weekend has increased. PWs quickly build back AOA 2-2.25" Thursday through Saturday, renewing the potential for strong convection and heavy rain along the stalled boundary. Broad forcing for ascent will increase ahead of the initial shortwave Thursday afternoon, resulting in increasing shower coverage. These showers will encounter favorable jet dynamics (RFQ of a 60-80 kt upper jet) and DPVA from the approaching shortwave, serving to enhance low-level convergence along and ahead of the frontal boundary over the I-95 corridor and points E-NE. HREF is already indicating a 30% probability of 3"/3hr over the VA Northern Neck and Eastern Shore on Thursday. The front lingers over the region Friday before pushing toward the coast on Saturday, keeping our area downstream of the slow-moving trough axis with rounds of convection persisting Friday and Saturday along coastal areas.

Regarding severe weather potential, CAMs key in on weak low pressure developing along a subtle pre-frontal trough to our NW, slipping across northern portions of the area Thursday afternoon and evening. The exact front location will be critical, as some CAMs generate notable helicity tracks near the surface low track, which could portend increasing SRH and potential spin-up tornadoes if the boundary sinks far enough southward. In either event, deep-layer shear is most favorable tomorrow, and with MLCAPE increasing to 1500-2000 J/kg over the eastern half of the area, conditions should support multi-cell clusters and bowing line segments capable of producing damaging wind gusts and at least marginally severe hail.

SPC maintains Marginal Risk outlooks for Day 2 (Thu) and over the far SE day 3 (Fri), more than reasonable given referenced uncertainty. WPC has placed the eastern half of our area in a Slight Risk ERO for both Thursday and Friday, with a Marginal Risk for much of the area on Saturday.

KEY MESSAGE 3...Cooler and drier air briefly moves back in early next week.

Model ensembles generally agree that the main trough axis eventually shifts east Sunday into early next week, driving the front through and briefly introducing a cooler, drier air mass across the mid-Atlantic late in the weekend into early next week before temperatures moderate again by midweek.

AVIATION /09Z WEDNESDAY THROUGH SUNDAY/

As of 545 AM EDT Wednesday...

Mainly VFR conditions prevail to begin the 12Z TAF period, with VFR expected through at least midday Thursday. Only exception will be with localized reductions in short-lived ground fog/low stratus given light winds and moist conditions. Currently seeing IFR LCL LIFR CIGs and VSBY at SBY, but have included MVFR VSBYs at PHF for patchy ground fog (MIFG) as well. After any lingering MIFG clears by 12-13z, mainly partly sunny and dry today, with a very low chance for a shower or storm in the vicinity of KECG. Chances are still too low for inclusion in the TAF at this time. Winds will be light W-NW inland, and E-NE at the coast.

Outlook: Potentially turning unsettled Thursday into the weekend ahead of a slow-moving frontal boundary that could bring additional rounds of showers and storms and sub-VFR conditions.

MARINE

As of 310 AM EDT Tuesday...

Key Messages:

- Generally benign marine conditions expected through the end of the week, outside of afternoon/evening thunderstorms.

Benign marine conditions are expected to continue through the end of the week. Winds are N/NW early this morning around 5 kt, and will veer to the S/SE by late this afternoon, remaining around 5-10 kt. A weak frontal boundary will approach the waters Thursday, and will likely stall over the area Friday. Even with the boundary nearby, not expecting much of an increase in wind speed outside of convection, although winds may become more variable. Today will be dry, but scattered showers and storms return Thursday and Friday. There is a higher likelihood of strong to severe storms on Thursday than Friday but both days could bring strong storms to the waters, which would be covered by SMWs if needed.

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.