textproduct: Wakefield

WHAT HAS CHANGED

WPC has introduced a Day 2 Slight Risk for Excessive Rainfall for portions of the area Saturday-Saturday Night and SPC has issued a Marginal SVR risk for today for inland areas approximately along and S of I-64.

KEY MESSAGES

1) Unsettled and humid through Sunday as a frontal boundary lingers near the region, bringing scattered to numerous showers, thunderstorms, and localized heavy rain.

2) Dry with seasonable temperatures early next week, with temperatures warming above normal by midweek as an upper ridge builds back into the region.

DISCUSSION

As of 330 AM EDT Friday...

KEY MESSAGE 1: Unsettled and humid through Sunday as a frontal boundary lingers near the region, bringing scattered to numerous showers, thunderstorms, and localized heavy rain.

Latest surface analysis indicates a sfc cold front slowly dropping south of the Mason-Dixon line early this morning, with scattered showers across the far northern portions of the CWA. Sfc-based and ML CAPE values are generally ~500 J/Kg but CIN is also present so there has been little to no thunder over the past several hrs. PWAT values are elevated however, around 1.80" to 1.90" over northern portions of the FA, so these showers are putting down heavy rain and have been backbuilding so will continue to monitor the potential issuance of Flood Advisories although there has been a downward trend over the past few hrs. The CAMs have not been handling this activity particularly well thus far, so the diminishing coverage depicted after sunrise is a bit uncertain. As the front sinks south later today, most of the guidance shows showers/storms redeveloping mainly along and S of I-64 this afternoon into this evening.

The cold front drops south into the region late tonight, with the front stalling across southern VA and NE NC Friday afternoon. The 11/00z HREF PMM mostly highlights a 70% signal for 1"/3-hr QPF along and south of this boundary (southern VA/interior NE NC, but most areas are only in the 10% prob for 3"/3 hr, indicating too much uncertainty for any Flood Watches. Nevertheless, localized downpours and some localized flash flood issues remain the primary hazard, focused S-SW of I-64, with a Day 1 Marginal ERO. Depending on how much sunshine and instability develops, there is a Marginal SVR threat as well for areas along and south of I-64 (minus the immediate coast). Shear is not overly impressive, but with steep low level lapse rates, isolated wet microbursts can't be ruled out. Temperatures will feature a relatively sharp gradient today with more sunshine through mid aftn across the south, expect highs into the lower 90s, with northern areas in the low- mid 80s. The front continues to sink south tonight, with most of the showers/storms ending overnight. There does appear to be a good signal for low stratus and possible some fog across the piedmont overnight. Humid with lows in the upper 60s to lower 70s south, with somewhat drier air to the north where lows drop into the mid 60s.

Widespread precipitation chances peak Saturday, as the stalled boundary lifts back north as a warm front, along with a more pronounced mid-level shortwave disturbances push across the area. High precipitable water values, modest instability (skinny CAPE profile), and weak steering flow should yield efficient warm rainfall processes and additional localized hydro concerns (supported by an area-wide WPC ERO Marginal Risk and a localized upgrade to Slight for portions of the I-95 corridor, including metro RIC. Considerable cloud cover will keep a lid on Saturday highs to the low to mid 80s N, but highs reach into the upper 80s SE. There may even be some weak CAD, potentially keeping far NW zones even cooler (but still very humid). The boundary washes out Sunday, leading to noticeably lower convective coverage for the NW 1/2 of the area, but PoPs remain high chc to likely for the SE.

KEY MESSAGE 2: Dry with seasonable temperatures early next week, with temperatures warming above normal by midweek as an upper ridge builds back into the region.

The upper level flow becomes NW on Monday as a strong upper level trough dives SE from the Great Lakes and pushes off the NE and mid-Atlantic coast Monday night, with an upper level ridge slowly expanding NE from the lower MS Valley. This looks strong enough to drive the sfc cold front south of the CWA Monday, and bring significantly lower dew pts more typical of September. Becoming mostly sunny with highs in the 80s Monday, followed by a cooler, more pleasant night Monday night/Tue AM with lows mostly in the low-mid 60s with some 50s possible across the piedmont and interior MD eastern shore as sfc high pressure builds south. Diurnal shower and thunderstorm chances gradually tick back up mid-to-late week as heat and moisture start to return as the upper level ridge expands E-NE to the TN Valley and central/southern Appalachians.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

As of 700 AM EDT Friday...

Mainly VFR conditions early this morning, aside from areas of low stratus across central VA (affecting RIC), and a few showers with reduced VSBYs across far northern portions of the FA THAT may impact SBY as the cold front drops into the northern portion of the area. Another round of showers and storms are possible this afternoon/evening, with the best chances at RIC/ECG where PROB30 groups have been included. Areas of low stratus and possible fog are expected to develop overnight into Saturday morning, with the highest chc for IFR- LIFR restrictions inland which would favor RIC.

Outlook: The frontal boundary gradually lifts back north later Saturday-Saturday night/early Sunday. A high chance for showers/storms is currently forecast from late Saturday afternoon into Saturday night. Periodic IFR-LIFR VSBY restrictions in heavy rain will be possible during this timeframe. Remaining unsettled Sunday, with the highest shower/storm coverage across SE VA/NE NC. Becoming dry and mainly VFR by Monday with NE winds.

MARINE

As of 125 AM EDT Friday...

Key Messages:

- A period of generally benign marine conditions is favored from this weekend through Monday morning.

- Low-end SCAs are possible with NE winds behind a front late Monday- Monday night.

A weak cold front is just north of the waters early this morning, though there is some variability in wind direction as convection crossed portions of the area an hour or two ago. Wind speeds are 5- 15 kt (highest south). A few gusts to 20 kt cannot be ruled out across the lower Ches Bay from now-sunrise, but no SCAs are planned. Seas are 2-3 ft with 1-2 ft waves. The front is progged to cross the waters from late morning-aftn. A wind shift to the NE is expected following the FROPA, with wind speeds increasing to 10-15 kt by late in the day. The front appears too weak to bring SCA conditions, and local wind probs show less than a 10% chc of sustained 18 kt winds.

The flow becomes E then SE Friday night into Saturday, with winds generally 10-15 kt (highest north) through Saturday night as the front moves back north as a warm front. Winds become S-SW at ~10 kt on Sunday. Sub-SCA marine conditions are favored through early Monday. Another front is expected to cross the marine area on Monday, with a wind shift to the NE following the FROPA. This front appears to be a bit stronger, with some of the 00z models showing the potential for low-end SCA conditions behind the front late Monday. Winds quickly subside and shift to the east Mon night-Tue so any SCAs would likely be relatively short duration. Though it is 72- 84 hours out, local wind probs for sustained 18 kt winds have increased to 30-40% across the lower bay and southern coastal waters from Mon aftn-Mon evening. Waves and seas will likely remain 1-2 ft and 2-3 ft from late tonight into Monday morning, with SCA level seas possible (mainly south) by late Monday-Monday night as winds become NE.

The rip current risk will remain low today, with the northern beaches bumping up to moderate on Saturday as flow becomes onshore. A low rip current risk returns to all beaches on Sunday.

AKQ WATCHES/WARNINGS/ADVISORIES

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