textproduct: Wakefield

WHAT HAS CHANGED

-Updated aviation discussion.

KEY MESSAGES

1) A Severe Thunderstorm Watch has been issued through 2 AM, which includes Southeast MD and portions of the Northern Neck.

2) Hot and humid conditions with heat indices around 105F are expected through the rest of the week. Heat Advisories remain in effect for nearly the entire area through this evening, and have been issued for central and SE portions of the area on Friday.

3) A few thunderstorms are possible mainly across northern portions of the area this evening and tonight (possibly severe with damaging winds). More widespread storms are expected on Friday, with storm chances continuing on Saturday (mainly SW). Some storms may be severe with damaging wind gusts and possibly large hail (especially on Friday).

DISCUSSION

As of 915 PM EDT Thursday...

KEY MESSAGE 1...A Severe Thunderstorm Watch has been issued through 2 AM, which includes Southeast MD and portions of the Northern Neck.

An MCS is congealing across SW/S-central PA and the MD Panhandle this evening and tracking ESE, with some additional convection developing across the northern Shenandoah Valley. Max mid-level lapse rates were ~7.3C/km on the 00z LWX sounding with SBCAPE of 4978 J/KG and 30kt of effective bulk shear. Additionally, the latest SPC mesoanalysis suggests this favorable environment extends into portions of the Northern Neck and SE MD. The latest trends from the HRRR bring the MCS ESE and merge it with some scattered convection in advance across NE portions of the local area. However, this does not occur until after 04z, so there is some question as to how late the damaging wind threat will linger. However, the MCS activity may not push offshore until after 06z, so there is a potential that the watch may need to be extended in time if the damaging wind threat persists after 06z.

KEY MESSAGE 2...Hot and humid conditions with heat indices around 105F are expected through the rest of the week. Heat Advisories remain in effect for nearly the entire area through this evening, and have been issued for central and SE portions of the area on Friday.

The backdoor front has slowly lifted north and lingers near our northern CWA border this afternoon. Upper heights have slowly risen with a 594dm upper high centered from TN to the Carolinas. Isolated convection has developed to our north and west. Heat Advisories remain in effect for all areas except the MD/NC beaches. While temperatures have been a few degrees cooler than expected, dew pts in the mid to upper 70s have allowed mach of the area to reach Heat Advisory criteria (aside from the eastern shore). Regardless, will let the current advisories run until 8 PM. The ridge starts to break down and a cold front will approach from the north going into Friday, though temps in the mid to locally upper 90s and lower-mid 70s dew pts along/east of I-95 will allow heat indices to peak in the 105-109F range across the SE 2/3 of the area. Therefore, have issued another round of Heat Advisories from 11 AM-8 PM from I-95 east and roughly I-64 south.

Afternoon clouds and storms ahead of the front will likely limit temps across the north, and lower dew pts in the Piedmont may limit heat indices to the low 100s. So have held off on advisories attm for these area. Relief from the heat will come this weekend with no additional advisories anticipated.

KEY MESSAGE 3...A few thunderstorms are possible mainly across northern portions of the area this evening and tonight (possibly severe with damaging winds). More widespread storms are expected on Friday, with storm chances continuing on Saturday (mainly SW). Some storms may be severe with damaging wind gusts and possibly large hail (especially on Friday).

As mentioned above, a few thunderstorms have developed to our NW this afternoon, but will struggle to reach the area through 4 PM as mesoanalysis shows some CIN/subsidence in place and the best forcing/upper flow is still across the southern Great Lakes and northern Mid-Atlantic. It remains uncertain whether the storms to our north will be able to make it into the Piedmont/central VA this evening, with PoPs generally no higher than 30% through 8 PM. However, if storms are able to make it down here, they could be strong to severe with damaging wind gusts. Another round of storms is possible overnight across our N and NE counties as a southwesterly 925-850mb jet strengthens some, with the most likely timing for this from 10 PM-3 AM (best storm chances overnight are across the MD Eastern Shore).

The most favorable overlap of forcing, shear, and instability is expected Friday. At the surface, the aforementioned front to our north will approach the local area but remain just to our north. Aloft, NW flow will remain in place and strengthen to 35-45 kt across much of the area by late in the day. The strong surface heating and humidity will allow for ample instability, and dry mid levels should enhance the potential for strong to severe winds. With falling upper heights and the approaching front, scattered to potentially numerous storms are expected to develop during the aftn and spread southeast through the evening. Given the overlap of strong heating/instability and deep-layer shear, continue to think that there is a legitimate severe wx threat for much of the area, with the potential for several fast-moving clusters capable of severe (50kt+) wind gusts, along with isolated marginal supercell structures capable of producing large hail (and damaging winds) as well. The lack of LLVL shear and high LCLs will greatly limit the tornado threat. The most likely timing for storms is between 4-10 PM with the highest storm coverage closer to the coast. SPC has maintained the Slight Risk (Level 2 out of 5) for severe wx across the entire area on Friday.

The risk for storms (and any potential severe weather) Saturday is dependent on where the front is situated during peak heating. The 12z/03 models have trended slightly slower with the front, and while winds switch to the north across the majority of the area Sat aftn...the main push of cooler/drier air may hold off until late Saturday. Therefore, it appears as if scattered storms are possible across a decent portion of the area along/south of I-64. There severe wx risk on Saturday is lower than on Friday, though a few storms could produce damaging wind gusts (especially across far southern portions of the area). Storms should be moving fast enough on Fri/Sat for no worse than a highly localized flood threat. Cooler/drier wx with onshore flow is expected on Sunday and Monday, with a gradual warm up after that (w/ mainly dry wx).

AVIATION /06Z FRIDAY THROUGH TUESDAY/

As of 130 AM EDT Friday...

VFR conditions prevail for RIC and south, with conditions deteriorating at SBY currently due to TS moving into the area. These TSRA will be capable of producing gusty winds and VIS restrictions for a few hours. Guidance shows them moving out after 10Z with generally clearing skies to start the day. W/NW winds will be AOB 10 kts through the TAF period. Thunderstorm chances will increase again after 04/19Z, though confidence in exact coverage is low. Currently only have a PROB30 in for ECG after 20Z since guidance continues to indicate slightly higher confidence further south. Once again, gusty, erratic winds and VIS restrictions from +RA will be likely in any storm that develops. Storm coverage will decrease towards the end of the TAF period.

Outlook: A stronger cold front is set to pass through the area Friday night into Saturday. Tstm chances continue on Saturday, with the highest PoPs S and SW of RIC. Mainly dry/VFR Sunday through Tuesday behind the front, though brief MVFR CIGs are possible near the coast with NE flow.

MARINE

As of 400 PM EDT Thursday..

Key Messages:

- South to southwest winds increase today and tonight ahead of a cold front. Conditions are expected to remain below Small Craft Advisory criteria, but there could be wind gusts ~15 knots at times in the Chesapeake Bay and ~20 knots across the southern coastal waters.

- A cold front drops south over the waters Friday night into Saturday morning. This will allow winds to turn northerly, then northeasterly. Wind gusts may approach 20 knots late Friday night into early Saturday. A more substantial increase in NW winds is expected Sunday into early Monday as high pressure builds in from the north, with SCAs possible.

A light S-SE wind late this aftn will shift to the SSW and increase to 10-15 kt tonight. A few gusts of 15 to 20 knots will be possible, with the strongest gusts across the southern half of the coastal waters. Winds diminish overnight into early Friday. The cold front begins to drop south across the waters Friday night into Saturday morning with winds turning to the N and eventually NE later Saturday into Sunday. There will not be a strong pressure push behind the front initially, but slightly cooler/drier air filtering in over warmer waters will lead to the potential for gusts of 15 to 20 knots Saturday. NE winds increase a bit more Sunday into Sunday night, leading to the next potential for SCA conditions across a majority of the waters (highest probs for coastal waters for seas and the lower Bay/lower James fro 15-20kt sustained winds. Calmer, more benign conditions look to take hold for early next week as high pressure builds back over the region, though seas stay elevated, potentially 5ft+ through Monday for the southern waters.

.Tides/Coastal Flooding: Added a Coastal Flood Statement for mainly nuisance flooding w/ the high tide cycle this evening across Bayside portions of the Maryland eastern shore.

CLIMATE

No records were set on Wednesday, 9/2 at any of the climate sites. Record highs are possible today (Thursday, 9/3) at Norfolk, Richmond, and Elizabeth City.

Richmond: Record High:

Thu (9/3) 99/1984 Fri (9/4) 98/2023

Norfolk: Record High:

Thu (9/3) 97/1977 Fri (9/4) 96/1985

Salisbury: Record High:

Thu (9/3) 99/1930 Fri (9/4) 95/1944

Elizabeth City: Record High:

Thu (9/3) 97/2020 Fri (9/4) 98/1944

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ012>017-030>032-102. VA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for VAZ080>090-092-097-098-511>520-523>525-528>531. MARINE...None.