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WHAT HAS CHANGED

Updated discussion. Adjusted highest rain chances across south central VA into interior NE NC tonight. Increased QPF for Friday, with some locally heavy rainfall possible across Hampton Roads and northeast NC Friday morning.

KEY MESSAGES

1) Very warm this afternoon, and a bit humid along the coast.

2) A conditional severe weather threat continues into this evening, mainly across central and south central VA into northeast NC.

3) Brief locally heavy rainfall will be possible Friday morning across southeast VA into northeast NC.

DISCUSSION

As of 345 PM EDT Thursday...

KEY MESSAGE 1...Very warm this afternoon, and a bit humid along the coast.

SW flow has increased ahead of an approaching cold front. Breezy conditions continue into this evening with peak wind gusts around 30mph. Due to clouds from convective outflow earlier this morning, highs are a few degrees cooler than expected. However, these clouds have also limited mixing to a degree, keeping dewpoints a bit higher. Highs will generally be in the low to mid 90s with the hottest temps in the southeast. Due to convective outflows and increasing cloud cover, the Heat Advisory previously in place for Hampton Roads and the interior southeast was cancelled. Heat indices around 100 are likely into this evening, mainly across central VA.

KEY MESSAGE 2...A conditional severe weather threat continues into this evening, mainly across central and south central VA into northeast NC.

A decaying early morning MCS threw the expected weather pattern into a bit of disarray earlier today. CAMs resolved this system quite poorly, and the remnant outflow allowed for some mid-to- late morning showers across the VA Piedmont. It also laid down a pair of weak convective boundaries that have been the focus for convection over the past couple of hours.

A Slight Risk for severe storms is now in place for the entire area through this evening. Looking at the latest mesoanalysis, 1000-2000 J/kg of MLCAPE is in place across the region, though a reasonably strong capping inversion remains established across the northern CWA within the cool, stable outflow from this morning's convection. Bulk shear values are generally running between 30-40 kt, with locally higher values focused across the northwest half of the area, particularly along and just south of the US-360 corridor.

Damaging winds remain the primary concern given a high DCAPE environment (800-1200 J/kg, peaking just south of US-360 as of 18z), though large hail will also be possible with any stronger, sustained updrafts, especially if any convection can develop N of RIC/SBY, where mid-level lapse rates increase to 6.5 to 7 deg C/km. That said, since the northern cap will take some time to erode, and with the primary convective trigger likely to remain across the remnant boundaries to the south for the next several hours, expect majority of isolated to scattered convection to fire over the Piedmont into south- central VA and northeast NC through early evening, with isolated activity farther north.

KEY MESSAGE 3...Brief locally heavy rainfall will be possible Friday morning across southeast VA into northeast NC.

After a brief lull to rain chances late this evening into early Friday morning, rain chances ramp back up toward dawn Friday into early Fri afternoon. This will coincide with a cold front dropping across the region, as moisture from the tropical remnants of TC Arthur push across the Carolinas and far SE VA. This will likely occur in a narrow band along the frontal zone, though the warm rain processes with the tropical moisture should make for highly efficient rain producers capable of producing briefly impressive rain rates. Have increased QPF across the far SE and there still may be a narrow corridor that locally sees 1-2" of rainfall between sunrise and midday Friday, with locally higher totals possible. Moisture slides offshore tomorrow afternoon, with quick clearing from SW to NE tomorrow afternoon into tomorrow evening.

AVIATION /19Z THURSDAY THROUGH TUESDAY/

As of 220 PM EDT Thursday...

VFR conditions prevail for most of 18z/18 TAF period. SW flow increases ahead of a cold front with 15-20 kt winds gusting to ~30kt. Showers and storms ahead of the front move into the area this evening into the overnight hours. While a scattered storms will be west of the terminals late this afternoon into this evening, terminals likely will not see impacts until after 00-03z. Scattered convection continues through the night with highest chances of impact at RIC/PHF/ORF. Latest guidance indicates CIGs start dropping to MVFR after 09z, with IFR/lcl LIFR between 11-15z, with best chances at PHF/ORF/ECG. CIGs gradually returning to VFR tomorrow afternoon as convection pushes offshore.

Outlook: Drier conditions/VFR conditions return Fri evening through the upcoming weekend.

MARINE

As of 220 PM EDT Thursday...

Key Messages:

- Elevated SW winds continue today into tonight, with Small Craft Advisories remaining in effect for all waters.

- A Gale Warning is in effect for the offshore 20-60nm zone south of the VA/NC border this afternoon into tonight.

Deep low pressure has moved into Ontario and New England this afternoon with a cold front extending to the SW across the Ohio Valley. SW winds 15-20 kt with gusts to 25 kt are noted over the local waters. A few gusts have approached 30 kt, mainly just downstream of land areas where deeper mixing is present vs farther offshore. Waves are 1-3 ft in the bay with seas building to 3-4 ft.

SW winds continue this evening and tonight ahead of the cold front. SCA headlines remain in effect for all local waters. A few strong storms remain a possibility this evening and tonight but outflow and debris cloudiness from early morning convection over the Midwest lends considerable uncertainty to the storm coverage and intensity forecast. However, the environment will support the potential for strong to severe wind gusts with any storms that manage to form. The Gale Warning for the far offshore zone south of the VA/NC border continues through late evening with gusts up to 35 kt. Seas will peak this evening at 4-6 ft nearshore and 5-8 ft in the 20-60nm zones. Winds are expected to gradually decrease after midnight tonight with Small Craft Advisories coming to end for most of the area around sunrise. The southern Chesapeake Bay may linger in marginal SCA territory through mid morning.

The latest model guidance has thrown a wrench into the Friday afternoon portion of the forecast with the remnant circulation from TS Arthur expected to quickly translate eastward across the Carolinas tomorrow. At the same time, the previously referenced cold front drops southward across the local waters with W/SW flow becoming N and NW behind the boundary. The ECMWF and NAM are farther north or stronger with the remnant circulation, which would allow winds to briefly increase again as the low makes its closest approach during the afternoon. Have increased winds to 15-20 kt with gusts to 25 kt across the southern Chesapeake Bay and adjacent waters southward Friday afternoon. This portion of the forecast is very low confidence, however, with the GFS continuing to show a much weaker and more suppressed low. Will hold off on extending current SCA headlines given substantial model disagreement but the areas of most concern for brief SCA conditions are the southern bay, lower James River, Currituck Sound, and coastal waters S of Cape Charles Light. NW winds 10-15 kt are expected to continue into early Saturday. High pressure builds into the region Saturday into Sunday with southerly flow expected to strengthen ahead of the next system early next week.

CLIMATE

As of 230 PM EDT Thursday...

While no record highs are anticipated, they are included for reference.

Record Highs for today 6/18

Record High/Year Location 6/18 -------- ---- Richmond 100 (1970) Norfolk 99 (1944) Salisbury 98 (2014) Eliz. City 100 (2011)

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 AM EDT Friday for ANZ630-631. Small Craft Advisory until 10 AM EDT Friday for ANZ632-634. Small Craft Advisory until 7 AM EDT Friday for ANZ633-639-650- 652-654-656-658. Small Craft Advisory until midnight EDT tonight for ANZ635>637. Gale Warning until 1 AM EDT Friday for ANZ688.