textproduct: NWS Wilmington

WHAT HAS CHANGED

Another Heat Advisory has been issued for Thursday. Forecast coverage of storms has decreased slightly for Thursday, and has also decreased along the beaches on Friday. Forecast storm chances remain nearly unchanged Friday night through the weekend.

KEY MESSAGES

1) Dangerous heat to continue through Thursday.

2) Isolated severe storms possible on Friday.

DISCUSSION

KEY MESSAGE 1...Dangerous heat to continue through Thursday.

Above normal temperatures will continue through at least Thursday before increasing coverage of thunderstorms brings slightly cooler temperatures by Friday. As with the last few days, the main nuance will be tracking where deep daytime vertical mixing dilutes high surface dewpoints with drier air from aloft, perhaps keeping apparent temps/heat index values below the Heat Advisory threshold of 105 degrees F for three hours. The Pee Dee region appears to have the best chance for enough dry air to mix down Thursday, and is the only portion of our forecast area not included in a new Heat Advisory.

Only isolated thunderstorms along and west of seabreeze are expected again on Thursday. Dry mid level air continues to inhibit more widespread convective coverage and associated relief from the heat.

KEY MESSAGE 2...Isolated severe storms possible on Friday.

An upper trough and attendant cold front progressing eastward into the Carolinas on Friday should yield good coverage of showers and thunderstorms, possibly including some severe storms. Forecast storm motion has apparently decreased from previous model runs, now to only 10 knots on Friday, which could allow isolated flash flooding to occur in heavy downpours. Bulk shear across the 0-6 km layer is only forecast to run 10-15 knots on Friday, enough for some weak multicell organization. The primary storm mode should be single cells, with outflow boundaries likely the organizing factor. Inland areas should have the highest coverage of storms, with slightly cooler onshore flow perhaps remaining convectively capped until Friday night.

Another round of showers and thunderstorms appears likely on Saturday as the front slides farther south into the area.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Scattered cumulus with bases 3000-5000 ft AGL could grow into isolated thunderstorms this afternoon. The odds of direct impacts on any airport are very low, but are just large enough I've included a PROB30 group at KILM through 22z for possible MVFR conditions. VFR conditions should prevail through the first half of the night, but light winds and clear skies should allow areas of ground fog to develop. MVFR visibility is expected at this time for all local airports except for KMYR, and conditions should improve by 13z Thursday.

Extended Forecast...Brief MVFR/IFR conditions are possible in isolated thunderstorms Thursday afternoon, and in areas of ground fog or low stratus late Thursday night/Friday morning.

Chances for thunderstorms will become moderate to high Friday afternoon and again Saturday afternoon as a cold front approaches the eastern Carolinas. Low stratus or ground fog is possible again Saturday night. Scattered thunderstorms may continue through Sunday and Monday, mainly in the afternoons near the coast affecting KILM, KCRE, and KMYR as the old stalled front decays.

MARINE

Light and variable winds continue today with a front stalled just inland. Southeast swell energy is present but weak. Light winds are producing a weak wind wave, so dominant seas remain around 2 feet. This weekend there may be a slight increase in southerly flow but forecast confidence is low as models now show the increased gradient remaining outside of the 20 nm zones. The only minor uptick in winds and seas should be confined to the 20-60 nm zones.

The biggest marine impact will likely be from increasing coverage of showers and thunderstorms beginning Friday evening and continuing through the weekend. There will likely be several rounds of storms, accompanied by reduced visibility and possible gusty winds.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory from 11 AM to 7 PM EDT Thursday for NCZ087-096- 099-105>110. Heat Advisory until 8 PM EDT this evening for NCZ096-099- 105>110. SC...Heat Advisory from 11 AM to 7 PM EDT Thursday for SCZ024-033- 054>056-058-059. Heat Advisory until 8 PM EDT this evening for SCZ039-054>056- 058-059. MARINE...None.