textproduct: NWS Wilmington

WHAT HAS CHANGED

Issued Heat Advisory for Tues afternoon for eastern portion of area. Also issued Coastal Flood Advisory for minor coastal flooding along the lower Cape Fear River in the vicinity of downtown Wilmington for high tide just after 830 pm this evening.

KEY MESSAGES

1) The combination of deep moisture and a passing weak disturbance aloft will continue to trigger showers and thunderstorms into late this afternoon.

2) Drier midweek with increasing potential for extreme heat Tuesday through Friday.

3) Thunderstorm chances should increase again Friday and Saturday with the approach of a cold front from the north.

DISCUSSION

KEY MESSAGE 1...The combination of deep moisture and a passing weak disturbance aloft will continue to trigger showers and thunderstorms into late this afternoon.

Showers and thunderstorms will continue to develop across the area until heating cuts off for the day and shortwave moves eastward late this afternoon into early eve. Bermuda high pressure centered just south of Bermuda is directing a flow of moisture from the Gulf and Bahamas northward across the Carolinas. Plenty of moisture exists with precipitable water values of 2.0 to 2.4 inches and CAPE greater than 3500 J/kg. A weak shortwave moving through will enhance the storms and should see periods of torrential rain associated with any storms that develop, along with potential for wet microburst producing some strong gusty winds, and a fair amount of lightning. The steering flow aloft will drive these storms toward the east and should see decent coverage over the coastal counties where storms along the sea breeze boundary will end up.

KEY MESSAGE 2...Drier midweek with increasing potential for extreme heat Tuesday through Friday.

Heat Advisory has been issued for the eastern (coastal) portion of SE North Carolina and NE South Carolina for Tues aftn. The Bermuda high will shift south Tuesday, then expand a ridge axis westward across the Gulf Coast Wednesday and Thursday. The westerly flow this will create across the Carolinas will bring a hot airmass overhead with 850 mb temps expected to exceed +20C through the period. Mixing this down to the surface implies high temperatures away from the coastline should reach the mid 90s, perhaps even upper 90s in spots. With dewpoints remaining seasonably high in the 70s, forecast heat indices should reach 105-110 degrees for at least portions of the area through midweek with Heat Advisories likely. Heat indices could reach heat warning criteria (greater than 110 degrees)in spots by Friday.

KEY MESSAGE 3...Thunderstorm chances should increase again Friday and Saturday with the approach of a cold front from the north.

The upper air pattern should amplify late this week as a longwave trough takes shape just off the East Coast and the former Bermuda ridge retrogrades to the Mississippi Valley. Northwest flow aloft may push a cold front southward into the Carolinas for the weekend, accompanied by cooler temperatures and an uptick in the coverage of showers and thunderstorms.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Scattered thunderstorms will be widespread enough to produce at least VCTS at all terminals this afternoon. South-southwest winds around 10 kts today, could gust up around 15 kts, or possibly higher in and around thunderstorms. VFR conditions forecasted for tonight with elevated, mainly westerly, winds and drier air hindering fog or stratus development.

Extended Forecast...VFR should prevail through the rest of the week. Shallow ground fog is possible inland each early morning. The approach of a cold front from the north may lead to increasing coverage of showers and thunderstorms again by Friday.

MARINE

Bermuda high pressure centered just to the south of Bermuda will become suppressed farther south over the next few days as a series of low pressure systems move across southeastern Canada and New England, lowering surface pressures across the northwest Atlantic. A very weak piece of one of these disturbances will move southeastward across the coastal Carolinas this afternoon into this evening, contributing to showers and thunderstorms, some with gusty winds, moving eastward over the waters. Otherwise a typical wind pattern for August should continue through the week with southwesterly winds backing southerly in the afternoon with the seabreeze, and veering westerly overnight with the landbreeze.

Thunderstorm chances should decrease Tuesday through Thursday as high pressure builds westward along the Gulf Coast. A stronger disturbance to our north should approach the Carolinas on Friday, potentially pushing a surface cold front into the area. This should lead to a larger coverage of showers and thunderstorms.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory from noon to 8 PM EDT Tuesday for NCZ099-105>110. Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for NCZ107. SC...Heat Advisory from noon to 8 PM EDT Tuesday for SCZ054>056-058- 059. MARINE...None.