textproduct: NWS Wilmington

WHAT HAS CHANGED

Scattered showers and thunderstorms are possible this weekend. The best chance for widespread showers and storms is late Sunday with a backdoor cold front. Dangerous heat remains possible next week.

KEY MESSAGES

1) Heat and humidity returns for the weekend. Rain chances increase as well.

2) Dangerous heat remains possible next week.

DISCUSSION

KEY MESSAGE 1... Heat and humidity returns for the weekend. Rain chances increase as well.

Bermuda high pressure will solidify southeasterly flow on Friday. Moisture transport and a building ridge to our southeast will push temperatures into the low and mid-90s. Despite the advection of surface moisture, boundary layer RH indicates that some lingering dry air aloft will mix down on Friday afternoon. This should keep minimum dew points in the mid and upper 60s, to around 70 at the coast; heat indices holding around 100.

Incremental increases in heat and humidity on Saturday and Sunday bring us close to (or exceeding) heat advisory thresholds across the region each day. Temperatures will be in the upper 90s to near 100. Stay hydrated, take breaks, check-in on neighbors with higher susceptibility to extreme heat, and never leave kids or pets unattended in vehicles.

Scattered diurnal and sea-breeze driven convection returning Friday and Saturday could offer some relief from the heat for some locations. Hot daytime temperatures and focused surface lift along a back door cold front will produce widespread thunderstorms late Sunday. With some dry air aloft, a strong wind gust will be possible with a few storms. Ensemble probabilities favor convection arriving on Sunday evening.

KEY MESSAGE 2...Dangerous heat remains possible next week.

A back door cold front drops southward late Sunday and early Monday. This will bring lower dew points and drag temperatures back into the mid 90s through Tuesday. An upper level ridge will take shape over the Ohio River Valley on Tuesday, baking a large portion of the eastern US through much of next week. These hot temperatures combined with our climatological dew points could lead to prolonged and dangerous heat through the period.

Ensemble probabilities are widely favoring dangerous heat occurring through much of next week, but there is some uncertainty in how extreme temperatures and dew points will be. An area of low pressure over the southwestern Atlantic (off of the SC coast) may persist for a portion of next week. This would funnel lower dew points and cooler 925-850 mb temps into the region through late next week, softening the currently extreme outlook. In support of this operational solution found in the GFS and ECMWF, MSLP ensembles clusters with the highest membership favor slightly cooler temperatures than the ensemble mean due to high pressure over the northeastern US and vague hints at the trapped surface low to our southeast. Despite these signals, confidence is not high enough to stray from the ongoing message: a prolonged period of dangerous heat is possible late next week.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR conditions should persist for the next 24 hours. Daytime heating should help develop scattered to locally broken cumulus with bases ranging from 4000 at the coast to 6000 feet inland. The depth of instability should be too limited for any showers to develop today. Light and variable winds should become southeasterly 7-10 kt after 15-16z at KILM, KCRE, and KMYR with today's seabreeze circulation.

Extended Forecast... Patchy fog is possible Saturday morning. with low confidence. Otherwise, VFR conditions should dominate. Scattered diurnal and sea-breeze driven convection returns Friday and Saturday. More organized and widespread shower and storm chances are expected Sunday afternoon as a weak backdoor cold front approaches the area.

MARINE

Light winds today will become dominated by the sea breeze during the afternoon. Bermuda high pressure becomes re- established tonight and Friday as southeasterly flow increases. Seas around 2 feet today, increasing to 2-3 on Friday. Southerly flow increases on Saturday (up to 20 knots sustained at times) as an area of low pressure traverses the Mid-Atlantic. Wind waves dominate the wave spectrum at 3-4 feet, 4-5 feet in the offshore waters. Recreational boaters should be cautious in area inlets on Saturday. With the surface low moving offshore on Sunday, winds return to 10-15 knots. A back door cold front will drop southward through the region late Sunday into Monday. Northeasterly flow behind the front will peak around 15 knots on Monday afternoon. Seas increase to 3-4 feet in the nearshore waters, 4-5 feet in offshore NC waters.

ILM WATCHES/WARNINGS/ADVISORIES

NC...None. SC...None. MARINE...None.