textproduct: NWS Wilmington

WHAT HAS CHANGED

NBM dew points and heat indices lowered slightly for this weekend, consistent with known biases. Ensembles continue to favor widespread thunderstorms this afternoon. Strong thunderstorms are possible Saturday and Sunday. Chances for dangerous and prolonged heat have increased for late next week, surrounding the July 4th holiday. Aviation section updated for the 06Z TAFs.

KEY MESSAGES

1) Warmer This Weekend with Rain Chances Returning. Stronger Storms Possible on Saturday and Sunday.

2) Dangerous Heat Likely Next Week.

DISCUSSION

KEY MESSAGE 1... Warmer This Weekend with Rain Chances Returning. Stronger Storms Possible on Saturday and Sunday.

Heat and humidity make a return this weekend as the Bermuda high builds eastward and an upper level ridge takes shape over the Midwest. Warmer temperatures are expected across the Carolinas today with afternoon highs in the low 90s. Mixing should keep dew points around 70 (upper 60s inland) which will hold heat indices in the upper 90s to near 100. Heat indices will increase near the coast behind a sea breeze early this afternoon.

A weak mid level shortwave will lift northward across the region this afternoon, producing afternoon convection. HREF and associated CAMs have been consistent with the development of widespread storms. Severe weather parameters largely favor pulse convection, but a strong wind gust is possible with dry air aloft. Mean cloud layer winds will keep most of this convection inland with coastal areas also limited by the sea breeze.

Slightly warmer and more humid on Saturday with temperatures a degree or two warmer than Friday. Dew points also increase after 24 hours of southerly moisture advection. Heat indices should remain just shy of our heat advisory threshold (reflected in the latest forecast after tweaks to the NBM systematic biases). However, the threshold is only a number, please consider heat- related precautions in any weekend plans.

Convective activity on Saturday will be more isolated across the forecast area with the bulk of activity remaining north into NC and southern VA. A surface front will be the main driver of precipitation in northern NC, but a series of shortwaves will favor isolated to scattered convection developing southward through the afternoon, aided by outflow. Westerly flow aloft and an unstable atmosphere will introduce the potential for a few strong to severe storms on Saturday afternoon, continuing into the evening.

Sunday will likely be the warmest day of the weekend ahead of an approaching cold front. West-southwest winds will pin the sea breeze to the immediate coast, bringing temperatures in the upper 90s within a few miles of the coast. Westerly flow will keep dew points well mixed and in the upper 60s and lower 70s. Heat advisories are possible across the forecast area on Sunday. Afternoon showers and storms will be similar to Saturday with a chance for a few strong storms along a weak cold front approaching the area later in the afternoon and evening.

KEY MESSAGE 2... Dangerous Heat Likely Next Week.

Following a weak cold front on Monday, high temperatures will duck into the low and mid 90s through Tuesday with high pressure to our northeast. This surface high abandons us during the middle of next week, allowing the growing ridge centered over the Ohio River Valley to push temperatures to near record highs. Combined heat and humidity will produce prolonged, dangerous heat through much of next week. Extreme heat will be centered around the July 4th holiday.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

VFR is expected for the majority of the next 24 hours. Marine stratus may bring brief restrictions for CRE/MYR early this morning. Shallow ground fog is also possible at coastal locations where boundary layer moisture is highest.

High confidence in VFR by mid-morning for all terminals. Thunderstorms are likely to develop in response to a weak shortwave along the Piedmont trough this afternoon at FLO/LBT. Restrictions would be IFR for a brief period, but may see multiple rounds of storms prior to sunset. VFR this evening for all terminals. Low confidence in the potential for stratus tonight for areas that see heavy rainfall.

Extended Forecast... VFR will dominate outside of brief morning fog or stratus and afternoon storms. Scattered convection expected on Saturday. More organized and widespread convection is expected late Sunday. Convection becomes more isolated on Monday. VFR on Tuesday.

MARINE

Southerly winds increase today as the Bermuda high pushes eastward. Seas will build to 2-3 feet today, increasing tonight. Southerly flow increases on Saturday (up to 20 knots sustained at times with gusts to 25 knots) as an area of low pressure traverses the Mid-Atlantic. Recreational boaters should be cautious in area inlets on Saturday.

Winds diminishes to 10-15 knots on Sunday, turning southwesterly. Seas gradually subside but remain elevated at 2-4 feet. 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 respond by building to around 3 feet in the nearshore waters, around 4 feet in offshore NC waters.

ILM WATCHES/WARNINGS/ADVISORIES

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