textproduct: NWS Wilmington

WHAT HAS CHANGED

Heat Advisory in effect for all areas this afternoon. Small Craft Advisory in effect for all waters this afternoon through much of tonight.

KEY MESSAGES

1) Above-normal heat and humidity remain a concern through Sunday.

2) Periods to monitor for enhanced precip chances are Sunday/Monday and Wednesday/Thursday ahead of cold fronts.

DISCUSSION

KEY MESSAGE 1... Above-normal heat and humidity remain a concern at least through Sunday.

Mid-upper ridging will keep plenty of dry air and subsidence in place on Saturday, supporting another abnormally warm day with isolated pop-up showers and storms offering little relief due to their small size and short-lived nature. Although the drier air aloft will help to knock dew points down into the low-mid 70s inland of the sea breeze during the afternoon, max temperatures in the middle 90s and increased dew points behind the sea breeze still support heat indices reaching around or above 105F.

On Sunday, an approaching cold front and moisture pooling ahead of this stalling boundary will help to increase moisture aloft. Guidance tools depict the forecast area being on the southern fringes of greater precip coverage attendant to the front. Thus, another hot and noticeably more humid day is likely to occur. Although isolated to perhaps scattered showers and storms should produce cloud cover that can locally reduce max temperatures, dew points are unlikely to drop as low as on Saturday, leading to higher heat indices despite similar or slightly lower max temperatures. Another Heat Advisory is considered likely at this point.

Additional warm and humid days will follow into the first half of the new week as the aforementioned stalled front lifts back northward on Monday. However, the overall pattern aloft supports high temperatures that are closer to normal with typical isolated to scattered pop-up showers and storms, so Heat Advisories may not be necessary.

KEY MESSAGE 2... Periods to monitor for enhanced precip chances are Sunday/Monday and Wednesday/Thursday ahead of cold fronts.

As a trough axis passes to the north on Sunday, a cold front will settle southward into North Carolina and stall. Guidance tools and ensemble systems show the forecast area being on the southern fringes of greater precip coverage over Sunday afternoon into Sunday night, with areas around and north of US-76 having the best relative chances for at least scattered showers or storms to nose down from the north. There is also a low risk for strong to locally damaging wind gusts from storms on Sunday afternoon and evening. With weak lingering troughing in place and the front lifting back northward, isolated to scattered pop-up showers and storms appear likely on Monday.

As troughing becomes reinforced over the eastern CONUS during midweek, a stronger cold front is progged to push southward during the Wednesday/Thursday timeframe. This is likely to enhance precip coverage into the scattered to numerous realm, even during the overnight hours. How far south this front reaches before stalling, and when this occurs, carries low confidence as guidance tools have only recently trended towards a further south/offshore solution, so this will need to be monitored as shower and storm coverage could be enhanced each day if the front is stalled along the coast as opposed to further offshore over the Gulf Stream. In addition, this front may bring another risk for thunderstorms with strong to locally damaging wind gusts.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

A very humid airmass has allowed IFR stratus to develop prior to sunrise at KFLO and KLBT. This should very quickly burn off with the rising sun this morning. Any lingering low ceilings inland are expected to scatter out by 13z. For the coastal airports, scattered to occasionally broken cumulus with bases 1500-2000 feet AGL are streaming onshore, but with daytime heating bases should rise above 3000 feet between 14-16z. Seabreeze-enhanced winds should increase to near 15 knots sustained with gusts in the 20-25 kt range by mid afternoon.

There may be isolated showers and thunderstorms that develop inland during mid to late afternoon. Odds are very low for impacts at the coastal airports. The best potential, still only 20-30 percent, will exist at KLBT after 20z.

Extended Forecast...Scattered to numerous showers and storms are expected mainly across North Carolina between late Sunday afternoon and Monday night with brief periods of MVFR-IFR restrictions possible. Chances for these restrictions are lower in SC due to anticipated lesser storm coverage. Forecast storm chances decrease on Tuesday and Wednesday, leaving a low risk for transient MVFR-IFR restrictions in convection.

MARINE

Saturday through Wednesday... Steady south to southwest winds are expected through the period with daily enhancements nearshore due to the sea breeze. In addition, an approaching cold front will help tighten the pressure gradient on Sunday and again from Tuesday through Wednesday, warranting Small Craft Advisories for both periods. Seas respond accordingly, rising to 3-5 ft tonight in the 0- 20nmi zones and 5-6 ft in the 20-60nmi zones. Seas subside somewhat for the Sunday night into early Tuesday period before rising again to 4-6 ft in the 0-20nmi zones and 6-7 ft in the 20-60nmi zones between late Tuesday and Wednesday night. The area of interest for possible tropical development in the northeast Gulf remains at 30% through 7 days. Recent model guidance trends keep this low in the Gulf, although the strong cold front arriving around midweek may either help to funnel the low out of the Gulf or yield a weak surface low of its own after the front stalls offshore. Confidence remains low on this feature.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NCZ087-096-099-105>110. Beach Hazards Statement through this evening for NCZ106-108. SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for SCZ017-023-024-032-033-039-054>056-058-059. Beach Hazards Statement through this evening for SCZ054-056. MARINE...Small Craft Advisory from 4 PM this afternoon to 11 PM EDT Sunday for AMZ250-252. Small Craft Advisory from 4 PM this afternoon to 6 AM EDT Sunday for AMZ254-256.