textproduct: NWS Wilmington

WHAT HAS CHANGED

Increasing dry air aloft will limit any shower activity this afternoon.

Updated 18Z aviation discussion.

KEY MESSAGES

1) Good chances of showers and thunderstorms will accompany a cold front on Monday.

2) The next cold front expected to reach the area early Thursday could bring another round of showers.

DISCUSSION

KEY MESSAGE 1: Good chances of showers and thunderstorms will accompany a cold front on Monday.

Models haven't changed appreciably with the timing of the arrival of Monday's cold front, still anticipated to enter southeastern North Carolina during the early afternoon hours. Should be little if any convective activity during the morning hours Monday as plenty column begins to moisten from the top down. Temperatures rising into the 80s should support uncapped surface CAPE of 1000 J/kg (GFS) to nearly 2000 J/kg (NAM) which when coupled with low level convergence along the front should support the development of showers and thunderstorms.

Latest sounding profiles show sfc winds shifting to the north as early as late morning across inland areas with deeper southerly flow remaining closer to the coast. Expect best moisture and instability, and therefore coverage, over eastern third portion of the forecast area, just inland of the coast, also aided by convergence along sea breeze with localized boundaries contributing to the lift. CAMs also suggests storm coverage will be best in the Cape Fear area during the mid to late afternoon, with a minimum in coverage in the Bennettsville- Lumberton area given the earlier arrival of the front there. The eastern portions of the forecast area is also the area outlined in a marginal risk (level 1 of 5) of severe thunderstorms with damaging wind gusts being the greatest threat and hail more limited chance.

As the cold front begins to push offshore on Monday night, lingering shortwave energy near the coast and into extreme eastern SC could produce a few additional showers ahead of the main surface front later Monday night. Chances for elevated convection during this period have decreased slightly as instability appears to be quickly decreasing after 03Z. Further adjustments have been made to QPF through Tuesday morning with up to a half inch of rain near the coast and up to a tenth for inland areas (thunderstorms could produce some isolated pockets of rainfall up to an inch).

KEY MESSAGE 2: The next cold front expected to reach the area early Thursday could bring another round of showers.

Model guidance continues to show a strong shortwave moving out of the Great Lakes on Wednesday evening and early Thursday. This shortwave will push a cold front through the region early Thursday with another chance of showers. Operational guidance keeps the strongest shortwave energy and more significant height falls north of our area overnight Wednesday into Thursday. This should limit the potential for elevated convection with little surface-based convection possible due to the timing of the frontal passage. Therefore, the forecast should be for showers with a slight chance of an elevated thunderstorm. Probabilistic guidance is maintaining slightly inflated CAPE values for the time of day and environment.

Forecasted rain chances have increased for this event, but the expectation of coverage remains similar to the previous forecast. Mid level west to northwest winds will have no connection to Gulf or Atlantic moisture, so a forecast of 30-40 percent coverage of showers Wednesday night into Thursday morning seems reasonable, driven more by dynamics than by deep moisture or instability. The increase is likely due to probabilistic guidance converging on the timing and better agreement on coarse spatial coverage of rain chances (note that PoPs only indicate the chance of rain exceeding 0.01"). In other words, this is unlikely to bring a significant amount of rainfall.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions will exist for majority of TAF period. Only expecting stratocu this afternoon around 3500-5000 ft, clustering the most along the sea breeze boundary as it pushes inland. SW to W winds less than 10 kts will back to a more southerly flow at coastal terminals in afternoon sea breeze. Included some MVFR VSBYs from shallow fog after 09z for a few hours, but confidence is low. Very light to calm winds overnight will be out of the west. A cold front moving into the area from the northwest should help to shift winds around to a light northerly flow by noon at LBT and early afternoon at FLO. Winds will remain variable at coastal terminals due to sea breeze but will eventually shift around to the north. Included a Prob group for lower vsbys and ceilings due to shra at FLO, but for the most part, convection should hold off until just after this TAF period, after 18z.

Extended Forecast...MVFR/IFR likely Monday afternoon into Tuesday. VFR returns Tuesday. Potential for restrictions increases later Wednesday into Wednesday night associated with next cold front.

MARINE

Through Monday...Prevailing winds mainly out of the W to SW and remaining quite light except right along the coast where more southerly winds can be found due to the sea breeze. Winds may veer a bit more westerly overnight, but basically, light south to southwest winds are expected into Monday up until a cold front arrives during the late afternoon hours. Seas will remain less than 3 ft up until front moves through and northeast surge occurs, but that will not be until Mon evening.

Monday night through Friday...The next cold front will be pushing southward across the CWA on Monday evening. Northeast winds follow the front. The NE surge of winds may eclipse SCA thresholds through Tuesday afternoon. Seas will be dominated by the northeast wind wave and maintain 4-6 feet throughout the day on Tuesday.

With surface high pressure rapidly entering and exiting the region on Wednesday, winds turn easterly and southerly on Wednesday night. The surface gradient peaks on Wednesday night as a cold front moves through the area through Thursday morning. The initial front will be weak and lack any significant potential for elevated winds on Thursday, winds will be offshore at around 10-15 knots. However, the secondary front approaching the area on Thursday evening will bring stronger northerly winds; conditions are expected to remain below SCA thresholds for now.

ILM WATCHES/WARNINGS/ADVISORIES

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