textproduct: NWS Wilmington

WHAT HAS CHANGED

All sections updated with little change in forecast reasoning.

KEY MESSAGES

1) Strong storms possible this evening/tonight.

DISCUSSION

KEY MESSAGE 1...Strong storms possible this evening/tonight.

KEY MESSAGE 1 DESCRIPTION... Storms firing in the upstate region of the Carolinas/Appalachian mountains benefiting from both warm advection and some increasingly vort-laden northwesterly mid level flow. These storms should meander over those locations in the very near term before they start to congeal into a forced line that moves southward. The RRFS (a well initialized model at this time) brings the storms into northern zones by 00Z clearing the Grand Strand area close to 04Z. And while this sense of timing may work out just fine NW flow-forced lines tend to be quicker than progged and so shaved about 2 hours off of aforementioned windows. Timing is not the only uncertainty with the line as it arrives, so too is the severe potential. DCAPE and MLCAPE will be maintained but also both be waning with the loss of daytime heating. 0-3km SRH remains in the 200-250 range. Mid level lapse rates are forecast to remain quite poor and thunder PROBs stay quite low. One area of slightly enhanced concern is along the immediate coast (NC moreso than SC) where composite convective indices jump right as the line comes through. The RRFS Supercell Composite rises into the 10-15 range in the Cape Fear Region from about 22-01Z. Combining these ingredients could be suggestive of fairly low to medium height storms that may not be the lightning producers that we saw last weekend, but there could still be enough storm structure or even weak LL mesos that put down wind damage. The tornado threat continues to be small but non-zero as cloud bases have trouble getting below about 4kft.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Most of the forecast will be VFR and with southwesterly winds well ahead of a cold front. The only deviation from VFR will be a line of showers and thunderstorms that will move N to S across the terminals. All sites appear to have an equal chance of having the storms and so continue to have PROB30s. And although northwest flow events tend to occur a bit faster than forecast our current thinking is that northernmost LBT could start seeing activity as early as 22Z. Confidence in the timing remains low however as the storms still need to organized well upstate before the the line starts to march southward. Even the last few runs of the HRRR have slowed.

Extended Forecast... VFR conditions should dominate Wednesday through Saturday.

MARINE

Tonight through Saturday... The most unsettled weather of the forecast will be at its beginning. The approach of a cold front will tighten the gradient through early Wednesday. A marginal SCA is in effect through then after which time the boundary moves through and winds/seas both start to abate. The remainder of the period could very well feature winds capped at 10 kt and short period wind waves of less than 3 ft as the pressure pattern remains weak due to a broad trough extending SW into the region from a slow moving storm system trying to exit the midAtlantic region, its progress slowed by the fact that it spends time under a cutoff low aloft.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory until 8 PM EDT this evening for NCZ087-096-099- 105>110. Beach Hazards Statement until 8 PM EDT this evening for NCZ106- 108. Coastal Flood Advisory from 8 PM this evening to midnight EDT tonight for NCZ107. SC...Heat Advisory until 8 PM EDT this evening for SCZ017-023-024- 032-033-039-054>056-058-059. Beach Hazards Statement until 8 PM EDT this evening for SCZ054- 056. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for AMZ250-252- 254-256.