textproduct: NWS Wilmington

WHAT HAS CHANGED

Aviation discussion updated for the 12Z TAFs.

A Flood Watch remains in effect for our southeast North Carolina areas tonight through Friday afternoon. Need to see how rainfall trends go before that watch potentially extends further out into the weekend.

KEY MESSAGES

- 1) A slow-moving cold front will bring periods of heavy showers and thunderstorms mainly between Thursday and Saturday night, with an attendant risk for localized flash flooding.

KEY MESSAGE 1

A slow-moving cold front will bring periods of heavy showers and thunderstorms mainly between Thursday and Saturday night, with an attendant risk for localized flash flooding.

Latest surface analysis shows the front nearly stationary across parts of Appalachia, as it begins its crawl towards the Piedmont region today. A line of rain has already formed well ahead of this front, basically situating itself right along the I-40 and I-85 corridors along and north of the NC Triad and Triangle.

This line of rain and embedded thunderstorms will very slowly approach the coast by sometime tonight. Before it, the seabreeze may try to kick up some isolated shower and storms just inland from the coast this afternoon. Triple digit heat indices expected east of I-95 this afternoon, and while a couple of spots right along the coast may reach 105+ degrees at times, the signal does not appear widespread or consistent enough for a Heat Advisory.

All eyes on tonight through Friday, and perhaps into the weekend, where this front will trudge its way towards the coast and stall out sometime late Friday into Saturday. Precipitable water values skyrocket to over 2.25", potentially up to 2.5" in some spots. This is near or even over the daily maximum values recorded on previous CHS and MHX RAOBs, per the SPC Sounding Climatology page. Ample moisture transport spotted at 925 mb, and the forecast soundings certainly look soaked throughout the column. No doubt, this is a tropical environment without the tropical system in place.

Much agonizing occurred with this particular forecast, particularly when it came to issuing vs. not issuing a Flood Watch. There are reasons to hold off, with the extreme to exceptional drought being the main reason. Upshear and downshear Corfidi vectors are a bit too speedy to suggest flash flooding, and CAPE profiles look a bit too wide, as opposed to a skinny appearance. 850 mb moisture transport vectors are also a bit more continental than what you would traditionally think for a flash flooding setup around these parts.

Ultimately though, decided to go with the Flood Watch for all of southeast NC. This appears to be one of the best tropical environments we've seen in quite sometime, and training storms looks to be a sure thing at some point along the way. Probabilistic data broad-brushes the area with 1-3 inches, but I'm wondering if that's a bit underdone in southeast NC. This environment is capable of producing 2+ inch/hour rainfall rates, even upwards of 6+ inch/hour. In fact, this is already happening, per KRAX data in parts of Forsyth and Guilford Counties.

I think more reasonable rainfall amounts are in the 2-4 inch range for southeast NC, stepping down towards 1-3 inches across northeast SC. Locally higher amounts possible (perhaps likely) in some spots, particularly in the Cape Fear region. We have a long way to go before we think about busting the drought, but perhaps this helps restore a bit more order in the water table.

Generally, the peak of this event is late Thursday through Saturday. Low pressure forms along the stalled front offshore late Friday into Saturday, where it will gradually drag out into the Atlantic. Rain chances gradually come down Sunday and especially into next week. With clouds thinning out at that point, temperatures start shooting up towards Heat Advisory thresholds again by next Tuesday or Wednesday.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Another night of SCT/BKN MVFR clouds, mainly at coastal terminals. These should scatter out further through ~10AM. Afternoon showers/storms expected 18Z-24Z but activity may persist even later into the period as a cold front approaches, especially for inland terminals. Predominant SW winds with inland spots turning more northerly through the day with the front. More solid CIG/VSBY restrictions should arrive in the late afternoon/evening but there's uncertainty due to convection. Tried to at least get MVFR in there.

Extended Forecast...Potential for periodic MVFR/IFR due to storms remains possible through late Sat, most numerous in the afternoon and evening. Conditions should start to dry out Monday with predominant VFR returning.

MARINE

Small Craft Advisory has been cancelled, thanks to an approaching cold front pushing the tighter gradient out to sea. This will become more pronounced heading into Friday as the front stalls along the coast. Right now it looks like winds only veer as far as westerly and no northerly component becomes established. Seas comprised mostly of shorter period wind chop, not forecast to change appreciably through the period as even late in the forecast any swell energy that develops will remain well offshore in S to SW flow.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Flood Watch from this evening through Friday afternoon for NCZ087-096-099-105>110. Beach Hazards Statement through this evening for NCZ106-108. SC...Beach Hazards Statement through this evening for SCZ054-056. MARINE...None.