textproduct: NWS Wilmington

WHAT HAS CHANGED

Aviation discussion updated for 12Z TAFS.

436am Changes... Aviation coastal terminals amended to include the low stratus from off the Atlantic waters affecting those local terminals. CRE/MYR IFR ceilings, possibly to LIFR ceilings. ILM MVFR ceilings, possibly lowering to IFR ceilings. Could see sea fog at those 2 Grand Strand terminals.

245am Changes... Slightly adjusted the timing quicker with regard to the convection and the cold frontal passage across Northeast SC and Southeast SC later today.

Aviation discussion updated for 06Z TAFs.

KEY MESSAGES

1) Marginal risk for isolated strong to possibly severe thunderstorms ahead of an eastward moving cold frontal passage from late this morning thru late this afternoon.

2) A cold front on Monday brings a complete pattern change and an abrupt return of winter temperatures.

DISCUSSION

KEY MESSAGE 1...Marginal risk for isolated strong to possibly severe thunderstorms ahead of an eastward moving cold frontal passage from late this morning thru late this afternoon.

Amplified trough aloft will push a strong sfc cold front across the area from late this morning, along the I-95 corridor, to off the NE SC and SE NC Coasts by mid to possibly late this afternoon. Accompanying the amplified trof is a southern stream upper dynamics that was once associated with an upper closed low off Mexico/California in the beginning of the week. It interacts with forcing from the cold front and could be the delimiter of whether the FA experiences strong or severe thunderstorm activity ahead of the cold front. The late Spring early Summer like airmass has been over the FA for several days but will still have the marine layer closer to the coast but given 220-240 wind directions, the marine layer depth will be negligible inland. Given the strong wind field in the lower levels with 40-50 kt speeds, the shower/tstorm activity may tap those winds and bring them to the sfc. Will continue to highlight the isolated svr threat. Have stayed on the hier side of guidance for max temps today and the same goes with tonights lows, kept them just above freezing eventhough various MOS guidance indicated 32 degree readings. Soil temps are quite on the "warm" side with readings well into the 60s. If winds do decouple, the threat for patchy frost will increase but likely just prior to sunrise.

KEY MESSAGE 2 A cold front on Monday brings a complete pattern change and an abrupt return of winter temperatures.

Zonal flow across the nation over the weekend will be shaping up for a major change in the form of fairly extreme amplification. These changes get underway Saturday as a mid to upper level ridge starts to develop off the Pacific Northwest. This initially results in a 165kt jet diving SE across WA/OR that strengthens to 185kt across MT on Sunday, the upper jet being tightening by among other factors, the partial phasing in of the northern mid level trough. By Monday morning this leads to a cutoff over the Great Lakes with a sub-980mb low under the parent low in the vicinity of MI. The trough acquires a negative tilt which helps to partially offset the vertical baroclinic fracturing that the mountains can cause. A testament to this fact is that by 00Z Tuesday 850 mb temperatures across NC go from 11C (52F) in ILM to -8 (18F) at AVL. This will lead to afternoon temperatures that take a non- diurnal plummet, most pronounced over western zones due to the earlier FROPA and mega- CAA. Temperatures will support frost Monday and when radiational cooling conditions setup Tuesday night, a possible freeze. The 17th is usually very close to when we declare the growing season underway so it's conceivable that we need a freeze warning on it's very first night as the leading edge/cold front impressively dives into western Cuba.

AVIATION /12Z THURSDAY THROUGH MONDAY/

IFR/LIFR to affect the coastal terminals including CRE/MYR/ILM. The worse conditions will be at CRE and to a lesser degree MYR/ILM mainly from the low ceilings and possible sea fog at CRE. As winds become more SW-WSW later this morning, expect the low stratus and sea fog to retreat back across the waters. For the remainder of the morning and afternoon, an approaching strong cold front accompanied by showers and isolated thunderstorms (not enough to place in the individual TAFS attm) will push across the FA, from west to east, while the individual storms track northeast. Flight restrictions to MVFR likely with an outside brief period of IFR possible from any of those core showers or even from a direct tstorm. The CFP to clear the coast mid to late afternoon, with pcpn ending and clouds moving out rather quickly. This leaves VFR conditions for the remainder of the period. Various model time height displays for winds indicate low level 45-50 kt SW winds to push across the FA during the morning/early aftn. Look for some of these winds to mix down with 30+ kt wind gusts not out of the question. Post CFP, looking at CAA and the tightened sfc pg to continue producing gusty winds into the early evening but should dissipate rather quickly by 06Z as the center of sfc high moves quickly to the Eastern Carolinas.

Extended Forecast...VFR is expected Friday thru the first half of the weekend. Flight restrictions are possible due to increasing rain chances Sun into Mon as the next frontal system affects the area.

MARINE

Through Tonight...SW becoming W winds will further increase to Gale conditions by early afternoon as the eastward moving cold front pushes closer to the coast by midday, further tightening the sfc pg as it approaches. CFP will occur mid to late this afternoon, with winds veering to the NW, followed by a northerly direction this evening. The tightened sfc pg and CAA will keep Gale conditions ongoing thru late this evening. There-after, the winds will diminish-some as the center of sfc high pressure reaches the Eastern Carolinas by Fri morning. Seas will be governed by short period wind waves, highest across the waters from Cape Fear to north of Murrells Inlet. Could observe 8 footers across the outer waters off and south of Cape Fear.

Friday through Monday Night...Friday finds weakening high pressure moving east across the area. The eastward translation will be veering winds while the weakening means abating winds. In the absence of a fetch-induced swell only the wind waves will remain, which will also be on the downward trend in height. Saturday may well offer the weakest pressure pattern and thus light and variable winds. Late Sunday into Sunday night a strengthening southerly wind regime is expected ahead of a pattern-changing cold front that will likely necessitate headlines.

ILM WATCHES/WARNINGS/ADVISORIES

NC...None. SC...None. MARINE...Gale Warning from 2 PM this afternoon to midnight EDT tonight for AMZ250-252-254-256.