Area Forecast Discussion
Issued by NWS Wilmington, NC

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846 FXUS62 KILM 210014 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 814 PM EDT Mon Mar 20 2017 .SYNOPSIS... Mild weather will precede a cold front that moves through during the predawn hours of Wednesday. A late week cooldown will be followed by a weekend warmup and slow rise in rain chances. && .NEAR TERM /THROUGH TUESDAY/... As of 300 PM Monday...Fair conditions to prevail into the evening with a thin arrival of high altitude ice clouds overhead, and perhaps a few mid-level clouds into the predawn hours as increasing moisture arrives on W-NW trajectories. The team-play of weak return southerly flow and thin clouds aloft should help to keep temperature considerably milder than last night, mainly middle and upper 40s. Big diurnal temperature range on tap for Tuesday as 40s leap into the middle 70s to lower 80s by afternoon ahead of an approaching cold front. The large land versus ocean temperature differential will drive a robust sea breeze circulation, spreading cool air into the coastal interior, while producing hearty afternoon wind gusts of 25 mph or so along and near the coast. Dewpoints in the upper 50s to around 60 and good heating inland, will lead to a chance of TSTMS over the interior by late afternoon as 850-700 mb moisture become richer. Approaching short-wave will increase bulk-shear parameters but mainly after sunset. A few strong TSTMS NW of the area may begin to approach the I-95 corridor late in the day, which by then could already have a history of hail and strong wind gusts. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...A cold front comes through Tuesday night though forecast soundings show that it only has a depth of about 1200 ft. This will not be very conducive of the higher QPF seen in the GFS but likely the much more paltry amounts depicted by the WRF. The former is also stronger with a mid level shortwave, and should this come to pass then rainfall amounts may be a tad higher. Current forecast will thus be in between the two models and show up to a tenth of an inch inland. Getting the low temp forecast correct is tricky and depends highly on the timing of the boundary. Most of the night will be exceedingly mild but there could be quite a drop in temps towards daybreak. The depth of the inversion increases to 4kft Wednesday afternoon but an overall drying of the deep layer column will likely mean measurable rainfall becomes hard to come by. The low amplitude mid level flow and highly sloped front will help to slightly temper the cold advection Wednesday afternoon. Though much cooler than Tuesday afternoon temperatures will still be only about a category below climatology. The upper trough off the East Coast slightly sharpens Wednesday night turning a deeper layer locally to the north. Nighttime lows will not vary as much N to S as previously thought with southern zones staying in the low 40s while far northern zones may dip into the mid 30s. A light freeze may be possible over the cool spots in Pender County. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 AM Monday...Canadian high pressure over the eastern Great Lakes Thursday morning will move off the Mid-Atlantic coast Thursday night and farther offshore Friday. After a chilly day Thursday with highs only in the 50s we could see one last night of frost or freeze conditions Thursday night with light winds in the vicinity of the high. By Friday return flow around the high should begin to modify the airmass with highs returning to the 70s by Saturday. The next synoptic frontal system should begin to move across the Southeast states this weekend, perhaps spreading showers and t-storms into the Carolinas Saturday, but with better chances by Sunday. SPC, in their extended range convective outlook, mentions weak instability across the warm sector including the Carolinas but with too much uncertainty to consider a severe weather risk for now. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 00Z...VFR conditions expected thruout the 24 hr TAF Issuance Period. High pressure`s center will become elongated and stretch from the Gulf of Mexico across Florida to off it`s east coast. Weak sfc warm front will push north of the area this evening. A low level southwesterly jet will develop overhead late this evening and persist into daylight Tue. A sfc cold front dropping southward during Tue will be on the northern doorsteps of the ILM CWA by the end of this period. Will see 25k ft ceilings thru out this period, occasionally a 10k to 15k foot ceilings later tonight thru much of Tue. And possibly a Cu or SC scattered deck at 4.5k to 6k ft at the end of this period. Pcpn chances too low to include at the end of this period. Extended outlook...VFR expected through the period except for possible MVFR/IFR conditions from ceilings and convection associated with the cold frontal passage Tuesday night into early Wednesday. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 300 PM Monday...Nice marine conditions this afternoon to early evening, will begin to deteriorate a bit as SW winds increase tonight, and remain elevated through Tuesday ahead of a cold front. Right now it doesn`t appear an Advisory will be needed but an Exercise Caution statement cannot be ruled out entirely on Tuesday as seas approach 5 feet offshore with gusts to 20 KT. The wave spectrum will be built by moderate to heavy S-SW chop Tuesday with 1-2 foot E waves every 10-11 seconds. No TSTMS expected until Tuesday night. The period from this afternoon into evening will see the E swell as the dominant wave energy until winds increase late. SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM Monday...Tuesday afternoon`s agitated pre-frontal wind field will actually relax slightly Tuesday night as a cold front pushes into the area thanks to a pressure trough along the boundary. Any response in seas may be too gradual to be very noticeable. What will be much more noticeable is the post-frontal wind and wave regime that sets up by Wednesday. Flow will veer markedly to the NE and increase. A small craft advisory will be needed Wednesday and Wednesday night in the pinched gradient. LONG TERM /THURSDAY THROUGH FRIDAY/... As of 300 AM Monday...Canadian high pressure over the Great Lakes on Thursday will sink southeastward to the Virginia coast Thursday night, then will move offshore Friday. Clockwise winds blowing around the high will probably maintain Small Craft Advisory conditions for most of Thursday, if not Thursday night. By Friday a weaker pressure gradient on the west side of the high should allow veering winds to diminish to less than 15 knots. A significant east to northeast backswell is expected to continue through Friday due to the large area of strong winds covering the western and central Atlantic around the periphery of this high. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MBB NEAR TERM...MJC SHORT TERM...MBB LONG TERM...TRA AVIATION...DCH

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