Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210526 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 126 AM EDT Tue Mar 21 2017 .SYNOPSIS... Warm temperatures will precede a cold front that drops south across the area during the predawn hours of Wednesday. This will be followed by a late week cooldown with high pressure ridging from the north. The weekend will see a warmup along with a slow rise in rain chances as low pressure approaches from the west late Sun. && .NEAR TERM /THROUGH TODAY/... As of 845 PM Monday...A weak warm front just north of the FA, will lift further north overnight. Will see high level moisture push across the FA tonight thru Tuesday with occasional mid level clouds during tonight. This shown well in rh model time height displays across locations within the CWA. A low level SW jet will develop late this evening and persist into daylight Tue. This will keep the boundary layer mixed and keep fog development to a minimum at best. The clouds and sfc wind action will keep temps from dropping too fat or too far like what was observed last night which exhibited excellent Rad cooling conditions. Widespread mid to upper 40s will be tonights lows per various model mos blends. Previous................................................ 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 /TONIGHT 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 /06Z TUESDAY THROUGH SATURDAY/... As of 06Z...VFR through much of the valid period, but restrictions become possible late Tuesday night. Weak mid level impulse moving overhead tonight will create increasing mid-level SCT/BKN cigs but no showers or restrictions are anticipated. These clouds will break after sunrise leaving FEW/SCT VFR through the daylight hours as elongated high pressure dominates, but increasing clouds will again develop cigs ahead of a cold front tonight. This front will drop into the region late, with tstm chances increasing from north to south at the end of this valid period. Still some uncertainty into coverage and intensity of tstms, but there is a good chance the terminals will see MVFR in vsby and cigs. Winds through the valid period will be predominantly from the SW, increasing to 10 kts this aftn before easing after dark. Gusty and erratic winds are possible in any tstms, but will hold off on any mention until we get closer to the event. Extended outlook...MVFR/IFR conditions from ceilings and convection associated with the cold frontal passage Tuesday night into early Wednesday. Otherwise VFR. && .MARINE... NEAR TERM /THROUGH TUESDAY/... As of 845 PM Monday...Looking at rather benign wind and sea conditions tonight. The SW low level jet will have a difficult time transitioning to the cold ocean sfc. As a result, looking at SW winds at 10 to occasionally 15 kt. The sfc pg tightens during the day on Tue and will see winds increase to 10 to 20 kt thruout. Significant seas for tonight will be ruled by a prevalent 11 to 13 second period ESE ground swell around 2 ft. Wind waves will mix in later tonight but will hold odd in dominating the seas spectrum until daytime Tue mid to late morning. Previous.................................................... 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...DCH/JDW SHORT TERM...MBB LONG TERM...TRA AVIATION...JDW MARINE...

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