Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 071721 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1221 PM EST Wed Dec 7 2016 .SYNOPSIS... Weak high pressure will offer up dry and seasonable weather today and tomorrow before considerably colder air arrives late in the day Thursday. The coldest temperatures of the season will greet the area Saturday daybreak with widespread lows in the 20s. A warming trend will follow Sunday and Monday. Several cold fronts will bring rain chances on Monday, and again mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 1145 AM Wednesday...A warmer and drier day compared to 24 hours ago. Temps on the order of 3-7 degrees warmer since midday yesterday and RH values 20-30 percent lower, and notably higher SLPs to boot. Additional adjustments were needed to reduce overall sky cover across the region, as low-level drying keep the gears turning through a sunny day. Consequently the newest temperature guidance suggests we may need to increase Max-Temp values a degree or two into the lower 60s. No other changes were made and the previous forecast discussion follows. Weak, dry and seasonable high pressure will build into the area today and persist thru tonight. The sfc pg will relax this morning thru tonight as the low off the VA Capes progresses ene further away from the FA. Looking at NNW to NNE winds diminishing to less than 5 mph this aftn and likely becoming nearly calm after sunset thru tonight. An overcast low stratus cloud deck this morning should scour out later this morning by midday due to drier air aloft mixing down to the sfc. This will leave thin to opaque upper level cirrus traversing the area and visible thru tonight. Temperatures this period will run at to slightly higher than the 30 year normals. Overall, not bad of a day compared to the previous 2. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 345 AM Wednesday...Longwave upper pattern this period exhibits a rather small amplitude but large wavelength trof affecting the entire conterminous U.S. with the strong westerlies having been pushed southward to Mexico and the southern Gulf of Mexico. This pattern in itself would result in temps this period running at or slightly below the 30 year normals. However, for Thu, brief warm-up prior to the sfc cfp in the late aftn. Very limited moisture accompanying this front itself along with no tapping of any source expected. As a result, have only indicated low chance POPs ie. Isolated or widely scattered at best. And even this may be too high. Models indicate the flow aloft ends up with enough amplitude to tap some of the Arctic air in Canada and bring it southward into the U.S. and into the southeast U.S. this period. After the 1st CFP late Thu, a secondary CFP occurs Thu night. Modified Arctic air will follow the 2nd CFP and advect across the FA during late Thu night thru Friday night. This round of Arctic air is associated with a 1035-1040 mb High that broke off from the main Arctic High of 1055+ mb, over west central Canada. The broken off High will ridge into the FA from the south central U.S. during Friday, with it`s center just NW of the ILM CWA by daybreak Sat. Dry and cold conditions expected. Wind chill readings Fri night will drop into the upper teens inland to near 20 at the coast. Other than a brief warm-up ahead of the CFPs on Thu, temps there-after will average 10 to 15 degrees below the climo norms thru Sat. This definitely is the 1st bonafide cold air outbreak to commence the Meteorological Winter which started Dec 1st. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 3 AM Wednesday...A very cold airmass remains in control on Saturday though as the center of the high builds overhead winds will diminish. Warm advection will begin atop this airmass Saturday night but surface temperatures will still fall below 30 for all but SC beaches. It is then on Sunday when we will appreciate the warming at the surface as high pressure moves off the coast and the chill abates. Moisture will be on the rise in the low levels but zonal flow in the mid levels should preclude much moistening above. This would imply that the next cold front will be hard-pressed to produce any rainfall but some very low POPs seem warranted Sunday night into Monday. This zonal flow will also mean little meaningful cold air with the front. Late period temperatures look seasonable if not a few degrees above. && .AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
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As of 18z...A very weak pressure gradient will persist across the area this afternoon and through the valid TAF period. Guidance is strongly hinting at stratus and br tonight especially inland but with initializations at overcast conditions this gives me pause. My forecast is a little less bullish on these conditions but still points to some IFR ceilings and fog inland. Extended Outlook...VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1145 AM Wednesday...Improving marine conditions expected today with `Caution` flags dropping midday. The gusty NNW to NNE winds this morning will diminish from south to north. Flat pressure pattern tonight will result in a variable wind direction and light speeds. Sea-heights will also subside this period. The ocean spectrum will be comprised of S waves 2-3 feet every 7 seconds and E waves 1-2 feet every 9 seconds, mixed with a light to moderate N chop. SHORT TERM /Thursday THROUGH FRIDAY NIGHT/... As of 345 AM Wednesday...Subtle marine conditions Thursday will give way to 2 CFPs, the 1st late Thu aftn and the more potent one during Thu night. Potent, meaning modified Arctic air will advect across the area later Thu night thru Friday night. A tightened sfc pg and cold surge will combine to produce gusty NW to NNW winds at SCA thresholds. Models may be underdone with the winds across the area waters due to mild SSTs near the coast. Will have plenty of mixing across the area waters and especially across the warmer waters of the Gulf Stream and any warm eddies that may have broken off. The center of the modifying Arctic High will lie just NW of the area waters by daybreak Sat. This will result in winds diminishing-some later Fri night. Significant seas will be at their lull of this period during Thu...with a 6 to 8 second period SE pseudo ground swell temporarily dominating. Wind driven waves at 3 to 5 second periods will become the dominant player in the significant seas spectrum after the CFPs, Thu night and continue thru Friday night. With a slightly hier offshore windspeed forecast than what the models indicate, the seas will end up slightly hier, by 1 to 2 feet, than what Wavewatch3 indicates. NWPS runs, ie. Swan Model, has taken into account our local wind fcst when this model was executed. With an offshore wind trajectory, a relatively large range of seas will occur, with 1 to 3 ft near shore and 3 to 6 ft across the outer waters. LONG TERM /SATURDAY THROUGH SUNDAY/... As OF 3 AM Wednesday...Chilly high building in from the north Saturday to bring an abating N wind that will veer slightly. Additional veer to E early Sunday as a weak boundary develops along the coast. Later Sunday the wedge will break down, bringing a rapid turn to the S or SW. Wind speeds will be on the rise as a cold front approaches from the NW but advisory not expected at this time, but cautionary headlines are possible. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...8 NEAR TERM...8 SHORT TERM...DCH LONG TERM...MBB AVIATION...SHK MARINE...Bacon/Colby is the U.S. government's official web portal to all federal, state and local government web resources and services.