Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 212325 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 725 PM EDT SAT MAY 21 2016 .SYNOPSIS... Showers and thunderstorms will move across portions of the area tonight ahead of a cold front which will move offshore late. An area of low pressure aloft will bring a slight chance of showers Sunday and Monday. Summer-like temperatures and mainly dry weather will develop by the middle of next week with above normal temperatures into next weekend. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... As of 700 PM Saturday...mid-level shortwave energy will approach the Carolinas tonight with one spoke of this energy moving through on Sunday. A surface front is coincident with this shortwave. A line of showers and thunderstorms was moving across the central Carolinas early this eve. Consensus amongst the high resolution models continue to support the best coverage of showers and thunderstorms moving across the I-95 corridor 00-03z and then the remainder of the area...moving offshore around 06-07z. However... there is some discrepancy as to how much convection will actually reach the more immediate coastal areas as with time...the environment will continue to slowly stabilize. At this time... have decided to include pops in the 40 percent range for most of the area...lower as you move south across the southern Grand Strand and South Santee River areas...furthest removed from the best upper level support. A few of the upstream storms have been strong to severe... although a slow weakening trend is expected with the loss of heating through the evening. Will mention an isolated strong thunderstorm in the HWO into late this evening. A cold front should be moving off the coast late tonight. Light winds and only slowly lowering dewpoints toward morning may result in patchy to areas of significant late night fog...especially in locations where heavy downpours occur later this eve. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... As of 300 PM Saturday...The start of this period will feature the upper trof extending down the east coast Sunday morning. The upper trof closes off and nearly becomes a cutoff low depending on your definition. The upper low`s center over the VAs Sunday afternoon is progged to drop southward to a position over eastern NC by daybreak Mon. And remarkably, the models are in pretty good agreement in lifting this closed low northward to basically off the NJ Coast by daybreak Tue. Like spokes on a bicycle wheel, there will be mid level s/w trofs or vorts rotating around this upper low. With decent or o.k. lapse rates, available moisture, and if enough daytime insolation to further aid instability, convective chances should increase ahead and in the vicinity of these rotating s/w trofs. Models are at times different with the timing of their movement across the fa, but nevertheless the threat for convection will exist especially during each day. At night, depending on the strength of the upper s/w trof rotating thru, will likely have to carry low pop convection well into Sun night. In addition...model sounding data indicate 500mb temps drop to -19 degrees C and as a result, small hail from any of the convection will become a possibility. The end result is that this cold core upper low affecting the area Sun thru Mon night means temperatures will average 5 to 10 degrees below normal this period. Normal daytime highs run in the low to mid 80s and night time lows in the lower 60s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...Warm summertime weather forecast for the upcoming week as a pattern more typical for this time of year finally sets up. Upper level low will be migrating off to the northeast on Tuesday as ridging blossoms northward from the Gulf of Mexico. As this happens...surface high pressure will re-center itself off the southeast coast...with a Bermuda High type setup forecast for the remainder of the period. The combination of warm return flow around the surface high and bulging heights beneath the mid-level ridge will create warm and mostly dry conditions as subsidence prevents much in the way of even diurnal convection. The exception still looks like Thursday when a weak impulse will rotate atop the ridge and cause subtle height falls...which when combined with the increasingly unstable airmass as heat and humidity increase...should fire off some storms Thursday/Thursday night. Otherwise...the extended looks very nice with highs and lows slightly above climo under ample sunshine. && .AVIATION /18Z SUNDAY THROUGH THURSDAY/... As of 18Z...All shwrs/tstms moved off the coast this morning leaving a fairly solid field of stratus which has broken up into stratocu around 2k-4k ft. Expect cu field to break up further this aftn, but increased sunshine will lead to increased instability and therefore potential for tstms later this aftn into this eve ahead of an approaching cold front. After midnight expect some MVFR fog with potential for stratus heading into Sunday morning as winds shift from W-NW to N as cold front comes through. Extended Outlook...Possible MVFR conditions on Monday, otherwise VFR. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 700 PM Saturday...A cold front will move across the waters early Sunday morning. A wave of low pressure on this front may slow the push offshore. The wind direction will remain from the SW at 10 to 15 kt through late eve...then shift to the W and NW well after midnight. Wind speeds will decrease to 10 kt or less overnight before bumping higher Sun morning. Seas will be mainly 2 to 3 ft. Isolated to scattered showers and thunderstorms are expected to move across the waters late tonight. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 PM Saturday...The sfc cold front will slowly drop south of the area waters early Sunday morning. Winds behind the cfp, will veer to the NW and NNW Sunday and persist in this direction thru Monday. For Monday Night, with the upper low now lifting to the north, away from the area waters, the sfc pressure pattern will become less dominated by the cyclonic flow associated with this upper low. This will result in winds slightly backing to a westerly direction. The sfc pg thru Monday will remain weak across the ILM SC waters, and 1 step hier than weak across the ILM NC Waters. This will yield wind speeds in basically the 10 to 15 kt range...with the hier side of this range across the ILM NC Waters. Significant seas will range between 2 and 4 feet thru the period, with the 4 footers occurring primarily early in the period, basically thru early Monday and mainly across the ILM NC Waters. Dominating periods will basically range between 7 and 9 seconds. With an offshore wind, wind driven waves will be minimal due to the limited fetch. As a result, an ese 1 to 3 foot ground swell will become the primary significant seas producer, hence the hier dominating periods. Upper s/w trofs rotating around the upper low will sporadically move across the area waters thruout this period. Dynamics from these will be enough for convection to also sporadically occur. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Saturday...Westerly winds Tuesday will transition to the S/SW Wednesday and then remain from that direction for several days as high pressure offshore becomes the dominant feature. The gradient in the vicinity of this high will be wind speeds will be around 10 kt each day regardless of direction. Although a SE 8-9 sec swell will amplify within the spectrum...especially late in the period...wave heights will remain just around 2 ft Tue/Wed...rising to 2-3 ft late thanks to that growing aforementioned swell. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD SHORT TERM...DCH LONG TERM...JDW AVIATION...RGZ is the U.S. government's official web portal to all federal, state and local government web resources and services.