Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 221729 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 127 PM EDT Tue May 22 2018 .SYNOPSIS... Isolated to scattered showers and thunderstorms will become more numerous Wednesday into Thursday as a cold front sags into the area from the north before slowly dissipating Friday. The holiday weekend looks unsettled as a tropical airmass brings the likelihood for showers and thunderstorms and possibly more heavy rain, especially Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 10 AM Tuesday...models continue to show the lower precipitable waters (<1.5") through the mid afternoon before moistening. The 12 UTC HRRR is showing isolated convection mainly west of a line from Lumberton to Andrews. The high resolution models are showing the development of a resultant sea breeze beginning late morning along the Grand Strand and expanding across the entire coastal area by the afternoon. The HRRR does not indicate any convective development with this boundary. ---Previous Discussion--- Atlantic ridge has pushed far enough west to hold the tropical feed of deep moisture just south and west of local forecast area. Moisture profiles and sounding data show moisture limited to near the surface and above 18k ft. Pcp water values were down near 1.25 inches early this morning. This shallow moisture should produce some fog and stratus through daybreak. Once mixing occurs the fog and stratus will break up and dissipate leaving some stratocu around and cirrus through the afternoon. Have included isolated convection mainly along sea breeze boundary today. Should be enough sunshine to push temps into the mid 80s most places this aftn with light southerly to on shore winds. As the ridge slips back to the east later today through tonight, expect a deeper moisture feed to set up once again as winds veer around to a more SW direction. As the moisture increases from the SW, there will be an increasing chc of a shower or thunderstorm across northeast SC mainly later this afternoon. Pcp water values increase up to 1.8 inches by late this evening across the Pee Dee region. The tip of Cape Fear and up the NC coast toward Hatteras will be the last to see this increase in moisture with pcp water values only near 1.15 inches through late this eve but reaching up near 1.75 inches by daybreak Wed. As this moisture flow increases, mid to upper trough will dig down from the north edging closer the area. Looks like the shortwave will remain west of local forecast area overnight and therefore expect best chc of showers over central and western Carolinas, but expect an increase in shower activity to return later today into early Wed. Also expect a nocturnal uptick in showers over the adjacent coastal waters which could begin to brush the coast overnight into early Wed. The cloud cover and increasing moisture will keep overnight lows up around 70. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Bermuda ridge will weaken across the area Wed. Upper ridge building across central portions of the North American continent will help to carve out a trough across the northeastern United States and down along the east coast. This should be enough to allow a surface cold front to sag south and into if not through the area late Wed night and Thu morning. High pressure to the north will then briefly nose into the area later Thu and Thu night as the front begins to dissipate in close proximity. The result should be a period of unsettled weather. Current thinking is deep moisture and a frontal boundary will help to enhance the development of numerous showers and thunderstorms Wed with seabreeze convergence also a focus for deep convection. Rainfall rates should be high given precipitable water values will be very near 2 inches and this may lead to at least some pockets of minor flooding given the antecedent soil conditions from recent heavy rainfall. Drier air will struggle to make inroads into the area later Thu and Thu night and will show POPs trending downward from N to S, especially later Thu and Thu night. It will be humid through much of the period, but later Thu and Thu night, we should see dewpoints slowly trend lower from N to S. Highs will be near or slightly above normal for late May while low temps remain mid and late June-like. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...A brief break in the pattern is forecast to continue into early Fri as a mid-level trough digs into New England driving a surface cold front through the area. This front will dissipate on Fri. While scattered showers and storms will remain possible Fri, it is possible that northern areas of the FA will get a break from the convection and may see a little lower humidity for about 24 hours. As southerly flow returns to the area Friday and through the weekend, shower and storm chances will ramp back up again for the holiday weekend. Temperatures through the extended range will remain in the lower to middle 80s by day and upper 60s to lower 70s at night. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 18Z...VFR today. Have added VCSH to all TAFs except KLBT to account for current radar trends. Isolated showers along the sea breeze boundary SW-NW of KCRE/KMYR/KILM expected to dissipate or develop further inland by mid afternoon. VCSH also expected at KFLO/KLBT through the afternoon. An isolated thunderstorm is possible this afternoon, but confidence is low. Winds will be SW 5- 10 kt, except S around 15 kt along the coast. MVFR/IFR with BR/stratus again possible overnight. Confidence of occurrence is high, but timing/duration low. VFR/SW winds 5-10 kt expected by 12- 13Z. Extended Outlook...The potential for MVFR/tempo IFR will increase late Wed/Thur as a cold front drops across the area and again during the weekend as tropical moisture returns. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Tuesday...High pressure still in control over the waters with very weak south to southwest winds less than 10 knots. Seas are running around 2 to 3 feet from a southeast swell at 10.5 seconds. A slight increase in both winds and seas will occur near shore in aftn sea breeze. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Bermuda ridge will weaken across the waters Wed. Upper ridge building across central portions of the North American continent will help to carve out a trough across the northeastern United States and down along the east coast. This should be enough to allow a surface cold front to sag south and through the coastal waters Thu morning. High pressure to the north will then briefly nose into the area later Thu and Thu night. SW winds Wed and Wed night will shift to NW early Thu morning and then veer quickly to NE and then E during Thu, remaining onshore Thu night. The strongest winds this period will be around 15 kt Wed afternoon and eve. Seas of mainly 3 to 4 ft Wed will subside to 2 to 3 ft Thu. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 PM Monday...The gradient will ease considerably as a cold front wavers and then dissipates Fri. E-SE winds Fri will turn to the S Sat. Winds look to be 15 kt or less with seas of 2 to 3 feet through the period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RH SHORT TERM...RJD LONG TERM...JDW AVIATION...MRR

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