Area Forecast Discussion
Issued by NWS Wilmington, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KILM 181927 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 327 PM EDT Fri May 18 2018 .SYNOPSIS...
-- Changed Discussion --
Tropical moisture will continue to stream northward across the Carolinas much of the period, bringing humid conditions and rain chances each day, along with occasional sunshine between daytime showers and storms. Temperatures will be near to slightly above normal into late next week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
As of 3 PM Friday...Tropical moisture plume will continue to spread over the region from the south through Saturday. Periods of heavy showers along with isolated thunderstorms are expected during this time. Precipitable water values will hover around 2 inches overnight and tomorrow. Deep moisture and high freezing level/low LCL will keep rainfall efficiencies very high and flooding, particularly urban and small stream, may be an issue later in the period. Overall synoptic pattern has not changed a lot during the last few days. Moisture is being drawn north by the combination of 5h ridge over the western Atlantic and a 5h trough well west of the area. A series of shortwaves will move across the area from the south, with the strongest expected later this evening followed by another around midday Sat. These features will be able to enhance convection already occurring due to weak low level convergence, surface based instability, and divergent flow aloft. Guidance is showing some low level jet convergence moving into the area Sat which could further enhance convection across the area during tomorrow. Other than being able to pick out times that seem a little more favorable for convection cannot say with any certainty which areas will see rain at any given time. Temperatures will be near to slightly below climo on Sat while overnight temps will be above to well above climo. After coordination with neighboring offices have decided to hold off on a Flash Flood Watch(FFA) for the local area at this point. Areas to the north have received more rain recently than most of the ILM area of responsibility. In fact the 14 day percent of normal rainfall for the ILM area ranges from 25-50% while areas to the north range from near normal to almost 200% of normal. Flash flood guidance also highlights this with much of the guidance for the local area running around 3 inches per hour and around 6 inches over a 24 hour period. Compare this to areas to the north which are showing FFG values closer 1.5 inches per hour and around 3.5 inches for 24 hours. Do think there will be a few isolated pockets of flooding during the next 24 to 36 hours but right now not confident a FFA is warranted. This could quickly change if widespread significant rainfall occurs this evening and later issuance of a FFA is certainly possible.
-- End Changed Discussion --
&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
As if 300 PM Friday...Some changes with the short term forecast can be expected. A decent mid level trough will move across the Ohio Valley and the result will be a subtle but important shifting of the deep tropical plume to just offshore. The forecast reflects this with a slight decrease in pops for daytime Sunday and especially for overnight Sunday into early Monday. Pops remain somewhat elevated overnight Saturday into Sunday morning as the shift will not have taken place as of yet. Certainly no air mass change at the surface thus temperatures are essentially unchanged with highs in the lower to middle 80s and lows a couple of degrees either side of 70.
-- End Changed Discussion --
&& .LONG TERM /MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
As of 300 PM Friday...A brief reprieve in total shower and thunderstorm activity is still forecast for Mon/Tue, but a return to this humid, unsettled, tropical airmass is forecast by the middle of next week. Ridge of high pressure offshore should expand westward Monday into Tuesday bringing a decrease in shower activity as well as slightly warmer temperature and lower humidity. PWATs are forecast to fall to around 1 inch, down from the near-record 2 inches this weekend, which combined with weak subsidence and lack of any notable forcing is likely to create a break in convection early next week. While scattered showers/tstms cannot be ruled out, total coverage will be much less than nearly every day of the past 7, and more diurnally driven as well. More sunshine, a drier column, and slightly greater thicknesses will allow temps to climb into the mid 80s Mon/Tue. By Wednesday the upper mid-level ridge begins to break down in response to a trough digging from the north. This will push a cold front towards the area, and cause the surface high to retreat back to the SE. Although guidance begins to differ by mid-week with the upper pattern, it appears that pinched flow between a weak mid-level low developing to the west, and the high to the east, will again begin to transport tropical moisture back into the Carolinas Wed/Thu. This combined with a stalling surface front, especially Thursday, will regenerate scattered to widespread showers/tstms with periods of heavy rainfall possible. It is possible that on Friday another reduction in coverage could occur as the front wavers back to the north, but guidance suggesting renewed tropical moisture pooling to the south suggests lowered confidence and will maintain at least CHC POP through the end of the period. The more significant cloud/precip coverage and lowered heights will keep highs Wed-Fri more towards seasonable norms. Mins through the week will remain a degree or two either side of 70.
-- End Changed Discussion --
&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... As of 12Z...Very difficult to time these waves of convection coming ashore, safe to say we will see periods of showers for most of the coast, transitioning inland as we move into the afternoon. Southerly winds will be around 10 kts through the afternoon hours. Ceilings will likely bounce around today, ranging from scattered to near IFR. Tonight some lingering showers. Ceilings are forecast to lower to IFR after midnight at the inland terminals. Another round of nocturnal convection expected along the coast. Saturday, continued tropical flow with scattered convection possible at any time during the day. Extended Outlook...Periods of MVFR/IFR cigs/vsbys associated with tropical type showers and tstorms through the period. Activity will be more numerous along the coast pre-dawn hours thru mid-morning hours each day, then translate to the inland terminals midday-early evening. && .MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH SATURDAY/... As of 3 PM Friday...Small Craft Advisory continues for all zones beyond the end of the period. Gradient between the Bermuda High and low pressure moving north through the Mississippi Valley will remain tight through the period. Southerly flow will range from 15 to 20 kt with higher gusts expected. There are likely to be periods where winds speeds dip below 15 kt, but these will be short lived. Seas continue running 4 to 6 ft through the period with buoy wave power data suggesting the south to southeast wind wave has transitioned to a southerly swell. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...The pressure pattern that has been in place for some time will weaken somewhat with flag or headline conditions coming to an end later Sunday There will be some lingering six foot seas into Saturday evening but by Sunday afternoon 2-4 feet should be in place and continue through Monday morning. In between these times some five footers will likely remain especially across the outer waters. Winds will be southwest at 10-15 knots for the most part. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Little change through the middle of next week other than subtle variations in wind trajectories as offshore high pressure remains in place. This will continue the S/SW winds of 10- 15 kts each day through the period. The long fetch around the high will persist a 2-3ft/8sec SE swell, which will be present in the spectrum in addition to a 2-3ft/5sec SW wind wave. These two wave groups together will produce seas of 3-4 ft with little change each day.
-- End Changed Discussion --
&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...Small Craft Advisory until midnight EDT Saturday night for AMZ250-252-254-256. && $$ SYNOPSIS...JDW NEAR TERM...III SHORT TERM...SHK LONG TERM...JDW AVIATION...III MARINE...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.