Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 241454 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1037 AM EDT Thu May 24 2018 .SYNOPSIS... A weakening front oriented east to west across the area will provide a focus for storms today and Friday. This weekend, a tropical system will move north into the central Gulf of Mexico, bringing increased downpour chances to the Carolinas Sunday into next week, as the tropical feature moves sluggishly over the Gulf Coast states much of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 1037 AM Thursday...Perturbations which aided enhancement of rain-rates and coverage, tapping into a tropical connection, have left the building seaward, while in addition, low-level convergence is waning along the frontal boundary. These factors have brought downtrends in +RA hazards, and positive destructive lightning bolt coverage. Visible confirms the absence of over- shooting tops and IR, a loss of cooling cloud tops. The sunlit areas of NE SC will prompt discreet cellular pop-ups as outflows move south, and also a broken line of sea breeze convection should play in some fashion into this mix, providing good rain chances for NE SC this afternoon. Differential heating may produce enough vertical motion to pop a few cells over SE NC near edges of cloud cover. Will adjust pops and distribution accordingly, but overall changes are not large. As of 300 AM Thursday...A backdoor cold front remains well to the north this morning under a weak northwest flow aloft. The front, as it pushes southward will once again be the focus for showers and thunderstorms. Previously we were anticipating more coverage to the south, but with the slower progression, it seems most of the area will be in play with the northern areas early on and the southern zones later. We are advertising good chance pops in most areas. Severe weather once again seems unlikely with weak shear and moderate instability. Once again activity could linger into the overnight hours tonight but chances are less. Its a tossup regarding high temperatures today as the MET guidance, which had performed so well in previous days was routed by the warmer GFS numbers Wednesday. I basically applied a blend to show mostly middle 80s. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...A weak front across the area should be all but dissipated by the start of the period. An area of high pressure to our NE Fri morning will slip further offshore. The Bermuda ridge will become better established during the second half of this forecast period. Low pressure should be moving slowly north across the central and eastern portions of the Gulf of Mexico through the period and may gradually take on tropical characteristics. This scenario will allow tropical moisture to surge northward and into the Carolinas during the later half of the holiday weekend. The pattern is quite summery with the Western Atlantic upper ridge building back into the area. This should provide some degree of subsidence. However, precipitable water values are forecast to be near or above 1.5 inches through much of the period. No discernible shortwave troughs to help enhance convection. Expect what we will see is isolated to perhaps scattered convection initiating along the seabreeze and Piedmont trough each day. This would tend to favor a higher risk for showers and thunderstorms in the morning at the beaches with the risk lowering here during the afternoon. Further inland, the afternoon and eve risk for thunderstorms would be highest. We may begin to see widespread showers and thunderstorms approaching from the S Sun morning. High temps of late have been underforecast by model consensus. Therefore, I went above most guidance packages in this regard, forecasting mid and upper 80s. Highs at the beaches and nearby locations will be as cool as the upper 70s and lower 80s. Early morning low temps will be in the upper 60s and lower 70s. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...A return to a very wet period appears to be in order for the extended time frame. A ridge of high pressure will weaken and the trough will open up across the eastern half of the United States. The models continue to show a low developing over the Gulf either as a subtropical or tropical system. For our area this means we should expect to see increased moisture and the chance of heavy rain. The models continue to show a surface low developing over the Gulf of Mexico, the 12Z ECMWF shows the low moving northward to Louisiana and slowing off the coast on Tuesday. The GFS is near the Florida peninsula and the Canadian is in middle. With the recent rains flood watches may be required Sunday into early next week. With cloud cover and rain chances high temperatures are expected to remain in the middle 80s and lows should be range from 68 to 73 through the period. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... As of 12Z...A cold front will move S across the terminals today. This morning, showers with isolated thunderstorms are occurring from KLBT to KILM with heaviest rains N of these terminals. Within this area there is a good chance of tempo MVFR, but brief periods of IFR could occur in the heavier showers. Elsewhere it will be VFR with tempo MVFR cigs. The area of convection will move very little, and should slowly dissipate by late morning as new development occurs along the front as that moves into the southern terminals. There will also be a good chance tempo MVFR/IFR in heavier showers late morning through mid-afternoon at the southern terminals and possibly KLBT, although coverage is expected to be less. After the area of precipitation moves through the terminals, VFR will become likely as drier air filters in. This should occur at the northern terminals by late morning, and the southern terminals by late afternoon. Overnight, IFR possible as fog develops. Densest fog will be most likely KFLO where humidities will be highest. Remaining terminals should be worse case MVFR. Extended outlook...VFR except for morning patchy MVFR/IFR in fog. Tropical moisture will be returning to the area Sun/Mon with more widespread thunderstorms with periods of IFR ceilings/visibility possible. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1037 AM Thursday...SE waves 2 feet every 8 seconds will mix with light south chop, and this will prevail through today, and overnight. Mariners should get radar updates before heading out, as isolated TSTMS will troll the waters. As of 300 AM Thursday...West to southwest winds currently over the waters will gradually shift to the east as a backdoor front moves across later this morning. The direction basically remains intact through tonight with speeds in a range of 10-15 knots mostly leaning toward the lower end. No impetus for significant seas to change much if at all with a range of 1-3 feet. SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 300 AM Thursday...A weak front across the area should be all but dissipated by the start of the period. An area of high pressure to our N Fri morning will slip further offshore. The Bermuda ridge will become better established across the waters during the second half of this forecast period. Low pressure should be moving slowly north across the central and eastern portions of the Gulf of Mexico through the period and may gradually take on tropical characteristics. E and SE winds Fri will veer to S during Fri afternoon. S to SSW winds should dominate the remainder of the forecast period. The highest winds are expected in association with the seabreeze circulation Sat afternoon and night, up to 15 to 20 kt. Seas will be 2 to 3 ft Fri and are expected to grow to mainly 3 ft Sat and up to 4 ft by Sun morning as a SE swell with a period of 8 seconds strengthens. LONG TERM /SUNDAY THROUGH MONDAY/... As of 300 PM Wednesday...As high pressure off the coast shifts eastward and a trough of low pressure exists over the east half of the United States, the winds will be from the south- southeast to south- southwest at 10 to 15 knots. This extended period of fetch will see the seas rising to 4 to 7 later Sunday and through Monday. A Small Craft Advisory may be required during this time. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MJC NEAR TERM...SHK/MJC SHORT TERM...RJD LONG TERM...DRH AVIATION...MRR

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