Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 211644 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1244 PM EDT Wed Jun 21 2017 .SYNOPSIS... Bermuda High pressure will remain offshore of the Eastern Carolinas. A stalled front just inland from the coast will slowly move east and wash out today. Tropical moisture will continue over the area through Friday. The remnants of Cindy will arrive this weekend as a stalled front, moving offshore early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 930 AM Wednesday...Plenty column moisture across the region, but decreasing support aloft and a near absence of surface warming today, may result in lighter rain rates and low hourly accumulations compared to yesterday. POP values remain elevated but the flooding threat appears low. No significant changes to the forecast except that will remove any wording or grid depiction of heavy rain as this appears to be a low-end threat. Clouds will keep maximums in the low to middle 80s and no big changes are planned with this. As of 300 AM Wednesday...Tropical moisture continues to stream up from the Gulf in deep S-SW flow through today. Although deeper convection was confined to eastern half of CWA early, the I-95 corridor west was also seeing some lighter pcp through early this morning, and shwrs and thunderstorms will again become more widespread as the day progresses. A cold front will get nudged eastward and essentially wash out over the eastern Carolinas, as mid to upper trough pushes eastward. Overall dynamics aloft, this surface boundary and the sea breeze front will act as main players producing showers and thunderstorms through this afternoon. Pcp water values over 2 inches will produce potential for localized flooding in mainly brief periods of heavier rain. Some drier mid level air will try and work its way south and east behind exiting mid to upper trough through tonight, but plume of deep layer moisture from Tropical Storm Cindy in the Gulf will continue to feed into the Carolinas. Therefore, should see pcp chances diminish and clouds may thin a bit in westerly flow aloft behind exiting mid to upper trough. Max Temps will be in the lower to mid 80s while overnight lows will hold in the 70s in very moist air mass. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...The upper level pattern Thursday and Friday will feature a 500 mb high just off the Florida east coast which will deflect the main jet stream flow well to our north across the Great Lakes and northern New England. A lobe of vorticity sheared off the outer circulation of Tropical Storm Cindy will move northeastward around the periphery of the ridge and should cross the Carolinas on Thursday. At the surface Bermuda high pressure will remain offshore while a cold front will advance southeastward across the Ohio Valley by Friday, compressing the pressure gradient across the Carolinas and producing a breezy day, particularly near the beaches where surging inland temperatures should fuel a healthy seabreeze circulation. Wind gusts could exceed 25 mph at the beaches Friday afternoon. With plenty of low-level moisture both days, my attempt at assembling a thunderstorm forecast hinged on mid level moisture and temperatures. With the upper impulse from Cindy shearing out to the northeast across the area on Thursday, mid-level temps should cool slightly. Add to that the deeper moisture associated with the disturbance and my forecast PoPs range from 40-60 percent, highest in a band just inland from the coast where seabreeze wind convergence should enhance t-storm coverage. By Friday, much warmer and drier mid level conditions should develop with both the GFS and NAM forecast soundings indicating a strong enough subsidence inversion to limit, if not eliminate, deep convection. I have trended PoPs back to 20-30 percent, but have not removed them entirely to retain continuity with the previous forecast. A good number of showers and storms and their attendant cloud cover Thursday should help keep temperatures from rising any higher than 87 most places inland. But by Friday much more sunshine should allow temps to soar to 90 or better inland. Nighttime lows will remain quite warm with low to mid 70s expected, except some upper 70s possible Friday night near the beaches. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Seasonably warm and unsettled weather will continue through at least Monday as the Bermuda ridge retreats eastward, with a cold front slowly descending from the NW. Confidence is not high regarding an actual clean FROPA for this time of year, but a consensus of guidance for now moves the front offshore Monday night, followed by dryer and slightly cooler weather. && .AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
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As of 17Z...BKN-OVC conditions but primarily a VFR TAF cycle expected this period. Isolated to scattered 2SM SHRA bkn030 through Thursday morning. Overall light winds SW 11 KT or less at all sights as little to no sea breeze circulation gustiness expected through 18z Thursday. VCSH wording planned for much of this TAF period. Isolated TSTM coverage expected at best. Extended Outlook...MVFR ceilings/VSBYS late Saturday and Sunday as tropical moisture associated with Cindy remnants traverse the region. Patchy fog possible 10z-12z both Thursday and Friday.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 930 AM Wednesday...Seas around 3 feet every 6-7 seconds will prevail in the waters, but as low as 2 feet in the near shore waters off SC. No significant changes to the marine forecast at this time. As of 300 AM Wednesday...Winds generally will be S to SW 10 to 15 kts around Bermuda High pressure. This will maintain seas mainly 2 to 3 ft, dominated by a southerly 5-6 second wave period. Showers and thunderstorms will be more widespread, especially this morning as deep layer moisture continues to feed into area waters from the Gulf. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...Bermuda High Pressure will remain anchored offshore through the period, maintaining a warm and humid airmass along the Southeast coast. The GFS model has the best definition of a weak front stalled over coastal South Carolina Thursday morning that should lift northward and out of the area Thursday night. Thursday`s winds should be light as a result of the baggy pressure gradient near the front, but Friday`s winds will be much stronger, 15-20 knots with gusts to 25 knots, as the pressure gradient tightens up between the Bermuda High and an approaching cold front in the Ohio Valley. Seas could build to 5 feet by late Friday. Tropical Storm Cindy and its remnants should remain too far west of the Carolinas through Friday night for any direct impacts on our weather. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 PM Tuesday...Expect SWly winds of 10 to 15 kts on Friday increasing to 15 to 20 kts on Saturday as the gradient around the backside of the Bermuda Ridge tightens. Seas will likewise increase and it is possible that a Small Craft Advisory may need to be raised for Saturday. Some improvement is expected as the gradient again loosens on Sunday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...RGZ/8 NEAR TERM...RGZ/8 SHORT TERM...TRA LONG TERM...REK AVIATION...8

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