Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 270539 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 139 AM EDT Thu Oct 27 2016 .SYNOPSIS... Canadian high pressure will lose its grip on the area tonight and Thursday. A cold front will cross the area and move offshore Friday morning. High pressure will follow for the weekend with above normal temperatures expected. Another dry cold front should move across the area on Monday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 1230 PM Thursday...Latest IR loops show cirrus increasing over the forecast area. That, plus the onshore flow, should aid help keep a floor on temperatures for the rest of the overnight period. Temperatures now range from around 60 at the beaches to the lower 50s just a little way inland. Previous discussions follow: A few tweaks have been made to temperatures as a decoupled boundary layer over SE North Carolina allowed temperatures to fall more quickly than expected. Cirrus and 3-5 mph winds in the Florence-Darlington area and along the immediate South Carolina coast have held temperatures up higher here. Overall no significant changes to the forecast with this update. Discussion from 730 PM follows... Surface high pressure is centered up over northern Quebec, but extends a ridge axis all the way down into the Carolinas. The upper ridge along the east coast will weaken tonight as a shortwave advances eastward across the Mid- Mississippi Valley region, and this should cause surface pressures to fall. A heavily modified Canadian airmass over much of the western Atlantic shows up as an expansive deck of stratocumulus clouds offshore. As the surface ridge decays away, veering low- level winds will begin to advect this moisture onshore, with skies becoming partly cloudy late this evening over coastal South Carolina, perhaps spreading northward to encompass the entire area by daybreak Thursday. A couple of models (12z WRF-NMM and 18z NAM) try to squeeze small amounts of rain out of this stratocumulus deck overnight. The NAM appears to erode the impressive subsidence inversion away too quickly, allowing the moisture depth to increase enough for showers. I like the GFS soundings which show the inversion weakening, but remaining intact enough to keep stratocumulus clouds thin. No significant changes have been made to forecast lows, still anticipated to reach 50 inland and mid 50s along the coast. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure extending into the Carolinas will be squeezed out by a weak trough just off shore and a cold front approaching from the northwest. The weak trough just off the coast may produce enough convergence through the morning hours to produce some clouds. Moisture profiles show this moisture, as well as some mid to high level moisture from system upstream producing a mainly partly cloudy sky through the morning hours. The NAM is actually producing a few spotty showers in the waters just north toward Cape Lookout. By afternoon, expect temps to soar into the 70s and close to 80 portions of northeast South Carolina in warm southerly return flow. A westerly flow just above the surface will also aid in downslope heating. With relatively cooler water temps in the mid 60s to near 70 expect to see a sea breeze develop. Convergence along the sea breeze boundary will produce some aftn cu and therefore expect partly cloudy skies most of the day tomorrow. Winds should remain southerly through Thurs night which will combine with higher dewpoint air and some cloud cover to allow overnight temps to remain well above normal...55 to 60 most places. The winds will veer around to the W and then NW to N as front sinks S-SE through the morning hours on Fri. Not expecting much in the way of cooler air following the front as ridge builds in from the west with increasing h5 heights. This will combine with a warm start to the day on Fri and will offset any CAA to produce temps well into the 70s once again with a slightly drier northerly wind. High pressure at the surface will establish itself over the area into the weekend. Expect clear skies by Fri night along with a drier airmass following the front and therefore expect temps to drop into the low to mid 50s. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...Quiet and warm weather to dominate the extended as ridging builds aloft and high pressure remains dominant at the surface. The weekend looks beautiful with weak ridging aloft and an elongated area of high pressure extending east to west across the southern tier states. This will produce temps about 10 degrees above climo, and most locations will top out at 80 or better both Saturday and Sunday. Mins both nights will also be quite warm, about 10-15 degrees above normal for the end of October. A weak impulse will move overhead Monday early Monday dragging a mostly dry cold front through the area. Attm will keep mentionable POP confined north of the CWA, and the FROPA will be identified only by a wind shift, somewhat increased cloud cover, and slightly cooler temps - although these may hold off until Tuesday as cold advection lags. Halloween night will be warm and clear. Ridging amplifies across the southeast through the middle of next week, but high pressure axis to the west will keep cool NE winds at the surface, so temps will be somewhat cooler than this wknd, but still well above climo for the date. Once again, no measurable precip is seen during the extended. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 06Z...VFR will continue to dominate the period however, brief interludes of MVFR fog will be possible at inland terminals around daybreak. Latest forecast soundings have backed off on the SCT cloud around 3k ft through the morning hours and instead trended in favor of the MVFR ground fog. Winds will remain light with east to southeast winds in the morning becoming south to southwest in the afternoon. Speeds will remain 10 kt or less at all terminals. Anticipate development of SCT to BKN flat cumulus around 5k ft anywhere from late morning to early afternoon lingering into the evening hours and possibly overnight. Cold front approaches from the northwest late tonight, crossing the area Fri morning. Limited moisture return ahead of the front and overnight timing will prevent shower development. Winds may shift to northwest as the period comes to an end but weak gradient and lack of cold advection will keep wind speeds under 10 kt. Extended Outlook...VFR expected. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1230 AM Thursday...Latest obs show seas of right around 2 ft with easterly winds in the 10 to 15 kt range. This fits in well with the latest updated forecast, of which there is no change. Previous discussion follows: 1036 mb high pressure is centered way up over northern Quebec, but extends a ridge axis all the way into the Carolinas. Pressures will fall tonight as the ridge decays away. This will allow east- northeasterly winds to veer more southeasterly with time, with wind speeds 10-15 kt this evening falling to near 10 knots overnight. Area buoys report sea heights of 2-3 feet with dominant periods around 4 seconds. There`s also a small swell at around 8-9 seconds period showing up in spectral wave data from the southeast. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...High pressure will extend into the Carolinas while a very weak coastal trough develops over the waters. Overall expect winds to continue to veer from E to SE and eventually S as a cold front approaches from the northwest. This front will drop through the waters early Fri with limited CAA in a light northerly flow. May see an isolated shower or two in the waters but overall expect just some clouds and a slight uptick in winds and seas through Fri night. Expect winds 10 to 15 kts through the period with seas up to 3 ft. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...High pressure will slowly move across the waters during the wknd, followed by a weak cold front which will cross offshore early Monday. Ahead of this front, the weak gradient and return flow will create light SW winds of 5-10 kts, before turning to the N/NE during Monday behind the front with an increase in speed to 10-15 kts. Seas will be 2-3 ft Sat/Sun with a SE ground swell and low-amplitude SW wind wave, before a NE short period wave develops on Monday in continued 2-3 ft seas. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...REK/TRA SHORT TERM...RGZ LONG TERM...JDW AVIATION...III MARINE...REK/TRA/JDW/RGZ is the U.S. government's official web portal to all federal, state and local government web resources and services.