Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 171721 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 121 PM EDT Tue Oct 17 2017 .SYNOPSIS... Canadian high pressure building into the Mid-Atlantic states today will bring several days of cool, dry weather to the Carolinas. Temperatures should begin to warm up this weekend as the high moves off the coast. && .NEAR TERM /THROUGH TONIGHT/... As of 10 AM Tuesday...Strong mid-level trough continues slowly working its way east today, moving off the coast late this afternoon. Trough has a slight positive tilt which has allowed moisture above 400 mb to linger along the coast, in the form of a cirrus shield of varying thickness. Cirrus will hang around into the late afternoon hours along the coast while inland areas should see it decrease around midday. Other than the cirrus the period will be quiet with surface high building in and the mid- level trough exiting as weak shortwave 5h ridge builds over the southeast for the middle of the week. Deep dry air will keep skies clear overnight but boundary layer winds will prevent strong radiational cooling. Lows will dip a few degrees below climo ranging from around 40 at inland cold spots to around 50 along the coast. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...Classic fall weather will remain in place Wednesday and Thursday across the Carolinas. The mid and upper level flow should be northwesterly as a 700-500 mb ridge develops across the lower Mississippi Valley. Subsidence downstream of this ridge should support a surface high across the Mid-Atlantic states and a well-defined subsidence inversion across the Carolinas. The only potential for cloud cover through the period appears to be Wednesday night or early Thursday as some thin maritime stratocumulus developing just beneath that subsidence inversion could approach the coast. As the surface high sinks southward later Thursday and Thursday night any clouds should get squashed back offshore. Models are in good agreement with highs (71-73 Wednesday and 75-77 Thursday) but only in fair agreement with lows given differences in low-level winds and their impact on the strength of the nighttime radiational inversion near the coast. My forecast is on the low end of MOS guidance, especially near the coast Wednesday night. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 300 PM Monday...It will remain high and dry through much of the period as one area of high pressure slips off the northeast coast and another one takes hold over the Southeast. Will maintain a northerly flow throughout much of the period. The pcp water values remain down near a half inch Fri with a slight rise as winds come around to a more easterly direction Sat aftn. Any clouds or pcp over the waters should remain off shore as winds stay parallel to the coast through Saturday, but as coastal trough develops Sat night into Sunday may see greater potential for clouds along the coast and some pcp, mainly over coastal SC. At this time the pcp water begins to increase as moisture profiles show an increase in shallow moisture below 4k ft Sat night into Sun and increase in potential for higher clouds through Sunday. The moisture returns just beyond the long term period when a deep southerly return flow develops heading into Monday as coastal trough/warm front pushes on shore and north. The temps will warm through the period as air mass modifies and winds come around to a more easterly direction allowing for some moisture return off at the low levels. Min temps within a few degrees of 50 Fri night will end up around 60 by early next week. Max temps will make a return to 80 or above over the weekend. Overall temps will be running above normal once again. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As of 18Z...High pressure will persist across the TAF sites for the next 18 hours with VFR/no cigs. Winds will be 10-50 degrees at 10-15 kt with gusts to around 20 kt, decreasing to less than 6 kt by late afternoon. Time height progs low level moisture will increase at coastal terminals below a substance inversion after 12z. Attm expect sct stratocumulus at best coastal terminals late morning. Extended Outlook...Possible MVFR cigs Thurs AM. Otherwise VFR.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 10 AM Tuesday...Small craft advisory continues for all zones. Pinched gradient as high to the northwest builds south will maintain winds in the 20 to 25 kt range for much of the day. Speeds may dip under SCA thresholds this evening but prolonged period of strong northeast flow will keep seas in zones open to northeast fetch at or above 6 ft through the end of the period. Headlines remain unchanged and only a few minor tweaks to the forecast were needed. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday...High pressure will remain situated across the Mid- Atlantic states through the period. This should maintain a 15-20 kt northeasterly wind across our coastal waters Wednesday and Wednesday night. By Thursday night the center of the high will begin to sag into North Carolina, reducing the pressure gradient across the area and allowing wind speeds to fall to only 10 knots or so. Winds and seas will probably remain high enough for the Small Craft Advisory to remain posted through the day Wednesday. LONG TERM /FRIDAY THROUGH SATURDAY/... As of 300 PM Monday...Winds will become more easterly over the weekend. The northerly surge will abate as winds diminish as well, allowing for seas to subside to 2 to 4 ft Fri and Sat. && .TIDES/COASTAL FLOODING... As of 300 PM Monday...Astronomical tides are increasing as we approach a new moon. This coupled with strong NE winds, may breach minor coastal flooding thresholds at Wrightsville Beach beginning today, and advisories may be needed along portions of the coast the next several days. The same will be true of the lower Cape Fear including the downtown Wilmington area. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Beach Hazards Statement until 9 PM EDT this evening for SCZ054- 056. NC...Beach Hazards Statement until 9 PM EDT this evening for NCZ106- 108. MARINE...Small Craft Advisory until 6 PM EDT Wednesday for AMZ250-252- 256. Small Craft Advisory until 9 PM EDT this evening for AMZ254. && $$ SYNOPSIS...TRA NEAR TERM...III SHORT TERM...TRA LONG TERM...RGZ AVIATION...MRR

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