Area Forecast Discussion
Issued by NWS Wilmington, NC

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833 FXUS62 KILM 170217 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 917 PM EST Sat Dec 16 2017 .SYNOPSIS... A cold front will move into the area and stall Monday and Monday night. Low pressure from the Gulf coast states will push across the area Wednesday through Thursday with a chance for substantial rainfall. High pressure will follow Friday. Another cold front may arrive on Saturday. && .NEAR TERM /THROUGH SUNDAY/... As of 915 PM Saturday...Cirrus discernible on IR satellite loops is too thin for any impact on radiational cooling. Light winds and a very dry atmospheric column are allowing excellent radiational cooling to occur, and temperatures continue to plunge through the 30s except right on the beaches where some 40s are still showing up. A few more downward revisions have been made to overnight low temp forecasts based on 9 PM observations, otherwise no significant changes have been made. Discussion from 300 PM follows... Southern stream upper low exiting northern Mexico along with the belt of stronger winds from the northern rockies into the Great Lakes and southern New England will maintain an area of confluence across the Eastern United States. Other than some thin high clouds the column in our area will remain mostly dry as a result through tonight. As the upper low lifts across the Central Plains late tonight and further dampens across the Midwest during Sunday moisture (generally above H85) will begin to increase across the Carolinas. Thus clear/mostly clear skies will give way to increasing cloudiness, especially later in the near term period. After another night with lows at or below freezing temperatures will finally recover to near climo for Sunday`s high temperatures. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM Saturday...The primary caption for his period is `Milder With Light Rain Showers Monday Night`. The short-wave ejecting NE across Texas tonight, forced to move by the diving trough along the west coast, will de-amplify as it migrates into the southern Ohio Valley and Virginia Appalachians Sunday evening. Water vapor channel indicates/confirms this solution is now underway. A cross- sectional analysis from the vantage point of our forecast area, shows pronounced 925-750 mb moisture advection on westerly trajectories late Sunday night. Upper support appears weak although it is highly kinetic aloft, as we become positioned near the entrance region of a jetlet Monday night. This coupled with the expected moisture may result in light showers, but if so, overall a light QPF output this period. At the surface, high pressure will slip offshore by Sunday evening. The resulting warm-air advection, will bring warming of 12-16 degrees fahrenheit Monday morning, compared to the chilly air early Sunday morning, thus noticeably milder daybreak Monday. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM Saturday...Moisture poised to advect into the area on Tuesday, perhaps rapidly, ahead of a decelerating front that may stall over the region. The GFS is quickest with the moisture advection and is likely too fast. Will ramp POPS more in accordance with slower guidance like the EC and Canadian, both implying a Tuesday night into Wednesday rain event. The rain seems to shut off on Thursday as low pressure developing off Hatteras helps to push the boundary to our south. There may not be much to scour out cloud cover while we are in this wedge-like setup. Moisture will then further increase in a prefrontal southwesterly flow regime on Friday. This front may arrive on Saturday, with rain chances seemingly limited to FROPA and not so much ahead of it. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... As of 00Z...High confidence in VFR forecast throughout the forecast period as high pressure across the region continues to dominate our weather. The high will move off the coast Sunday and winds will shift around to the S-SW at 5 kts or less. Small potential of ground fog at KCRE with light SW flow. Mid layer clouds start to stream into the region after 20z with a broken deck forecasted between 8-10K-ft ahead of next system approaching from the west. Extended Outlook...Sunday VFR. Unsettled weather Monday through Thursday morning as a near stationary front moves in and out of the region. && .MARINE... NEAR TERM /THROUGH SUNDAY/... As of 915 PM Saturday...A little jet of westerly breezes which gusted at high as 15 knots north of Cape Fear appears to be weakening according to latest buoy data. No significant changes are needed to the forecast for the remainder of the overnight period. Discussion from 300 PM follows... Benign marine conditions will prevail through the near term period. A ridge of high pressure currently exists across the coastal plains. The ridge will shift east through tonight and Sunday resulting in a period of light wind. Seas will be 2 to 3 ft this evening, then subside to 2 ft or less later tonight and Sunday. SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 200 PM Saturday...A changeable but manageable marine period as winds transition from NE to SW Sunday night as high pressure over the area slips offshore. As the high offshore drops farther south, straddling Florida and the Bahamas, winds will become more westerly. The west winds will begin to increase to 15 KT and gusty Monday night, as the high interacts with deepening low pressure to our north. With offshore winds however, inshore seas will remain relatively docile, with exception of moderate choppiness off the Brunswick coast Monday night, with the winds paralleling shore there. Due to lack of swell energy this period, and offshore wind, sea heights generally this period will hold at 2 feet or less, except 3-3.5 feet Monday night across the outer waters. A few light rainshowers can be expected late Monday night, but should not restrict visibility a great deal. No fog or TSTMS expected. LONG TERM /TUESDAY THROUGH THURSDAY/... As of 300 PM Tuesday...Westerly wind on Tuesday as high pressure roosts in the Bahamas and Florida peninsula. A cold front will drop into the waters and likely stall Tuesday night as a wave of low pressure develops to our west. This low remains fairly flat as the boundary sinks to our south on Wednesday allowing a NE wind to spread southward across the waters. Northerly winds will veer as Thursday progresses as the day initially starts with a wedge of high pressure that weakens later in the day. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MBB NEAR TERM...TRA/SRP SHORT TERM...MJC LONG TERM...MBB AVIATION...MAC

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