Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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891 FXUS62 KRAH 231913 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 213 PM EST Mon Jan 23 2017 .SYNOPSIS... A potent low pressure system over the southern Appalachians will track east-northeast through the Carolinas today, then track off the Mid-Atlantic coast on Tuesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 AM Monday... Previous forecast is in pretty good shape. The stacked low over southwest NC, a little further south than previously projected, will move east across central NC today. The associated occluded front moved north through the area this morning and has resulted in a period of breaks in the clouds and even total clearing in the east. Wrap around moisture will be pulled back east today and lead to mostly cloudy skies by this afternoon. The early clearing in the east will allow temps to reach the low/mid 60s, which combined with a -22C cold pool at 500mb will yield a few hundred J/KG of MLCAPE and should support scattered low-topped convection. This seems most like to form around the leading edge of an area of stratiform precip/low clouds and surface troughing currently pivoting up from eastern SC, keeping POPs mainly focused in southern half of the Coastal Plain. While instability isn`t terribly impressive, the freezing level was between 7-10kft this morning per RAOBs and will fall throughout this day, so some small hail or graupel may accompany a few isolated storms. Otherwise, the wrap around moisture may produce a few showers in the west late this afternoon, but the trend should be for this to diminish as the flow becomes northwesterly behind the low. Highs generally 53-63 west to east. Tonight: Drier air filtering into the area with the departure of the system should lead to SW to NE clearing late tonight into Tuesday morning. Lows in the lower 40s NW to mid 40s elsewhere. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 400 AM Monday... In the wake of the vertically stacked low progressing offshore the Mid-Atlantic coast, a shortwave ridge aloft will build eastward over the Carolinas and Mid-Atlantic Tue afternoon/evening, progressing offshore by Wed morning as an upper level trough (moving ashore the Pacific coast today/tonight) digs/expands across the Intermountain west/Rockies and shortwave energy rounding the base of the trough (in vicinity of the 4-corners region) ejects northeastward through the Central Plains into the Upper Great Lakes, establishing southwest flow aloft downstream along the Gulf/Southeast Coast and Eastern Seaboard. A cold front assoc/w a sfc cyclone attendant the aforementioned shortwave energy ejecting NE into the Upper Great Lakes will slowly approach the Appalachians from the west Wed aft/eve. Expect dry conditions through this period, with a breezy NW wind gusting 20-30 mph on Tue and a breezy SW wind gusting 20-30 mph on Wed. Highs near 60F on Tue will fall into the upper 30s to lower 40s Tue night, then rebound into the upper 60s on Wed. -Vincent && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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As of 210 PM Monday... A transition from mild conditions to more seasonable, but generally dry ones, will occur during the medium range. Ridging aloft will crest over the Ern U.S. on Wed, then move offshore in advance of a broad, positive tilt longwave trough that will migrate Ewd and encompass the Ern two thirds of Ern North America by the weekend. A surface cold front --one related to the lead shortwave trough that will initiate the Ewd progression of the longwave trough, and which will trail a parent surface cyclone that will migrate NEwd across the Great Lakes-- will settle across NC late Wed night-Thu. Both moisture and lift are forecast to be limited, as the parent forcing lifts to our NW, so rainfall chances and amounts are likewise expected to be limited. Behind this lead front, temperatures will cool to more seasonable/ average levels for the end of the week and weekend. The positive tilt configuration of the trough aloft will cause surface high pressure to sprawl into the SErn U.S. and suppress any additional precipitation chances until Sun-Mon, at which time a Nrn stream shortwave trough in NW flow aloft will amplify into the Middle Atlantic region and possibly support some degree of cyclogenesis over the Wrn Atlantic. At this time, it appears that a generally dry reinforcing cold frontal passage will result for our region, though the prosepcts of nearby coastal cyclogensis will be worth watching in the coming days.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/... As of 130 PM Monday... the passage of an occluded front early this morning helped clear some of the low level moisture and VFR has resulted for much of eastern NC. Clouds are beginning to fill back in this afternoon as a low pressure system crosses the area and 1)kicks off some scattered showers around FAY and RWI, and 2) brings wrap around moisture back across the area this evening. MVFR is expected to redevelop this afternoon, with a band of IFR level stratus moving west to east across the area between 00Z and 09Z.. Confidence is fairly high at this point. Winds will turn to northwesterly with the aforementioned band of moisture tonight and may gust to 15-20kt as cold advection kicks in a scours all remaining moisture. Winds should weaken by 12Z but then increase again by 15z, with wind gusts to around 20kt again on Tuesday afternoon. Looking ahead: VFR conditions are expected Tuesday and Wednesday. A cold front will cross the region late Wednesday night/early Thursday, bringing with a chance of showers and sub-VFR ceilings to the area. VFR conditions should return late Thursday afternoon/evening. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL/SMITH SHORT TERM...Vincent LONG TERM...MWS AVIATION...Smith

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