Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 132350 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 650 PM EST Mon Nov 13 2017 .SYNOPSIS... High pressure will gradually build into central NC through Wednesday, leading to a dry and seasonably cool stretch of weather. && .NEAR TERM /THROUGH TONIGHT/... As of 250 PM Monday... Main forecast challenge in the near term is the extent of fog coverage overnight and if dense fog will occur. Last vestige of lower clouds slowly eroding/exiting the northern coastal plain early this afternoon while pockets of stratocu persisted over portions of the Piedmont. The relatively moist layer trapped a subsidence inversion based just above 850mb will promote the development of another stratocu deck shortly after sunset. The prevailing nely flow in the 925-850mb layer will gather the moisture primarily over the NW Piedmont into the southern Piedmont. The GFS and the NAM suggest another batch of low clouds will exists across the coastal plain, though this signal is not as strong as the one for the NW Piedmont. Where low clouds initially do not develop, areas or widespread fog will likely form with the potential for dense fog at a few locations. The occurrence of fog versus low clouds currently favors the highway 1 corridor. Confidence not high enough for a fog advisory at this time but one may be needed later tonight. Min temps tonight generally in the upper 30s to around 40. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 250 PM Monday... Another minor mid-level s/w will approach from the west-NW Tuesday morning, and cross our region Tuesday afternoon. This system will provide enough lift to maintain a deck of stratocu through most of the day, though the mid-upper layers of the atmosphere are too dry to generate precip. The deck of clouds will inhibit insolation enough to result in another afternoon of temperatures 6-9 degrees below normal. Currently anticipate at least partial sun by late morning-early afternoon. If the partial sun does not materialize or is delayed until mid-afternoon, then high temperatures may end up being 3-4 degrees cooler than forecast. High temperatures mid-upper 50s. The passage of the s/w late Tuesday will likely aid to diminish the mid layer inversion, allowing the drier air aloft to mix into the moist layer and lead to mostly clear skies Tuesday night. Residual ground level moisture will likely promote the formation of fog towards morning though widespread dense fog not expected at this time. Low temperatures generally in the mid 30s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 305 PM Monday... Wednesday: Surface high pressure will remain over the region through Wednesday while transient ridging between two upper level troughs exists aloft. Expect dry weather and relatively clear skies for Central NC with highs in the mid 50s to near 60 degrees and lows in the upper 30s to around 40 degrees. Thursday and Friday: Low pressure over south-central Canada will swing eastward through the Great Lakes and into New England through Friday night. The attendant cold front extending from the Upper Great Lakes into the Midwest will push east and southeast toward the Carolinas and Virginia. The associated upper level trough will swing through the Mid-Atlantic and northeast through Thursday. Expect a dry cold frontal passage in association with this system Thursday, with the best cold advection delayed about 6-12 hours. Cool high pressure will be in place Friday before the front retreats northward once again. A high temperature roller coaster begins Thursday and continues into the weekend. For the weekend: A second, stronger, frontal system will approach the region on the heels of the previous one. The upper level trough amplifies Friday night over the Midwest and quickly swings eastward as the parent upper low deepens over the Great Lakes and Ontario. There are still significant timing issue between the medium range models. Generally, expect increasing temps ahead of the front, chances for rain as the front moves through the region, and strong cold high pressure building in behind it. The cold front and associated pre-frontal rain could move into Central NC as early as Saturday or hold off until late Saturday night. Regardless, rain should exit by Sunday afternoon, if not much earlier. The temperature roller coaster will continue, albeit dependent upon the timing of the front. The parent low/trough this system develops from should be sampled better by the models mid-late week, resulting in (hopefully) increasing confidence at that time. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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As of 650 PM Monday... Low-level NELY flow is expected to advect the IFR to MVFR stratus currently across southern VA and northern NC , south-southwest into central NC this evening and overnight. In areas where the low clouds do not develop, patchy fog is possible, likely reducing the visibility to less than a mile with pockets of dense fog probable. Similar to this morning, the fog and low clouds will linger through mid morning then lift and scattered into a cu field in the afternoon. Aside from pockets of early morning fog/low clouds, expect VFR conditions Wednesday through Friday night. The next threat for sub VFR conditions will occur with a frontal system that is expected to affect our region Saturday.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...CBL is the U.S. government's official web portal to all federal, state and local government web resources and services.