Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 242330 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 630 PM EST Fri Nov 24 2017 .SYNOPSIS... High pressure will remain over the Carolinas through tonight then weaken Saturday. A dry cold front will approach from the northwest Saturday afternoon and cross our region Saturday night. Cool high pressure will build into the Carolinas Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 140 PM Friday... An area of high pressure at the surface will gradually weaken tonight as an area of low pressure develops offshore and moves newd away from the coast. The cool dry air mass deposited by the high will allow temperatures to coll quickly after sunset. Most locations will be in the 30s to near 40 degrees by late evening. Under mostly clear skies and a near calm wind, overnight temperatures will bottom out between 30 and 35 degrees. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 140 PM Friday... Saturday, an upper level disturbance accompanied by a dry sfc cold front will drift across our region late Saturday and Saturday night. Proceeding the s/w will be a deck of mid-high level clouds that will thicken during the afternoon. While skies will be mostly cloudy- overcast, little if any rain will occur as the overall lift appears too weak to generate precip. Southwest low level flow will advect a warmer air mass into central NC. This should lead to afternoon temperatures 3-5 degrees above normal for late November, in spite of the thickening cloud cover. High temperatures should range between 63-68 degrees. The sfc cold front will cross our region late Saturday evening into the overnight hours. NW flow behind the front will advect a drier, cooler air mass. Expect clouds to thin/dissipate from the northwest overnight. Min temps will be a touch warmer than previous nights thanks to warm air ahead of the front. Min temps 35-40 degrees. && .LONG TERM /Sunday through Friday/... As of 210 PM Friday... Still appears to be a mostly dry week, and fairly mild. The forecast vertical wind and thermal profile suggests that we may see some orographically enhanced cirrus across the northern Piedmont early Sun, but otherwise expect generally clear skies as a cold front pushes well to our SE. Cooler air will funnel in behind the front, dropping thicknesses down to 5-10 m below normal for Sun, yielding near to slightly below normal highs in the mid 50s to lower 60s. Moderation begins Mon as surface high pressure builds in from the west before settling over the Mid-Atlantic region by Tue. A mid level shortwave trough dropping through the Gulf States and Southeast Mon into Tue will have little impact given the dry and stable column in place. But the GFS does show this feature enhancing baroclinicity along the SE coast and potentially drawing some stratocu into the SE CWA late Tue through Tue night, as the surface high weakens further and pushes offshore. The low level wind field should remain weak, though, with a dry trajectory aloft, so it should stay dry, albeit with a few more clouds. Another fast-moving shortwave trough tracks through the Mid Miss Valley and Ohio Valley through the Mid-Atlantic coast from late Wed through Thu, and this will pull a diffuse warm front northeastward through the area, reinforcing the warming trend. With thicknesses rising to slightly above normal Tue and 20-25 m above normal for Wed/Thu, high temps should trend to at least a couple of categories above normal, into the 60s to around 70, under fair to partly cloudy skies. The GFS/ECMWF solutions diverge considerably by Fri. While the ECMWF has backed off its deep low over the Carolinas, the latest run still depicts a progressive full latitude trough from E Canada down through GA/FL early Fri, with ridging over Mexico/NM/TX. The GFS lags the southern portion of this trough over the Southwest with a broad/flat and progressive northern portion crossing SE Canada/St. Lawrence Valley/Northeast states. The inconsistent ECMWF is still rather wet on Fri (despite limited 850 mb moisture return) while the GFS has a more westerly preceding flow and as a result is mostly dry. Have opted to stay with the drier and more consistent GFS at this time range, but overall confidence is not high. Highs Fri 60- 67. -GIH && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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As of 630 PM Friday... VFR with surface winds under 10 knots through Sunday. A surface cold front will cross our region Saturday night. While clouds will thicken and lower late Saturday through Saturday night, ceilings are expected to remain between 5000ft and 10000ft. Southwesterly surface winds Saturday ahead of the front will become northwesterly behind the front Sunday. The next threat for sub VFR ceilings appears to be late Tuesday through early Wednesday, mainly eastern half of the area, as a deck of stratocu may spread into the region from the coast.
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&& .RAH WATCHES/WARNINGS/ADVISORIES...
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NC...None.
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&& $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...Hartfield AVIATION...WSS/Franklin

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