Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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705 FXUS62 KRAH 181810 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 210 PM EDT Sun Mar 18 2018 .SYNOPSIS... Weak high pressure will extend across the southern middle Atlantic states through tonight. A warm front will retreat north across the southeastern U.S. Monday, ahead of a series of low pressure systems that will track along the front, and across and offshore the Carolinas, Monday night through early Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1135 AM Sunday... Cold air advection was evident in 12Z upr air data at 850-925 mb, behind a surface cold front that was analyzed at 15Z extending from a ~1008 mb frontal wave several hundred miles se of KHSE, wwd across swrn SC and n-cntl GA. Following weak, 1018 mb high pressure over nrn-cntl VA this morning will build swd into NC today. A multi-layered band of post-frontal, mostly scattered stratocumulus and altocumulus, will continue to pivot swwd across the srn and wrn half of the RAH forecast area during the next several hours, with following drier air and clear skies arriving from the ne. With resultant mostly sunny conditions, dry adiabatic mixing through around 900 mb favors high temperatures ranging from upr 50s ne to lwr-mid 60s sw. A low to mid level warm air advection regime, and contribution to forcing for ascent, will develop on the wrn periphery of the aforementioned ridge as it drifts toward the srn middle Atlantic coast tonight. Initially clear skies will consequently become cloudy or mostly so from west to east, from a developing multi-layered cloud deck through particularly the lowest 10 thousand ft, overnight. Temperatures will accordingly likely reach lows earlier than is typical, then rise with the development and ewd expansion of the clouds - in the wrn Piedmont around or shortly before midnight, ranging to an hour or two before sunrise in the Coastal Plain. As such, low temperatures are expected to range from lwr-mid 30s in the nrn and cntl Coastal Plain to mid 40s over the srn and wrn Piedmont. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 345 AM Sunday... High pressure transitions off the Mid Atlantic Coast before sunrise Monday, as a Mid to upper-level low ejects east across the Great Plains states. Southerly to Southeasterly flow across the SE CONUS is enhanced between these two systems, lifting a warm front north into the Carolinas Monday. The result will be lowering overcast on Mon, with an increasing probability of rain from SW to NE with time along with subsequent likely to categorical probability of rain/showers Mon night, with nrn (climatologically-favored) counties likely to remain in a cooler and more stable wedge air mass, while srn ones experience milder and slightly unstable conditions, with an associated slight chance of thunder Mon night. Elevated thunder will be possible as far north as roughly the HWY 64 corridor. && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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As of 210 PM Sunday... Longer range forecast remains on track for a cold and unsettled Tuesday through Thursday with a warming trend toward the weekend. A brief lull in the precip is generally expected on Tuesday as the first in a series of disturbances shifts to the east of the area. However, skies will continue to remain mostly cloudy to overcast will low level moisture lingering. Highs on Tuesday are expected to range from the mid 40s north to the lower to mid 60s south. Additional mid/upper level energy is expected to dive southeastward and into our area for Tuesday night into Wednesday. Models continuing to advertise the potential for some wintry precip late Tuesday night into Wednesday morning across the area, with the best chance of seeing some light accumulations of snowfall across the climatological favored northern Piedmont. The system will be similar to the last one, where the boundary layer will need to cooled by melting snow in order bring temps down to near freezing. Have kept temps ranging from the lower/mid 30s to lower 40s for the entire wintry event. Dry weather will return for late week with the mid upper level trough axis expected to shift to the east of the area. The next system is expected to approach the area next weekend, with increasing chances for showers. Temperatures will make a run toward seasonal normals by the weekend.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/... As of 645 AM Sunday... 24 Hour TAF Period: Variable CIGS are likely to continue at KRDU/KFAY/KRWI early in the period as northerly flow reestablishes behind the departing mesolow which is pushing east of the Outer Banks at this hour. This should be the case through roughly 13/14z, with rapid improvement and clearing expected to follow. All sites are expected to return to VFR no later than the noon hour, with clearing skies continuing. Winds will remain light to moderate (<10kts) and from out of the north/northeast, with only a periodic gust possible. Some MVFR potential returns overnight Sunday into Monday as easterly/southeasterly flow returns and a warm front drifts north. Outlook: The threat for Sub-VFR conditions will continue most of Monday, and likely persist into the middle of next week as a series of disturbances passes overhead. Confidence is not high regarding timing of these disturbances, so aviation interests should check back for the latest thinking. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...JJM/MWS LONG TERM...BSD/Franklin AVIATION...JJM is the U.S. government's official web portal to all federal, state and local government web resources and services.