Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 191903 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 300 PM EDT Mon Mar 19 2018 .SYNOPSIS... A warm front will lift north into the area this evening, where it will then stall tonight. There will be a series of low pressure systems developing along the front as it pushes slowly south of the Carolinas through early Wednesday. && .NEAR TERM /THROUGH TUESDAY/... As of 300 PM Monday... High pressure edging further offshore and thinning clouds allowed highs to rise well into the 60s, which further weakened the isentropic gradient which resulted in anemic patches of light rain or virga into the afternoon. Expect the cloudiness to become widespread and lower quickly as we lose sun and low level flow strengthens atop a surface warm front lifting north into the area where it will creep slowly north to the I64 vicinity by late tonight. Isentropic lift will be on the increase progressively tonight as well, and will raise the PoPs to near 100 percent, progressing from southwest to the east by morning as a surface wave moves east across the southern tier. Rainfall amounts should range from a minimum of at least a half inch to perhaps 1.25 inches across the northern tier where frontal zone enhances rain rates. Most unstable CAPE across the southern tier reaches 300-400 Joules, with increasing low level shear south of the frontal zone, so will include a chance for thunder across the southern couple of tiers of counties. Lows will be mild, from the mid 40s north of the front to mid or even upper 50s across the south. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 350 AM Monday... Tuesday: 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 lower 40s north to the lower to mid 60s south. Very tricky forecast for Tuesday night through Wednesday as an upper trough digs down into the area spurring surface cyclogenesis along the NC/SC border. While this surface low will quickly move up the Carolina coast, the upper low will linger behind and bring cold air down from the north. This in turn with some leftover moisture could lead to some deformation banding behind the system which could result in a brief period of rain mixed with snow, or if precipitation rates are high enough, a quick burst of snow resulting in some spotty accumulations, particularly across the northern counties. There are several mitigating factors however, that could result in very little to no snow. These include warming temperatures with the heating of the day. Thickness values in the wintry mix to indeterminate areas of the nomogram for much of the event except the very tail end where thicknesses drop to levels suggestive of all snow for a couple of hours when moisture may or may not still be available. Finally, lift drops off considerably after the surface low pulls off to the northeast, making it very hard to produce the rates needed for accumulating snow. What we are expecting at this time is a period of a few hours of rain/snow mix during the Wednesday morning hours resulting in very little to no impacts. There could be some localized heavier snow showers if precipitation rates are high enough. These should be brief but could result in some minimal accumulations of less than a half of an inch if they persist long enough. By the time a changeover to all snow would occur Wednesday night, there will likely not be enough lift or moisture left to produce more than a period of flurries. Bottom line is a late March nuisance event will minimal impacts. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 300 PM Monday... The surface low will be lifting rapidly northeast with dry and cooler high pressure building into the area on Thursday through Friday. Temperatures will be cool, from upper 40s north to mid 50s south on Thursday, and a couple of degrees warmer on Friday. Lows Friday morning will fall below freezing over most of the area, with northern tier counties perhaps falling into the upper 20s. Northwest flow into the weekend will provide increased cloud coverage and some light rain into the west to tighten up our damming signature and produce highs ranging from the low 50s north to low 60s south. Return flow will increase rain coverage on Sunday, further strengthening the ridging, with highs in the 50s to lower 60s Sunday and Monday. && .AVIATION /18Z MONDAY THROUGH SUNDAY/... As of 140 PM Monday... 24-Hour TAF Period: Initial VFR conditions this afternoon will linger through 00Z. Southerly surface flow will strengthen ahead of a low pressure area moving across the southern tier of the state tonight. Increased moisture and upglide will induce ceilings to lower quickly through MVFR to IFR from 00-06Z, with light rain blossoming and becoming widespread through the period. IFR/LIFR ceilings are expected after 06Z, to linger past 12Z with marginal improvement to MVFR towards 15Z. Looking ahead: Passage of a series of low pressure systems will result in sub-VFR conditions and periods of rain, probably mixed with or briefly changing to snow at the northern TAF sites late Tuesday night into Wednesday. Drying and a return to VFR conditions from west to east will occur as the fianl trailing low lifts away from the middle Atlantic coast Wednesday night. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...Ellis LONG TERM...Ellis AVIATION...mlm is the U.S. government's official web portal to all federal, state and local government web resources and services.