Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221842 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 245 PM EDT Sun Apr 22 2018 .SYNOPSIS... High pressure will extend south through the mid Atlantic states today. Low pressure will track slowly eastward over the lower Mississippi Valley and Mid South region before tracking northeast over the East Coast through midweek. && .NEAR TERM /TODAY AND TONIGHT/... As of 950 AM Sunday... Quiet day overall ahead of the unsettled weather to start the work week. High pressure continues to build in from the north with shortwave ridging in the mid levels, as a surface frontal zone sits well to our south, allowing for stable air and dry low-mid levels over NC. A weakening wave ejecting out of the base of the mid level low over OK/AR will sweep NE over NC later today through tonight, and corresponding high clouds will slowly increase and thicken from SW to NE, with a deck of mid clouds in SW sections. This is reflected well in the RAP-adjusted sky cover forecasts through tonight, with a trend to partly (NE) to mostly (SW) cloudy. Observed morning thicknesses were about 15 m below normal, so have kept highs around a category below normal, 70-74. -GIH Earlier discussion from 220 AM: Surface high pressure will get reinforced as it extends down the eastern seaboard into NC this afternoon and tonight. This occurs as the cut off mid/upper low tracks slowly east toward the mid-Mississippi Valley. Expect increasing high level cloudiness today. Highs are expected to reach near normal, with lower to mid 70s at most locations. A light and mostly easterly wind 5-10 mph is expected. The cloudiness will gradually lower and thicken tonight, reaching the far NE zones late. Lows generally in the 45-50 range NE, and lower to mid 50s elsewhere. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 241 AM EDT Sunday... The center of the high is expected to slowly drift SE and off the New England coast late Monday. The ridge axis will extend SW into the western part of VA/NC Monday and Monday night. As the mid/upper level low pressure east toward the TN Valley region Monday, it is forecast to slowly turn more NE toward central KY by 12z/Tuesday. Rain is expected to become widespread over western and southern parts of central NC Monday morning, slowly spreading over the rest of the region Monday afternoon. Highs will hold in the 50s west, ranging to near 70 in the Coastal Plain (last area to see rain). The strong, deep, and long fetch of sub-tropical moisture is expected to be tapped from the Caribbean and western Atlantic and pulled NW into the system, courtesy of the circulation around the strong high pressure to the north, and low pressure to the west Monday night. Rain should become heavy, with local minor flooding possible. Some model solutions depict strong convection in the Gulf Stream off of SC/NC, potentially disrupting some of the moisture flux. However, most model solutions still depict 0.5 to 1 inch of rain at a minimum over central NC, with some models as robust as 2-3 inches in the western, more upslope, Piedmont region. Therefore, we expect plenty of rain late Monday and Monday night, with increasing winds from the east at 15-25 mph, with gusts to 30-35 mph (windy). Temperatures should hold steady or slowly rise with the strong flow off the Atlantic. Readings in the lower 60s SE, 50s NW. The severe threat really looks very minimal for all of our region as CAD will develop over the Piedmont late Monday and Monday night, rain will be widespread over all the region - ensuring no surface destabilization through 12z/Tuesday at least, if not beyond. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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As of 245 PM Sunday... Unsettled weather is expected through the middle and end of the work week, with mean mid level troughing dominating over the eastern states, and generally more clouds than sun, at least through Fri. The first shortwave trough (responsible in part for the Mon/Tue rain) will be sitting overhead early Wed before lifting off to the NE, culminating in a phasing with a strong polar stream wave over the Northeast states Wed night. Models suggest that we may see enough low and mid level moisture (focusing on 850-700 mb) for a few late-day showers with heating, however the overall forcing for ascent will be small, and expect no more than chance pops. Expect temps to stay slightly below normal, with thicknesses about 10 m under normal and reduced insolation. The next shortwave, which will be located over NE/KS early Wed, will cross the Gulf states and swing NE over the Carolinas Thu night into Fri. As this feature will be deeper and provide stronger forcing for ascent along with an opportunity for moisture return, we should have higher rain chances, targeting late Thu through Thu night, and some of this may be heavy, as the GFS shows a PW over 1.5". After dry weather late Wed night through the first half of Thu, will bring in good chance pops Thu afternoon through Thu night. Temps should again be a bit below normal figuring in the cloudiness and cooler thicknesses. Then, a deep mid level trough from central Canada through the Upper Midwest early Thu should be our next weather-maker. The GFS/Canadian are in fair agreement on a deep low just to the W or NW of NC late Fri, crossing the Carolinas Fri night or early Sat, although uncertainty and model spread grows at this range. Will keep a chance pop, higher N closer to the cooler mid levels and better lapse rates aloft, Fri/Fri night extending into early Sat. We should see subsidence and drying behind this wave for Sat afternoon through Sun, and will trend toward dry weather and fewer clouds as high pressure builds in from the west. -GIH
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 1120 AM Sunday... VFR conditions are likely through much of tonight, as surface high pressure noses into NC from the N. But high and mid clouds will steadily thicken with lowering bases late today through tonight, ahead of a slow-moving deep low pressure system crossing the mid and lower Miss Valley. MVFR cigs are expected after 06z tonight in the SW part of the forecast area toward CLT, and cigs are likely to drop to MVFR at INT/GSO after 10z late tonight/early Mon. Vsbys are also expected to drop to MVFR at INT/GSO after 13z Mon with rain spreading in from the WSW. After 15z Mon, IFR conditions are possible at INT/GSO with MVFR at RDU. Surface winds will increase from the SE and become gusty late tonight and through Mon, particularly over S and W sections (including INT/GSO/FAY), with stronger and shifting winds with height, potentially resulting in handling difficulties with smaller aircraft starting early Mon. Looking beyond 18z Mon: Poor aviation conditions will dominate all sites through Tue as a strong and slow-moving storm system crosses the area. Periods of showers and sub-VFR conditions are likely. On Tue, FAY and perhaps RDU/RWI may see some breaks in the sub-VFR conditions with a risk of storms. Rain should taper off Tue night but sub-VFR stratus/fog may linger into Wed morning. VFR conditions should return Wed, although a few showers are possible Wed afternoon, and again Thu into Fri, as a series of upper level troughs cross the region, bringing unsettled weather and perhaps brief periods of sub-VFR conditions. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NC...None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/Badgett SHORT TERM...Badgett LONG TERM...Hartfield AVIATION...Hartfield

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