Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190652 RRA AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 252 AM EDT Sat May 19 2018 .SYNOPSIS... A Bermuda high offshore and an area of low pressure over the TN Valley will maintain a moist southerly flow over central NC through Saturday night. A series of disturbances aloft will trigger periods of showers and thunderstorms through Saturday night, producing locally excessive rainfall. && .NEAR TERM /TODAY AND TONIGHT/...
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As of 250 AM Saturday... Flash Flood Watch remains in effect for most of central NC through Saturday evening. A persistence forecast today with a primary focus for convection over the eastern half of the area, US-1 and east. The surface boundary remains to the north, with south-southeasterly return flow around the Bermuda High, ushering moist air into Central NC. MUCAPE values will max out in the 500-1000 J/Kg range while PWAT values will range from around 1.5" in the west to around 2.0" in the east. Expect the greatest convective coverage and precipitation totals to be across the eastern half of the area, mainly the Eastern Piedmont and Coastal Plain regions. Very heavy rain is likely to accompany any showers and thunderstorms that develop. As for temperatures, generally expect highs in the mid 70s NE to low 80s SW. With the expected high dewpoint temperatures (hovering around 70 degrees) the air will feel quite muggy as min RH values will bottom out around 70 percent in the SW to near 85 percent in the NE. Though there may again be a lull/decrease in convective activity tonight, still expect some scattered showers and isolated thunderstorms. Overnight lows will again bottom out in the mid 60s to around 70 degrees with near 100 percent RH values, making for another muggy night.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 335 PM Friday... Saturday and Saturday night, the deep sly flow will shift ewd and be positioned primarily over the eastern counties. This shift is due to the mid-upper level low currently over the TN Valley lifting into the lower Great Lakes. With the low pressure system to our NW and the Bermuda high anchored offshore, upper divergence will remain over eastern NC. Model guidance continues to depict a series of perturbations lifting nwd in the deep sly flow. With the abundantly moist and unstable atmosphere in places, rounds of showers and storms will continue through Saturday evening. Model guidance currently suggest the axis of deeper moisture and best lift drifting east, and out of our region late Saturday night. Rainfall through early Saturday evening should total one to two inches over most of central NC with locally higher amounts between 3 and 4 inches possible. Some portions of central NC have already received amounts of 3 inches. This added rainfall will likely lead to rapid run off and flooding of creeks and streams. && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 215 PM Friday... ...Unsettled weather is likely to continue through much of the long term period... The upper-air pattern at the beginning of the long term period will feature a well established sub-tropical ridge centered off the Southeast coast with a shearing trough across the southern Appalachians and mid-Atlantic while an upper-level low drifts north across the eastern Gulf of Mexico. The ridge off the Southeast coast shifts east during the work week as the upper low drifts onshore across the northeast Gulf Coast and lingers in the Deep South through mid-week. Broad troughing develops across the Northeast late in the work week producing a weak northwest flow across the Carolinas by Friday as the main westerlies remain well to our north. Elevated amounts of deep layer moisture are forecast to persist across the Carolinas through much of the long term period. A persistent frontal zone across the Virginias potentially drops into the Carolinas toward end of the work week as the upper flow becomes more northwesterly. The result should be a period of scattered, mainly afternoon and evening showers and a few thunderstorms from Sunday through most of the work week. Precipitation chances may trend downward by the end of the work week depending on the position of the front. A large fraction of each day will be dry but with a threat of scattered convection. With a little change in air masses, a good deal of cloudiness and scattered convection, highs will consistently range in the lower to mid 80s with low mainly in the mid to upper 60s. -Blaes && .AVIATION /06Z SATURDAY THROUGH THURSDAY/... As of 140 AM Saturday... 24-Hour TAF Period: Scattered showers and isolated thunderstorms continue across Central NC. Ceilings will predominantly be around 1000-1500 ft for the remainder of the overnight, with many sites fluctuating between sct and bkn 600-900 ft before sunrise today. Expect any LIFR/IFR cigs to lift back into the MVFR/VFR range this morning. Some sub-vfr visbys will also be possible for brief periods tonight, mainly accompanied by showers. Expect more by the way of showers and thunderstorms today, resulting in periods of very heavy rain and accompanied by low visbys and gusty winds at the affected terminals. KFAY and KRWI are likely to be affected most by heavy rain, though it is possible across the area. Cigs will generally remain in the MVFR range, though a brief scatter out to VFR is possible. Looking ahead: The pattern of daytime showers and thunderstorms resulting in heavy rain and reduced visbys, with a relative lull in precipitation accompanied by sub-vfr cigs and visbys overnight, will continue through the week. && .RAH WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Saturday evening for NCZ007>011-021>028- 040>043-075>078-085-086-088-089. && $$ SYNOPSIS...WSS NEAR TERM...KC SHORT TERM...WSS LONG TERM...BLAES AVIATION...KC

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