Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280007 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 815 PM Sat EDT May 27 2017 .SYNOPSIS... A surface trough will be located over the Piedmont this afternoon through Sunday. An upper level disturbance will cross the region this afternoon and early evening, followed by another disturbance Sunday afternoon. && .NEAR TERM /TODAY AND TONIGHT/... As of 1255 PM Saturday... A 40-50kt westerly flow in the mid levels is in place from the mid- Mississippi valley east across NC/VA. At the surface, surface dew points are in the lower 60s. With ample sunshine, temperatures are expected to peak in the upper 80s to around 90F resulting in MLCapes on the order of 2000+ J/KG. A shortwave moving through KY/TN will support the development of scattered thunderstorms after 21Z and mainly over the northern Piedmont. Latest model trends have the storms moving east-southeastward, crossing much of central NC from 22Z Sat to 06Z Sun. Considering the expected favorable elevated mixed layer (EML) and the degree of instability expected, some of the thunderstorms may contain damaging wind and hail expected. After the evening thunderstorms move by, areas to our west will have to be watched in the fast flow aloft as storms upstream may be able to make it east of the Mountains, albeit in a weaker state, toward daybreak due to the lingering instability and strong steering flow. Lows tonight will be in the mid 60s to near 70. && ..SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 330 PM Saturday... Sunday and Sunday night: The MCV currently over northern Missouri/southern Iowa is generally forecast to stay north of the area while shearing out across the Ohio Valley/Lower Great Lakes overnight, with new convective development and associated MCV predicted across parts of Missouri/Ozarks later this afternoon/evening. This will be the region to watch over the next 12 hours, with Sunday`s convective forecast highly dependent on the magnitude/timing of these convectively enhanced disturbances. Adding to the already complex convective forecast will be the evolution of this evening/tonight`s convection, with the potential for the convection to leave behind an old convective outflow/TMB across the area which could served as a secondary focus for convective initiation. Will maintain good chance pops,highest across the western/central Piedmont during the afternoon and into the early evening, with decreasing pops by 03 to 06z due to a cooling BL. Steep mid-level lapse rates will linger across the region, with models showing 1500- 2500 J/KG of MLCAPE developing amidst a moistening boundary layer( dewpoints in the mid to upper 60s). When combined with deep layer shear of 40 to 50 kts, if organized convection develops or moves into the area on Sunday, the environment will be supportive of supercells capable of producing straight line winds and large hail. Highs Sunday very similar to today with highs ranging from mid 80s north to lower 90s south. Lows 65 to 70. Monday and Monday night: The closed low over the Upper Great Lakes will wobble slowly east on Monday. A surface cold front, attendant to a northern stream shortwave trough lifting off to the north/northeast, will weaken and likely stall as it moves the area late Monday afternoon into Monday night. Meanwhile, models suggest the potential for shortwave disturbances, embedded in the SW flow aloft between the upper low to our north and the subtropical ridge over the SE States, to move through the region. Scattered to numerous showers and storms are possible across the area Monday afternoon and evening as the front approaches from the west and with the continued threat of disturbances moving through the region. While storm intensity should weaken with loss of heating, with the front expected to stall across the area, the chance of showers could linger well into the overnight hours. Strong daytime heating within the moist and moderately unstable airmass combined with continued strong mid-level flow that will support favorable/strong deep layer shear of 40-50 kts will result in another slight risk for severe storms across the area with damaging winds and large hail the primary threats. Highs in the mid 80s north to near 90 south. Lows in the mid 60s NW to lower 70s SE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 230 PM EDT Saturday... Closed low will move slowly east across SE Canada and NE U.S. through the period. Central NC will find itself near the base of the associated upper trough and accompanying strong belt of westerlies extending south into the region. While there is generally good agreement on the synoptic scale pattern, sensible weather next week will be greatly influenced by the many shortwave disturbances that are forecast to track through the region within the low amplitude west-southwesterly flow aloft between the aforementioned closed low to the north and the subtropical ridge to our south. Additionally, the exact evolution of these disturbances timing/track/magnitude) will likely play a role in the location of a nearby sfc boundary that`s forecast to stall across the SE states. Thus, expect pops near to above climo each day, dependent on difficult to time disturbances, with convection likely to exhibit a diurnal trend. Expect seasonable temperatures with highs ranging from lower 80s north to mid/upper 80s south. Lows in the 60s. && .AVIATION /00Z SUNDAY THROUGH WEDNESDAY/... As of 815 PM Saturday... Widespread shower and thunderstorm activity will be approaching central NC from the north and also from the west tonight. The convection will be weakening but will still pose a modest threat at INT & GSO through around midnight, and perhaps at RDU towards midnight, but chances are rather low. Expect a repeat of convection developing along the northern tier Sunday afternoon/evening, but low confidence at this point regarding how much coverage we might receive. All told, outside of convection, VFR conditions are expected through the 24 hour TAF period, although there could be patches of MVFR fog in the predawn at locations which do receive rain. Outlook: There be a chance of mainly late day storms Monday through Wednesday as a cold front slowly approaches from the west and potentially stalls over the area. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett/Franklin SHORT TERM...CBL LONG TERM...CBL AVIATION...mlm

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