Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 220143 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 940 PM EDT SAT MAY 21 2016 .SYNOPSIS...Surface low pressure and an upper level disturbance over the region will move northeastward tonight. A strong upper- level low pressure area will settle over the area Sunday through Monday, producing unsettled weather. Warmer and drier weather will follow from Tuesday through late week as the upper low moves offshore and high pressure builds across the area. && .NEAR TERM /through tonight/... As of 940 PM Saturday... Primary forecast change with this update was to adjust toward reality, raising short term pops across the southern CWA, and reducing them across the north. Latest surface map shows the strong low off Delmarva and weaker low over the southern Piedmont, connected by a frontal zone that is slowly sliding to our SE. Storms were only able to achieve marginal severity late today into this evening given poor mid level lapse rates which hindered updraft growth, although the current scattered storms over the south will continue to feed on marginal instability and a favorable deep layer shear environment in place as they track toward the SE over the next few hours. Otherwise, the loss of heating and subsequent stabilization behind this band of convection should limit coverage and upscale growth of any subsequent showers or storms. However, there remains a fairly potent vorticity maximum diving ESE into the southern Appalachians, and this feature acting on lingering low level moisture (the result of weak low level flow) could spawn additional isolated showers and perhaps another storm or two into the overnight hours, diminishing late as the southern Piedmont low sinks to our south and southeast and the DPVA departs. Low level moisture will deepen further over the northern and eastern CWA as it advects in from eastern VA on the back side of the offshore low, so will maintain cloudy skies there through daybreak, while areas in the southwest and western CWA should see a trend to partly cloudy skies overnight. Lows 55-61, with dewpoints dropping a bit across the south as cooler air spills in. -GIH && .SHORT TERM /Sunday and Sunday Night/... As of 330 PM Saturday... Unsettled weather will continue on Sunday as a deep upper low, 2 to 3 SD below normal, becomes centered over northeastern NC by Sunday night. DCVA and steepening mid-level lapse rates coincident with peak but tempered daytime heating will support scattered showers. Expect highest POPS invof of the upper level core and deepest moisture across the NE coastal plain/piedmont. Temperatures will continue to run below normal underneath the anomalous negative height anomalies. Highs ranging from upper 60s/near 70 northeast to mid 70s southwest. && .LONG TERM /Monday through Saturday/... As of 230 PM Saturday... Monday and Monday night: To start the day off on Monday, a closed upper low is progged to be over northeast NC and it will make its way eastward/northeastward throughout the day. As such, shower chances will continue, but will likely stay confined to the northeast half of the forecast area. Any precip is expected to come to an end Monday night as the upper low slowly pulls away from the region. Temps will remain below normal given the proximity of the upper low and associated cloud cover/precip, with highs expected to be in the lower 70s across the northeast and the mid/upper 70s further to the southwest. Overnight lows should fall into the mid 50s. Tuesday through Saturday: Conditions should dry out by Tuesday as the upper low pulls further away and shortwave ridging builds over the region. However, one model is now showing one last piece of energy rounding the backside of the departing upper low and triggering some precip across the northeast. Given the lack of other model support, have kept the forecast dry for now but will keep a close eye on it. Otherwise, the ridge that will build in, will keep the main storm track to our north, resulting in mostly dry conditions through the end of the week. There are indications that the ridge may weaken some towards the end of the forecast period, allowing an uptick in mostly diurnal type convection. However, there is some disagreement among the models with regard to this and therefore, will just show an increase in clouds and bring in a slight chance of precip. Temps will gradually moderate through this time frame, from mostly lower 80s on Tuesday to mid/upper 80s by for the remainder of the period. && .AVIATION /00Z Sunday through Thursday/... As of 715 PM Saturday... 24 hour TAF period: A cluster of showers and thunderstorms will move east through the area between 00z-06z, resulting in local IFR conditions. Model guidance suggests the re-development of low clouds/stratus and possibly some fog between 06 to 12z, especially across central and eastern terminals(KRDU,KFAY,KRWI). Drier air advecting into the area behind the a surface front is expected to preclude stratus development at KINT and KGSO. The low ceilings/stratus across central and eastern areas will be slow to lift through the day on Sunday morning, with the potential for MVFR ceilings to persist at eastern/northeastern NC(KRDU and KRWI)until late in the afternoon. Meanwhile...western and southern most terminals could see VFR conditions return by mid morning. A deep upper low moving over the region will bring scattered showers across the area on Sunday, with greatest coverage expected across the east/northeast invof of the upper low. Beyond 00z Monday: The risk for sub-VFR conditions with scattered showers will continue through at least mid-day Monday as a closed low gradually moves south across eastern NC. VFR conditions expected to return by Tuesday and remain for the mid-week period as the closed low moves east and short wave ridging moves over our region. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...CBL LONG TERM...KRD AVIATION...CBL

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