Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201926 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 325 PM EDT Tue Jun 20 2017 .SYNOPSIS... A stalled frontal zone over the region will gradually dissipate this evening into tonight. A low-level southwesterly return flow will prevail through the remainder of the week. && .NEAR TERM /Today and Tonight/... As of 1145 AM EDT Tuesday... As of 16Z, the synoptic cold front that crossed the mountains yesterday evening has stalled over portions of the N/NW Piedmont (where dewpoints have fallen into the 60s). However, extensive cloud cover and an outflow boundary attendant a line of convection that surged SE into the Sandhills and SE Coastal Plain earlier today has created an effective frontal zone well southeast of the synoptic front, extending WSW-ENE from Florence-Whiteville-Jacksonville (roughly). A tight PWAT gradient exists across central NC, ranging from ~1.00" in the far NW Piedmont to ~2.00" in the far SE Coastal Plain. In the upper levels, central NC remains at the southern periphery of the westerlies in broad cyclonic flow aloft. With the above in mind, expect numerous elevated showers and isolated thunderstorms on the northern periphery of the effective frontal zone in the Sandhills and SE Coastal Plain this afternoon, primarily S/SE of the Triangle. By 21-00Z, low-level flow (SFC-H85) will veer to the south as the height/mslp gradient tightens between potential tropical cyclone 3 in the GOMEX and high pressure offshore the Southeast coast. As a result, the effective front (and elevated convection on the northern periphery of the front) should gradually shift N/NW toward the Triangle/Piedmont this afternoon and evening. An isolated flash flood threat may exist along/south of a line from Wadesboro-Smithfield-Wilson where elevated convection will repeatedly affect the same areas, with the relative best chance in far S/SE portions of central NC in closer vicinity to the effective front. With widespread mid/upper level cloud cover north of the front and lower ceilings/precipitation in closer vicinity to the front, expect highs in the upper 70s to lower 80s across much of central NC. Lows tonight should range from the mid/upper 60s far N/NW to lower 70s far S/SE. -Vincent && .SHORT TERM /Wednesday and Wednesday Night/... As of 1200 PM EDT Tuesday... The aforementioned frontal zone is expected to wash out tonight as richer low-level moisture returns to central NC via a S/SW return flow. Central NC will remain at the southern periphery of the westerlies in broad cyclonic flow aloft on Wed, however, flow aloft will veer from the SW/WSW to WNW during the day, advecting a drier mid-level airmass into the region during the afternoon and evening. With the above in mind, expect a potential for ongoing convection Wed morning, however, expect activity to wane from W-E during the afternoon as a drier airmass aloft advects into the region. Expect highs in the lower/mid 80s, lows Wed night in the mid/upper 60s to lower 70s, warmest far S/SE. -Vincent && .LONG TERM /Thursday through Tuesday/...
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As of 320 PM EDT Tuesday... Deep southerly-southwesterly flow between newly formed T.S. Cindy that`s currently over the Gulf of Mexico and the subtropical ridge over the western Atlantic, will channel a plume of tropical moisture(PWATS ~2.25")northward into the region as early as Thursday night and could linger over the area until a cold frontal passage late Sunday and into Monday. Model spread remains high, specifically WRT to the timing heavy rain chances and qpf amounts across the Carolinas, largely due to the uncertainty in the interaction/phasing of the northern stream shortwave and the remnant circulation center associated with T.S. Cindy. Given the low confidence, will refrain from getting to specific in forecast details. While we do not expect continuous heavy rain through that period, conditions will be favorable for episodic heavy rain through the period, perhaps initially from the initial surge of tropical moisture and embedded upper disturbances (potentially convectively induced) ejecting NEWD across the region, and then followed by a second or quite possibly even third heavy rain event associated with Cindy`s remnant circulation center/energy aloft and then if separate, with the actual cold frontal passage. Early indicators suggest that central NC could see widespread heavy rainfall amounts of 2 to 4 inches from Thursday night through early next week. Rainfall totals over the past 5 to 7 days are already at 400 to 600 percent of normal across much of the area. Numerous creeks/small streams as well as main stem rivers are running high. Thus, any additional heavy rainfall over the next 5 days will result in prime conditions for both Flash and River flooding. A flood watch may will likely be needed, once better forecast confidence is reached. Highs will be highly dependent on rain chances through the period, ranging from mid 80s to lower 90s. Warm overnight lows in the upper 60s to lower/mid 70s. Cooler drier conditions should follow in the wake of the cold front on Tuesday.
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&& .AVIATION /18Z Tuesday through Sunday/... As of 1200 PM EDT Tuesday... Light/variable winds and VFR conditions are expected to prevail through at least 21Z at the RDU terminal and 00Z at the INT/GSO terminals, on the northern periphery of a front stalled across portions of SC and southeast NC. Periodic sub-VFR ceilings/visbys associated with elevated convection on the northern periphery of the stalled front can be expected at the FAY/RWI terminals through the afternoon. Ceilings are expected to deteriorate to IFR and perhaps LIFR everywhere between 00-06Z as low-level flow veers to the south, pushing the frontal zone slowly N/NW as a warm front. Looking Ahead: Diurnal convection and early morning stratus will be possible each day Wed-Sat. Otherwise, VFR conditions will prevail. More widespread precipitation /sub-VFR conditions/ will be possible late this weekend, depending on the track/timing of Potential Tropical Cyclone 3 (currently in the GOMEX). -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...CBL AVIATION...Vincent

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