Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270738 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 338 AM EDT Mon Mar 27 2017 .SYNOPSIS... A warm moist southerly flow will hold over the area through Wednesday. An upper level trough will cross the region tonight through Tuesday, bringing unsettled weather. A backdoor cold front will drop southward through the area late Wednesday through Wednesday night, followed by cooler high pressure pushing in from the north on Thursday. Another storm system will cross the area Thursday night through Friday night. && .NEAR TERM /THROUGH TONIGHT/...
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As of 330 AM Monday... The western edge of surface high pressure will remain over central NC today as a few shortwave disturbances track across the area in between two larger systems, one moving through New England and the second back across Arkansas and southern Missouri. These shortwave disturbances could supply the area with periodic showers and potentially thunderstorms later in the day as forecast soundings show tall skinny CAPE resulting in 700-1000 J/KG across the Northwest Piedmont where forcing will be best, and lesser amounts to the south and east. With little CAPE in the hail growth zone, damaging winds would be the most likely threat from storms but not expecting storms to be severe at this time. SPC outlook has the area in general thunder only. With that in mind attention turns to temperatures which will once again be warm under southerly return flow as highs expected to soar into the upper 70s to near 80 degrees. Without a frontal passage, lows on Tuesday morning only expected to drop into the upper 50s. Some gusts are possible up to 15 knots or so this afternoon.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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As of 330 AM Monday... Tuesday and Tuesday night low pressure currently over the Arklatex area will track north of the area through the mid-Atlantic states and bring a very weak cool front with it. Maybe a bit better chance for thunder Tuesday afternoon, especially in the central and eastern portions of the forecast area as instability look a little better than on Monday afternoon and low-level lapse rates remain very steep. The proximity of the low to the north will provide upwards of 25-30 kts of bulk shear to work with. As a result SPC, currently has the forecast area in a marginal risk for severe thunderstorms. While damaging wind should remain the primary threat, some better CAPE values aloft could result in some small hail. Temperatures will continue to be in the upper 70 to low 80s across the forecast area on Tuesday afternoon with lows in the mid 50s.
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&& .LONG TERM /Wednesday through Sunday/... As of 205 AM Monday... Wed-Thu: Behind the departing shortwave through, the mid level ridge axis will shift eastward over the Southeast through Thu, although by Thu it will be deamplifying as the next mid level low tracks through the central CONUS. NC will remain in the warm sector for much of Wed, as the backdoor front holds to our north until late in the day, when energy dropping into the polar low SE of the Canadian Maritimes helps drive the cool dense surface high pressure area southward into NC, with the front dropping through NC NNE to SSW Wed evening/night and settling south of the forecast area by Thu morning. Expect partly to mostly sunny skies Wed with flat cumulus beneath the warm layer focused around 700 mb. The low levels will cool/stabilize Wed night with increased moisture pooling around 900-800 mb, so expect cloudy skies, thickest in the west where moist isentropic upglide will be deepest. While a uniform northeasterly low level flow into the area will set up behind the front, the 850 mb anticyclone will shift off the Carolina coast, resulting in increasing 850 mb winds and strengthening moist overrunning atop the cool stable pool Thu, most evident over the NW CWA. Will keep skies mostly cloudy to cloudy with a chance of light rain or drizzle in the W from late Wed night through Thu. Highs Wed from lower 70s NE to around 80 SW. Lows 45-55 NE-SW Wed night as cooler air pushes into the NE. Highs Thu from mid 50s NW to the mid 60s SE within a wedge regime. Thu night through Fri night: A volatile period as another strong mid level shortwave moves from the central Plains through the Miss Valley and Ohio Valley before crossing the Mid Atlantic region. At the surface, models depict the primary surface low tracking NE over or just south of SE MI through Fri, while the front to our south shifts back northward as a warm front, and a triple-point low forms over SW VA. While we would normally be skeptical about the complete passage of a warm front through NC immediately following a wedge regime, the parent high is rather weak and progressive and may be unlikely to put up much of a fight, so will depict a northward surge of higher dewpoints through much of the forecast area (excluding the far NW) on Fri. The primary low will then track up the St. Lawrence Valley Fri night while filling, as the triple-point low crosses WV and N VA and becomes the primary low near or just off the Delmarva peninsula, with W-to-E cold frontal passage through central NC. In terms of sensible weather, given the improving mechanisms to force ascent including mid level DPVA, strengthening upper divergence, and increasing 850 mb moisture transport, expect numerous showers and thunderstorms starting Thu night, peaking in coverage and intensity Fri, then exiting to our east Fri night as the mid level trough moves off the coast. A few strong storms are possible Fri, although the DPVA will have weakened a bit by the time the trough gets here, and we`re lacking the instability and strong kinematics that might prompt greater concern. Lows Thu night mid 40s to low 50s, highs Fri 62-72, and lows Fri night 49-55. Sat-Sun: Weak modified surface high pressure builds in behind the front with another rough of shortwave ridging in the wake of Friday`s trough and ahead of the next system moving from the Four Corners into the S Plains. Expect dry weather and partly cloudy to mostly clear skies. Thicknesses are projected to stay a bit above normal through the weekend, so expect highs from around 70 to the mid 70s. -GIH && .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 140 AM Monday... 24 Hour TAF Period: A few bands of light to moderate showers moving through the Triad at this time and this will continue for the next few hours. Further east, many of the showers will move north of the area, avoiding the TAF sites. MOS guidance products were hinting at some fog or low stratus in the south and east near daybreak, but higher resolution models are not as bullish and therefore have removed any mention of fog in these areas. For the Triad sites plus KRDU have left in some MVFR stratus closer to and just after daybreak. Have left out any mention of rain for Monday afternoon but there is a nonzero chance of a few lingering showers or maybe even a thunderstorm that will re-evaluate with the 12z package. Confidence was low enough at this time to leave out of the forecast. Winds will be mainly out of the south at 5-10 kts with some gusting to 15-20 kts possible during the Monday afternoon hours. Long term: A low pressure system will move through the mid-Atlantic states on Tuesday brining a chance for rain Tuesday evening. A more potent system will cross the area on Friday through Friday night with the potential for showers and Thunderstorms. Otherwise, Some potential for some fog/low stratus in the Triad on Tuesday morning. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Ellis SHORT TERM...Ellis LONG TERM...Hartfield AVIATION...Ellis

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