Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 150617 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 215 AM PM EDT Sun Apr 15 2018 .SYNOPSIS...
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A strong cold front will move east across the region late this afternoon and this evening, proceeded by a few strong to severe thunderstorms. Dry, cooler, and breezy conditions will follow for Monday.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 935 PM Saturday... Bermuda high pressure continues to bring warm and moist air advection from off the western Atlantic SC and SE NC. The dew points were already in the mid to upper 60s along the SC coast, with 60+ dew points having reached the Southern Pines to Smithfield areas as of mid-evening. A stratocumulus bank of cloudiness was seen on satellite moving northward, onshore into eastern SC and NC. Expect areas of low clouds to spread/develop into our region after midnight, yielding a trend to mostly cloudy to cloudy skies by daybreak. Isolated showers or sprinkles remain possible, more so later tonight and mainly over the SE sections, closest to the Atlantic-source inflow in a zone of low level mass convergence. But coverage and amounts should be small, as the mid levels stay fairly dry. Lows primarily in the lower to mid 60s. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 350 PM Saturday... ...Risk of severe storms and locally heavy downpours late Sun through Sun evening... Strongly forced convection, mostly linear but with a chance of leading discrete cells, is still anticipated late Sun well into Sun night, focused on the 21z-06z time frame. The powerful mid level low will track from S IA across IL/IN to W OH through Sun night, with the surface cold front progressing eastward (perhaps just north of due east) through the Carolinas. The corresponding mid level trough will take on a negative tilt as it swings ENE through the Carolinas, resulting in a strengthening wind field, including 0-6 km bulk shear of 50-60 kts and 35-50 kts of southerly flow at 925 mb. These intense kinematics along with drastic 150-200 m height falls will induce vigorous forcing for ascent, supporting a wide band of heavy showers and strong storms within a prefrontal PW surge to around 1.5". Moderate instability is anticipated ahead of the front Sun afternoon into the evening, aided by incoming surface dewpoints near or over 60F, especially over the eastern two-thirds of the CWA. Most models including the HREF mean indicate an SBCAPE of 1000-1500 J/kg from late afternoon into the evening, highest E, and this with the deep layer shear will support strong to severe storms with damaging winds as a primary threat, given the intense dynamic forcing for ascent and strong background wind field. It`s worth noting, though, that if daybreak stratocu holds on longer, this could limit heating and potential instability somewhat. QLCS mesocyclones and isolated tornadoes are possible as well, with strong line-normal low level winds, a long curved hodograph, and decent probs (aoa 50%) of an STP over 3 according to the HREF mean. While the heaviest precip is likely to fall well to our NW, over the mountains (orographic enhancement of lift) and near the inflection point of the tilting system, a period of heavy rainfall is also a concern across all of central NC, with a deep warm layer (LCL-0C depth near 4 km) facilitating warm rain processes, and the potential for training echoes leading to locally higher amounts. Storm total rainfall near 2 inches, give or take a quarter to half inch either side, seems attainable areawide. Confidence in any one location exceeding FFG is low, however, so will not consider a flash flood watch at this time, but will certainly look at this again Sun morning. Precip chances will taper down behind the main band after midnight from W to E, although trailing stratiform rain and a few lightning strikes may linger for a few hours overnight. Will trend pops down to lower chances W to E, but will need to keep shower chances going through the night with waves of mid level DPVA traversing the base of the negatively tilting trough as it crosses the region SW to NE. Expect highs from the mid 70s to lower 80s Sun, with some eastern sections likely to see partial heating (although, again, this will depend on the extent of morning clouds). Lows Sun night from around 50 W to around 60 E. -GIH && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 210 PM Saturday... Fairly quiet long term forecast as the frontal system exits to the east on Monday. There will still be a slight chance of some showers in the northeast as the northern stream cold front pushes through behind the initial surge from the main front and as the upper low moves north of the CWA. Any showers that do occur would be confined to the northern counties with the rest of the area remaining dry but cloudy for much of the day. Temperatures will be much cooler than previous days with a 15 degree drop in daytime highs which will top out in the lower 60s Monday afternoon. A warming trend will then begin through Wednesday as surface high pressure resides over the Florida Peninsula and zonal flow aloft keep things warm and dry. On Thursday a low pressure system will cross well to the north of the area and drag a dry cold front over the area late in the day. This will set up a fairly decent temperature gradient over the area with the Triad topping out in the low 70s with southeastern locations achieving 80 degrees. A few showers could be possible across the VA border counties but otherwise no precipitation is expected. Behind this front, continental high pressure over the Ohio Valley will turn surface winds to northerly and thus cooler temps for the end of the week with highs in the upper 60s to near 70 degrees both Friday and Saturday. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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As of 215 AM Sunday... Aviation conditions will deteriorate through 12Z as low level moisture will lead to the development of a low stratus deck, resulting in IFR/LIFR ceilings across central NC. These ceilings will slowly lift after 13Z, with low end VFR ceilings probable at KRDU, KFAY, and KRWI by early afternoon. MVFR ceilings will likely dominate in the Triad terminals through the afternoon. Spotty light rain showers will be possible this morning across central NC. The shower coverage will increase this afternoon as the atmosphere destabilizes. Sfc winds ahead of a strong cold front will be gusty with gusts in the 27-33kt range expected. The strong cold front approaching from the west will increase the shower coverage by late afternoon in the west with a few severe thunderstorms likely. This band of heavy showers and severe storms will progress east across central NC this evening. In vicinity of the stronger/severe storms, expect wind gusts 40-55kts along with some hail and torrential downpours. The shower coverage will decrease from the west after 02Z, with ceilings lifting after 06Z. The improving aviation conditions will continue into Monday. VFR parameters anticipated Tuesday through Thursday.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS/Badgett NEAR TERM...Badgett/Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...WSS

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