Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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608 FXUS62 KRAH 241053 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 650 AM EDT SAT SEP 24 2016 .SYNOPSIS... Weak high pressure will hold over the area today. A backdoor cold front will approach from the north early tonight, and then move southward through the area late tonight through Sunday morning. A cooler air mass will push in from the north Sunday morning through Monday. The front will move back northward as a warm front late Monday, with brief high pressure following, before a cold front crosses the region west to east late Tuesday. && .NEAR TERM /today through tonight/... As of 305 AM Saturday... Today: Once the areas of shallow fog wear off an hour or two after daybreak, a fairly quiet and warm day is expected with plenty of sunshine. The latest surface analysis shows the remains of the weak trough just off the coast, with weak high pressure covering the rest of the region, although weak Piedmont trough development is anticipated this afternoon. Pronounced ridging is noted throughout the mid and upper levels centered just to our west, with a weak mid level flow from the NW or NNW over our area, and observed PW according to blended TPW imagery is low (1.0-1.4"). With deeply dry and stable air in residence and upstream, expect mostly sunny skies today. Thicknesses are expected to be 10-20 m above normal, favoring highs in the 86-90 range, highest west. Tonight: Warm conditions will hold through the evening, then the backdoor front currently stretching across central IN/central OH/ southern PA will push southward into NE NC overnight, propelled by cool dense high pressure to the north and flow around a strong vortex over SE Canada. Plenty of low stratus is currently found near and north of this front, and see no reason why this won`t hold as the front drops into NC. Models agree on light precip near the front with considerable low level moisture pooling taking place, and will hold onto low chance pops over the NE and far N CWA tonight, with low QPF overall given the shallow nature of the incoming moisture. Lows in the mid-upper 60s. -GIH && .SHORT TERM /Sunday through Sunday night/... As of 325 AM Saturday... The backdoor front should continue its southward trek through NC Sun morning, with thick low stratus enveloping the forecast area as a cool stable air mass builds in from the north. Overrunning is initially weak but becomes more robust late in the day and into Sun night, especially over the southern and western CWA where the 295- 305K moist upglide is strongest. Expect very low chances of patchy light rain or drizzle in the morning, followed by better (but still low) pops across the southern and western CWA with the strengthening upglide atop the incoming cool stable wedge. With minimal sunshine over much of the area and falling thicknesses, have shaved a couple of degrees off forecast highs, going with a range of mid 70s north to lower-mid 80s south. Variably to mostly cloudy skies will hold through Sun night as the ridge axis continues to extend southward into the area with the ridge itself shifting slowly eastward over the Northeast states. Lows from the lower 60s NE to mid-upper 60s SW. -GIH && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 320 AM Saturday... Model solutions are very much in step for the beginning of the long term with surface high pressure over New England heading out to sea on Monday and a deep low pressure system over the northern Great Lakes bringing a front over the Appalachians which will approach the forecast area Monday night into Tuesday. The best vorticity and jet dynamics will remain well to the north with this system. Couple that with nocturnal timing and there is not a lot going for the system as far as any kind of deep convection. Despite that, rain showers and some thunderstorms will be possible Monday night and Tuesday. There is some debate over how quickly the front will move through the area, so will keep slight chance pops in for the east through Wednesday but most of the forecast area should start to clear out by Tuesday night. Highs near 80 degrees Monday and Tuesday, dropping into the upper 70s Wednesday. Lows in the 60s. After Wednesday, the forecast is expected to be generally dry and cool for Thursday and Friday. There is a caveat, however, that the latest run of the ECMWF model has put a new wrinkle in the forecast and that is a strong upper low becoming cutoff from the main flow and sinking southward along the NC/TN border. If this were to happen, the dynamic support would be enough to bring precipitation into the region late in the week, however this is an anomalous scenario at this point so we will watch it but for now have decided to stay with the dry and cool forecast which will feature highs in the mid to upper 70s with lows in the upper 50s to low 60s. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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As of 650 AM Saturday... IFR/LIFR conditions will hold over the NE CWA including RWI through 13z, while elsewhere over central and eastern sections including near RDU/FAY, IFR conditions will be more patchy and isolated, with conditions at these sites most likely to see VFR or MVFR conditions dominate for the next couple of hours. VFR conditions are likely to hold over the western CWA including INT/GSO. Any sub-VFR conditions will trend to VFR by 14z this morning, mixed out by dry air aloft. Dry weather and very few clouds are expected areawide from mid morning through the evening. As a backdoor front moves in from the NNE, cigs will trend to IFR at RWI/RDU after 04z, and at INT/GSO after 06z and FAY after 09z, with light/variable surface winds becoming light from the ENE or NE. Looking beyond 12z Sun morning, sub-VFR cigs (likely IFR or LIFR) will spread over all of central NC through daybreak as the backdoor front progresses toward the SSW through the area. Patchy light rain or drizzle is possible. These low cigs will trend slowly to MVFR during Sun afternoon, with a slight chance of light rain lingering, especially over the west and south at INT/GSO/FAY. The chance for light rain will increase in the west (INT/GSO) Sun night with IFR conditions, while MVFR conditions are expected elsewhere. A trend back to VFR conditions are expected Mon as the front starts to head back northward as a warm front. MVFR to IFR fog is expected late Mon night into early Tue morning. VFR conditions will dominate Tue into Wed, although passage of a cold front late Tue or Tue night will bring shifting winds from light/variably to N and NE. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.