Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 211551 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1145 AM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure will bring dry and seasonably hot weather to the region for the start of the work week. A strong cold front will bring increasing rain chances for the middle of the week, then move east and off the coast by Friday, with cooler drier weather in its wake. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1145 AM Monday... Latest surface analysis shows a decaying stationary from extending east to west across northern SC into GA with weak surface high pressure off the Mid-Atlantic coast. A light east to southeast flow has developed across central NC which has allowed dew points to climb back into the 70s with lower 70s observed across the Piedmont and northern Coastal Plain with mid 70s across the Sandhills and southern Coastal Plain. The forecast problem of the day is the sky cover given all of the the eyes looking up at the solar eclipse this afternoon. The mid and upper pattern should lend itself to few if any mid or high clouds. More consequently, the increase in low-level moisture along with surface heating and a weak disturbance aloft will support the development of a decent fair weather cumulus cloud field this afternoon, resulting in a 25 to 50% sky cover during the afternoon. Good but not perfect viewing weather. In addition, there is a slight chance of a shower or thunderstorm this afternoon across the far northwestern periphery and far southwestern corner of the CWA. But chances are small and almost all of the RAH CWA will be dry this afternoon. Morning radiosondes note that low-level thicknesses have increased 3 to 8 meters from yesterday which support highs today generally comparable if not slightly warmer than yesterday. Have adjusted hourly temperatures up a degree or two over the previous forecast and included a 2-4 degree temp drop in the hourly temperature forecast during and just after the eclipse. Mainly clear skies are expected this evening and overnight before a layer of low stratus and fog develops in the Coastal Plain, Sandhills and eastern Piedmont. Lows will range in the lower to mid 70s. -Blaes
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 230 AM Monday... Heights aloft fall slightly on Tuesday with the approach of the northern stream trough and attendant cold front into the Ohio and Tn Valleys late Tuesday/Tuesday night. While we do see the development of pre-frontal sfc trough in the lee of the mountains Tuesday afternoon, central NC remains in a void of appreciable synoptic scale lift. And as such, convective rain chances should remain rather low and generally confined across the far SE zones in the vicinity of the sea breeze and across the western part of the state along the pre-frontal trough. One minor caveat that needs to be mentioned is a sheared vorticity centered that`s currently off the SE coast. If this feature can hold together as it moves westward over the SE states, where it will encounter the upper level anticyclone, DPVA from this feature could serve to support slightly higher/better rain chances across the southern zones. Will continue monitor will only slight chance pops for now. Loss of daytime heating should Tuesday evening should lead to dry conditions overnight as the cold front doesn`t`t arrive from the NW until late Wednesday afternoon. Highs in the lower 90s with lows in the lower to mid 70s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 315 AM Monday... A rather strong cold front will progress slowly southeast and across central NC Wednesday through Thursday night, perhaps stalling along the coast as high pressure builds south down the Atlantic coast behind the front. Convection will be on the increase by Wednesday afternoon in the northwest as the front pulls out of the mountains, with highest probabilities for precipitation (60%-ish) from Wednesday evening in the west through Thursday morning east of I95. At this early juncture, seeing mixed signals in the potential for severe convection. The strongest low level forcing looks to lag the best diurnal instability, and while there will be good directional shear in the low level winds, it will be offset by weak wind speeds (i.e. ~20Kt at H85). Meanwhile, upper diffluence will be fairly strong, as the entrance region of an 80KT upper jet pulls off the mid Atlantic coast. Highs Wednesday will have time to reach the lower 90s in the south, while cloudiness and PM cool air advection will halt the diurnal cycle in the upper 80s across the north and northwest. Will have only slight chances lingering in the west Thursday morning, with PoPs in the east tapering off to slight chance early Thursday night. Thursday`s highs will cooler with lower humidity as high pressure builds in from the north...mostly lower 80s. Friday through the weekend will be below normal and dry, with highs from around 80 across the north to mid 80s across the far south. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 730 AM Monday... Fog/stratus at KRWI and KFAY will lift between 12 to 15z, with generally dry VFR conditions for the afternoon and evening. Will follow persistence in terms fog and stratus for tonight/Tuesday morning, with LIFR to MVFR conditions at KRWI and KFAY. Outlook: Isolated to scattered diurnal showers and thunderstorms are expected on Tuesday. A cold front will move through the area Wednesday and settle near the coast on Thursday providing an opportunity for adverse conditions during this time period before returning to VFR for the end of the week and into the weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ NEAR TERM...Blaes SHORT TERM...CBL LONG TERM...mlm AVIATION...CBL/Ellis is the U.S. government's official web portal to all federal, state and local government web resources and services.