Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 241942 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 245 PM EST Sat Feb 24 2018 .SYNOPSIS... Warm and deep high pressure centered off the Southeast coast will extend over the Carolinas today, before weakening tonight as a cold front approaches the Appalachians from the west. This front will move slowly east across the area Sunday night and into Monday. Cooler high pressure will build in from the north Monday night and Tuesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1010 AM Saturday... Deep ridging centered off the SE coast will continue to rule today. It`s looking like any appreciable shower activity today will hold just to the NW and N of the forecast area, closer to the 850 mb speed max, given the otherwise lack of any kinematics or dynamic forcing for ascent. But moisture will be increasing, as noted by the 12z GSO sounding compared to upstream soundings such as FFC, and as seen on model output with rising PWs through the day. Given the increase in moisture, have left in a mention of isolated showers over the extreme NW and N through the day as a weak 700 mb trough passes through. Morning stratus is hanging firm over the southeast CWA but has started to break up elsewhere, allowing at least some insolation amid passing mid and high clouds. Very warm highs in the mid 70s to around 80 still seem achievable, and will make only minor tweaks to temps through the rest of today. -GIH Earlier discussion from 330 AM: Latest surface analysis shows a stationary front draped across central North Carolina separating a rather significant N/S dewpoint and temperature spread. Currently, dewpoints/temps near the VA/NC border reside in the mid to upper 40s while those along the NC/SC border are in the lower 60s. Intermittent fog formation is ongoing across much of the area, with additional fog formation likely, especially between 4am and 10am on Saturday. Little in the way of movement with the boundary has been witnessed thus far tonight, but guidance continues to indicate a slow retreat northward likely after sunrise. This should allow temperatures to steady to even slightly increase through dawn, with intermittent mid to upper level clouds overspreading from west to east associated loosely with the cold front draped west of the Appalachian Mountains. -JJM && .SHORT TERM /SATURDAY AND SUNDAY/... As of 330 AM Saturday... Sub-tropical ridging will remain centered in the vicinity or just northeast of the Bahamas, with associated surface high pressure extending from just south of Bermuda, westward into the southeaster U.S. This pattern will maintain unseasonably warm and relatively humid conditions across central North Carolina both Saturday and Sunday. Expect afternoon temperatures in the mid 70s to low 80s each day under intermittent cloud cover, with mild overnight low temperatures in the lower 60s expected Saturday night into Sunday. Cloud cover will be thickest across the western Piedmont Counties, where intermittent shower chances will be possible Saturday afternoon and evening, and again Sunday afternoon as the front pushes into the western portion of the state. Southwesterly winds will accelerate Sunday ahead of the approaching cold front, with sustained winds 10 - 15mph with gusts up to 30mph possible. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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As of 245 PM EDT Saturday... Models maintain their consensus on a wave lifting northeast along the stalled cold front on Monday, and will be raising PoPs to categorical across the southern tier. In addition, will add a chance for rumblers in the southeast where even though instability will be very weak to non-existent, we will have just about everything else needed - low level convergence, shear, and upper dynamics - to support at least modest convection. Cool air will be flowing in behind the wave, and highs will struggle to make much headway in the cloudy and moist airmass, so expect the northern tier to stall in the upper 50s, while the southeast should reach mid 60s. Cooler airmass settles in Monday night, with lows bottoming out mostly in the lower 40s, with some upper 30s possible across the north where radiational conditions (decoupling) will be more favorable. Dry high pressure will build across the area, and quickly offshore Tuesday into Tuesday night, with sunny skies and highs climbing to 60 to 65 on Tuesday with mins in the mid 40s Tuesday night. Moisture will increase rapidly in return flow on Wednesday, with showers increasing in the west and spreading into central NC during the afternoon. There is a bit of uncertainty as to how shortwaves in the northern and southern streams, respectively, will phase during the mid to late week period. Regardless, it looks pretty wet as a warm front lifts north up the Atlantic coast ahead of what will be a strong low pressure area and associated cold front moving east across the Ohio Valley/Great Lakes region. The surface cold front will move across the area later Thursday, so will have likely PoPs Wednesday night through Thursday as timing confidence is not high this far out. Highs Wednesday will reach the low to mid 60s, while we should be mild Wednesday night ahead of the front...50 to 55. Strong warm air advection ahead of the front will allow us to reach 65 to 70 on Thursday. The low pressure system is expected to slow and make a southeasterly jog as it moves offshore, which could change the equation, but at this point, lingering showers should be gone by Friday morning, with seasonable highs Friday and cooler air settling south on Saturday. Highs Friday will be mostly in the lower 60s, with Saturday topping out from 55 to 60.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 100 PM Saturday... Passage of a mid level trough and increasing moisture generated patchy light precip in the Triad late this morning, however these have moved to the NE, and any further chance of impactful showers will hold well north of the central NC terminals through the next 24 hours. This morning`s sub-VFR cigs have broken up to scattered, and VFR conditions will hold through this evening. There is a chance for development of MVFR or high-level IFR cigs after 09z tonight, however a steady SW wind overnight will keep the low levels stirred, such that confidence in the occurrence of sub-VFR cigs late tonight is low. And vsbys are likely to remain VFR regardless. Any sub-VFR cigs will start to lift and break up by 16z Sun. Looking beyond 18z Sun, a trend to sub-VFR conditions will begin Sunday night as a cold front moves slowly SE through the area, settled across SE NC Mon morning. Sub-VFR conditions with showers and isolated storms will be the most likely and the longest lasting over the SE (FAY), lasting through much of Mon, while at other sites, high pressure will start to build in behind the front, leading to a trend to mostly VFR conditions Mon at INT/GSO/RDU/RWI. VFR conditions will dominate Tue/Wed under high pressure. The next chance for sub-VFR conditions will be Wed evening/night into Thu as the front heads back northward into the area as a warm front, bringing a chance for showers. -GIH && .CLIMATE... RDU Records: Date | High Year | High Min Year ------------------------------------------ 02/24 81 1982 58 1985 GSO Records: Date | High Year | High Min Year ------------------------------------------ 02/24 79 1982 55 1985 FAY Records: Date | High Year | High Min Year ------------------------------------------- 02/24 83 1930 60 1975 && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/JJM SHORT TERM...JJM/MWS LONG TERM...mlm AVIATION...Hartfield CLIMATE...RAH

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