Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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980 FXUS62 KRAH 260755 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 355 AM EDT Sun Mar 26 2017 .SYNOPSIS... A backdoor front will settle into and stall over central VA today, while a weakening upper level disturbance pivots northeast across our region. Bermuda high pressure will otherwise extend west into the southeastern U.S. through Mon. && .NEAR TERM /THROUGH TONIGHT/... As of 345 AM Sunday... On the sern periphery of an upper low that will become an open wave as it lifts from the Middle MS Valley NEwd across the Great Lakes through tonight, a lead mid level trough axis now extending across the TN Valley will edge Ewd into the wrn NC Piedmont this afternoon. An associated axis of moisture aloft, and weak forcing for ascent, will likely result in the slow NEwd maintenance of a band of showers now moving through W-central GA. While these showers will likely weaken with Ewd extent into the W-central Carolinas, as they near the wrn periphery of a sub-tropical ridge and associated dry and capping influence centered near Bermuda, a few may drift into the wrn Piedmont by mid-late afternoon. While CAM`s also indicate the potential for much shallower showers to the east, ones capped above by the aforementioned subsidence inversion sampled by proximity RAOBS around 5-6 k ft last evening, it`s unlikely that barely positive CAPE would support deep enough cumulus to indeed support any showers elsewhere. Otherwise, like Sat, diurnal heating of a seasonably moist BL characterized by surface dewpoints generally in the lower 50s should again support a scattered to broken cumulus field by midday-early afternoon, but with enough breaks of sun to allow temperatures to again reach the middle to upper 70s. While shortwave ridging aloft behind the departing mid level trough will likely yield dry conditions tonight, the mid level moist axis accompanying the trough will be left behind; and this may support a lingering shower or two over the wrn Piedmont tonight. Low temperatures centered in the middle 50s. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 255 PM Saturday... A lead s/w rotating around the mid MS Valley upper low will lift newd from eastern TN into the central Appalachians Sunday, brushing our nw sector. This system projected to weaken with time and while atmosphere continues to moisten, model rh cross sections still depict a decent layer of dry air in the mid levels of the atmosphere. Accordingly, models have been trending drier, so will follow a similar trend. Plan to confine chance PoPs to the NW Piedmont, with slight chance PoPs elsewhere across the Piedmont. Over the east and far south sections, will advertise PoPs less than 15 percent. Expect quite a bit of cloudiness, limiting insolation. Still, warm sly flow along with partial sun should be able to boost temperatures back into the low-mid 70s. Continued mild Sunday night under variably cloudy skies. Weak confluence and a series of weak perturbations aloft will continue a minor threat for a few showers over the NW Piedmont. Elsewhere, probability of a shower appear too remote to mention at this time. Overnight temperatures in the mid-upper 50s. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 230 PM Saturday... A warm, moist airmass will be in place to kick off the work week. Precipitable water in excess of 1.2 inches and highs Monday through Wednesday reaching the mid 70s to lower 80s will provide modest instability and widely scattered showers Monday, with coverage ramping up somewhat on Tuesday as a progressive but relatively weak short wave moves east across the area. Timing of the short wave will be favorable to tap afternoon instability and a few thunderstorms will be possible in the afternoon...especially east where instability and upper diffluence are favorably aligned ~18-21Z. Dry and continue warm temperatures are initially on tap Wednesday as ridging aloft builds over the area ahead of another upper low moving into the central Plains. High pressure over the Great Lakes will surge south ahead of the Plains system, pushing a dry backdoor cold front south into the state later Wednesday, but highs will have time to reach the mid and upper 70s ahead of the cooler air. The "seasonally-adjusted" cold air damming setup will promote overrunning rain in the west as early as Thursday afternoon. PoPs will be ramping up Thursday night and lingering all the way through Friday night as low level southerly flow increases ahead of the Plains system. Low level instability will be meager at best, with no indication as yet that we might see a thermal moisture boundary encroach inland, As such, will have only a slight chance for elevated thunderstorms on Friday. Highs both Thursday and Friday will be mainly in the 60 to 65 range, with some lower 60s across the piedmont and northern coastal plain where cool air will be deeper. Lot of uncertainty as to how the Plains system evolves, i.e. the latest GFS re-establishes cool air advection with development of a coastal low, while the 00Z ECMWF was scouring out the cool airmass and allowing highs to rocket quickly back to the upper 70s...will go middle of the road 70 to 75 for now to await some consensus. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... As of 155 AM Sunday... Mainly VFR. Morning to midday heating of a seasonably moist air mass around Bermuda high pressure will favor the development of a field of stratocumulus that will initially develop around 2500-3000 ft, and may be briefly broken in that range this morning in the few hours surrounding 15Z, before lifting into the 3500-5000 ft range this afternoon. The passage of an upper level disturbance and associated moistening aloft may allow a few showers to move into and affect INT and GSO this afternoon and evening. Otherwise, SSWly surface winds will increase into the 8-13 kt range after 14-15Z, with occasional gusts up to 20 kts, then lessen after sunset. Outlook: Late night-early morning fog and/or stratus, then MVFR range cloudiness as that moist layer is heated through midday, will be possible each day through the middle of next week. Otherwise, a chance of showers and associated sub-VFR conditions will exist late Mon through Tue. The probability of any such shower at any given TAF site will be relatively low, however, given limited overall coverage. Lastly, a backdoor cold front will settle into SC Wed night; and "overrunning" flow atop the boundary will result in the development of MVFR-IFR conditions and associated cold air damming as early as late Thu, but more likely just beyond the outlook TAF period - Thu night-Fri. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...WSS LONG TERM...mlm AVIATION...MWS is the U.S. government's official web portal to all federal, state and local government web resources and services.