Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 140108 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 910 PM EDT Fri Oct 13 2017 .SYNOPSIS... Cool high pressure will extend into central NC from the northeast through Saturday. This high will weaken Sunday, with a return to a warm southerly flow ahead of an approaching strong cold front. This front will cross the region Monday, bringing in much cooler air. && .NEAR TERM /through tonight/...
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As of 910 PM Friday... Minor breaks in the cloudiness across the southeast are expected to fill back in overnight with increased moisture advection as the surface low and coastal trof cozy up to the northern outer banks. Isentropic lift is essentially neutral except for in the northeast, with low level flow parallel to the isentropes. As such, forecast of slight chances in the northern Coastal Plain looks good. Temps will only fall a few more degrees (3-5) tonight to match dew points, so no trend modification in the forecast is needed. Weather grids updated to include a bit more coverage of patchy fog after midnight. Previous Discussion: Areas south and east of the Triangle have broken out of the surface based stable pool, although the damming air mass remains locked in across the north and west, where temps remain in the 60s. The center of the parent high will continue to shift east through tonight, pushing well off the New England and Canadian Maritime coast this evening and overnight. The offshore low pressure center clearly see on satellite imagery off the northern Outer Banks is expected to keep drifting to the WNW, effectively cutting off the wedging air mass over central NC from the exiting parent high tonight. This will result in light and erratic surface winds becoming nearly calm, and with nowhere for the low level moisture to go and decent nocturnal cooling due to the lack of higher clouds, we should get redevelopment (or, in the case of the NW, persistence) of low stratus, fog, and isolated patches of drizzle overnight. There is a small lingering chance of measurable precip in the far NW overnight, although moist upglide will be weak to absent. And the offshore low may pull a few showers into our NE sections as it approaches the VA shore. Otherwise, it should be mostly dry. Following high resolution guidance, expect lows in the upper 50s to lower 60s. -GIH
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 245 PM Friday... With a loss of maintenance mechanisms and a disconnection from the departing parent high, the damming air mass will dissipate Sat. Weak mesoscale high pressure will hold over the central and western Carolinas, with mid level ridging extending over the area from the SW. We should see a gradual lifting and breaking up of low clouds Sat morning, with a trend to partly then mostly sunny skies in the afternoon. Thicknesses will be about 10-15 m above normal, favoring highs about a category above normal, in the mid 70s to near 80. Expect fair and dry weather Sat night with lows of 60-65. -GIH && .LONG TERM /SUNDAY THROUGH FRIDAY/... As of 255 PM Friday... Any lingering damming will scour rapidly Sunday morning with the subtropical and surface ridging sinking south of the area, resulting in deep southwest warm air advection in return flow. This will, however, be our last really warm and humid day for a while, with highs edging up into the low and mid 80s. A strong low pressure system will be lifting northeast across the Great Lakes, with its associated cold front stretching south across the Ohio Valley. This front will be moving swiftly into the mountains early Sunday night, and across central NC on Monday. Showers ahead of the front will spread into the western Piedmont by midnight Sunday night, with increased PoPs spreading east to reach the Coastal Plain by late afternoon. Convection will concentrated on a 6 hour window associated with strongest low level convergence associated with the front which will be needed to overcome the lack of instability due to the early frontal passage`s unfavorable diurnal timing and strong capping aloft in the warm regime. Highs Monday will be clobbered by the ensuing cool air advection following the morning cloudiness, and highs will stall in the mid 60s northwest to lower 70s southeast. Showers will diminishing by midnight in the east, with perhaps a lingering shower in the southeast after midnight. Otherwise, cold air advection will settle our drier and much cooler airmass into place, and mins on Tuesday morning will be right chilly...in the mid and upper 40s. Dry, mostly clear skies will be then remain with us through the end of the week. Highs Tuesday will range from 65 to 70....with a very gradual warming trend of a couple of degrees per day through Friday when highs reach the mid 70s. Morning mins will be cool through the period under good radiational conditions, mostly in the mid and upper 40s each night. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 840 PM Friday... 24 Hour TAF Period: Low level moisture will continue to linger overnight, with with MVFR/low end VFR cigs across the area falling back to IFR after midnight, with possibly a few sites dropping into the LIFR range (most likely KGSO/KINT). Expect generally dry conditions though. Cigs will slowly rise/scatter on Saturday, becoming VFR by afternoon Saturday, first at KFAY, then spreading northward. Outlook: Areas of shallow sub-VFR fog are possible 08z-13z Sun morning, but otherwise VFR conditions should hold. The next greatest chance for poor aviation conditions will be Sun night through much of Mon, along and behind a cold front crossing the region, with areas of rain. A drier air mass with a high probability of VFR conditions will arrive for Mon night through Wed. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. $$ SYNOPSIS...Hartfield NEAR TERM...mlm/Hartfield SHORT TERM...Hartfield LONG TERM...mlm AVIATION...BSD/Hartfield

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