Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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734 FXUS62 KRAH 141953 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 253 PM EST Thu Dec 14 2017 .SYNOPSIS... A weak and dry surface cold front will stall south of the area tonight. An area of low pressure will develop along the NC coast Friday, then tracks northeast while staying offshore Friday night. High pressure will build into the area through Sunday. && .NEAR TERM /TONIGHT/... As of 253 PM Thursday... The cold front will finally settle just to our south this evening, stalling in an W-E fashion near the NC/SC border. High pressure currently centered over the Midwest will build eastward and to our north, thus turning low level winds to the N/NE this evening. Meanwhile, a southern stream jet streak now moving across LA will help induce a wave of low pressure to form along the old boundary to our south late overnight. As such, look for increasing clouds (both mid and high clouds) tonight across our CWA...and some low-mid clouds along and north of the boundary and developing low pressure wave. ATTM however, most models agree that any precip assoc with this low pressure wave should hold off until it further deepens well to our NE. As such, will keep our forecast dry tonight, under increasing cloudiness. The aforementioned NE flow later tonight will result in subtle CAA; however that should be offset by the increasing clouds. As such, lows tonight around 32. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 253 PM Thursday... The aforementioned low pressure wave will quickly lift to the NE Friday morning as a northern stream short wave, currently over the central Plains, moves east and sweeps across our area during the afternoon. As the wave departs and the short wave trough axis moves across, dry NW flow will return in their wake, clear the sky out by late afternoon. Other than clouds early in the day, look for fair weather with highs from the mid 40s NW to lower 50s SE. Clear and cold Friday night with high pressure building over the area, light or calm winds, and good radiational cooling conditions. That should set us up for lows dipping down in the mid 20s...perhaps even colder in the usual spots. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 247 PM Thursday... Surface high pressure over the area will produce sunny skies with slightly cooler than normal temperatures to kick off the weekend. Highs Saturday will reach the upper 40s north to low 50s south followed by lows at or slightly below freezing Saturday night. The high pressure will edge offshore Sunday, with cloudiness increasing in return flow and associated moisture advection along with low amplitude ridging aloft on Sunday. The warm air advection and rising heights will produce modestly warmer highs in mostly the mid and upper 50s. Skies will become cloudy with scattered showers Sunday night as a series of waves begin to lift northeast into the area in deep southwest flow off the Gulf. The low amplitude ridge will linger through Tuesday, providing a conveyor for these waves and associated periods of enhanced shower activity. As we remain in the warm and moist airmass through the period, highs will be similar both Monday and Tuesday, ranging from upper 50s north to low and mid 60s south. Very difficult to forecast how much rain we might get given the duration of the event and model difficulties with timing and strength of the waves. A strong but relatively flat short wave in the northern stream moving across the Tennessee and Ohio Valleys will push a cold front east, effectively cutting off our moisture Tuesday night. The upper flow is basically zonal and the high pressure building in behind the front is only modesly colder than the air it is replacing, so highs will take only a mild hit Wednesday and Thursday...mostly in the low and mid 50s. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... As of 109 PM Thursday... Clear skies ATTM will give way to increasing high clouds, and perhaps some mid clouds as well, as cirrus currently over the Midwest moves across our area through approx 15/06z, then mid and high clouds currently over the deep South and Gulf Coast region lift to the NE and across the Carolinas. Despite this increase in clouds, CIGs and Vsbys should remain high enough for VFR conditions through the evening and overnight hours. W-NW winds 10-15kt will shift to N-NE 5-10kt as high pressure builds to our north. After 15/12z, winds will shift back to SW as a wave of low pressure develops along the old frontal boundary to our south and lifts NE. In addition, we could see a narrow corridor of low clouds develop on the NW side of the aforementioned low pressure wave, which could mean a brief period of MVFR cigs between 12-18Z across much of central NC, but esp at KRDU and KRWI. After 15/18Z: Dry air and VFR conditions will return by late-Friday and for most of the weekend in the wake of the departing low pressure wave. The next southern-stream system will lift NE toward our area late Sunday and early next week, resulting in possible sub- VFR conditions. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...np NEAR TERM...np SHORT TERM...np LONG TERM...mlm AVIATION...np

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