Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 170111 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 811 PM EST Mon Jan 16 2017 .SYNOPSIS... High pressure along the Mid-Atlantic coast will gradually shift offshore tonight and Tuesday, in advance of a cold front approaching the mountains from the west. The cold front will progress east of the mountains Tuesday night, track southeast through North Carolina Wednesday morning, then southward offshore the Carolina coast Wednesday afternoon as an associated upper level disturbance tracks offshore the Mid-Atlantic coast. && .NEAR TERM /THROUGH TONIGHT/... As of 1245 PM Monday... Expect little change in sensible wx conditions this afternoon into tonight. High pressure centered along the Mid-Atlantic coast will gradually shift offshore (though continue extending SW into central NC) late tonight as a shortwave ridge progresses through the Mid- Atlantic. Weak southwesterly warm advection atop the cool/shallow airmass extending into the region from the NE will help maintain the CAD wedge in place for the remainder of this afternoon. Weak nocturnal cooling of the shallow moist layer in place over central NC should result in lowering ceilings and perhaps fog /lowering visbys/ tonight. Expect only several degrees of diurnal variation between highs this afternoon and lows tonight. -Vincent && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 105 PM Monday... The lingering CAD wedge is expected to undergo top-down erosion during the day Tuesday as southwesterly low-level flow strengthens in advance of a shortwave approaching the Mid-Atlantic from the W/NW. Initially overcast skies should become broken by early afternoon, perhaps scattering out entirely from the Triangle southward and eastward. Broken to overcast cloud cover is most likely to persist the longest across the N/NW Piedmont where occasional sprinkles cannot be ruled out. Challenging temperature forecast. Expect highs in the upper 50s (N/NW) to mid 60s (S/SE) Tuesday afternoon. Expect rather mild lows Tuesday night as the MSLP gradient tightens in advance of the approaching cold front and a southwest breeze persists much of the night. Expect lows in the mid to upper 50s, possibly a few degrees cooler in the Northern Piedmont/NE Coastal Plain where precipitation assoc/w the front is most likely to occur prior to sunrise Wed. It should be noted that a large amount of uncertainty persists with regard to the precise coverage/timing of precip assoc/w the upcoming cold frontal passage early Wed. -Vincent && .LONG TERM /Wednesday through Monday/... As of 230 PM Monday... Fast progressive flow through the extended period will produce several frontal passages Wednesday through early next week. The sensible airmass change behind each system will be minor as arctic air will remain blocked across the northern tier of the CONUS and we will remain unseasonably mild through the period. A rather vigorous short wave skating across the Ohio valley will nudge a backdoor front south into the area by sunrise on Wednesday, with fairly widespread rain in the morning tapering off during the early afternoon. Despite the modest cold air advection, we will benefit from a warm overnight min in the mid 50s bolstered by increasing sun as the day progresses to allow highs to reach the mid 60s over most of the area, with some readings near 70 along the southern tier. Lows Wednesday night will be cooler under mostly clear skies...40 north to 45 south. Dry weather will linger through Thursday night as upper ridging and surface high pressure migrate overhead. The modestly cooler airmass will be in place and highs on Thursday will stall within a degree or two either side of 60. Will see some light rain begin to spread into the west by late Thursday night as overrunning ensues in south to southwest flow as the stacked ridging moves offshore. Mins will remain mild in the southerly flow under increasing cloudiness... again mostly in the 40 to 45 range. A quick and perhaps vigorous round of showers is on tap on Friday as a low over the plains rotates northward and deep southwest flow lifts the stalled surface front north concurrent with reasonably supportive mid and upper dynamics. Will increase PoPs to likely across the entire area as uncertainty is on the rise with time in this fast flow regime. Highs Friday should uptick a degree or two in the warm air regime with mainly upper 50s north to lower 60s south. We then see a repeat of a short-lived dry spell with low amplitude mid level ridging Friday night and Saturday. Lows Friday night will be in the mid 40s with highs Saturday mostly in the lower 60s. Somewhat similarly, a stronger short wave moving across the mid west will reassert southerly flow Sunday, pushing another mild but potentially much wetter front across the area through Monday night. This upper low will be deepening as it moves into the Tennessee Valley, and as such, will produce more favorable conditions for convection as H85 winds are progged to 50kt and supported aloft by a favorably aligned upper jet. Will have 50-60 PoPs both Sunday into early Monday as we let the details resolve themselves. Mild temps linger both days...mid 50s northwest to lower 60s southeast. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 740 PM Monday... 24 Hour TAF period: MVFR cigs are expected to spread areawide this evening, before falling into the IFR/LIFR range during the overnight hours in assoc/w a lingering CAD wedge. Cigs will gradually lift on Tuesday in advance of a cold front approaching from the west. Winds will increase in advance of the front Tuesday morning into the afternoon as cigs slowly lift. We could see some gusts of up to 20- 23 mph or so. Looking Ahead: Any improvement in conditions Tue aft/eve will be short-lived, as conditions are likely to deteriorate from N/NW to S/SE (earliest at Triad and latest at FAY) Tue night/Wed morning as an upper level disturbance tracks through the central Appalachians into the Mid-Atlantic and an attendant cold front /SFC-925 trough/ progresses east of the mountains into VA/NC. Expect the best potential for rain and low ceilings to occur between midnight and noon Wed as the slow moving front progresses SE through central NC. Expect a clearing trend in the wake of the front with a brief return to VFR conditions Wed night/Thu. A pattern similar to the one affecting the region today is progged to develop over the region again late this week. With this in mind, expect ceilings to begin deteriorating Thu night/Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Vincent LONG TERM...mlm AVIATION...BSD/Vincent

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