Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 060617 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 117 AM EST Tue Dec 6 2016 .SYNOPSIS... High pressure will build across the Middle Atlantic states through tonight, ahead of a Miller B low pressure system and associated cold air damming, which will result in the development and deepening of an area of low pressure through the eastern Carolinas on Tue. Another area of high pressure will build overhead for the middle of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 1010 PM Monday... Conditions continue to slowly deteriorate as short lived Miller-B CAD setup progresses pretty much on schedule. Rain coverage will approach 100 percent of the area by morning as southeast isentropic flow and attendant lift strengthens on the 290K surface between 09Z and 12Z. No changes of note are needed except minor timing adjustments on the temps, which are falling a little more slowly than forecast. Previous discussion: The weather will be quiet through early evening, as surface high pressure continues to ridge across the Middle Atlantic states. Clouds will then quickly thicken and lower, with light rain having already been observed at 21Z as far E as Wrn SC and SWrn NC, in association with a lead deamplifying perturbation now lifting across the Lower MS Valley. This light rain, from mid level ceilings, will overspread our region overnight, with temperatures expected to wet-bulb into the lower to middle 40s by daybreak. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 415 PM Monday... WV imagery indicates the primary mid-upper low has already begun to lift more quickly across TX today, and this associated shortwave trough is forecast to pivot NEwd through the Central Appalachians Tue and reach the Chesapeake Bay region by 00Z Wed. Associated forcing for ascent will strengthen and deepen, the latter as isentropic upglide/WAA rapidly increase from S to N across central NC Tue morning. A few rumbles of thunder will be possible around midday, when both deep layer lift and lapse rates aloft become maximized with the passage of the shortwave trough and associated cold pool aloft. Widespread rain and overcast will result in cold air damming and temperatures that are likely to only rise a few degrees throughout the Piedmont, while a few 50s will be possible in the far S and E as a secondary low migrates through the Ern part of the state. The passage of the trough axis aloft will cause the widespread rain to end, and clearing to commence, from SW to NE throughout the afternoon and early evening hours. Storm total precipitation amounts are expected to range from three quarters of an inch to one inch. The clearing, in conjunction with wet soil, will then result in the development of patchy fog Tue night. Lows upper 30s to lower 40s. && .LONG TERM /Wednesday through Monday/... As of 350 PM Monday... In the wake of the departing low pressure on Tuesday, and preceding a strong arctic front moving through the Midwest, the flow will be weak over central NC on Wednesday. Forecast soundings show enough drying to erode the lingering low clouds and/or fog early Wednesday, with daytime heat into the mid 50s (per statistical guidance) likely to result in a cu field, mainly east. Weak but moist southerly flow should redevelop late Wednesday in response to weak height falls and an intense upper jet associated with the aforementioned cold front and result stratus Wednesday night. Lows 39-44. The cold front, progged to be just west of the Yadkin early Thursday morning, will will cross the area during the first half of the day, with strong cold advection behind it Thursday evening and overnight. The front itself is not expected to produce much precip, if any, though the GFS cranks out some light qpf, owing likely to a period of strong low-level FGEN and sufficiently deep moisture across the northern half of the area. The current slight chance POP will be maintained. Highs in the upper 40s to mid 50s. Strong cold advection Thursday night should result in gusts to 15- 20kt and wind chills in the upper teens, as lows drop into the mid to upper 20s. Arctic high pressure will then build in over the weekend, with forecast thicknesses progged to approach 1270m Sat/Sun morning. Lows should have little problem hitting the upper teens and lower 20s. The high then quickly moves offshore and the synoptic front return north with the next chance of rain early next week. && .AVIATION /06Z TUESDAY THROUGH FRIDAY/... As of 115 AM TUESDAY... 24-Hour TAF period: Conditions will Deteriorate to IFR to LIFR between 06 to 12z and should remain that way through the taf period as rain overspreads the area ahead of Miller B low pressure system and associated CAD. The low pressure system will lift northeast away from the area during the late afternoon, allowing precip to taper off from SW to NE across the area between 21 to 00z. However, IFR to LIFR conditions in low clouds and possibly fog could persist well into the overnight hours Tuesday night. Finally, concerning LLWS, given little variation in directional wind component between 1000-925mb along with recent guidance showing sustained winds of 10 to 12 kts at KRDU, KFAY, and KRWI, have removed the mentioned of LLWS from 06z terminal forecast. Looking ahead: VFR conditions will return on Wednesday. However, sub- VFR ceilings could return Wednesday night and linger into the day on Thursday ahead of an arctic cold front moving through the area. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...mlm/MWS SHORT TERM...MWS LONG TERM...SMITH AVIATION...CBL

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