Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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933 FXUS62 KRAH 212029 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 330 PM EST Sun Jan 21 2018 .SYNOPSIS... High pressure will continue to drift offshore through tonight. A frontal system will approach from the west Monday, and cross central NC late Monday night through early Tuesday. A seasonably cool air mass will settle into the region for mid-week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 330 PM Sunday... A mild air mass has overtaken central NC, pushing temperatures well into the 60s, with a few spots across the Sandhills and the southern coastal plain hitting 70. Expect the tranquil weather to persist tonight as central NC will experience weak s/w ridging aloft in the wake of an upper level low departing off the SE U.S. coast. A sfc high positioned offshore will initiate a weak low level moisture influx, primarily aimed at central NC towards daybreak. Still uncertain as to the extent of fog that may develop overnight. Earlier, it appeared that the threat for fog was best over the coastal plain, eastern Piedmont and Sandhills. Latest guidance now shying away from this perspective. For now, will limit fog coverage to patchy, and no worse than 2-3 miles.
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As of 330 PM Sunday... A deep, mature upper level cyclone over the central Plains will lift newd into the Great Lakes Monday and Monday night. A sly flow ahead of this system will strengthen during the afternoon-evening with sustained wind 10-15kts Monday night, and gusts 20-25kts probable after midnight. While clouds will thicken/lower Monday, and more so Monday night, based on model rh cross sections and upstream observations, expect a veil of high clouds Monday, likely thin enough to allow at least partial sun to occur. This warming, coupled with a steady sly flow, should allow temperatures to recover into the low-mid 60s, possibly upper 60s across the southeast. Cannot rule out the possibility of a shower or two toward sunset across the southern counties though feel that most locations across the south will remain dry. Kinematics very strong Monday night thanks to a 130+kt upper jet crossing the TN Valley and a low level jet 45-50kts. Bulk shear more than sufficient to support banded convection. However, sfc based instability meager at best, with most of the instability elevated as per skinny areas of CAPE seen on model soundings. Thus, while expect band of heavy showers with the system, an isolated storm or two possible. As better upper level support passes to our nw late Monday night, expect a band of showers to lift east-ne across central NC after 06Z, with the band projected to be in vicinity of highway 1 around 10-12Z. The warm sly flow and thickening cloud cover will maintain mild temperatures. Overnight temps mainly 55-60 degrees. Tuesday, a band of showers will exit the coastal plain counties by mid day as the sfc cold front sweeps across the region. Strong subsidence and a surge of drier air wrapping around the mature cyclone will lead to rapid clearing sw-ne across the region Tuesday morning. The onset of sunshine will initiate mixing which will bring the stronger winds aloft toward the surface. Expect a period of wind gusts 30-35kts through mid afternoon. If the GFS winds verify, could see gusts 5-10kts stronger, possibly prompting the need for a wind advisory. The low level west-sw flow will maintain a warm air mass, delaying the onset of cold air advection. Based on this, have adjusted max temps upward a few degrees, ranging from the low-mid 60s nw to the lower 70s southeast.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 200 AM Sunday... Wednesday through Sunday: Expect dry weather through Saturday, with a reinforcing dry cold frontal passage on Wednesday night/Thursday. Surface high pressure is expected to build into the area in the wake of the secondary cold front and remain over the area into Saturday. Chances for precipitation will increase over the weekend as another frontal system approaches the region, but details are still far from nailed down at this time. Highs will be generally in the 50s through Friday and lows in the upper 20s to low 30s Wednesday and Thursday night. High and low temperatures will increase Saturday and Sunday as the next system approaches. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As of 1250 PM Sunday... There is a high likelihood that VFR parameters will persist across central NC through 06Z Monday as high pressure to our south- southeast maintains good to excellent aviation conditions. As the high drifts offshore late tonight through early Monday morning, an influx of low level moisture may lead to the development of patchy fog after 08Z Monday, primarily across the Sandhills and coastal plain of central NC. For now, will advertise a 3-5 hour period of mostly MVFR visibilities at KRDU, and KFAY, with a period of IFR/LIFR visibility at KRWI. Any fog that develops should lift and dissipate by 14Z Monday. There is a high probability of VFR parameters late Monday morning through Monday afternoon. The chance for MVFR ceilings along with scattered showers will increase after 00Z Tuesday in the west, more so after 04Z. By 08Z, expect a high potential for MVFR/IFR ceilings and scattered to numerous showers across the bulk of central NC as a cold front approaches from the west. This boundary expected to sweep eastward across the area early Tuesday morning, leading to improving ceilings and diminishing the shower coverage west-to-east. In the wake of the front, a period of strong sw sfc winds expected with gusts 30-38kts possible. This wind threat should diminish/subside by mid-late afternoon Tuesday. VFR parameters anticipated Tuesday night through Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...KC AVIATION...WSS is the U.S. government's official web portal to all federal, state and local government web resources and services.