Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291902 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 302 PM EDT Wed Mar 29 2017 .SYNOPSIS... Weak high pressure will move over central NC today and remain in control through Thursday before low pressure brings unsettled weather to the area for Friday and Friday night. && .NEAR TERM /THROUGH TONIGHT/... As of 1250 pm Wednesday... Central NC will be under the influence of a very remote surface high centered over northern Ontario with building heights aloft as shortwave ridging shifts overhead. Widespread stratus with ceilings between 2 to 4kft, has overspread the area, as depicted by the HRRR and NAM, within the stable low-level NELY flow. Expect these low ceilings to lift and eventually scatter out into a stratocu layer. High temperatures ranging from mid to upper 60s NE , to mid/upper 70s southwest. It should start out mostly clear this evening, but an area of expanding stratus, developing within the 925-850mb SELY upslope flow along the higher terrain, is expected to spread into the western and possibly central piedmont between 06 to 12z. Lows ranging from the mid 40s NE to mid 50s SW. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 405 AM Wednesday... Thursday will be quiet during the day as a meso-high develops over the Delmarva Peninsula which will throw temperatures into question a bit for Thursday afternoon. if flow remains southeasterly over the area, we should see temps near 60 degrees across the north with highs closer to 70s in the south. If flow remains more northeasterly temps could come in quite a bit cooler, especially across the north. By Thursday night, the first waves of precipitation associated with an approaching low pressure system will begin to overspread at least the western portions of the CWA, and perhaps everywhere by 12z Friday. Diurnal timing should keep most of this activity limited to convective showers as instability is non-existent. That being said, model soundings show every strong veering with height and wind profiles suggest bulk shear of 50 knots or so with a large heaping pile of helicity in the lowest levels of the atmosphere. Will certainly keep an eye on these details as they evolve. Lows Thursday night mainly in the 50s. && .LONG TERM /Friday through Wednesday/... As of 300 PM Wednesday... Fri-Fri Night: The 12Z GFS/ECMWF are in fairly close agreement showing the upper low tracking ENE through the OH valley during the day Friday, progressing into western PA late Friday into Friday night. However, differences in timing persist between the GFS/ECMWF, and the 12Z NAM (an outlier) shows the upper low tracking east through KY into WV Fri/Fri night (much closer than the GFS or ECMWF). Forecast confidence remains lower than normal, esp given uncertainty in the evolution of upstream convection across the Deep South Thu/Thu night in addition to uncertainty in the strength/ extent/evolution of the CAD wedge expected to develop over central NC on Thu. Although confidence in precipitation chances remains high, forecast specifics such as precip amounts, temperatures and intensity/mode of convection remain relatively low. With the latest guidance in mind, will indicate highs ranging from the mid 60s in the Triad to the mid 70s in the Sandhills/SE Coastal Plain. Expect precipitation to end from SW-NE as early as late Friday aft/eve, with skies clearing in the wake of a cold frontal passage Fri night. Lows Sat morning will depend primarily upon fropa timing, ranging from the upper 40s/lower 50s (N/NW) to mid 50s (S/SE). The 12Z GFS/ECMWF suggest a lower potential for severe weather given an upper low track further to the north and a slightly faster progression of the system. The 12Z NAM would suggest a more robust potential for severe weather due to the closer proximity of the upper low and slightly slower progression of the system which would result in favorable diurnal timing, as well. Uncertainty remains too high to say much more w/regard to the severe weather potential. Sat-Sun night: Expect dry conditions and a warming trend over the weekend as a shortwave ridge builds east across the Mid-Atlantic and Carolinas. Expect highs in the lower/mid 70s Sat and mid 70s Sunday as a shortwave ridge aloft tracks across the region from the west. Mon-Wed: Expect increasing cloud cover during the day Monday and a chance for convection Mon Night through Tue as the next upper level low /attendant sfc cyclone/ approach from the west. -Vincent && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 200 PM Wednesday... 24 Hour TAF Period: High pressure will wedge south into the area tonight and into the day on Thursday. The stable low-level NELY flow has advected a shallow marine layer into the area, producing ceilings between 3 to 4kft. GOES-R 16 visible imagery shows these low-end VFR ceilings quickly morphing into a scattered to broken stratocu deck. There is medium confidence to high confidence that an area of MVFR stratus will at KINT and KGSO, within the 925-850mb SELY upslope flow along the eastern slopes of the higher terrain. Though confidence is not as high, ceilings at KRDU, KRWI and KFAY are expected to remain VFR, with the potential that KRDU could be on the eastern periphery of the sub-VFR ceilings. A strong mid-level subsidence inversion over the area on Thursday will result in slow lift/improvement of the stratus layer, with a high likelihood that sub-VFR ceilings at KGSO and KINT could linger into the mid to late afternoon. Long term: A warm front associated with a low pressure system tracking through the Middle MS Valley will bring the chance for showers and thunderstorms Thursday night late Thursday night through mid to late morning hours on Friday. High pressure with VFR conditions should return Friday afternoon and will persist through the weekend. The next storm system is expected to impact the area on Monday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ellis NEAR TERM...CBL SHORT TERM...Ellis LONG TERM...Vincent AVIATION...CBL

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