Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280145 RRA AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 945 PM EDT Mon Mar 27 2017 .SYNOPSIS... An upper level trough will cross the region Tuesday, along with a trailing cold front. High pressure will build in from the north on Wednesday, then shift offshore Thursday. A strong storm system is expected to affect the region late in the week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 945 PM Monday... Diurnally driven isolated convection across the southern piedmont earlier this evening has since died down with loss of heating. However, we will see an increase in pops late tonight(at least over the western piedmont) with the approach of the mid/upper level trough into the southern Appalachians aoa daybreak. Hi-Res models continue to show significant weakening of the upstream convection currently across TN as it crosses the mountains, encountering weak buoyancy in place across the area owing to nocturnal cooling. Will show high chance pops in the west, decreasing to small/slight chance pops in the east, given the potential for the convection to dissipate altogether as it reaches the eastern zones. It will be a very mild night with lows generally in the 60s.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 235 PM Monday... The latest Hi-Res convection allowing models suggest that only a few showers will remain from tonight`s convection that tries to cross the Piedmont. Regardless, the timing of the approaching mid/upper trough appears to be during the morning and early afternoon for the western Piedmont, which is essentially not diurnally favorable for strong or severe storms in the western zones. Models do favor redevelop of at least scattered showers and thunderstorms along the surface wind shift line that is forecast to move SE into central NC Tuesday afternoon. The favored lift area out ahead of the mid/upper trough is forecast to reach the eastern Piedmont into the Coastal Plain and Coastal Areas during the peak heating period. Convection may blossom as early as late morning or around noon near the wind shift line, and should spread and develop ESE during the afternoon. It appears that the most favored area for optional heating and destabilization should occur just to the east and south of the Triangle area, just before the convection develops in the early afternoon and tracks into the region. The earlier timing of the front and trough should limit the strong to severe threat in the NW Piedmont Triad region, with the focus in the eastern zones. Even in the east where the instability and shear is expected to be higher, most parameters for severe storms are forecast to be marginal. Highs in the upper 70s to lower 80s in the east, with dew points nearing 60, should lead to MLCapes near 1000 J/KG. Mid level lapse rates may still be in question but some subtle warming aloft may be a negative factor for organized severe storms. Still, look for at least scattered thunderstorms with the potential for wind gusts to 40-50 mph and possibly up to 1 inch hail in a few of the strongest storms. We will highlight areas east of the Triad area for this potential due to timing in the Hazardous Weather Outlook. The convection should be east of the region by around sunset or so, but the lagging wind shift line may aid in some weaker trailing storms into the evening in the east. Otherwise, partly cloudy with lows in the 50s expected. && .LONG TERM /Wednesday through Tuesday/... As of 145 PM Monday... Wed-Wed Night: With shortwave ridging aloft, expect mostly sunny to partly cloudy skies and above normal temps in the mid/upper 70s Wed afternoon. Subsidence in the wake of an upper level low moving offshore New England Wed evening will result in pressure rises along the eastern seaboard as an inverted sfc ridge extends southward through the Mid-Atlantic into the Carolinas, the leading edge of which will be marked by a backdoor cold frontal passage /wind shift to the NE at ~15 mph/. Lows Wed night will be determined by the precise timing of fropa. At this time, expect temps ranging from the mid 40s NE Coastal Plain to lower 50s in the SW Piedmont. Thu: NE low-level flow in the wake of the back door cold front early Thu morning will gradually veer to the E/ESE during the day, allowing temperatures to recover into the mid 60s across the Sandhills and SE Coastal Plain Thu afternoon. A cold air damming wedge is expected to develop across portions of the N/NW Piedmont where broken/overcast cloud cover (and possibly evap cooling attendant intermittent light rain or sprinkles in the foothills) are largely expected to offset diurnal heating, keeping highs in the mid 50s, coolest in Forsyth/Person county. Thu night: Expect an increasing potential for showers across the western half of the state (primarily along/west of Highway 1) between midnight and sunrise Fri as an upper level low progresses into the OH valley and low-level warm advection strengthens downstream over the Carolinas. Expect lows Fri morning ranging from the mid/upper 40s to lower 50s, coolest in the W/NW Piedmont where precipitation /evap cooling/ is more likely. Fri-Fri Night: Confidence in the evolution of the aforementioned upper level low, attendant sfc cyclone and associated fronts (warm/cold/wedge) remains below normal for several reasons, ranging from antecedent conditions (CAD wedge in place across portions of central NC Fri morning) to significant disagreement amongst the GFS/ECMWF. The 12Z GFS suggests the upper level low over the central MS river valley on Thu will track east across the Carolinas/VA late Friday/Friday night. In stark contrast, the 00Z ECMWF shows the upper level low deamplifying and lifting NE through the lower Great Lakes into New England late Fri/Fri night. While the precipitation forecast appears to remain on track (e.g. a solid potential for showers across the entire area during the day Friday), significant uncertainty is present w/regard to the intensity of convection/ amount of precipitation. From a hazardous weather standpoint, the 12Z GFS solution would favor a potential for severe storms whereas the 00Z ECMWF solution would not. The temperature forecast on Fri/Fri night is challenging to say the least. At this time will show the coolest temps in the Triad (highs in the lower 60s) and warmest temps in the Sandhills and SE Coastal Plain (lower 70s). A clearing trend from SW-NE is expected in the wake of a cold frontal passage late Fri night, though the timing thereof remains in question. At this time anticipate lows in the lower/mid 50s, coolest NW Piedmont. Sat-Sun night: Confidence in the forecast for Sat has decreased, with the 12Z GFS guidance now showing a potential for showers assoc/w DPVA digging SE on the western periphery of the upper level low tracking offshore the Mid-Atlantic/Carolinas. The 00Z ECMWF suggests dry conditions and a warm-up with the upper low deamplifying/lifting into New England and clear skies in the wake of the cold front on Sat. Dry conditions and further warming are expected on Sun as a shortwave ridge aloft tracks across the region from the west. Mon-Tue Night: Expect increasing cloud cover during the day Monday and a chance for convection by Tue as the next upper level low /attendant sfc cyclone/ approach from the west. -Vincent && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 830 PM Monday... 24 Hour TAF Period: VFR conditions are expected to continue this evening, with the bulk of any convection remaining to the west of central NC. However, ongoing convection over TN/GA/AL is expected to continue to move eastward overnight, while weakening. Whatever is left of this activity is expected to move across central NC in the 08-16Z time frame (from west to east), which may allow for some IFR/MVFR cigs and/or visbys. Afterwards expect a lull in the convection before the main s/w and associated cold front move across the area. Scattered thunderstorms, possibly severe with gusty winds and hail, are expected across the eastern terminals tomorrow between 18z/Tues and 00z/Wed (along and ahead of the front). Once these storms pass thru our area, a return to VFR conditions is expected in the late evening and overnight hours. Long term: A storm system is expected to push into the region Thursday night and Friday with showers/storms, low CIGS, and fog. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...CBL SHORT TERM...Badgett LONG TERM...Vincent AVIATION...BSD/RMR/Badgett

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