Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260516 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 115 AM EDT MON SEP 26 2016 .SYNOPSIS... A quasi-stationary front across southwestern NC will return north as a warm front tonight as a cold front approaches from the west. The cold front will move very slowly southeast through the area Tuesday and into Wednesday. && .NEAR TERM /OVERNIGHT/... As of 905 PM Sunday... A band of moisture in the lowest 8k ft of the atmosphere underneath a mid/upper level ridge will result in a deck of low clouds over most of central NC overnight. The exception will be the far southern- southwest sections where skies may remain partly cloudy. Most of the convective allowing models as well as successive runs of the HRRR suggest scattered showers in vicinity of the Triad late this evening into the overnight hours. Based on current moisture profile and upper air analysis, moisture appears too shallow and synoptic lift virtually non-existent to suggest anything more than a slight chance PoP for the western counties through the night. May see pockets of fog over the western and southern counties though dense fog not anticipated at this time. Overnight temps will vary from the upper 60s over the southwest to near 60/lower 60s over the northeast. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 245 PM Sunday... Monday will be a murky day as hybrid CAD is expected to develop over the western Piedmont as a warm/moist advection pattern sets up between the surface and 850 mb. This occurs as the low level ridge axis begins to shift east and the next cold front approaches the Appalachians from the west. Expect the moisture profile further increase though the day, except for the far eastern zones were some drying will linger with the ridging. As a mid level trough and the cold front approach the mountains late, the associated lift and upslope easterly flow generate areas of rain. This will aid in locking in the hybrid CAD over the damming region. This pattern will persist overnight with rain likely in the west, spreading east into the rest of central NC overnight. We will cap of POP in the high chance category in the SE Coastal Plain through 12Z/Tue as they will be farther away from the approaching trough and cold front through then. Highs Monday from the lower 70s NW to mid 80s south. Lows Monday night 65-70. QPF of 0.25 to 0.50 forecast for the NW with less than 0.10 in the SE through 12Z/Tue. && .LONG TERM /Tuesday through Sunday/... As of 330 PM Sunday... Tuesday through Wednesday night: A mid/upper low will settle southward across the Great Lakes on Tuesday, with an associated cold front moving into central NC Tuesday... before stalling across eastern portions of central NC Tuesday night. Given sufficient moisture advection in advance of the cold front, PW`s increasing to around 1.75", we should see scattered to numerous showers and some storms on Tuesday into Tuesday evening with potentially even some localized minor flooding in urban areas/poor drainage areas. With regard to a severe threat, instability still looks to be weak to (maybe) modest (with the NAM more robust with its instability). Deep shear of around 20 to 30 kts is expected. The best height falls and stronger winds are expected to remain to our north though, yielding poor mid level lapse rates. Thus, any severe threat will remain low. However, as noted in the day 3 convective outlook from SPC, we still could see a few strong to potentially severe storms with the main threat from damaging winds. High temps on Tuesday are expected to be generally be in the upper 70s to lower 80s. Lows temps, with the front stalling across eastern/southeastern half of the area are expected to range from the mid to upper 50s nw to the mid 60s se. The deep mid/upper low will continue to slowly sink south/southeastward into the Ohio Valley region on Wednesday, with the mid level flow across our area becoming parallel to the lingering front. As the mid/upper low approaches, an area of low pressure is expected to form along the stalled front and track north/northeastward across central NC, allowing for a continued chance for showers and some storms on Wednesday into Wednesday night, with the best chance across the eastern half of the area. Highs Wednesday are expected to range from the the mid to upper 70s north to around 80 south/southeast. Lows Wednesday morning are expected to range from the mid to upper 50s north/northwest to the lower 60s southeast. Thursday through Sunday: Forecast confidence is low for this period of the medium range, with uncertainty about what will happen with the deep mid/upper low expected to be near the Southern Appalachians to start the period. The GFS lingers the mid to upper low just to the north of the area late week, before it lifts off to the northeast over the weekend. Meanwhile, the latest ECMWF retrogrades it westward and northward to around IN/IL by 12Z Sunday, allowing the front to dissipate across our area. The GFS on the other hand allows the front to shift to the east of the area allowing for below to near normal temps for the remainder of the period, and dry conditions generally by Friday. The GFS has been more consistent with the medium range ensemble guidance. Thus, plan to stay closer to the GFS (which is wetter than in previous days through Thursday thank to the GFS now not being as progressive as it past runs). && .AVIATION /06Z MONDAY THROUGH THURSDAY/... As of 115 AM Monday... IFR to MVFR ceilings are expected overnight, lowest at KINT and KGSO in closer proximity to a a quasi-stationary frontal boundary that extends across the western/southern piedmont. Additionally, sely moist upglide atop a quasi-stationary frontal boundary will support a small chance of showers over the TRIAD overnight and into the morning hours. Any sub-VFR conditions in the east(KRWI and KFAY) should become VFR by 14 to 15z, with KRDU expected to become VFR between 15 to 18z. Ceilings will be much slower to improve at KGSO and KINT, with MVFR or low end VFR lingering into the afternoon 18 to 21z time frame. Moisture pooling ahead of a cold front moving into the mountains will also support a small chance of showers and possibly a thunderstorm late in the afternoon/early evening with rain chances increasing overnight with sub-VFR ceilings as the front approaches the NW Piedmont. Looking beyond the 24 TAF Period: A cold front will move very slowly se through the area Tuesday and into the day on Wednesday. Showers and storms with associated periods of sub-VFR conditions are expected to accompany the front. Conditions are expected to improve to VFR from northwest to southeast Wednesday-Wednesday night as drier air filters into the area. During midweek, a rather unsettled pattern is expected to evolve as a deep upper low sags southward from the Great Lakes into the Central Appalachians. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...WSS SHORT TERM...Badgett LONG TERM...BSD AVIATION...CBL is the U.S. government's official web portal to all federal, state and local government web resources and services.