textproduct: Raleigh

SYNOPSIS

High pressure will build in from the north tonight through Monday, then move east off the Mid Atlantic coast Monday night. This will allow a warm front to lift northward through the region late Monday night through Tuesday. A cold front will move through the region Wednesday, ushering in Arctic high pressure that will build in from the northwest through Saturday.

NEAR TERM /THROUGH TONIGHT/

As of 100 PM Sunday...

Aloft, nwly flow will prevail over central NC through tonight. As a nrn stream s/w tracks ese off the New England coast, a mid/upper disturbance will track across the area, ahead of the sub-tropical ridge approaching from the west. At the surface, a dry, reinforcing cold front will slide south across the area this eve/tonight, with high pressure building into the region behind it. Dry weather will prevail through tonight, with perhaps a few mid-high clouds tonight associated with the disturbance aloft. Highs mainly in the 60s today. Winds could get a bit breezy with the dry cold fropa this eve and remain a bit stirred into tonight, then taper off across the north late tonight/early Mon morning. Lows tonight should generally range from mid/upper 30s north to low 40s south, but will depend on the winds. If winds go calm earlier and/or over a greater area, temps could be a couple/few degrees lower in those places. Likewise, if winds do not taper off across the north as expected, lows may be a couple/few degrees higher there.

SHORT TERM /MONDAY AND MONDAY NIGHT/

As of 100 PM Sunday...

Overview: The sub-tropical ridge will progress across the region on Mon, and off the East Coast Mon night as a potent s/w tracks eastward from the central Plains to the mid-MS Valley. At the surface, high pressure will move ewd across the region Mon and offshore Mon night. Expect increasing high clouds Mon night as the s/w approaches from the west, which should limit the radiational cooling, especially west. Otherwise, dry weather and seasonably warm temperatures are expected, with highs mainly in the low to mid 60s and lows ranging from mid/upper 30s NE to low/mid 40s SW.

LONG TERM /TUESDAY THROUGH SUNDAY/

As of 250 PM Sunday...

* Unsettled weather Tue through Wed night.

* Dry and colder Thu through Sat, then moderating Sun.

Tue-Wed night: Still anticipating an active period, with models in fairly good agreement on timing and amplitude of a sharpening mid level trough tracking from the Dakotas/Upper Midwest across the U.P. of MI to the Ontario/Quebec border. The surface high just off the Mid Atlantic coast Tue morning will push further out over the NW Atlantic during the day, putting NC in a deepening return flow pattern, with falling heights aloft as the mid level ridge over the Southeast flattens and pushes offshore. The LREF ensemble cluster analysis shows small variations which can be largely explained by differences in trough amplitude, with decreased timing differences from yesterday's runs. PW increases Tue particularly over our NW half, where moist isentropic upglide at 290K-305K also strengthens, supporting chance to low-end likely pops spreading into N and W sections where PW will trend to over 200% of normal. MUCAPE Tue should be no greater than 200 J/kg, but with high deep-layer bulk shear and periods of enhanced upper divergence passing overhead from the upper jet streak to our NW, we could see an isolated afternoon storm or two across the N and W. Regarding temps Tue, the departing surface high is of mild continental origin with a lack of strong cold/dry air advection from the N that might prompt strong CAD formation. But with rain chances arriving in our NW early in the day when surface dewpoints may still be in the 40s, development of at least a surface-based stable pool is favored in the NW Piedmont. Temps in the Triad may struggle to reach the upper 50s/near 60, while in our southeast within good WAA and thinner clouds, highs in the 70-75 range are expected. Lows Tue night are expected to be quite mild, in the mid 50s to around 60. The most likely time of cold front passage through central NC is mid to late Wed afternoon, slightly faster than that indicated in yesterday's models. Prefrontal PW will remain well above normal Tue night through much of Wed, so will retain above-climo pops. We have another chance for a few thunderstorms Wed ahead of the front, with the greatest potential for MUCAPE of 200-600 J/kg over our SE half. We'll still have strong deep layer bulk shear of 50-60 kts with long and generally straight hodographs, so a few strong storms with sub- severe gusts and small hail could occur, best chance S and E of the Triangle. Expect highs Wed in the upper 60s to mid 70s, with lows behind the front Wed night in the mid 30s to low 40s.

Thu-Sun: Within post-front subsidence, expect lots of sunshine Thanksgiving Day, with fair, dry, and cool conditions through Sat as the mid level trough shifts over E NOAM. Despite the abundant sunshine, since the incoming surface high will be of Canadian/Arctic origin, the CAA will keep temps below normal, esp Fri through Sat as the surface high settles overhead and just to our N. We should see highs in the upper 40s to mid 50s Thanksgiving Day and Sat, and mid 40s to lower 50s Fri, with are about 5 to 15 degrees below normal. Lows should be coldest Fri night, in the 20s. As the mid level trough lifts quickly NE over the Canadian Maritimes into the far N Atlantic over the weekend, our mid level flow will back and strengthen from the SW, while at the surface, the high will track over the Mid Atlantic region Sat then off the New England coast Sun. This will result in a gradual air mass modification with increasing high clouds from the SW Sun. Expect continued dry weather, though, with highs in the mid 50s to mid 60s. -GIH

AVIATION /00Z MONDAY THROUGH THURSDAY/

As of 655 PM Sunday...

VFR conditions will prevail for the 24 hour TAF period. Overnight, light to completely calm winds and clear skies are expected. A brief period of gusts in the teens may be possible shortly after sunrise, but high pressure overhead may suppress any gusts. Monday afternoon, mid to upper level VFR clouds should start to spread over the region from the west.

Outlook: IFR-MVFR ceilings and patchy light rain will likely overspread the Piedmont ahead of a retreating warm front Tue morning. A chance of rain, increasingly convective in nature, and also flight restrictions, are expected later Tue through Wed, as a strong frontal system traverses the region.

RAH WATCHES/WARNINGS/ADVISORIES

None.