textproduct: Raleigh

WHAT HAS CHANGED

As of 300 PM Tuesday...

* Nothing appreciable

KEY MESSAGES

As of 300 PM Tuesday...

1) Despite multi-layered cloudiness and somewhat shallow boundary layer mixing, Wed will be unseasonably mild and windy.

2) Above normal temperatures continue through Saturday, falling below normal next week.

3) An unsettled pattern will keep a chance of rain in the forecast from Thursday through Sunday.

DISCUSSION

KEY MESSAGE 1... Despite multi-layered cloudiness and somewhat shallow boundary layer mixing, Wed will be unseasonably mild and windy.

Fast, wswly srn stream flow, and associated cirrus/cirrostratus, will prevail from the Southwest to the srn Middle Atlantic, including across cntl NC. At the same time, areas of low ceilings, in return, sly/swly flow around an offshore anticyclone, will have likely overspread cntl NC during the morning. Associated 1500-3500 ft AGL ceilings will likely linger into the afternoon over the Piedmont, while they are expected to scatter more quickly across the Sandhills and Coastal Plain, where related boundary layer mixing should become relatively maximized. There, swly surface winds will probably gust to near 35 kts, versus around 30 kts otherwise and elsewhere. That swly flow regime will also be an increasingly mild/warm one, supportive of high temperatures that should range from middle 60s nw to lwr 70s se.

KEY MESSAGE 2... Above normal temperatures continue through Saturday, falling below normal next week.

A warm front will lift nwd across the area Wed/Wed night, but could creep swd, backdoor cold front style, across portions of the nrn Piedmont and nrn Coastal Plain on Thu as high pressure over the Northeast US ridges across the mid-Atlantic, then lift out of the area once again by Thu night. Meanwhile, the surface low will track enewd from the cntl Plains to the upper MS Valley where it will occlude, the attendant cold front continuing ewd across the OH and TN Valley regions Thu night/Fri. Despite cloudiness for several days, warm advection should keep temperatures above normal (highs in the mid to upper 50s and lows in the mid 30s). For Friday through Sun night, there are still significant differences between the medium-range model solutions wrt the front progression, timing of fropa, and potential development and track of additional areas of low pressure that may track along it. Those differences and uncertainties result in a low confidence forecast. Still expect Fri to be the warmest day of the period, with highs ranging from upper 60s NE to upper 70s south. While dependent upon the fropa and precipitation, temperatures should remain above normal for Fri night through Sat night, albeit lower than the preceding days/nights. In the wake of the front, when cold high pressure is finally able to build into the region, temperatures will swing back to below-well below normal for early next week.

KEY MESSAGE 3... An unsettled pattern will keep a chance of rain in the forecast from Thursday through Sunday.

Aloft, the amplitude of the sub-tropical ridge will vary as it moves across the region through Fri, with some weak disturbances traversing the ridge Thu/Thu night. Meanwhile, a nrn stream s/w will track ewd across the nrn Plains and into the upr MS Valley, while a trailing s/w moves across the Intermountain West. The leading s/w will close off briefly as it moves enewd across the Great Lakes Fri/Fri night, while the trailing s/w moves ewd across the cntl Rockies and into the Plains. Another nrn stream s/w will drop swd across the nrn Plains Fri night/Sat as the disturbance to the south continues ewd across the Plains. These two shortwaves may eventually merge and close off over the OH Valley/Great Lakes Sun/Sun night. However, there are still significant model differences wrt the strength and track of these disturbances. The surface pattern is outlined above (Key Message 1), a warm front will lift nwd across central NC on Wednesday, perhaps getting hung up across or dipping swd into the nrn Piedmont and/or nrn Coastal Plain as high pressure ridges swd across the mid-Atlantic Wed night/Thu. The warm front should finally lift out of the area Thu night as the surface low occludes and the cold front moves across the Appalachians. The attendant cold front should move across the area Fri/Fri night, while a secondary low forms along the front then tracks ewd across the mid-Atlatntic and offshore. The front should become quasi- stationary and more W-E oriented across the Southeast US/Carolinas Sat and Sun. Another low may develop along the front over the Deep South/Southeast Sat/Sat night, then track enewd along the front, across the Carolinas and off the mid-Atlantic coast Sat night/Sun.

Along the warm front with the weak disturbances aloft on Thu, there could be some light rain, highest chances across the north, primarily along the VA border. Showers will be possible Fri/Fri night as the front moves into and across the area. However, there are large differences in the model guidance on the coverage and amounts. Additional rounds of rain will be possible invof the front as it wavers over the Southeast US/Carolinas over the weekend. Given the continued uncertainty, confidence on location, coverage, and rainfall amounts remain low at this time. Precipitation should largely be liquid, with the cold air chasing the rain out late Sunday, with Sunday night looking dry.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

As of 115 PM Tuesday...

VFR conditions, and swly surface winds that will occasionally gust into the teens kts this afternoon, will continue through early tonight. While a chance of radiation fog will exist at RWI due to local effects tonight, areas of mostly MVFR ceilings, to possibly IFR ones at FAY and RWI, are expected to overspread cntl NC Wed morning, as will a 40-45 kt, swly low-level jet and related risk of low-level wind shear. MVFR ceilings may linger into the afternoon over the Piedmont on Wed, while they will likely scatter to VFR more quickly at FAY and RWI. Swly surface winds will also strengthen and become strongly gusty through the day Wed, particularly in areas where scattering and deeper mixing materialize most quickly (ie. FAY and RWI).

Outlook: Flight restrictions and rain will accompany a deepening area of low pressure across the region this weekend.

RAH WATCHES/WARNINGS/ADVISORIES

None.