textproduct: Raleigh

WHAT HAS CHANGED

* Nothing appreciable

KEY MESSAGES

As of 330 AM Wednesday...

1) Record or nearly so heat likely through Friday

2) A strong cold front will sweep across central NC Friday evening, with a significant cooldown for the weekend and the potential for some patchy frost.

DISCUSSION

As of 330 AM Wednesday...

KEY MESSAGE 1... Record or nearly so heat likely through Friday

An anomalously strong sub-tropical ridge centered over the lwr MS Valley, observed in 00Z/14th 700 mb and 500 mb data at 321 dam and 595 dam, respectively, will progress across and offshore the Southeast through 12Z Fri. A series of mid-level disturbances, convectively-generated and/or amplified from frontal convection from the mid MS valley to the cntl and srn Plains, will progress around the ridge in generally wly flow across the lwr OH Valley and Middle Atlantic through early Thu. Deep layer flow will then strengthen and back to swly ahead of a vigorous, positive tilt and increasingly- phased trough, comprised of a srn stream cyclone now over the srn UT/nrn AZ and a nrn stream shortwave trough over BC, forecast to reach the upr Great Lakes by 12Z Fri.

At the surface, a lee trough will develop and sharpen across VA and the Carolinas today, while 1018-1019 mb high pressure now centered over MS/AL will progress across and offshore the Southeast. Meanwhile, a wavy front now stretching from a 1008 mb low along the coast of ME, wwd across the nrn Middle Atlantic and lwr Great Lakes, then swwd across the mid MS Valley and srn and cntl Plains, will progress swd across the Middle Atlantic and reach the VA/NC border vicinity by 12Z Thu. The front should then drift swd into the far ne Piedmont and nrn Coastal Plain of NC on Thu, propelled by a ~1025 mb high (stronger than the preceding one over the Southeast) forecast to progress across the Great Lakes. The front will then retreat nwd across the Middle Atlantic Thu night-Fri, ahead of a cyclone forecast to deepen considerably while tracking newd from the OH Valley to the Canadian Maritimes (~20-25 mb from 00Z Fri to 12Z Sat).

Upr 80s to mid 90s temperatures that were present Tue across the Gulf Coast states will expand newd and across the Carolinas today, beneath and downstream of the anomalously strong ridge aloft. That heat will generally remain in a persistence pattern in the warm sector, equatorward of the aforementioned backdoor front that will offer cooling throughout VA and into the far ne Piedmont and nrn Coastal Plain of NC on Thu. However, mid and high-level debris cloudiness, from upstream convection and along the path of the convectively-augmented disturbances, may keep temperatures from reaching their full sun heating potential on Thu, especially across nrn zones that may otherwise remain in the warm sector/ahead of the backdoor front. Heat within the expanding and mostly sunny warm sector on Fri will be accompanied by a gusty swly surface wind, after lighter winds Wed-Thu.

KEY MESSAGE 2... A strong cold front will sweep across central NC Friday evening, with a significant cooldown for the weekend and the potential for some patchy frost.

A potent nrn stream s/w aloft will drop sewd across Ontario and the Great Lakes Thu and Fri, deepening the trough over the ern US as it interacts with another s/w ejecting enewd from the cntl Rockies to the Great Lakes. The trough will continue to deepen as it moves ewd across the eastern US and offshore Fri night/Sat. At the surface, an area of low pressure lifting newd across the mid-MS and OH Valley on Thu will rapidly deepen as it continues across the Great Lakes and Northeast US Thu night/Fri. The trailing cold front will move across central NC late Fri/Fri night. There is still a chance for some precipitation with the fropa, but amounts should be light and limited in coverage. The low-level jet is expected to strengthen over the area Fri eve, with 30-40 kts at 925mb. The pressure gradient will also be quite strong as a ~1035 mb high over the Plains builds ewd. Expect strong, gusty winds with and behind the front Fri eve through Fri night. The high may temporarily weaken ever so slightly as it builds ewd across the mid-MS and OH Valley regions on Sat, before settling over the mid-Atlantic Sat night/Sun, then offshore by Mon.

Temperatures should fall about 30 degrees from Friday aft to Sat morning. By Saturday, highs will be similar to the lows from Thu night (generally low to mid 60s). Lows should drop another 10 degrees or so Sat night, as the high settles over the mid-Atlantic, when lows may drop into the upr 30s across the nrn Piedmont and upper 30s to mid 40s elsewhere across cntl NC. The usual cooler, sheltered areas may see lows in the mid 30s, with some patchy frost possible should the mid 30s lows be realized.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

As of 740 AM Wednesday...

High pressure centered over the South Atlantic states will maintain VFR conditions and light swly surface winds across cntl NC through tonight.

Outlook: A backdoor cold front will settle across VA and into nrn NC on Thu. IFR-MVFR ceilings are likely to develop in the post-frontal airmass and mainly just to the north of cntl NC TAF sites Thu night. However, there is a chance (~30-40%) that the front and ceilings may edge as far south as RWI and RDU during that time. Strong and gusty nwly surface winds, and perhaps light (mainly VFR) rain, will result behind a powerful cold front Fri night.

CLIMATE

Record High Temperatures:

October 14: KGSO: 85/1975 KRDU: 86/1985 KFAY: 90/1954

October 15: KGSO: 87/1985 KRDU: 88/1985 KFAY: 91/1931

October 16: KGSO: 85/1953 KRDU: 86/1925

Record High Minimum Temperatures:

October 15: KGSO: 63/1985 KRDU: 66/1942

Latest 90 F days:

GSO: 10/12/1904 RDU: 10/10/1907 FAY: 10/26/1940

RAH WATCHES/WARNINGS/ADVISORIES

None.