textproduct: Raleigh

SYNOPSIS

A front will waver over the Carolinas through the weekend, lifting north to near the Virginia border this morning, then pushing back south into South Carolina as a cold front this evening. The front will again lift back north as a warm front Sunday night, then a strong Arctic cold front will sweep in from the west late Monday, bringing in a cooler air mass and blustery winds for Tuesday.

NEAR TERM /THROUGH TONIGHT/

As of 210 AM Saturday...

* Drastic temperature swings continue as a front wavers over the area, lifting north through the daylight hours and settling back south of the area tonight.

Regional observations and satellite imagery show a wedge-like stalled boundary encircling central NC with a weak area of low pressure racing across the northern Mid-Atlantic and its trailing cold shifting through the Ohio Valley. The stalled boundary to our south will move very little at the surface but we will see warming/moistening just above the surface through the early morning hours and may contribute to the development of patchy to areas of shallow fog over the southern Piedmont and Sandhills. Latest guidance is highly split on how far north it will reach, if into central NC at all. If it does reach up into our area, it may become dense at times through 13z.

After sunrise, a majority of central NC should warm rather rapidly as we begin to mix into the warmer air aloft and should see the warm front 'jump' northward into southern VA. This should result in another seesaw day for daily highs reaching into the upper 60s to mid 70s for a majority of the Piedmont, Sandhills and southern/central Coastal Plain. The only exception may be the far northeastern Piedmont and northern Coastal Plain where the cold front over the Ohio Valley pushes into the area from the northeast late morning into the early afternoon. The combination of CAA at the surface and increased cloud cover behind the front may cut into daily highs in these areas, but will highly depend on when the front arrives in our area. To account for this, decided to cut back highs by blending in hi-res guidance and results in highs in the mid 50s.

Overnight lows will be tricky and depend on the amount of CAA that can occur behind the frontal passage overnight, but latest blend results in lows ranging from mid 40s (SW) to low/mid 30s (NE).

SHORT TERM /SUNDAY AND SUNDAY NIGHT/

As of 210 AM Saturday...

* The forecast is trending towards the development of an in-situ CAD pattern favoring low overcast and drizzle Sun morning, resulting in a cool, cloudy, dreary day, especially for the Piedmont region.

Surface high pressure will continue to build into the region in in- situ cold-air-damming (CAD) fashion. The parent surface high will be fairly progressive, and weakening with time, as it shifts quickly off the coast of NC from the northern Mid-Atlantic between 12-18z. Widespread cloud cover behind the backdoor cold-frontal passage Sat night and newly deposited cooler/drier airmass will result in another drastic temperature change compared to the forecast highs on Sat. The latest suite of model guidance is coming in stronger/earlier with low-level WAA and lowering cloud bases through the daylight hours. This may result in drizzle and/or light rain developing as early as 12-15z and would further lock in the in-situ CAD process via diabatic process, lowering high temperatures even further and perhaps as low as low/mid 40s in the climatologically favored NW Piedmont. This forecast trend will be monitored and the official forecast will be adjusted accordingly as confidence increases.

With the lack of a steady supply of cold air at the surface from an unfavorable high location, the wedge boundary should slowly mix northward Sun night and result in rising temperatures overnight into Mon morning. Depending on strength of the in-situ CAD, this northward progress of the warm front will likely be much slower than hi-res guidance suggests and result in a low forecast confidence for low temperatures Sun night.

LONG TERM /MONDAY THROUGH FRIDAY/

As of 235 AM Saturday...

* Strong gusty winds and above normal temps Mon ahead of a strong Arctic cold front that will sweep through late Mon.

* Colder temps and blustery winds arrive for Mon night and especially Tue, when dry conditions and wind gusts may bring fire weather concerns.

* Continued cool Wed, then moderating for New Years Day.

* Apart from a chance of light rain Mon, dry weather is likely through much of this week.

Latest models remain in good agreement with the timing and magnitude of a mid level polar low over MI Mon morning, when its corresponding Arctic surface cold front is expected to extend along the spine of the NC mountains. The trailing mid level trough will be positively tilted, extending down through the Mid Miss Valley early Mon, but as the low pushes NE to the central Ont/Que border through Mon, the cold front should sweep swiftly ESE through central NC during the day, propelled by a cold/dense incoming air mass centered over the Upper Midwest. Patchy light rain is expected ahead of the front, given model consensus of PW ~150% of normal, but amounts should be limited given the preceding surface ridge from the NW Gulf across FL and off the Southeast coast that will decrease the low level moisture return potential, while aloft, there are indications of minimal ice in the clouds, leading to small hydrometeors. Will carry pops Mon that are slightly above climatology, but with light totals. With a tight MSLP gradient ahead of the front topped by a 40-50 kt low level jet, gusts should frequently reach 25-35 kts. Expect highs from the low 60s NW to low-mid 70s SE, although temps in the Piedmont are likely to reach their daytime highs early with readings falling during the afternoon. Rain chances should end by early evening. Lows in the mid 20s to low 30s.

Tue should be our coldest day of this stretch, as the Arctic high builds in post-front, supported by large mid level low over the Canadian Maritimes and a trough covering much of eastern NOAM. Despite ample sunshine in our area with NW flow and deep subsidence, the strong CAA and thicknesses 30-40 m below normal support highs in the upper 30s to upper 40s, with wind chills in the 20s and 30s for much of the day. Gusts of 20-25 mph should be common, infrequently up to 25-30 mph especially in the NE CWA, and these winds plus min RH values of 22-30 percent will bring about some fire weather concerns, although the chilly temps should mitigate this risk somewhat. Lows Tue night will be mostly in the 20s.

The mid level trough axis should push off the East Coast Wed, but the longwave trough will maintain a presence over eastern NOAM into Jan 2026. Our temps will moderate by Thu as the southern portion of the surface high settles over TX and the Deep South, as the polar surface cold front holds well to our N, extending from the Upper Midwest E across the St. Lawrence Seaway. But energy digging over the Great Lakes into the mean trough base by late Thu/early Fri is likely to nudge this polar front southward toward NC, potentially drawing another shot of much colder air into our area by Fri or early Sat (day 8). This should knock Fri highs back down into the 40s, although timing of such a feature is uncertain at this range, and these temps may go higher or lower in later forecasts. -GIH

AVIATION /11Z SATURDAY THROUGH WEDNESDAY/

As of 625 AM Saturday...

The IFR bank briefly cleared over the Triad, but has quickly returned as the flow aloft shifted to northwesterly. At the same time it has now lowered to a LIFR-VLIFR layer with patchy dense fog at INT. Confidence is low in LIFR cigs/vsby reaching GSO, but given its proximity and slow southeast motion via satellite imagery, opted to include a TEMPO to capture this threat. VFR conditions will return by early/mid morning. Surface winds will quickly shift out of the NW at 15z then to the NE to E behind a backdoor cold front moving into the area between 15-22z. Behind this front, SCT/BKN MVFR cigs will be possible. Timing and areal extent remains relatively low confidence so opted for FEW/SCT layer at all TAF sites around the time of onset in latest forecast. MVFR cigs are expected to become more widespread Sat night (between 06-12z) and lowering to IFR in the Triad towards daybreak.

Outlook: MVFR cigs will likely linger through a majority of the day on Sun with some patchy drizzle/light-rain Sun morning possible. Cigs may lower to IFR-LIFR in the Piedmont terminals (INT, GSO and RDU) late Sun afternoon into Mon. A stronger cold front will sweep across the region, bringing a chance for light rain, but should return conditions to VFR Mon afternoon through the evening hours. Gusty southwest winds are expected to develop ahead of the frontal passage Mon morning (gusts 15-25 kts), then veering to northwesterly behind the front and remaining gusty Mon afternoon into Tues (20-30 kts, strongest immediately behind the front and again Tues with low- level turbulent mixing).

RAH WATCHES/WARNINGS/ADVISORIES

None.