textproduct: Raleigh

SYNOPSIS

Arctic high pressure will build across the region today. The high will settle across the Southeast ahead of a strong, clipper low pressure system that swing across the Great Lakes tonight and Wednesday. A moisture-starved cold front trailing the clipper low will move across NC Wednesday night.

NEAR TERM /TODAY AND TONIGHT/

As of 320 AM Tuesday...

* Sub-freezing temperatures will allow any snow or moisture on area roads and sidewalks to freeze, producing hazardous travel through mid to late morning.

* Cold today with highs 15 to 20 degrees below normal

In the wake of exiting shortwave trough, a migratory Arctic high pressure will weaken while building over the area today before shifting offshore tonight.

Light snow/flurries have ended across the area, leaving behind widespread low clouds early this morning. However, dry low-level air advection from the north, combined with increasing subsidence aloft, should lead to NE to SW clearing/partial clearing through mid to late morning.

Across the area that received 1-2 inches of snow across the northern Piedmont and northern coastal plain, morning lows in the lower to mid 20s will support slick spots and patchy black ice, especially on shaded secondary roads, bridges and overpasses. Temperatures rising above freezing by late morning, combined with increasing solar radiation, will reduce the risk of slippery conditions.

Temperatures will be unseasonably cold for early December, with highs ranging from mid/upper 30s north to lower 40s south --about 15 to 20 degrees below normal. After the low stratus scatters out, expect periods of broken/overcast cirrus and cirrostratus, some of which may become orographically-enhanced, through tonight. Lows tonight will fall into the 20s area-wide.

SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/

As of 320 AM Tuesday...

* Windy conditions will develop ahead of a dry cold front.

The large-scale mid/upper trough over the central and eastern US will be reinforced by several digging shortwave troughs, including a clipper-type perturbation and it's accompanying dry cold front that will sweep through the mid-Atlantic states late Wednesday and Wednesday night.

The primary weather impact will be the development of windy conditions within the pre-frontal regime. SWLY winds will increase after daybreak and peak during the afternoon/max heat, with sustained winds of 15 to 20 mph and frequent gusts between 25 to 35 mph, occasionally reaching 35 to 40 mph at times. Residents should secure outside items and holiday decorations.

Expect considerable cloud cover, consisting of mid and high level clouds, ahead of the cold front. Temperatures will moderate closer to normal for early December, with highs ranging from near 50 north to mid 50s south.

Following the dry cold frontal passage Wednesday night, CAA will ensue. Skies will clear and gusts will diminish. Overnight lows will fall into the lower 30s north to mid 30s south.

LONG TERM /THURSDAY THROUGH TUESDAY/

As of 1215 PM Tuesday...

* Temperature roller coaster, below normal Thursday and Friday, moderating to near/above normal Friday night through Sunday, then falling back to below normal Sunday night through Tuesday.

* Highest chance (slight) for precipitation will be Saturday night into Sunday.

Aloft, a s/w traversing the base of the longwave trough will move across the region on Thu, while the parent low tracks ewd across the Northeast US/srn Quebec. In the wake of the s/w, the flow will become gradually more zonal Thu night through Sat. A weak s/w disturbance may track across the mid-Atlantic late Fri/Fri night. The longwave trough will again amplify over the central CONUS Sat/Sat night as a low tracks esewd across Ontario and a nrn stream s/w tracks esewd from the nrn Rockies to the mid MS/OH Valley. As the low continues its ewd progression toward the Northeast US, the s/w will continue ewd across the Appalachians and mid-Atlantic on Sun, then offshore Sun night. The longwave trough will linger over the ern US on Mon, with another nrn stream s/w swinging through it and across the region Mon night/Tue. At the surface, high pressure will modify as it builds ewd across the region in the wake of the front Thu and Fri. Meanwhile, a low pressure system will develop off the central Rockies and move ewd across the Plains and into the mid MS Valley Thu and Fri. As the low moves east across the region, a warm front may lift across the area. A trailing, secondary low may track ewd or newd across the region along the front late Sat/Sat night, though the track and strength varies between the available guidance. Regardless, as the low moves out, the attendant cold front will quickly move across the area, with Arctic high pressure building in behind it. The center of the high will track east from the mid/upper MS Valley and across the OH Valley/Great Lakes Sun night-Tue.

Precipitation: There is a non-zero chance of rain perhaps clipping central NC counties along the VA border, but for now will keep the forecast dry. The better chance for rain will be Sat night/Sun, however chances are slight given the model variability, with a chance the rain could split central NC entirely (GFS).

Temperatures: Highs mainly in the 40s on Thu, with lows mainly in the mid to upper 20s. Some moderation could start Fri, with the potential for highs to reach low/mid 50s across the south. Sat and Sun will be the warmest days, with temps near to above normal. Temperatures will drop in the wake of the cold front, with a return to below normal for Sun night through Tue.

AVIATION /11Z TUESDAY THROUGH SATURDAY/

As of 600 AM Tuesday...

Dry low-level air advection from the north and increasing subsidence aloft should support a return to VFR condition from NE to SW through mid to late morning(still some uncertainty on the exact timing). Thereafter, expect periods of broken/overcast cirrus clouds, especially across the northern terminals.

Light northerly winds this morning will shift to SWLY into the afternoon. A 45-50 kt LLJ will result in a period of LLWS late tonight into early Wednesday.

Outlook: A 45-50 kt LLJ will result in a period of LLWS early Wednesday, followed by turbulent conditions Wednesday with frequent SWLY gusts of 25 to 35 mph. Otherwise, predominately VFR is expected through late week.

RAH WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 7 AM Monday to noon EST Tuesday for NCZ007>011-021>028-041>043.