textproduct: Raleigh

SYNOPSIS

Arctic high pressure will ridge into the area from the north today as an area of low pressure tracks northeastward across the Southeast US and off the Carolina coast. The low will continue east over the Atlantic tonight, with weak high pressure settling over the region through the weekend. A mostly dry Arctic cold front will move through on Monday.

NEAR TERM /THROUGH TONIGHT/

As of 230 AM Thursday...

* Winter Weather Advisory in effect through noon today for portions of the northern Piedmont and northern Coastal Plain of central NC. Up to an inch of snow accumulation is possible, highest along the immediate NC/VA border, with lesser amounts south.

* Snow or sleet may briefly mix with rain along and south of I-85, no accumulation is expected and rain should be the dominant p-type.

Overview: Aloft, a pair of s/w disturbances embedded within the longwave trough extending from TX to the Southeast US will track enewd into and across the region through today, then continue offshore this eve/tonight. At the surface, the cold front has moved south of the area, while the 1020mb Arctic high was centered over ern NY as of 06Z, ridging sswwd across the mid-Atlantic in the wake of the front. The surface low was analyzed near the AL/FL panhandle, the frontal zone draped to the southwest and an inverted trough extending newd along the wrn Appalachians. The ridge should continue to amplify as it build into central NC this morning, while the surface low drifts slowly ewd along the Gulf Coast. A secondary coastal low should develop along the cold front, within a strengthening inverted trough off the Southeast US coast this morning, then deepen as it lifts newd offshore today and tonight.

Precipitation: The shield of stratiform rain associated with warm advection aloft should continue through this morning. While mostly rain, some places have had a mix of rain and sleet, but with the weaker ridge and later arrival of cold air, the extent of potential wintry precip has trended downward. Point soundings from the RAP and NAM along the NC/VA border still show saturation in the dendritic growth zone, with thermal profiles most supportive of rain changing to a mix of sleet and snow this morning. However, with the mix of sleet and a shorter expected duration , expected accumulations have also decreased. The thermal profiles become even less supportive of wintry precipitation with southward extent, with all rain expected south of I-85. Along I-85 from the Triad to the Triangle, wintry precip is looking less likely and while there could be some snow or sleet mixing with rain, latest point soundings indicate rain as the dominant p-type and little to no non-liquid accumulation. Locations where snow/sleet does occur should see a transition to all rain later this morning. The rain should then come to an end from NW to SE through the afternoon, possibly lingering over the far south or southeast into tonight. With all of the above in mind, have amended the advisory to end at noon instead of midnight. There is still enough uncertainty to not trim back the areal extent of the advisory at this time, however the advisory counties not touching the VA border may be trimmed prior to daybreak if snow does not materialize.

Temperatures: Lows this morning should range from low 30s along the VA border, to low 40s along the SC border. Highs still expected to be well below normal, ranging from mid 30s north to mid 40s south. Lows tonight expected to be in the upper 20s to mid 30s.

LONG TERM /SATURDAY AND SATURDAY NIGHT/

As of 100 AM Friday...

* Rain chances in the far SE, mainly Sat afternoon, and continued chilly.

The frontal zone will hold SE of the area Sat, with weak high pressure sitting over the Carolinas. As we'll stay within a fast WSW mid level flow, the potential remains that subtle and hard-to-time perturbations will ride within this flow over SC and SE NC Sat/Sat night. There remains some model agreement on the right entrance region of the upper jet scraping across NC Sat afternoon, yielding associated enhanced upper divergence and resulting in a brief northwestward bump in the NW edge of the precip shield Sat afternoon. But the overall forcing for ascent appears to be modest and fleeting and focused on the far SE CWA, with the bulk of the moisture restricted to the mid and upper levels, as the opportunity for moisture return in the low levels is lacking. As such, expect the chance for any rain to be largely confined to areas well SE of the Triangle, with light amounts overall, and pops tapering down and out toward midnight. Clouds should be largely overcast, especially over the S and E sections, and this low insolation will result in chilly highs in the mid 40s to around 50, followed by lows in the mid 20s to mid 30s. -GIH

LONG TERM /SUNDAY THROUGH THURSDAY/

As of 100 AM Friday...

* Chilly, below-normal temperatures to persist next week.

* Precip chances decreasing late Sunday into Monday.

A central to eastern U.S. mean upper trough(with 500 MB heights ~2 S.D. below normal) and broad cyclonic flow will dominate this period- -supporting persistent chilly, below-normal temperatures over central NC.

The reinforcing cold air behind a cold frontal passage Monday will make Monday and Tuesday the coldest day of the stretch. Expect high temperatures in the lower to mid 40s, while overnight lows Monday night could dip down into the lower to mid 20s, with some of the colder, more sheltered locales perhaps reaching upper teens. Wednesday may see only gradual moderation, but temperatures should still remain below normal through mid week.

Sunday should begin mostly dry across the area, with steadier rain and better precipitation chances suppressed to the south along a stalled frontal zone lingering across the SE US. However, weak cyclogenesis along the stalled boundary late Sunday-developing in response to a northern stream shortwave trough and approaching strong cold front--may allow a slight northward buckling of deeper moisture and light precip back into the area Sunday evening and into the day on Monday. That said, models indicate less phasing between these systems resulting in a drier trend across central NC during this period, with primary precip-type expected to be rain.

Dry conditions are expected to return Tuesday and Wednesday with a moisture-starved clipper trough brushing the area late Wednesday into Thursday.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

As of 1140 PM Thursday...

Precipitation has spread across the terminals, most notable at the northern sites of GSO, INT, RDU, and RWI. Thermal profiles and ground truth observations suggest that with the lighter radar returns, a mixture of sleet and rain is expected, with the exception of FAY, which will be all rain for the event. A mixture of snow and sleet is favored to develop over GSO, INT, and possibly briefly at RDU, between roughly 08z and 14z, most favored over the Triad terminals. Thereafter, forecast soundings indicate that thermal profiles favor rain and drizzle. Rain should taper off between 18 and 21z, latest at FAY. Aviation specific, flight conditions will deteriorate to IFR/MVFR with the onset of precipitation, with a good likelihood of LIFR after precipitation tapers off. IFR visibilities are most favored at GSO/INT in potential light snow early Fri. There is the potential for fog, mainly across the northern terminals late Fri night, especially at GSO/INT, but confidence was too low to include in the TAF at this time.

Outlook: IFR/LIFR conditions may persist into Sat with some improvement possible in the afternoon Sat. Dependent on the degree of clearing, a redevelopment of sub-VFR fog and stratus will be possible Sat night into Sun morning ahead of our next weather system Sun into early Mon. A strong Arctic front will scour out the lingering sub-VFR conditions and may bring gusty northerly winds Mon.

RAH WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until noon EST today for NCZ007>011- 021>025.