textproduct: Raleigh

WHAT HAS CHANGED

As of 235 PM Sunday...

* Minimal change to overall expectations, with a brief changeover to wet snow or a rain/snow mix in the NE CWA in late afternoon through mid evening, with a dusting to quarter inch expected, and a chance for up to a half inch. The risk of accumulating snow will be greatest along and NE of a Roxboro-to-Wilson line.

KEY MESSAGES

As of 235 PM Sunday...

1) Still expect rain to trend to a brief period of light snow or rain/snow mix in the NE CWA, mainly along and NE of a Roxboro-to- Wilson line, occurring between late afternoon and late evening, with a dusting to near a half inch possible. Brisk and gusty winds are likely from late this afternoon through Mon.

2) Temperatures gradually moderating this week. Temps above normal from Wednesday onward, with rain chances returning on Thursday.

DISCUSSION

As of 235 PM Sunday...

KEY MESSAGE 1... Still expect rain to trend to a brief period of light snow or rain/snow mix in the NE CWA, mainly along and NE of a Roxboro-to-Wilson line, occurring between late afternoon and late evening, with a dusting to near a half inch possible. Brisk and gusty winds are likely from late this afternoon through Mon.

Overview: The surface low that tracked E along the frontal zone over far S NC this morning and which was responsible in part for this morning's rain has moved to just off the NC Outer Banks, and has been followed by a period of drying aloft, noted on WV imagery, and a pause in the rain. But this short-lived relative precip lull is already giving way to rain blossoming over the Piedmont, a result of intensifying dynamic forcing for ascent associated with the incoming strong and negatively-tilting mid level shortwave trough. As the surface low quickly deepens just off the N NC / VA / Delmarva the rest of the afternoon through this evening, precip will expand and become more widespread esp over the N and E CWA, necessitating another peak in pops from late afternoon through mid evening.

Precip: The earlier rain generated wide-ranging amounts from a tenth inch or less in the far W and far SE, to a band of one-half to near one inch of liquid from near HBI to RDU to IXA. Rain will continue to overspread much of the area with the arrival of strong mid level DPVA and height falls and peak upper divergence, coinciding with an upturn in moisture through the low and mid levels. Surface dewpoints continue to fall as drier and colder surface air spreads in from the W and NW, but as the column cools aloft amidst the resurgence of forcing for ascent with steepening lapse rates, the surface wet bulb temps will drop through the 30s. According to the RAP-based analysis, the surface WBZ has already reached the NC Foothills and is quickly approaching the Triad. Much of the W Piedmont will see this colder air chasing the moisture, but in areas N and E of the Triangle, the overlap of lowering surface wet bulbs with sufficiently deep moisture (including up into the mixed-phase region) and max layer lift should support a change to a period of wet snow or a rain/snow mix, starting soon after 21z and expected to exit our NE counties by 03z. As has been noted in earlier discussions, the short window of wintry precip in any given area combined with recent warm ground temps should limit accumulation. But we may still see a short burst of higher snowfall rates, esp if any convective element is present (not out of the question given the rising lapse rates) and if our NE sections get on the tail end of banded precip. Still expect most areas will see a dusting to a quarter inch (the probabilities of a quarter inch or more are 30-45% NE of Oxford-to-Rocky Mount line) with isolated half inch totals possible (a 30-40% chance in parts of Granville, Vance, Warren, and Halifax counties). The threat of all precip is expected to be over by 06z/1 AM, with mostly clear skies thereafter but with continued brisk winds.

Winds: The cooling thermal column aloft and steepening lapse rates will increase the mixed layer depth and help mix down some of the stronger winds aloft, particularly after skies clear (and we're already seeing gusts up to 25-35 mph from the Foothills into the far W Piedmont). These conditions are expected to hold this evening through Mon, with sustained speeds of 15-20 mph and gusts up to 25- 35 mph common, and infrequent gusts of 35-40 mph possible, especially this evening and again mid morning to mid afternoon Mon. After consideration of a wind advisory, have decided to hold off for now given some uncertainty as to how much gustiness will persist during the nighttime hours when our surface-based stability should tick upward. But we may need a wind advisory for Mon, if later observations and model trends continue to support efficient downward momentum transfer with a very tight MSLP gradient as the surface low strengthens just off the Mid Atlantic coast. We'll also keep a close eye on fire weather concerns, given the gusty winds and the low RH in the 25-35% range, but this risk may be offset by the chilly temps, as highs should be no higher than the 40s Mon.

KEY MESSAGE 2... Temperatures gradually moderating this week. Temps above normal from Wednesday onward, with rain chances returning on Thursday.

Temps will remain below normal on Tuesday as weak northwesterly flow hangs on at the surface and aloft, however surface high pressure will slide offshore on Wednesday which will bring the return of above normal temperatures to the area. A weak clipper system will move through the Great Lakes into the Mid Atlantic on Wednesday but should be far enough to preclude any precip chances across the area. As such, temps should easily climb into the upper 50s/lower 60s Wednesday afternoon within a broad WAA regime.

Meanwhile, a deepening wave over the central Plains will move through the Ohio Valley and into the Southeast on Thursday. A period of weak WAA-driven precip is possible early Thursday as a warm front retreats northward into VA, with additional precip focused along a cold frontal passage late Thursday into Friday morning. There is generally good agreement among today's ensemble clusters on the placement of these features along with the idea that precip chances will increase through the day Thursday, although some timing differences remain with respect to when precip will arrive. For the time being we'll bring PoPs in early Thursday and carry them through Friday morning (sticking close to the ensemble consensus), although some of the recent deterministic solutions keep Thursday mostly dry with the warm frontal precip focused mainly to our north. Either way, it should be more than warm enough to support all rain with this event, with precip timing of arrival/departure the biggest source of uncertainty during this period.

Highs Thursday through the weekend reaching the upper 50s (NW) to mid 60s (SE). Overnight lows above freezing with lows in the mid 30s to mid 40s.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

As of 1235 PM Sunday...

TAF period: The greatest impact in the TAFs over the next 24 hours will likely come from the wind. As a surface low off the coast continues to strengthen, this will increase the pressure gradient across North Carolina, resulting in increased sustained wind and wind gusts. While gusts this afternoon will be around 20 kt, all sites are likely to approach or exceed 30 kt through much of the overnight hours, dropping to 20-30 kt Monday morning. The wind will begin out of the north-northwest, eventually backing to the west Monday morning.

From a ceiling/visibility perspective, no restrictions are expected at INT/GSO. Farther to the east, MVFR ceilings should remain into the evening hours before eventually scattering out with only VFR clouds remaining. An upper level low will provide another round of precipitation this afternoon. Have backed FAY off from prevailing rain to VCSH with much of the coverage expected to remain to the north, while continuing prevailing rain at RDU/RWI. Cannot rule out some flurries mixing in at the end at RDU, but RWI remains the most likely terminal to receive any snow along with IFR restrictions.

Outlook: Wind gusts up to 30 kt will continue Monday afternoon. Dry VFR conditions are in the forecast through Wednesday night, then rain is expected Thursday and Thursday night at all terminals with ceiling restrictions possible.

RAH WATCHES/WARNINGS/ADVISORIES

None.