textproduct: Raleigh

WHAT HAS CHANGED

As of 309 AM Friday...

* We will be very cold and windy tonight and Saturday. We will be nearing Wind Advisory and Extreme Cold Advisories.

* High confidence in strong and potentially impactful wind gusts on Saturday.

KEY MESSAGES

As of 309 AM Friday...

1) Areas of patchy black ice possible this morning over the Triad region.

2) Strong and gusty winds are expected tonight into Saturday behind a cold frontal passage. A Wind Advisory may be needed, especially Saturday through mid-afternoon.

3) Cold Weather Advisories possible either tonight or Saturday. Arctic high pressure will build in over the weekend, with temperatures 10-20 degrees below normal Saturday and Sunday.

DISCUSSION

As of 309 AM Friday..

KEY MESSAGE 1... Areas of patchy black ice possible this morning over the Triad region.

The Special Weather Statement will be in effect through 1000 AM for the NW Piedmont Triad region. This is where snow/ice linger and areas of black ice are expected with temperatures in the 20s this morning. Highs will reach the 40s this afternoon helping the situation.

KEY MESSAGE 2... Strong and gusty winds are expected tonight into Saturday behind a cold frontal passage. A Wind Advisory may be needed, especially Saturday through mid-afternoon.

The arctic front will surge through the region this evening. It may be accompanied by scattered rain showers. These showers may be mixed with some light sleet or snow, especially over the northern Piedmont early this evening. No accumulations are expected.

More importantly, winds will shift to the NW at 15-25 mph behind the front, with gusts to 30-35 mph. These winds will drop off a bit an our or two after the fropa, then steadily increase again later tonight and especially with mixing early Saturday. Wind gusts may exceed 40 to 45 mph. Later data will be analyzed for a possible Wind Advisory.

Strong subsidence on the backside of the slowly departing trough axis late tonight and Saturday will result in mostly clear skies during the daylight hours and favor efficient momentum transfer through the boundary layer. Wind gusts should rapidly develop through the early morning hours as daytime heating mixes into the elevated mixed layer just above the surface from CAA behind the front. Widespread wind gusts of 25-35 kts should be expected with both NAM and GFS highlighting similar intensity averaged through the mixed layer. Clear skies and abundant insolation, should result in efficient momentum transfer from the top of the mixed layer and may result in infrequent gusts of 35-45kts, strongest from the mid- morning to early afternoon and across the nw/nrn Piedmont. The winds/gusts should decrease/abate Sat night as the high builds in and the pressure gradient from the surface to H85 relaxes.

KEY MESSAGE 3... Cold Weather Advisories possible either tonight or Saturday. Arctic high pressure will build in over the weekend, with temperatures 10-20 degrees below normal Saturday and Sunday.

A ~1034 mb Arctic high will track SSE from the upper MS Valley to the OH Valley, then continue ewd across the Great Lakes/OH Valley Sat/Sat night. The high will ridge esewd across the Appalachians and into the mid-Atlantic/Carolinas as it moves across the OH Valley, with nwly flow advecting Arctic air into the area.

Current projections indicate sub-10 degree wind chills later tonight and Saturday. If the winds are forecast to remain very strong and the temperatures dip a few more degrees from current forecasts, A Cold Weather Advisory may be needed. An Extreme Cold Warning may be needed for the far NW and N counties of the Piedmont in later forecasts.

Actual temperatures will fall into the 20s late tonight, highs Saturday only 30-39, and lows Saturday night in the teens. Sunday will be sunny and cold, with highs in the mid to upper 30s.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

As of 1245 AM Friday...

Generally VFR conditions are expected through late day. However, a strong cold front will bring strong and shifting winds late today and tonight as it surges through the region between 23z/today in the NW to 02z-03z tonight elsewhere. Wind gusts to 30-40kt will likely occur with the fropa, settling to 25-30kt overnight, then peaking again after sunrise Saturday in the 35-40kt range.

Outlook after 00z/Sun: Winds will diminish Saturday night and Sunday. VFR conditions expected this weekend into early next week.

RAH WATCHES/WARNINGS/ADVISORIES

None.