textproduct: Raleigh

WHAT HAS CHANGED

No major changes were made to the going forecast.

KEY MESSAGES

1) Light rain moving across through this evening, then a chance of a few pockets of light snow in the far NE overnight. Turning much colder with wind chills in the teens to 20s by Thu morning.

2) Below freezing wind chills Thursday into Friday morning and potential for adverse fire behavior Thursday afternoon.

3) A chance for light accumulating snow across central NC on Sunday, especially in the east. As was stated on the last shift, there is still plenty of uncertainty so it is too soon to get into details.

4) Saturday will be the only day with high temperatures around normal, the rest of the forecast calls for highs in the 30s and 40s.

DISCUSSION

KEY MESSAGE 1... Light rain moving across through this evening, then a chance of a few pockets of light snow in the far NE overnight. Turning much colder with wind chills in the teens to 20s by Thu morning.

A strong Arctic cold front presently draped from the Great Lakes into the Mid MS valley region will be moving through overnight tonight, roughly between 12 am and 5 am Thu. Ahead of the front, we will continue to see some periods of light rain track northeast across the region into early evening. The best chance of some measurable rain will be over the eastern Piedmont, Triangle, Sandhills, Fayetteville, and Coastal Plain of central NC. Rainfall amounts in most places will be a tenth of an inch or less, though the 12Z HREF suggests a few isolated spots could see up to two tenths over the Sandhills and Coastal Plain, along the I-95 corridor.

As the front approaches overnight tonight, temperatures will turn much colder from the mid 20s NW to low 30s SE. Wind gusts behind the front may reach speeds of 25 to 35 mph post-frontal, with wind chills by Thu morning in the teens to 20s.

As the front crosses the region, there will be a very narrow window of some light snow. The best chance of this will be northeast of the Triangle over the northern Coastal Plain, roughly from Rocky Mount to Roanoke Rapids to Scotland Neck. Forecast soundings show maybe a 1-2 hr window of this changeover, but this scenario typically does not favor a good chance given cold air chasing the exiting moisture. No impacts are expected, as the HREF 90th percentile shows little to no accumulation.

KEY MESSAGE 2... Below freezing wind chills Thursday into Friday morning and potential for adverse fire behavior Thursday afternoon.

A strong Arctic front will be pushing off the NC coast Thurs morning as a potent mid/upper trough pivots across the Carolinas. Abundant sunshine and strong/deep northwest flow should allow for a favorable downsloping, post-frontal regime to develop during the daylight hours Thurs. Compressional warming/drying east of the mountains should help raise temps into the mid 30s to low 40s and subsequently dry surface dew points into the single digits to near zero. This will result in dry relative humidity values between 20 and 30% overlapping sustained 15-20 mph northwest winds with gusts 20-30 mph; infrequent gusts of up to 40 mph appear possible in unsheltered locations, based on the 12z GFS BUFKIT soundings. Adverse fire behavior appears possible, but should be greatly limited by the cold temperatures and rainfall expected today.

Wind chills may struggle to get above freezing on Thurs, especially north of NC-64, with the gusty winds coupled with well below normal temperatures through the afternoon. The winds should substantially weaken after 10 PM. Winds becoming calm and abundant clear skies should support a short period of optimal radiational cooling and support temperatures falling into the teens to near 20 areawide, and wind chills reaching 10 to 20 degrees by Fri morning.

KEY MESSAGE 3... A chance for light accumulating snow across central NC on Sunday, especially in the east. As was stated on the last shift, there is still plenty of uncertainty so it is too soon to get into details.

A large upper level trough will be across the eastern third of the United States for the weekend into next week. As low pressure moves across the Great Lakes into eastern Canada on Saturday, a cold front will extend south and move across North Carolina. There will be minimal moisture along the front, and the heaviest precipitation chances/totals will remain to the north on Saturday. However, a coastal low is expected to develop off the North Carolina coast Saturday night into Sunday, and this will give the potential for snow as colder air moves into the region during that time period. Both the GFS and ECMWF signal that temperatures should be cold enough for at least some snowfall, although there are still wide variations in how much precipitation occurs and how far west precipitation extends from the coastal low.

KEY MESSAGE 4... Saturday will be the only day with high temperatures around normal, the rest of the forecast calls for highs in the 30s and 40s.

Normal high temperatures are in the low to mid 50s, but after today, Saturday is the only day with widespread highs in the 50s. A majority of days have highs in the 40s, and the forecast calls for widespread highs in the 30s on Sunday and Tuesday. As for low temperatures, Friday night will be the warmest night out of the next seven with highs around freezing, while Sunday, Monday, and Tuesday nights next week all show widespread lows around 20 degrees or slightly colder.

AVIATION /00Z THURSDAY THROUGH MONDAY/

As of 730 PM Wednesday...

VFR conditions are generally expected over the next 24 hours across central NC, but a period of brief MVFR cigs is possible tonight, mainly 01-05z at INT/GSO, 03z-07z at RDU, and 04z-08z at RWI/FAY, all associated with a strong Arctic cold front that will cross central NC tonight between 04z and 09z. Outside of this MVFR cloud deck potential, bkn-ovc VFR mid-high clouds are expected until frontal passage. With this frontal passage, winds will shift to be out of the WNW and NW, lasting through Thu. Sustained speeds of 12- 18 kts are expected, with gusts as high as 22-30 kts, strongest from mid morning Thu through the afternoon. Skies will clear out behind the front, with fair skies Thu, although sct-bkn clouds based at 5k- 7k ft AGL are possible late morning through late afternoon.

Looking beyond 00z Fri, VFR conditions will prevail through Sat, although with periods of mid and high clouds, and winds will be gusty once again during the daytime hours Fri and Sat, although not as blustery as on Thu. A storm system may bring a risk of sub-VFR conditions Saturday night through Sunday night with a chance for rain or snow, but confidence in the details is low. -GIH

RAH WATCHES/WARNINGS/ADVISORIES

None.