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WHAT HAS CHANGED

As of 205 PM Thursday...

*An Extreme Cold Watch is in effect for all of central North Carolina from late Saturday night through Sunday morning. Wind chills could drop as low as 4 below zero, creating dangerous conditions for anyone outdoors. *Higher snowfall amounts trend slightly south, however accumulations of at least 2 inches areawide are possible with isolated areas of 6+ inches.

KEY MESSAGES

As of 205 PM Thursday...

1) A coastal low developing off the coast Friday into Saturday will bring a period of snow to central NC, with the higher totals trending farther south but still have the potential impacting accumulations.

2) A prolonged Arctic air mass will result in well below normal temperatures across central NC from today through much of next week.

DISCUSSION

As of 205 PM Thursday...

KEY MESSAGE 1...A coastal low developing off the coast Friday into Saturday will bring a period of snow to central NC, with the higher totals trending farther south but still have the potential impacting accumulations.

Model trends have shifted the upper-level low diving south from Canada on Friday slightly farther south of the region. This southward shift favors a corresponding southward adjustment in expected snowfall, with generally lower totals across central NC. Despite this, rapid cyclogenesis remains likely just off the Carolina coast, providing ample moisture to support snow showers across the area. With strong lift between the upper low and the developing surface low and very cold thermal profiles, snow-to- liquid ratios will be high, resulting in a dry, fluffy snow. The placement and timing of the deformation band remain uncertain, though recent trends suggest it could set up anywhere from near the US-1 corridor eastward into the Coastal Plain, possibly just outside the CWA. Snow totals will continue to vary until greater confidence is gained in when the upper low takes on a negative tilt and where the surface low ultimately developsboth key factors in the overall snowfall forecast, with cold air firmly in place.

Light snow may begin as early as Friday afternoon across the northwest Piedmont, gradually expanding west to east through Friday evening and night. Initial impacts may be limited, with more significant snowfall developing later Friday overnight as the upper low deepens and passes south of the area while the surface low strengthens just off the coast. Snowfall is expected to become more widespread and persistent on Saturday and Saturday night, with the heaviest snowfall currently favored across eastern portions of central NC Saturday afternoon into early evening. As the stacked lows pull offshore late Saturday night, snow will taper from west to east, ending first across the northwest Piedmont late overnight Saturday and then clearing the Coastal Plain shortly after sunrise Sunday. Strong cold advection will follow, with northwest wind gusts increasing to 2535 mph early Sunday morning, highest in the east. Snow totals are expected to range from around 2 inches area-wide to localized amounts of 6 inches or more, with blowing snow possible Saturday night into Sunday.

KEY MESSAGE 2...A prolonged Arctic air mass will result in well below normal temperatures across central NC from today through much of next week.

A strong Arctic high building down from south-central Canada into the Northern Plains and stretching into the Eastern US will result in continued very cold temperatures across central NC today and Friday. Forecast highs today range from lower-30s near the VA border to lower-40s in the far south, which is 12 to 18 degrees below normal. Tomorrow will be a couple degrees warmer on average in most locations, except still lower-30s in the far north. Lows tonight and tomorrow night will be in the mid-teens to lower-20s.

Temperatures will turn even colder this weekend as the coastal low that will bring a winter storm to our region reinforces the Arctic air mass with strong northerly flow. Forecast highs on Saturday are only in the lower-to-mid-20s in most locations (a whopping ~30 degrees below normal), with mid-20s to lower-30s on Sunday. Our current forecast has these highs getting close to or breaking the record daily low maximum temperatures on both dates at all three climate sites. See the climate section below for more details. Winds gusting up to 25-35 mph from Saturday through Sunday will keep wind chills from getting above the teens, potentially not getting out of the single digits across the north on Saturday. On Saturday night, lows in the lower-to-mid-teens will result in wind chills dropping as low as zero to 5 below zero. Thus an Extreme Cold Watch has been issued from late Saturday night through Sunday morning. Additional Cold Weather headlines may be needed on Sunday night when winds will be lighter but air temperatures should get lower (upper-single digits to lower-teens).

Very cold temperatures will continue behind the storm from Monday through Thursday, which will slow the melting process of whatever snow ends up accumulating this weekend, prolonging the travel impacts. One factor that will at least help with some snowmelt is the ample sunshine expected early next week. Forecast highs Monday are in the mid-to-upper-30s with lows in the mid-to-upper-teens. A slight modification is expected through midweek as the Arctic high weakens and moves to our south, but temperatures are still only expected to reach upper-30s to lower-40s on Tuesday and lower-to-mid- 40s on Wednesday and Thursday. Lows by Wednesday night will "only" drop into the 20s.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

As of 1220 PM Thursday...

TAF period: VFR conditions are expected through the next 24 hours. A veil of high clouds is currently over central North Carolina, and after those clouds move south, there should only be a short period of mostly clear skies before additional high clouds advect in from the northwest. While the wind this afternoon will primarily be out of the north-northwest, it should become light and variable overnight, then be light out of the east Friday morning.

Outlook: A strong winter storm is likely to form along the North Carolina coast this weekend, with widespread snow Friday night through Sunday morning at all terminals. IFR/MVFR restrictions are expected at all terminals, along with northwesterly gusts up to 30 kt. Snow will come to an end on Sunday, along with the wind subsiding Sunday night.

CLIMATE

Record Low Temperatures:

January 29: KGSO: -7/1940, KRDU: 7/2000, KFAY: 11/1986 January 30: KGSO: 4/1966, KRDU: 7/2014, KFAY: 8/2014 January 31: KGSO: 3/1966, KRDU: 3/1966, KFAY: 9/1934 February 1: KGSO: -4/1936, KRDU: 8/1981, KFAY: 1/1936 February 2: KGSO: 6/1971, KRDU: 5/1971, KFAY: 15/1971 February 3: KGSO: 7/1917, KRDU: 7/1980, KFAY: 10/1917 February 4: KGSO: 7/1996, KRDU: 7/1981, KFAY: 15/1980

Record Low Maximum Temperatures:

January 29: KGSO: 23/1966, KRDU: 27/2014, KFAY: 28/2014 January 30: KGSO: 13/1966, KRDU: 19/1966, KFAY: 29/1966 January 31: KGSO: 22/1936, KRDU: 27/1948, KFAY: 22/1966 February 1: KGSO: 27/1971, KRDU: 28/1900, KFAY: 32/1981 February 2: KGSO: 30/1951, KRDU: 31/1994, KFAY: 31/1948 February 3: KGSO: 23/1996, KRDU: 24/1996, KFAY: 30/1961 February 4: KGSO: 18/1996, KRDU: 19/1996, KFAY: 24/1996

RAH WATCHES/WARNINGS/ADVISORIES

Winter Storm Watch from Friday afternoon through Sunday afternoon for NCZ007>011-021>028-038>043-073>078-083>086-088-089. Extreme Cold Watch from late Saturday night through Sunday morning for NCZ007>011-021>028-038>043-073>078-083>086-088-089.