textproduct: Raleigh

WHAT HAS CHANGED

Models have trended toward a cyclone forming at some distance offshore the Carolinas on Sunday. This could result in some light accumulating snow, but still plenty of divergence in guidance so confidence is low at this time.

KEY MESSAGES

1) Mild with a chance of showers today. A slight chance of showers tonight with the frontal passage. Turning breezy and colder overnight with little if any light snow shower chance. No impacts expected.

2) Very cold temperatures Thursday and Thursday night, some moderating Friday. Dry.

3) There is a chance for light accumulating snow across central NC on Sunday, especially east. Still plenty of uncertainty so too soon to get into any details at this time, but it warrants watching.

4) Below to well below normal temperatures return Saturday night through Tuesday, but the timing of the coldest air early next week remains uncertain.

DISCUSSION

KEY MESSAGE 1: Mild with a chance of showers today. A slight chance of showers tonight with the frontal passage. Turning breezy and colder overnight with little if any light snow shower chance. No impacts expected.

SW flow ahead of the approaching trough/cold front will keep it mild today. There will be a chance of showers later this morning into the afternoon in the mild air ahead of the cold front. QPF will be so light - most likely less than 0.1 today, trace amounts tonight.

The strong cold front will arrive tonight. The low to mid level flow shifts to the west and drier air sweeps into the region. There may be a brief shower with the fropa, but it would be very light. The chance of a brief light snow shower or flurry is possible late tonight, but only in a narrow widow of opportunity just behind the front. No accumulations or impacts are expected. Highs today will be 50s. Temperatures will crash later tonight into the mid 20s to mid 30s NW to SE. Breezy NW winds will bring wind chills down into the teens and 20s at the bus stop Thursday AM.

KEY MESSAGE 2: Very cold temperatures Thursday and Thursday night, some moderating Friday. Dry.

Very cold temperatures expected Thursday and Thursday night. The arctic high will build in on Thursday with continued CAA. Adverse fire behavior should not be an issue due to the cold and the relative humidities generally 25-35 percent at the minimums.

Highs will range from freezing NW into the lower 40s SE. Wind chills in the teens/20s through the day.

Lows Thursday night in the teens to lower 20s with diminishing wind as the higher pressure builds overhead.

KEY MESSAGE 3: There is a chance for light accumulating snow across central NC on Sunday, especially east. Still plenty of uncertainty so too soon to get into any details at this time, but it warrants watching.

Within broad mid/upper troughing over the Eastern US, a shortwave will move NE across the OH Valley on Saturday as the prefrontal surface trough crosses central NC. This may result in some light rain, mainly north, but POPs are only slight at this time. Behind a cold frontal passage on Saturday night, the 00z GFS and ECMWF depict a more vigorous shortwave that swings across the Southeast US and Carolinas on Sunday, with a surface cyclone that develops off the coast of the Carolinas and moves NE. With very cold temperatures aloft by this point (and Sunday's surface temperatures staying in the 30s at least based on the latest raw guidance), any precipitation that falls over central NC is likely to be snow, but the question is how much precipitation (if any) we actually receive. The GFS is sharper with the trough aloft compared to the ECMWF, resulting in snow across a larger portion of the area compared to the ECMWF which is more focused in the east. Regardless, considering nearly half of ECMWF ensembles and over half of GFS ensembles depict accumulating snow across the area, it bears watching. WPC QPF is light at this time but could increase if models converge on a surface low track closer to the coast.

KEY MESSAGE 4: Below to well below normal temperatures return Saturday night through Tuesday, but the timing of the coldest air early next week remains uncertain.

The below to well below normal temperatures should return Saturday night/Sunday and continue through early next week. However, there continues to be plenty of model variability with the timing of the coldest air early next week, as the 00z GFS brings the Arctic High through the area on Monday while the 00z ECMWF doesn't bring it through until Tuesday.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

As of 145 AM Wednesday...

VFR conditions are likely to hold at central NC terminals over the next 12 hours, although there is a good chance for low-end low level wind shear early in the forecast period, primarily through 09z this morning.

Looking beyond 00z Thu, generally VFR CIGS can be expected with a few MVFR CIGS possible with the passage of the cold front Wednesday night. The front should move through the central NC terminals between 03z and 10z/15th, moving NW to SE.

Gusty SW winds will shift to be from the NW with frontal passage. A brief light shower is possible, but nothing really significant. Winds up to 15-25 mph are likely mainly during the daylight hours Thu, Fri, and again Sat, with LLWS possible Fri night/early Sat.

RAH WATCHES/WARNINGS/ADVISORIES

None.