textproduct: Raleigh

WHAT HAS CHANGED

As of 400 AM Monday...

* Areas of freezing drizzle and freezing fog may result in additional, very light ice accrual over the nrn Piedmont this morning.

* A Cold Weather Advisory has been issued for all of cntl NC for tonight through Mon morning.

* While confidence is increasing for coastal cyclogenesis along the East Coast this weekend, there remains uncertainty in the degree of associated impacts to cntl NC.

KEY MESSAGES

As of 400 AM Monday...

1) Areas of freezing drizzle and freezing fog may result in additional, very light ice accrual over the nrn Piedmont this morning. Hazardous travel and a risk of power outages will otherwise remain, at least until clearing skies and insolation later this morning-midday increase melting.

2) Dangerously cold conditions return tonight, accompanied by continued hazardous travel, as remaining snow/sleet/ice cover freeze solidly.

3) Continued bitter cold and dry through mid to late week.

4) A few chances for snow are possible Thursday and Saturday, but confidence remains low at this time.

DISCUSSION

As of 400 AM Monday...

KEY MESSAGES 1 and 2...

A combination of a saturated, in-situ damming airmass, and also lift accompanying a couple of approaching, positively-tilted troughs aloft, will maintain cloudy or mostly so conditions that will clear from west to east throughout the morning, to midday-early afternoon in the Coastal Plain. Patchy to areas of freezing drizzle and freezing fog will be possible within that in-situ damming airmass over the nrn Piedmont. RDU reported a couple of hundredths of additional ice from that freezing drizzle between 07-09Z. However, the freezing/melting line has retreated nwwd to an arc from near VUJ to RDU to ETC, and some additional nwwd retreat will likely result into the nrn Piedmont and nrn Coastal Plain this morning, which may initiate some melting. However, it will not be until the aforementioned clearing, and associated insolation, develop ewd and yield more significant melting later today.

Clearing of the low-levels will come courtesy of the passage of a cold front now working its way into-through the NC Blue Ridge. Developing and strengthening nwly winds behind that front, and with associated mixing/deepening of the boundary layer, will result in gusts between 20-30 mph, which may increase power outage potential while the aforementioned melting otherwise lessens that risk.

CAA today may be offset to some degree by downslope/compressional heating, with highs likely to range from lwr 30s across the nw Piedmont to lwr 40s across srn/sern zones. Temperatures will turn sharply colder tonight amid continued CAA that may lessen late and allow for areas of brief calm over the srn/wrn Piedmont around sunrise Mon. Low temperatures in the single digits above zero across the nrn Piedmont and nrn Coastal Plain will range to lwr-mid teens across srn zones. When combined with nwly winds that will be strongest both this evening and then again with mixing right after sunrise Tue, wind chill values mostly in the single digits above zero, to five below at times across the nw Piedmont will result. Those dangerously cold temperatures will also cause remaining snow/sleet/ice cover to freeze solidly tonight; and a Winter Weather Advisory will probably be needed.

KEY MESSAGE 3...

A short-wave will dive through the deep south on Wednesday while a re-enforcing high builds across the Ohio Valley. This synoptic setup, combined with likely some lingering snow/sleet pack on the ground will promote the continuation of well below normal temperatures. Highs on Wednesday and Thursday will generally range in the lower 30s across the north to around 40 at the NC/SC border. A series of short-waves will dive across the Mid-Atlantic and Deep South on Wednesday/Thursday. An associated sfc front will turn flow nwly Thursday into Friday which will promote a bit cooler highs in the upper 20s across the north to mid 30s across the south. Temps remain chilly Saturday with perhaps a warming trend into the early next week. Lows over this timeframe will dip into the upper single digits across the north to mid to upper teens across the south. Cold Weather Advisory criteria may be reached a few of these nights over portions of our area especially Friday and Saturday nights.

KEY MESSAGE 4...

The aforementioned mid-Atlantic short-wave early Thursday is likely to generate upslope snow over the Blue Ridge mountains. A few isolated models previously indicated the potential for some light snow in our northwest early Thursday. However, latest 00Z guidance and forecast point soundings are less supportive of snow Thursday in our area. Soundings indicate shallow saturation through the depth of the atmosphere, and perhaps not even reaching the dendritic growth zone. Given the nw flow and little moisture to play with, think the trend towards upslope snow isolated over the Blue Ridge mountains seems likely.

For Saturday, the latest 00Z guidance (including the GFS, ECMWF, their ensembles, and various AI-based output) is maybe trending towards some snow potential for our area. In general, most guidance depicts a strong northern stream trough digging south across the Great Lakes Friday and merging with a southern stream jet somewhere over the Deep South/Southeast Saturday. Additionally, while previous runs of the GFS/Euro/Canadian were each waffling back and forth between no coastal low and a definite coastal low, virtually all of these models are now depicting some sort of offshore cyclogenesis. Still a bit far out to talk in absolutes, but the synoptic setup may indeed be favorable for snow for our CWA. We'll see how the guidance trends wrt to handling the upper and lower level waves this week, and if a favorable setup for snow to spread inland over central NC unfolds, or if instead the Mid-Atlantic/New England region trends more favorable.

AVIATION /06Z MONDAY THROUGH THURSDAY/

As of 134 AM Monday...

A mix of mostly rain with some fleeting freezing rain continues at KFAY this morning. Some lingering drizzle is possible at KRDU and KRWI the next several hours as well. However, in all, the precipitation should continue to exit to our east through about sunrise Monday morning. Ceilings will slowly lift to VFR from west to east by mid to late Monday morning as a cold front moves through. Expect winds to turn wnwly and gust into the 15 to 25 kt range behind the front Monday afternoon and evening. Forecast soundings support the potential for periods of 15 to 20 kt gusts through 06Z.

Outlook: Generally VFR conditions are expected during the outlook period.

CLIMATE

Record Low Maximum Temperatures:

January 31: KRDU: 27/1948

Record Low Temperatures:

January 27: KRDU: 8/1940 KFAY: 11/1940

January 31: KGSO: 3/1966

February 1: KRDU: 8/1981

RAH WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning until 1 PM EST this afternoon for NCZ007>011- 021>028-038>043-073>077-083>086. Cold Weather Advisory from 7 PM this evening to 10 AM EST Tuesday for NCZ007>011-021>028-038>041-043. Cold Weather Advisory from 9 PM this evening to 10 AM EST Tuesday for NCZ042-073>078-083>086-088-089. Winter Weather Advisory until 1 PM EST this afternoon for NCZ078-088- 089.