textproduct: Raleigh

WHAT HAS CHANGED

As of 200 PM Monday...

* Will issue an Special Weather Statement for tricky and slippery travel conditions tonight.

* Concern for the potential of a coastal winter storm this weekend continues to increase. It is still too early to settle on the sensible weather details and associated impacts to cntl NC.

KEY MESSAGES

As of 205 PM Monday...

1) Dangerously cold conditions are expected tonight with lows ranging from around 5 to 15 degrees with minimum wind chill values in the single digits, to possibly below zero at times.

2) Cold temperatures tonight will promote the refreezing of residual moisture and slush on area roadways and walkways and result in slippery and rapidly changing traveling conditions.

3) Another cold airmass will build into the region during the mid to late week with well below normal temperatures each day. Morning wind chills each morning may fall into the single digits across many areas for Thursday into the weekend.

4) The potential development of coastal low during the weekend could bring some wintry precipitation to central NC, but impacts remain highly uncertain with the system still 56 days out.

DISCUSSION

As of 205 PM Monday...

KEY MESSAGE 1...Dangerously cold conditions are expected tonight with lows ranging from around 5 to 15 degrees with minimum wind chill values in the single digits, to possibly below zero at times.

* Cold Weather Advisory in effect from this evening through mid morning Tuesday.

Cold Arctic air will surge into central NC tonight as a 1036mb surface high centered over the Deep South slips east. The associated airmass with consensus 1000-850mb thickness values ranging in the lower to mid 1050s. Any lingering strato-cumulus clouds should largely dissipate this evening resulting in clear skies. The gusty northwest winds this afternoon and evening promoting vigorous CAA will continue into the overnight before relaxing after midnight. Forecast soundings support this pattern noting the boundary layer will stay mixed in most spots through the early morning hours with a tendency of winds relaxing and trending toward calm toward daybreak. This will be critical in determining how cold we get and how many locations will fall into the single digits. Not surprisngly NWP guidance varies with low temperatures tonight as factors such as the winds and possible snow cover drive differences. Have opted to steer lows away from the coldest options such as the ENS as I have some doubts that winds will totally slack off and I have some concern about the degree of snow/ice cover present and how NWP is interpreting it. Still, lows tonight will range from 5 to 10 in the Triad and VA border counties, the lower teens in the Triangle and Piedmont and the mid teens in the Sandhills. These temperatures when combined with northwesterly winds that will be strongest both this evening and then again with mixing right after sunrise, will support wind chill values mostly in the single digits above zero with readings of five below possible at times across the Northwest Piedmont.

KEY MESSAGE 2...Cold temperatures tonight will promote the refreezing of residual moisture and slush on area roadways and walkways and result in slippery and rapidly changing traveling conditions.

Temperatures will quickly fall below freezing this evening and with the arrival of darkness, the refreezing of residual moisture and slush on area roadways and walkways and result in slippery and rapidly changing traveling conditions. Will highlight the concern in a Special Weather Statement.

KEY MESSAGE 3... Another cold airmass will build into the region during the mid to late week with well below normal temperatures each day. Morning wind chills each morning may fall into the single digits across many areas for Thursday into the weekend.

A dry cold front will move across the region Thursday, ushering in another round of bitterly cold air. High temperatures will steadily trend lower through the weekend as a strong Canadian surface high builds southward into the Midwest and then eastward into the Mid- Atlantic, allowing cold air to continuously filter into the area. Temperatures are expected to be well below normal and approach climate records at times (see Climate section). Highs Thursday and Friday will range from the upper 30s to near 40 across the southern portions of the area, with overnight lows dropping into the teens and morning wind chills in the single digits. As the surface high shifts east into the Mississippi Valley, cold advection will persist, with highs over the weekend ranging from the mid to upper 20s on Saturday to the low to mid 30s on Sunday. Overnight lows will fall into the 1015 degree range, with wind chills near or below zero in some locations.

KEY MESSAGE 4... The potential development of coastal low during the weekend could bring some wintry precipitation to central NC, but impacts remain highly uncertain with the system still 56 days out.

Model guidance continues to indicate that an upper level trough digs across the Ohio valley and Mid-Atlantic late week into the weekend with some degree of offshore cyclogenesis along the Southeast coast. Recent runs of the GFS, ECMWF, their ensembles generally show a wave or low pressure development off the Mid- Atlantic coast, possibly spreading precipitation across central NC. However, significant uncertainty remains regarding the strength of the offshore system and more importantly, how close it tracks to the coast, which will ultimately determine whether the impacts remain offshore or spread inland. While the synoptic pattern suggests the potential for wintry precipitation across central NC, this system is still 56 days out, and run-to-run model variability is expected over the next few days. Forecast confidence remains very low at this time.

AVIATION /18Z MONDAY THROUGH FRIDAY/

As of 1217 PM Monday...

Much drier air continues to work in from the west this afternoon with VFR conditions already taking hold over central NC. VFR weather will extend through the entirety of the TAF period. Gusty northwest winds around 25-30 kts are possible area-wide through 00Z, then gradually becoming calm by 06Z.

Outlook: VFR weather anticipated through Friday,

CLIMATE

Record Low Temperatures:

January 26: KGSO: 3/1940, KRDU: 10/1940, KFAY: 14/1963 January 27: KGSO: -7/1940, KRDU: 8/1940, KFAY: 11/1940 January 28: KGSO: -2/1940, KRDU: 1/2000, KFAY: 10/1935 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

Record Low Maximum Temperatures:

January 26: KGSO: 22/1961, KRDU: 24/1961, KFAY: 29/2004 January 27: KGSO: 22/1940, KRDU: 25/1940, KFAY: 28/1940 January 28: KGSO: 23/1986, KRDU: 23/1897, KFAY: 32/1961 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

RAH WATCHES/WARNINGS/ADVISORIES

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.