textproduct: Raleigh

WHAT HAS CHANGED

As of 245 PM Sunday...

* Storm total liquid equivalent precipitation amounts continue to trend lower, but overall winter storm impacts will still be significant.

* Temperatures have been slow to rise during the day, decreasing confidence in how far nw the rise above freezing will occur. Highest confidence across the Sandhills and Coastal Plain, with greater uncertainty across the Piedmont.

KEY MESSAGES

As of 245 PM Sunday...

1) Winter storm underway, with Moderate to Major impacts occurring and/or expected across central NC through tonight.

2) An extended period of bitter cold temperatures into next weekend

3) A few periods where light snow could occur, but confidence remains low

DISCUSSION

As of 245 PM Sunday...

KEY MESSAGE 1...Winter storm underway, with Moderate to Major impacts occurring and/or expected across central NC through tonight.

The 18Z surface analysis shows the CAD firmly in place, with the Arctic high over se Quebec, having weakened to 1035 mb, continuing to ridge sswwd across the mid-Atlantic and Carolinas. The coastal low has progressed nwd to near the southern tip of the DELMARVA peninsula, while the other lows were located over cntl AL and ern KY. The Arctic high should continue to weaken and migrate nnewd this evening, while the coastal low lifts northward and deepens off the NJ/NY coast. A segment of the ridge may break off and remain over a portion of the NC Piedmont through this evening as the low over AL tracks ewd across the Southeast US before lifting newd along the wedge boundary this eve/tonight. It remains unclear if the wedge will ever fully erode tonight. It should at least gradually weaken and allow for some increase in temperatures, however slow or little, as the nely flow and associated feed of cold and dry advection weakens, with increasingly divergent flow in the CAD layer this afternoon-evening, between the coastal low and the inland low over KY tracking along an inverted trough west of the Appalachians.

From the 18Z GSO sounding, the warm nose has increased to 11C at H85, with the cold nose now -12C. RAP forecast soundings, which are closest to the observed at GSO, suggest GSO will remain well below 0 C at the surface through tonight, and RDU may not quite make it above 0 C tonight. However, FAY should rise above and RWI should but will be closer than FAY.

Despite the relative lull in overall precipitation and accumulations this afternoon (there is still some patchy intermittent fzdz/sleet occurring), one more round of precipitation, mainly freezing rain or rain, will move across central NC from W-E this evening and tonight. Overall liquid equivalent totals have trended downward, as earlier amounts were a bit less than expected. However, the bulk of the precipitation is still expected this eve/tonight. In addition to the p-type issues highlighted in the previous discussion, the air temperature trend today has been much lower, with very little if any upward movement through 18Z across the Piedmont. So, while the wet bulb zero line is still expected to retreat nwwd across the area this aft/eve, the slower erosion of the CAD could limit how far. Additionally, the precip rates with this next band are expected to be heavier and perhaps a bit quicker-hitting than the preceding precip and heavier rates of fzra generally accumulate less efficiently. All that said, there is still the potential for an additional 0.1-0.3" of ice accumulation where temperatures remain at or below 32F, but exactly how much will depend on the temps, rates, and duration at any given location. This additional freezing rain will continue the likelihood for significant icing, power outages, and hazardous travel. The most likely locations to change to rain and thus have lower if any additional ice accumulation will be across the Advisory area. Both Warning areas still have the potential for additional icing/impacts and will remain as is for now, but may be canceled from W-E overnight as the storm comes to an end.

KEY MESSAGE 2...An extended period of bitter cold temperatures into next weekend

A few Arctic fronts will bring reinforcing cold air to central NC over the next week. As very cold high pressure builds in Monday after the first cold frontal passage, an Extreme Cold Watch or Cold Weather Advisory may be needed for Monday night into Tuesday morning, as lows are forecast to drop into the single digits in the north/northwest and into the teens elsewhere. Additionally, sub-zero wind chills are likely in the coldest spots. Low temperatures look to stay in the teens to low 20s Tuesday and Wednesday nights, before cooling down further after the next Arctic front Thursday. Therefore, additional cold weather products may be needed again at the end of the work week.

In terms of high temperatures, Monday through Wednesday look to be generally in the low 30s to low 40s, dropping into the upper 20s to mid/upper 30s Thursday through Saturday after the next blast of cold air.

KEY MESSAGE 3...A few chances for light snow are possible Wed and Sat, but confidence remains low

The next chance of precipitation looks to return on Thursday with the next Arctic front. Chances appear limited as the cluster analysis from the 00Z LREF only has 1 of 4 clusters showing snow reaching into central NC. Therefore, there is currently a slight chance of snow in our northeast counties.

Next weekend, another system may form over the east coast, bringing another chance of snow. Models vary greatly in the timing and strength of the trough and whether a low is able to form or not. While ensemble data and cluster solutions are showing that snow may be possible Saturday and Sunday, confidence remains low at this time.

AVIATION /18Z SUNDAY THROUGH THURSDAY/

As of 205 PM Sunday...

Widespread IFR to LIFR conditions in fog and spotty light wintry precipitation are noted across central NC this afternoon. Much of central NC is in a lull of precipitation early this afternoon. Temperatures are still below freezing across the area and where any prediction is occurring the predominate precipitation type is light freezing rain and freezing mist along with some sleet in the northern Piedmont.

Another round of 3 to 5 hours of precipitation will push from west to east across central NC late this afternoon and evening with light to moderate intensity precipitation either in the form of rain across southern and southeastern areas including KFAY and freezing rain, freezing rain in the Triad including KINT and KGSO and a mix of freezing rain and rain in the Triangle and northern Coastal Plain including KRDU and KRWI. The precipitation should spread across KINT and KGSO between 21 and 02Z, KRDU between 22 and 02Z and KRWI and KFAY between 23 and 03Z. There is a limited threat of the a enhanced wind gust with the line but given the stable airmass at the surface this should be limited.

LLWS is developing across the area this afternoon and will continue into the evening before fading around 06Z. Lingering moisture may produce areas of fog, -DZ and -FZDZ at all TAF sites for a few hours later tonight. Winds will shift to northwest toward daybreak and then become gusty up to 16 or 18 kts during Monday morning. Ceiling restrictions will given way to VFR conditions from west to east from around daybreak to mid morning.

Outlook: Generally fair but cold conditions are expected during the outlook period. A system will move across the area on Thursday and could bring some scattered snow showers but confidence is low and any adverse aviation impact appears limited. -Blaes

CLIMATE

Record Low Maximum Temperatures:

January 25: KGSO: 23/1940 KRDU: 28/2013

January 29: KRDU: 27/2014

Record Low Temperatures:

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

January 30: KGSO: 4/1966 KRDU: 7/2014

RAH WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning until 1 PM EST Monday for NCZ007-021>024- 038-039. Winter Storm Warning until 1 PM EST Monday for NCZ008>011- 025>028-040>043-073>077-083>086. Winter Weather Advisory until 1 PM EST Monday for NCZ078-088- 089.