Lead Forecaster Daniel Crawley
Here we are in mid-January and for the Foothills and Western Piedmont we still have not seen any legitimate winter weather threats. Of course, the mountains cashed in this weekend as a moisture enhanced northwest flow event brought accumulating snow to a lot of areas above 2500 ft elevation and the highest mountain peaks received significantly more snow, measured in feet in a couple spots.
We have been fielding the questions lately from snow lover’s…Where’s it at and/or when it is coming? Unfortunately there is nothing in the short term that looks promising for our core area to receive accumulating winter precipitation.
We always start by looking at the global teleconnections to see if there are hints of favorable conditions for winter weather in the East or Southeast US. The Madden-Julian Oscillation is currently hovering just inside the null phase after spending a brief time in Phase 7/8. It is expected to remain in the null phase with brief ventures into Phase 1, 2 and eventually 3.
Quite honestly the MJO is not a dominate feature right now due to its generally weak presence and it hasn’t been so far this winter but the current forecast would suggest that extra upward motion (lift) is possible across North America over the next two weeks.
As we look at the teleconnections, we are not in a very favorable pattern right now. The late December cold blast was a scenario in which the pattern was overwhelmed with cold and therefor we had little potential to squeeze out a storm system.
The North Atlantic Oscillation (NAO) is slightly positive right now and will hover at or just above the neutral stage for the current forecast period and beyond. The NAO has taken on a strong negative phase at least once a month since October, however this month we have not seen that materialize. Strongly negative NAO, or as commonly known as the “Greenland Block” is a setup that can promote cold air southward into the United States.
Another teleconnection we closely monitor during the winter is the Pacific-North American Oscillation (PNA). That all relates to the height pattern along or just off the West Coast of North America. A “positive PNA” promotes tall ridging along the west coast which serves the purpose of allowing storm tracks to dig far south and to let cold air drain southeast into the Eastern US.
Meanwhile the negative phase allows a more zonal (west to east) flow to flood the Western US with mild and moist air. The bad news for Eastern US winter weather fanatics is the PNA is tanking in the wrong direction over the next 1-2 weeks.
Now that we have explained the teleconnections, let’s see if the actual weather maps fit the indicators on the teleconnections.
Over the next five days, strong zonal flow continues for the Western US, that brings additional moisture to places like California that has seen a lot of precipitation in recent times. The pattern also means fast changes nationwide as systems move in every 2-3 days.
Once we get toward the end of the current 7-Day forecast and into the long range, a few changes are happening. One in particular is that a ridge will begin to amplify but it will occur off the West Coast. That will push colder air into the United States but with the ridge in a less than optimal position, we are looking at least early on at the cold being focused more on the Plains and Texas rather than the Midwest/Ohio Valley/East Coast. You can see here on this anomaly map the pattern suggests a trough split where the cold air generally covers a landscape from the Four Corners States to the Northern Plains.
Once we get to the final week of January we still do not see much of a change. The 500 mb synoptics really fit the teleconnections of a (neutral NAO, negative PNA) pattern. Ridge off the West Coast continues, Southeast Ridge may flex its muscles and in-between a long positive tilt trough that would suggest an active storm track from the Southern Plains up into the Great Lakes Region.
So in conclusion, we see no teleconnections or synoptic setup that would enhance the chances of widespread winter weather across North Carolina through the last week of the month of January.
One thing we do see however is that the Eastern US will continue seeing consistent precipitation chances. The two week anomalies are for enhanced precip for nearly all of the Southeast which makes sense given the MJO and the synoptics.
If there is enough warm air in play, we could see more severe weather opportunities in the Southeast and there will be episodes of cold air damming as moisture overruns surface cold in the Western Carolinas