MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Eastern Two-Thirds Of U.S. Slowly Emerge From The Cold….
While still what could be called a rather chilly scenario, it seems that with no true high-latitude blocking nearby, a gradual moderation trend will set in across the Midwest and Eastern Seaboard by late week. Note that the European model has backed away from its earlier predictions of a cAk vortex passing through Ontario, Quebec and New England. Once a storm threat eases by next weekend, near-normal temperatures are possible along the Gulf Coast into Georgia and the Carolinas.
….But The Forecast For The West And South Is Complicated By Active Southern Branch Storm Track
Plymouth State University Weather Server (3)
There are inconsistencies among the numerical models, but it sees probable that a new storm will take shape along the Texas Gulf Coast around January 8. The strengthening of the heat ridge complex over Cuba and Hispaniola will aid in setting up a moisture advection channel across the Old South into the Midwest. While most of the precipitation would likely be in the form of rain, I can see the threat for freezing rain sleet and snow north and west of the track of the surface low, which as of now looks to be from SE TX into Lower Michigan during a January 8 – 11 time frame.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Untrustworthy Computer Models Provide “January Thaw” (Of Sorts….) To Eastern Third Of U.S.; Active Storm Track, Descending Circumpolar Vortex Suggests That Any Warming May Be Temporary
University Of Nebraska/HPRCC
Pennsylvania State University
The forecast for January temperatures look to be a real nail-biter. What is weighing on my mind is just how bad the various numerical models have been. Where is that Greenland block? Why are temperature forecasts verifying much warmer over the eastern third of the nation? And how can there be no appreciable rain or snow with that active southern branch storm track and deep moisture pooling over the equatorial Pacific Ocean? Do I believe the very warm look of the dynamic models such as the ECMWF and GFS, or stick with the better track record of the NAEFS and CFS versions, which overall seem to be pointing toward a colder outlook for much of the lower 48 states?
With so much potential for moisture advection, and the lengthy area of snow cover (which only the CFS series had predicted), I will lean toward a prediction that introduces only a temporary mild spell east of the Continental Divide between January 11 – 15. Note that the CFS January forecast shows abundant warming in Alaska and western Canada. If true (and it might not be; look at the average 500MB height anomaly over the last week or so), colder values would take over the U.S. with the possible exception of the Pacific Northwest and Florida Peninsula. The January 8 – 11 storm threat complicates the chance for a warm-up in some ways, especially over Texas and the Great Plains with the snow and ice threat.
I suspect that Arctic air will start to expand into the eastern third of the nation by mid-month, while the West Coast turns warmer and drier. But the lack of sustained blocking signatures bothers me, and for the analog-based forecast to be correct ridging will need to be taking shape across the northern and western parts of the continent within the next ten days for winter to “take charge” over the lower 48 states.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, December 29, 2012 at 6:30 P.M. CT
The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.
Copyright 2012 by Larry Cosgrove
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