MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)
Shifting Upper Air Pattern Enables Push Of Arctic Air Through Intermountain Region, Great Plains And Great Lakes....
Plymouth State University Weather Server (2)
The disturbance which will looks to pound Texas and Louisiana with flooding rainfall and intense convection on Tuesday and Wednesday will be swept northeastward as a larger, colder trough complex begins to dig into the western U.S. Since the upper level feature associated with the "forerunner" impulse will bring clouds and precipitation into the Ohio Valley and the Northeast, the process of introducing warmer air to the Eastern Seaboard may be delayed somewhat. It still seems likely that most of the Old South will be in a much above normal realm, however, by January 11 - 13. The West and Upper Midwest, on the other hand, are likely to see a radical drop in temperatures with some areas of snow or sleet. Las Vegas NV and Sacramento CA, not known for wintry weather, could see brief and light snowfall on Thursday and Friday.
....With Threat Of Major Winter Storm From Texas, Louisiana Into Ontario And Quebec
Using a mean of the 12z operational ECMWF and 18z GFS schemes, it seems apparent that a fairly impressive winter storm will organize along a frontal structure stretching from Texas into New England. The stubborn heat ridge complex over the Greater Antilles may bulge northward into Florida and the Bahamas, with tropical air to the left of that anticyclone pooling over the Bay of Campeche and western Gulf of Mexico. Energy digging southward in the formative western/central U.S. trough should initiate cyclogenesis along the western Gulf Coast on January 13, with the deepening surface low pressure center likely moving into the Ohio Valley and lower Great Lakes.
This may be an important snow and ice maker for parts of the Midwest (I am thinking that Wichita KS, St. Louis MO, Chicago IL, and Grand Rapids MI may be in the line of fire from winter weather), and there is potential for a center jump or redevelopment off of the VA Capes. The concern obviously is the impressive -NAO signal/Greenland block setting up in this time frame which in theory would dictate a shift of colder air and the storm track more to the south and east with time. Severe weather and heavy rainfall threats must also be mentioned for much of the Old South, what with the strong upper winds, thermal boundary and rapidly ejecting 500MB vorticity maximum from the lower Great Plains.
EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)
Expanding/Descending Circumpolar Vortex, In Combination With Active Polar Jet Stream Storm Sequence And Persistent Greater Antilles Heat Ridge, Provides Threat For Widespread Cold Weather With Snow And Ice Threats In Lower 48 States
University Of Illinois
Pennsylvania State University E-Wall
As I was going through the various synoptic factors entering into the making of the longer term forecast, I recalled the classic line uttered by Clubber Lang (played by Mr. T) in the movie, "Rocky III". What's your prediction for the fight?" was the question posed by a reporter. Clubber's answer: PAIN. Believe me, January's reputation of thaw accompanied by storms and ultimate return to bitter cold will be enriched over the next two to three weeks!
I can introduce the important "players" in this winter drama. Using satellite imagery, note the tropical forcing over the western and central Pacific Ocean, feeding into a vast mAk vortex over the Aleutian Islands (which in turn will soon pump up a -EPO "thumb projection" blocking signature). There is also the very important matter of the huge circumpolar vortex, clearly visible over the widespread snow and ice coverage in northern Canada (Nunavut AR). Because the cAk motherlode is so immense, it is forcing warm air from the Atlantic Ocean into Greenland and the Arctic Ocean (creating a -AO and -NAO Rex block). In time, the Rex signature expands to the point where stable anti-cyclogenesis starts to nudge the Arctic regime into lower latitudes. Last, but not certainly not least, is the persistent subtropical high seen over the Greater Antilles. As the colder values come in conflict with the warm/moist profiles across the Old South and Eastern Seaboard, storm energy tries to "solve" the imbalance of colder vs. warmer air. That battle will be played out in the 11 - 15 day period. Since this is the heart of winter, the colder and heavier air mass will ultimately win out. But that heat ridge will be a tough nut to crack, and I am afraid that a variety of miserable and ugly conditions are likely between the Continental Divide and Atlantic Coastline before January 21. Then pretty much everyone outside of the West Coast will be staring true "January weather" in the face.
The storms mentioned in previous paragraphs will start the proverbial ball rolling in slowly introducing the Arctic air mass into the lower 48 states. While I think the European model is closer to the truth about the storm track in the 6 - 10 day period, note that the model has a fairly impressive Greenland (-NAO) block taking shape which would seem to favor a stronger surface storm with potential for redevelopment off of the Virginia Capes around January 14. I like the ECMWF idea of holding on to warmth in the Southeast (note the high 500MB heights in Cuba and the Bahamas). When new southern branch storm energy enters the picture form northern Mexico, real trouble will be brewing.
I foresee the potential for cyclogenesis near Galveston TX, with a grinding, deepening storm moving into GA, then turning northward very close to the Atlantic shoreline from the Carolinas into ME and NS. The timing on this matter is up for grabs, but January 17 - 22 should fit the bill for now. Because of the vivid -NAO signal on the ECMWF and GGEM ensemble packages (remember that a concurrent -EPO ridge complex looks to be in place over or near Alaska), the potential exists for the incoming disturbance to interact or possibly phase with the cAk motherlode. Besides making most of the U.S. very cold, such a scenario implies very strong winds and heavy precipitation across the Old South, Appalachia, and the Eastern Seaboard (to say nothing of snow squalls over the Great Lakes, which could be plentiful with so much cold air and energy across open waters). While there is a fair chance that the Interstate 20 and 95 corridors could see mainly rain in such a situation, snow and ice will not be far away IF what the computer models are telling us is true.
Sleep well tonight.
Prepared by Meteorologist LARRY COSGROVE on
Saturday, January 5, 2013 at 7:30 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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