Winter outlook part 3: Larry Cosgrove

November 19, 10:59 AMBaltimore Weather ExaminerJustin Berk

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A very active season for storm tracks.  Not all would bring snow.

Yesterday's snow vindicated my forecast.  Today, Larry Cosgrove supports my call for an active snow season.  Since I am dedicating Wednesday's on Examiner to Winter Outlooks, I have more on the recent snow on my blog with abc2news.com. Part of Larry Cosgrove's analysis is below. I will post his full report on my web site.

Here is the forecast for the upcoming winter temperature trend, month by month. Notice that January is, by area and temperature deviation, the coldest month (while December chill impacts the Eastern Seaboard). A key issue with winters with a -PDO (coldness of Gulf of Alaska waters) is a recurrent ridge over the Southeast. I believe that as spring approaches, a tight gradient may emerge from the Ohio Valley into the Mid-Atlantic states. Think of the transition as a battleground between the entrenched colder regime associated with the transient +PNA and -AO related ridging , in concurrence with -NAO aligned blocking near Baffin Island or Greenland. This boundary could be a conduit for storms, with late-season snow and ice events across the Great lakes and Northeast. Colorado cyclones which undercut transient +PNA ridging may stimulate colder temperatures in parts of the Intermountain Region through the winter, while the unstable positive height anomalies over the Pacific Northwest keep mPk frontal structures off of the Gulf of Alaska from making frequent passages.

DECEMBER Repeated cold intrusions from the Upper Midwest into the Eastern Seaboard. Generally warmer across the Intermountain Region and Great Plains, with area from Utah and Colorado into Missouri and Arkansas a buffer zone between returning warmth along the western Gulf Coast and a mild regime parallel and west of the Continental Divide. Some potential for occasional occurrence of colder values in the heartland of the U.S. due to Colorado/Trinidad "A" storms with increasing snow. Greatest threat for major winter storm will be over the major cities along the Interstate 95 corridor.

JANUARY Widespread cold except for the West Coast and the Southeast. Active storm track from western Gulf of Mexico up along the Atlantic shoreline will create ice and snow hazards over the eastern third of the U.S. Lake effect snows may be crippling in Cleveland OH and Buffalo NY metro areas, with occasional issues from snowfall in Chicago IL, Indianapolis IN, Cincinnati OH and Pittsburgh PA. Ice storm risk may be higher through the interior of Dixie and along the Eastern Seaboard.

FEBRUARY While cold strengthens its grip over much of Canada and the Midwest, I suspect that ridging will be an increased presence over the Southeast (see the analogue mean 500MB composite anomaly above for insight into this possibility). Very active procession of both Alberta Clippers and Colorado/Trinidad "A" cyclones along gradient between FL-GA positive height anomaly and cAk intrusions that will reach as far south as Texas and Appalachia (some spillover into the Northeast as well).

MARCH Very similar to February scenario except that flat subtropical high may make inroads into the entirety of the Deep South (creating some warmth from Texas into the Carolinas). Extended winter for the Midwest as a whole; some risk present for late season surprise ice or snow event in the Northeast with a cold air damming scenario (i.e. backdoor cold front and overrunning). Storm Track Scenarios The tendency for storms over the western Atlantic Ocean and adjacent coastline stands out as we head into the colder months. Since stronger features tend to regress and deepen during winter, the lows which have formed near or east of Bermuda may instead pass closer to the Eastern Seaboard. Likewise, some potential exists for Piedmont cyclones, originating in the Deep South and passing west of the Interstate 95 corridor. The most likely options for track scenarios are for Colorado/Trinidad "A" cyclones and Hatteras (Nor'easter) Lows, as examples of these systems have already occurred, and will be favored to develop again under a transient +/- PNA configuration. Alberta Clippers may take shape in middle and late winter, precedent to cAk intrusions; Piedmont storms and Galveston Bay Spin-Up cyclones are also a strong possibility, with ridging over the Sargasso Sea setting up against digging energy from the High Plains.

 Precipitation, Ice, And Snowfall

A very clear pattern emerges with the averaging the 11 seasons used as analogues: the best risk of precipitation is over the Pacific Northwest and the Old South. If the overall synoptic pattern verifies, the presence of high moisture advection against incoming shallow cold air sends all kinds of alarm bells out for the possibility of major ice storm formation around Appalachia and the Piedmont (including the markets of Birmingham AL; Atlanta GA; Charlotte NC; Raleigh NC; and Richmond VA).

 Larry just confirmed his call for Maryland:

"My tentative snow range for Maryland runs from 42" at Frederick and 10" at Easton; so for Baltimore city 26" should be close. One caveat: I think that a 1993-94 double dose of ice storm is a strong possibility".