Sunday, December 4, 2011

Flooding potential. Snow may be coming.

After looking at several runs of the NAM and GFS, I have concluded that the snow threat with this next system may not be as much as we originally thought it was.  The GFS has really backed down on this system (It never really showed much snow anyway.), down from the several inches of snow that the 12z was predicting yesterday to less than an inch today.  The NAM is still supporting a snowfall of several inches in most of Northwest Ohio, with heaviest amounts along and north of U.S. Highway 24.  If this model were to verify, areas along and north of 24 would probably get into the range of 3-5 inches mainly in northern-most Ohio, where the cold air will probably arrive by mid-afternoon.  Down south, right along U.S. 24 westward into Fort Wayne, expect 2-4 inches, similar snow amounts to what fell last week.  Right now, I myself think these snowfall amounts are a bit high, but I think it is plausible, as this next polar outbreak is going to be much colder.  As for rain and flooding, don't expect much rain today, as rainfall amounts will be around a half an inch in most areas, with some areas receiving around a quarter of an inch, especially near Toledo.  By this afternoon, the rain activity will have tapered to showers as a strong cold front moves through, dropping temperatures into the lower 40's.  Tonight, another shortwave in the upper atmosphere will instigate more rainfall and possibly heavy rainfall.  By Monday morning, heavy rain is possible across the area as the storm system moves northward from the south.  Southern and eastern portions of Northwest Ohio will receive the heaviest amounts with the possibility of up to one and a half inches of rainfall.  According to the latest NAM run, rainfall of up to two and a half inches is possible across the Maumee River Basin, which will make the moderate flooding much worse, possibly pushing the Maumee River into major flood stage, something we have not seen in a while.  By mid to late afternoon, rain will begin changing to snow over extreme northern parts of Indiana and Ohio.  By mid to late evening, I expect most every place in Northern Ohio will have changed to snow, except for areas south of Van Wert and east of Findlay.  Most areas will receive around an inch of snowfall, while areas along and north of U.S. Highway 24 will have 1-4 inches, while areas in extreme Northern Ohio and southern Michigan to receive 3-5 inches and possibly higher amounts.  By Tuesday, cloudy conditions will remain for the morning, with some snow flurries possible.  Temperatures will only reach the mid to upper 30's as a cold polar air mass makes its way into the area.  By Wednesday and Thursday, temperatures will be even colder, with highs only around 33-35.  By Friday, a strong arctic cold front is expected to move through the area, bringing periods of light snow and possibly some accumulation, as temperatures on Friday will likely hover around 31-33.  By Saturday and through next week, a bitter arctic air mass will settle into the region according to the GFS and ECMWF, causing temperatures to barely make it into the twenties, and possibly some days may not make it above 15 degrees (F) according to the 18z GFS from yesterday.  Bitter arctic winds will accompany this air mass, causing temperatures to fall lower than they've been all season.  After that, I am not sure whether the air mass will stick around or get kicked out by another storm system.  Stay tuned for further updates.

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