Wednesday, February 20, 2013

Winter Storm Getting Underway Central Plains; Severe T-Storms Possible S. Plains Overnight...

An area of moderate to heavy snow has already developed early this morning from central Oklahoma, back to the Northwest into southern Kansas.  Snowfall rates of 1-2 inches per hour are taking place in some areas as the heavy, wet snow falls.

The snow is likely to change back to a mixture of rain, sleet and snow on the Southern end of the area (in central Oklahoma) later this morning or midday, before temperatures fall back below freezing for another wintry mix and snow event later this evening and tonight.

A Winter Storm Warning covers much of the central Plains through at least Thursday night, as shown in pink on the image below.  Winter Storm Watches have yet to be upgraded to warnings, but will later today, in the purple shaded areas.  An Ice Storm Warning is in effect for the lighter purple shaded area across portions of west-central, northwest and northcentral Arkansas for tonight and Thursday:

Widespread, heavy snow is expected across the majority of the Winter Storm Warning areas later today  through Thursday and Thursday Night.  The latest run of the GFS computer model is forecasting well in excess of a foot of snow across west-central and portions of central Kansas, with widespread 6-8 inch (plus) amounts from Kansas and southern Nebraska, eastward into southern Iowa and much of Missouri through 6pm EST Friday:

Strong, gusty winds will create blowing and drifting snow in some areas, with very hazardous driving conditions. The snow will also be heavy and wet, especially in the Southern one-half of the heaviest area of snowfall, which will produce a threat of widespread power outages.

Along and just to the South of the primary heavy snow axis, a significant icing event is possible tonight through Thursday.  The primary threat of 0.25 inch or more of glazed ice accumulation extends from portions of northeast Oklahoma into northern Arkansas and along the Missouri/Arkansas borders later tonight and Thursday morning:

The threat of significant icing will continue in northern Arkansas and along the Missouri/Arkansas borders durign the day  Thursday, and then spreading East/Northeast into the middle Mississippi and Ohio Valley regions later on Thursday Night:

The areas shaded in blue on the two ice accumulation probability maps above have the greatest chance of enough ice accumulating to bring down tree limbs and power lines.  Needless to say, travel conditions will also be extremely hazardous in this region, and is highly discouraged.

On the Southern end of the storm system, a threat of severe weather will exist later tonight and especially on Thursday across portions of the southern Plains and lower Mississippi Valley region.  The latest severe weather outlook for tonight from the Storm Prediction Center (SPC) in Norman, OK is shown  below:

The primary risk in this region will be that of hail approaching or reaching severe limits, especially after 10pm tonight, into the pre-dawn hours of Thursday.

During the day on Thursday, the threat of severe weather will shift East, encompassing much of the lower Mississippi Valley Region:

Hail to severe limits, damaging wind gusts and a few tornadoes will be possible with the severe storms on Thursday, especially within the yellow and red shaded areas on the above image.

Widespread, locally heavy rainfall will also take place across the already soaked Mississippi Delta and Deep South region, leading to significant flooding problems in some areas.  The rainfall forecast image below calls for amounts in excess of 4 inches (or more) in the darker purple shaded areas from tomorrow through early Saturday:

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