1st Big Winter Storm Threatens Blizzard, Severe Wx, Big Temp Contrast, 97L To Become Karen

Written by on October 3, 2013 in United States of America with 0 Comments

There is a lot of bad weather on the way as a storm system now enters the Pacific Northwest and is set to swing across the Rockies and eventually the Plains Friday through Sunday presenting heavy, wet snow to the Northern Rockies as well as the western high plains of Nebraska and South Dakota. As the low crosses the Rockies and enters the Plains, so the system deepens and really intensifies as it picks up heat and moisture from the Gulf. It’s as this system winds up, so winds increase on the rear and with heavy snow expected to fall over western Nebraska and South Dakota, combined with wind gusts of 40-60 mph, we could well see blizzard conditions with the risk of road closures due to blowing, drifting and significantly reduced visibility.

Heavy, pounding rains will affect much of the Northern Plains but another worrying and potentially dangerous side to this first major winter storm of the season is, severe weather.

As the low enters the Plains, you’ll got a cold front but out ahead of it will be a rush of warm, moist air within the warm sector and Friday as the warm sector sets up from Oklahoma to Wisconsin, just as the storm cranks and heavy snow and wind begins to break out on the western High Plains, so storm cells will develop along and ahead of the cold front and here, as well as flooding rain, expect thunderstorms with rotation packing damaging winds, large hail and even a risk of tornadoes.

Below is some of the models off the ECMWF which show the setup in the coming days.

48 hour ECMWF surface/precip

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By 48 hours you can see the system crossing the Northern Rockies and beginning to enter the Plains, as it does so, this forces air north out of the Gulf ahead of the eastward moving cold front while colder air in the mid and upper levels run over top of the increasingly warm, moist air. This leads to all the ingredients for thunderstorms to fire with the front acting as the trigger.

Below is the 500mb (upper) chart by Saturday and note the upper level (rotating) energy which is drawing a lot of heat and moisture north AHEAD of the system to the SE of the centre while on the backside, cold air is drawn out of Canada and with abundant moisture wrapping around the circulation, heavy snow is breaking out over Wyoming into the western half of South Dakotas and Nebraska. Temperatures will be stuck in the 30s here with windchills in the 20s while it’s 80s 200-300 miles further east where there’s a substantial severe weather risk.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the surface/precip chart by Saturday and you can see the low really winding up.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Check out the 850mb temperatures by Saturday and note the cold air diving south on the backside of the low while there’s a significant surge of warmth further east.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

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Big Temperature Contrast

As a result, check out these projected Friday afternoon temperatures between the Rockies and Plains.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

The model shows mid-20s over central Colorado and Wyoming while it’s in the mid-80s over Kansas even creeping into S Nebraska (at the same time it’s snowing in the panhandle) up into Iowa.

Check out early Saturday morning temperatures, 10 in Colorado, Wyoming verses 70 in Iowa.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s a national view Saturday afternoon

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

By Sunday the system begins to make a run at Ontario with enough cold air and moisture on the rear to bring some snow to North Dakota, Minnesota and even Wisconsin.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

A LOT of Snow Expected

The GFS is more bullish than the ECMWF by producing well over a foot of snow to west and north-central Nebraska as well as central South Dakota. Both models are confident in producing a big snow to Wyoming with somewhere likely to pick up 2 feet, probably a widespread 8-14 inches, including cities such as Casper and Cheyenne.

GFS

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

ECMWF

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Severe Weather Threat

As mentioned, there’s a pretty significant severe weather threat from this storm with all the right ingredients coming together.

Here’s the severe risk from the SPC for Friday. This map will likely display a MODERATE RISK tomorrow, for Friday.

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Below is the AccuWeather severe risk for Friday.

Source: AccuWeather.com

Source: AccuWeather.com

The severe risk extends slightly further east during Saturday.

Source: AccuWeather

Source: AccuWeather

97L Soon To Become Tropical Storm Karen

The system in the western Caribbean, 97L continues to look better and better organised tonight and is likely to become TS Karen within the next 24 hours as the system tracks north into the Gulf. It’s expected to make a southern Alabama, W Panhandle of Florida landfall this weekend as a minimal tropical storm with winds around 40-45 mph. It will drop several inches of rain around this region.

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