All Weather News

The Day Has Come! Another Is On The Way!

23 Mar 2009, 8:38 am
The storm we discussed developing a week ago today has certainly held its course with respectable perseverance. At the time of this writing blizzard warnings are active for all of western North and South Dakota, northwestern Nebraska, eastern Wyoming, and the extreme southeastern tip of Montana (note graphic at right).

In addition to the blizzard warnings and winter storm warnings covering our storm for today, the SPC has issued a Moderate Risk in their Convective Outlook category to cover the thunderstorms we said would also develop today. The moderate risk area is centered over southeastern Kansas and northeastern Oklahoma. More on this and the second storm we said would develop last week below.

Winter Advisories Valid 7:40am EDT 3.23.09
Winter Advisories Valid 7:40am EDT 3.23.09

  Main Animations Used In Discussion – Click For Full Size
3.5 Day Ptype2 Animation 7.5 Day Minimum Temperatures Animation 7.5 Day Ptype2 Animation
3.5 Day Ptype Animation 7.5 Day Minimum Temps Animation 7.5 Day Ptype Animation
Let’s begin today by examining our 3.5 Day Precipitation Type Animation. Todays run was from 06z this morning, with our first valid forecast hour of F003, valid 5am EDT today. Rains were forecast to occur over a wide swath of Minnesota, portions of North and South Dakota, and into Iowa, with mixed precipitation forecast to occur over NE Minnesota. This forecast is validated in our Radar Center using the Precipitation Type product, recall on the top right hand side you may overlay various fields of interest such as warnings, frontal boundaries, current conditions via station models and so forth.

On our next forecast hour valid ending at 8am EDT this morning, the rains are forecast to continue in the same general areas, with mixed precipitation still in the cards for NE Minnesota. Our Precipitation Type Radar still validates this forecast, as does the Freezing Rain Advisory for the state, calling for about 0.25″ of accumulation.

On our next frame valid 11am this morning, notice that the area of lower pressure we discussed all week is forecast to deepen to 991mb, and also dip a tad to the south. In this case it is not forecast to become another ‘Dodge City’ Low as we have had on the last several iterations this winter season, but instead settle near one of my favorite Nebraska cities: McCook, Nebraska. Notice however, if you choose the forecast link for McCook provided, that the blizzard warnings and winter weather advisories are to the north and west of the city, with only wind advisories active for them. This revolves around the previous discussions we have held on the nature of temperature advection and precipitation patterns associated with areas of lower pressure and the nature of their propagation.

Forecast hour F012 valid 2pm this afternoon shows the low beginning its northeasterly trek and a few splotches of rain showing up in Kansas and Nebraska. This could be an area of convective initiation for the thunderstorms we have discussed will develop today. Also notice that as the low begins to propagate northeasterly, the precipitation shield for snow also begins to extend eastward into Nebraska and South Dakota. As the low heads north and east, so does the snow on the western flank of the low.

Forward ahead to F018hr valid 8pm EDT this evening, and notice the snows are beginning to extend into South Dakota, where the breadth of the snows match fairly nicely the areas covered by the blizzard warnings active this morning.

By tomorrow morning F030hr, valid 8am EDT central pressure for the low is forecast to weaken to 995mb, with the snows extend fro NE Colorado NNE through Nebraska, South Dakota, North Dakota, with a smidgen of extreme Northwestern Minnesota.

As 8pm tomorrow rolls around the low becomes considerably weaker with a central pressure of 1000mb, while snows continue to fall over eastern North and South Dakota with and portions of western Minnesota. By 2pm on Wednesday Afternoon (F060hr) she begins heading into Canada with a central pressure of 996mb, and only portions of snow remaining for the U.P. of Michigan and extreme northeastern Minnesota.

Snow accumulations will be most impressive today, with at least a foot of snow occuring in eastern Wyoming, western South Dakota, and a tad of southwestern North Dakota. Tomorrows totals we be less impressive with the best chance for accumulations of around 8″ or so occuring in central and eastern North Dakota and a smidgen in northwestern Minnesota. Now for the thunderstorms we discussed would occur.

Thunderstorms for Today
Above we mentioned that the SPC has issued Moderate Risk in their Convective Outlook Category for today. The bullseye for their outlook is southeastern Kansas and northeastern Oklahoma, and their tornado probabilistic category contains a hatched area directly in that bullseye which means that there is a 10% or greater probability for an EF2-EF5 tornado within their defined region.

The reason this outlook has been issued are the shear parameters we discussed would develop today as a very impressive jet streak streams into the region this afternoon as our low above begins ascending into Nebraska with the triple point development we said would occur.

With the impressive 50knt+ deep layer shear, very long lived supercells can develop with sustained updrafts. Now while precipitable water is not very impressive, and a rather hefty cap is present especially over central and eastern Kansas, if storms do develop in the favored environment with the deep layer shear, the strong updraft environment will favor very large hail, very strong winds, and tornadoes if they burst and can sustain themselves, which seems likely.

The storms will likely continue through the evening and into tomorrow morning as additional activity develops both in northern Texas, and existing convective activity heads into Missouri. If you live in and around these areas, today would be a day to pay attention to your NWS Radio (or buy one if you do not own one – I can recommend this Midland or this search will yield alternatives).

More Stuff On The Way?
Last Friday we said it looks like another storm system is likely to form, and this morning’s run seems to verify that prediction. Using our 7.5 Day Precipitation Type Animation, choose “stop” and “forward one” until you reach F090hr Valid 8pm EDT on Thursday, March 26. Notice we now have another area of lower pressure centered north of Roswell, NM, perhaps our alien friends have a weather machine they are using!

Recall this product is at 6 hour intervals instead of 3, so our next frame is valid Friday morning at 2am EDT. Our low has trucked from Roswell into central Oklahoma rather quickly hasn’t it? Well here is where she gets interesting. Forward a few more frames until you reach F114hr Valid 8pm on Friday Evening. Notice she has dug to 990mb causing the more tightly packed isobars (wind), with snow along the northern and western fringes? Well what happens next?

F120hr valid 2am Saturday morning she digs all the way to 985mb and has settled herself over northern Missouri, where by the next frame F126r Valid 8am EDT on Saturday she digs to 980mb and is centered over northwestern Illinois. Whoo Boy! She could be a good one!

By 2pm Saturday afternoon (F132) she maintains an impressive central pressure of 981mb, with snows forecast to possibly reach Chicago, and most of Missouri through Minnesota will be unhappy by this point. Where 8am EDT on Sunday morning she is still holding together centered over northern Lake Michigan with snows trailing around her northern and western flank, and by F162hr valid 8pm EDT Sunday Evening, she begins to weaken a tad but snows should still be falling.

It will be interesting to see in later runs if she digs as deeply as this morning’s run forecasts her to do. Temperatures associated with both of these systems can be viewed on our 7.5 Day Forecast Maximum and Minimum temperature animations. The highpoint being that the northern through the southern plains will endure wintry conditions for the majority of the week.

Please be sure to view our Advisory and Radar Centers for the latest updates and developments.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

cheers,

–patrick

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