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Blizzard, Thunderstorms, Snow in SW Texas?

9 Mar 2009, 1:15 pm
Forecast Precipitation Type (7.5 Day)
Forecast Precipitation Type (7.5 Day)
Forecast Precipitation Type (3.5 Day)
Forecast Precipitation Type (3.5 Day)

Last Wednesday and Friday we discussed the double barrel low scenario that has evolved, and how the second low would develop to a fuller intensity than the first. The scenario is developing quite fully with the first low having moved through to spawn snows, thunderstorms, and tornadoes, with several reports of tornadoes yesterday.. thankfully with no fatalities.

Amazing with the second low, is how well our medium range forecast product has maintained the forecast track. Let’s examine our Medium Range Forecast Precipitation Type Animation again, to see what it has to say for the initial setup.

This product is a 180hr forecast product at six hour intervals, and shows that if precipitation were to occur, what form might it take for the six hours prior to and ending at that valid time (time stamp on bottom), as well as pressure center and distribution forecasts. Most users find stopping the animation, choosing “first image,” and advancing each frame individually the most useful after viewing the initial animation.

Our first frame for today is the six (F006) hour forecast, valid 2pm EDT. Note the second “Dodge City” low we discussed last Wednesday and Friday still appearing in the same location from this morning’s run. This low actually formed from an ejecting shortwave in the trough over the western United States we discussed last week.

From the center of lower pressure we see the possibility of snows in the north, which our Radar Center confirms at the time of this writing, with rains possible in the central plains which have the potential to become severe this afternoon, also confirmed by current radar. The remnants of the previous low is also shown along the Atlantic seaboard, with snows spread in the New England states and rains to the south, also confirmed again by our Radar Center .

Now advance the animation 24 hours to F030 valid 2pm EDT tomorrow. Notice how the low quickly ejects from the central plains to be centered on the border of northern Missouri and southern Iowa. A rain shield extends over the midwestern states extending south along a cold front that will extend from the system, with light snows extending along the northern flank of the system, and heavier snows extending from the region of cold air advection and tightening baroclinicity (note the tightly packed isobars) along the northwestern flank.

Moving forward to 8pm EDT the low is centered in Wisconsin, forecast to deepen at this point to 1000mb, with really stacked isobars in Minnesota which as you know by now means strong winds. Hey, there’s our previous low out in the middle of the Atlantic. Looks lonely doesn’t it? =)

At 2am Wednesday morning our Medium Range Ptype product forecasts the low to deepen to 994mb, with really packed isobars running from Minnesota into Wisconsin, and to a lesser degree eastern Iowa and northern Illinois. For fun look at the next two frames as she heads into Ontario and Quebec. Notice how the forecast pressure drops to 988, 982, and 978? heh =)

Reviewing the propagation of the low from 2am Wednesday to 2am Thursday as she heads into Canada, rains are forecast to spread through the midwest into the Mid-Atlantic and northeastern states, with snows possible in New England. Also interesting is at forecast hours F048 (8am Wed) and F054 (2pm EDT Wed) the little sliver of snow forecast to fall over Illinois, Indiana, and Ohio along the cold front. Will that hold true? Always fun to watch and see.

Also note at 2pm EDT Wednesday the bulging 1043mb ridge of high pressure pushing south. We mentioned last week the potential for cold air to push south by Thursday that also seems to be holding true. Notice as we move ahead to F078 Valid 2pmEDT on Thursday we have a the potential for snows begin showing up in New Mexico. Move ahead through F090 valid 2am on Friday, the potential for snows are holding true from Kansas through Colorado and New Mexico.

At 8am on Friday morning the potential for snows extend along a thin band from Missouri, through Kansas, southern Nebraska, Colorado, and northern New Mexico. Advance through 2am on Saturday snows extend in the southcentral plains into the Cherokee Strip (trail of tears), the panhandle of Texas almost down into Amarillo, and into New Mexico. By 2pm on Saturday the snows are forecast to extend past Amarillo just touching Lubbock, Texas and most of New Mexico all the way south into Carlsbad Caverns, so that by next Monday @ 2pm EDT we have a monster ridge of high pressure in the northern Rockies, and the potential for snows extending through the northern plains south into northern Texas and New Mexico.

Now as we have previously discussed our Medium Range forecast product is a generalized product and can not be used as exactly as I have just described above. However, as you have learned over time, she does a pretty good job =) From the discussion above we know that monster snows (haven’t said it yet, but blizzard) are in our immediate future, but what I will be interested to see is how snows will develop next week.

Well let’s now compare this discussion above with our shorter range Forecast Precipitation Type Animation. This product forecasts through 84hours at 3 hour intervals, and each window of time represents that if precipitation were to fall beginning 3 hours prior to and ending at the valid time (timestamp on bottom), what form might it take?

OK, from our 12z run this morning, the first frame F003hr is valid at 11am this morning. We see our “Dodge City” low that we discussed from last Wednesday (kind of crazy seeing it hold true on a short range product run this morning from a Medium Range product run last Wednesday isn’t it?), the remnants of our previous low causing rains and snows in the Northeast, and current snows in the northern Plains as verified by our Radar Center.

Slide ahead through F039hr valid 2pm EDT tomorrow afternoon. This looks a little different doesn’t it? Our shorter range forecast product feels the potential for mixed precipitation is possible with this setup. I tend to agree to a degree. However, examining other fields I will say i do not feel the potential for a major ice storm exists, but the possibility of freezing rain and sleet is not out of the realm of possibilities. So at 2pm tomorrow the low is shown as was on our previous product, centered between northern Missouri and southern Iowa, with snows extending along the north and northwestern flank with a forecast pressure of 1004mb.

By 8pm EDT tomorrow evening snows are still forecast through Minnesota and the northern plains, extending into Manitoba and Ontario, where by 2am Wednesday morning she is centered on the western tip of Lake Superior and finally by 11am morning is essentially out of the picture, with remnants of rains and snows remaining for the mid-Atlantic states and such as we discussed above.

Just for Grins and Giggles advance through F069 Valid 5am EDT Thursday morning. See that little blip of snow and mixed in southwestern Texas? Crazy huh? Will it really happen? We’ll see! Notice that monster ridge of 1042 high pressure in the northcentral plains? Well we discussed last week how cold air might descend, we’ll look at our forecast minimum temperatures in a bit.

As we advance through 11am Thursday morning notice the potential for snows still exist, with a large swath of potential icing running from Midland / Odessa Texas through Wichita Falls. By 2p Thursday snows still show for southwest Texas and the potential for icing in the same general area, and they hold on through our last valid forecast hour of 8pm EDT on Thursday evening. This is really going to be fun to see if it holds true. Snow in Pecos, Wink, Kermin, Monahans Texas is not unheard of, but it is still fun when it happens =)

On snow totals. From the snows currently falling in the northern Great Plains, and those forecast to fall I can say that today on a line extending from Wyoming through northwestern Minnesota we will see up to 4″ or so, with the highest concentrations in the Black hills as intensity will increase in the evening hours, where as much as 9″ may fall.

As the blizzard builds we will have some very respectable totals where a wide range of 4″ totals are expected from north and south dakota on a line northeast through Wisconsin and into Ontario wrapping back around through Manitoba back into the northern Plains. However, 12″ totals are definitely in the cards especially for northern and northeastern Minnesota if the track holds true. As far as what will happen in Canada, well let’s hope their igloos are solid structures =)

Notice that our Advisory Center already shows a blizzard watch for eastern North and South Dakota as well as Western Minnesota (but not Northeastern MN!). I recall seeing it pop up yesterday morning and was impressed that the NWS issued the watch a few days in advance, let’s see when the issue the warning =)

Oh I almost forgot, I promised to show you forecast minimum temperatures. Below are two images, from our shorter range product. Forecast minimum temperatures valid 8am and 8pm EDT on Thursday. Click either for full size.

Forecast Minimum Tempertures Valid 8am EDT Thursday
Forecast Minimum Tempertures Valid 8am EDT Thursday
Forecast Minimum Temperatures Valid 8pm EDT Thursday
Forecast Minimum Temperatures Valid 8pm EDT Thursday

As you examine both images, notice that at 8am a cold air tongue extends from New Mexico into southwest Texas, this is due to low level winds with the associated ridge of high pressure (and developing low) we discussed above causing cold air advection to stream into the region, so that by 8pm the small pocket of cold air at the surface remains from southwest through central Texas. Will this hold true? We will see! =)

Our Advisory Center also shows that the SPC has issued Convective Outlooks for both Today and Tomorrow. For today while convection has already initiated, it is expected to intensity througout the day. If thunderstorm intensification does occur, as it is expected to, favorable low level and vertical shear is present to support supercells and the possibility of tornadoes.

The centerline for the best chance of tornadoes will run along the I44 corridor from Lawton, Oklahoma through Oklahoma City, Tulsa, and into Joplin Missouri. The good thing about I44 is that it runs in a roughly northeastward direction with ample NSEW roads for interception.

For tomorrow severe storms are possible from northwestern Arkansas northeast through Missouri and most of Illinois.

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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