11/20/07-11/22/07 FCST: NE/MN/IA/WI/IL (WINTER PRECIP)

[Jeff Miller]

Operational Models the past few runs on GFS are painting an ominous picture for potential winter precipitation on the pre-thanksgiving holiday driving period. Due to the fact that this will be an extremely busy driving period, the first potential winter storm of the season, and the proximity to Thanksgiving, and within the 7 day forecast period allowed here at Stormtrack, I am starting a forecast thread for a potential significant winter storm event. I emphasize that, as most forecasters and meteorologists know, this is extremely far out, and normally I would wait a day or two longer before beginning a forecast thread. Due to the holiday season, I am starting it now.

The forecast models have caught on to a winter storm scenario for a few days now, however, the past two consecutive runs have painted a major winter storm to blizzard criteria storm over eastern Nebraska, most of Iowa into southern Minnesota to nw Illinois and also into Wisconsin. To note: Ensembles have not caught onto this and are keeping the system open and weaker, and this is a very distinct possibility. The other possibility that experience in early season storms dictates is that the storm will be more intense and pull further north with future runs, impacting more of a central Nebraska South Dakota to central Minnesota line up to the UP of Michigan as often happens in early season storms.

The operational GFS models at the 12z 156 are showing a major snowstorm with a 998 low - with a strong gradient between cold high pressure over the Northwest and the low producing potentially windy conditions with the heavy snow. These operational models deepen to 994 with a very strong and tight gradient as well.

Time will tell what will happen not only with this winter thread but severe threat in the southern plains and gulf coast states. Discussion is open for this potential winter storm situation - and all bets are on if the ensembles will catch on to what GFS portrays or if this winter storm will evaporate like virga on the high plains - leaving this thread dry as a bone and thanksgiving travelers in a much, much better mood.

From OMAHA WFO:

FORECAST BECOMES MUCH MORE UNCERTAIN AS LATEST TWO
CONSECUTIVE RUNS OF THE GFS PAINT A PRE THANKSGIVING DAY BLIZZARD
ACROSS THE AREA. MEANWHILE...THE GFSENSEMBLES KEEP THE SYSTEM
MORE OPEN AND PROGRESSIVE AS DID THE 00Z ECMWF. LATEST 12Z ECMWF
DOES EVENTUALLY CLOSE THIS SYSTEM OFF OVER THE CNTRL PLAINS
SIMILAR TO THE GFS...JUST LATER IN THE PERIOD DURING NEXT WEEKEND
WHICH IS JUST PAST OUR CURRENT FORECAST RANGE. IN A NUTSHELL...WL
NOT BITE ON THE BLIZZARD NEXT WEEK JUST YET AS INDICATED BY THE
OPERATIONAL GFS AS MODEL AND SURROUNDING OFFICES/HPC CONSENSUS
LOOKS TO REMAIN MORE OPEN AND PROGRESSIVE AT THIS TIME. WILL BE A
VERY INTERESTING EVOLUTION TO KEEP OUR EYES ON THOUGH AS WE HEAD
INTO THE HOLIDAY WEEK AHEAD.

From Des Moines WFO:

SEEMS THAT OVERALL
TREND IN THE BULK OF THE MODELS IS TO BLEED COOLER AIR SOUTHEAST
ACROSS IOWA THROUGH THE PERIOD...SO ALL RAIN INITIALLY WILL BECOME
RAIN OR SNOW...POSSIBLY EVEN SOME SLEET DURING THE TRANSITION
PERIODS...THEN LIKELY ANY PRECIP BY THANKSGIVING DAY WOULD FALL AS
SNOW. AT THE VERY LEAST...WE COULD BE LOOKING AT 2 TO 3 DAYS OF
UNSETTLED WEATHER...WITH SOME PRECIPITATION TYPE ISSUES DEVELOPING.
AGAIN...THIS IS OUR BEST ATTEMPT TO PROVIDE SOME HOPEFULLY USEFUL
DETAIL AS WE HEAD TOWARD A HOLIDAY TRAVEL PERIOD...BUT WE ARE STILL
SEVERAL DAYS AWAY AND THERE IS MUCH TO BE IRONED OUT.

http://rap.ucar.edu/weather/model/index.php?model=gfs
http://rap.ucar.edu/weather/model/gfs168hr_sfc_prcp.gif
http://rap.ucar.edu/weather/model/gfs168hr_sfc_mslp.gif
http://rap.ucar.edu/weather/model/gfs168hr_sfc_tmax.gif

 

[Brandon Sullivan]

Have been looking at it also. It appears the Models are now showing less of a cold air intrusion early in the period. Local WFO office hits at the 24th-28th as being the most impressive. GFS thickness and temp profiles do show a nice winter wx setup over the thread area in the alloted time. 850 RH values show almost full saturation. Surface temps around 34 degrees.. It will be interesting to see how fast the -RN/SN transition can occur.. By the 24th / 25th I really see some bitterly cold, and definitely the coldest air of the season moving in to the midwest!! Brrr I agree with your reasoning on starting the thread early, even with the uncertainties on such a high travel holiday!

FROM DVN - DAYS 8-15.../NOV 23-30/...INDICATIONS CONTINUE TO SUGGEST BELOW TO
POSSIBLY WELL BELOW NORMAL TEMPERATURES AND UNSETTLED CONDITIONS WITH
RISK FOR ONE OR MORE STORM SYSTEMS. SIGNALS VOLATILE DUE TO MAJOR
ENERGY PHASING ISSUES BUT CONTINUE TO SUGGEST FAVORABLE REGIME FOR
WINTER WEATHER OF SNOW...ESPECIALLY IN THE 24-28 NOV. TIME PERIOD.
SOME TECHNIQUES STILL SUPPORT POTENTIAL FOR EXTREMELY COLD AND NEAR
RECORD TEMPERATURES AND/OR WINTER WEATHER.

That says it pretty well.

 

[Joel Wright]

Well, looking at most of the model suites, it's definitely looking like something's up next week. All the major ingredients that you would need for a strong late autumn storm are apparently going to come together. Much of the cold air that has been allowed to build in northern Canada over the last several weeks is going to bodily crash southward across the middle part of the CONUS as the jet flow reconfigures.

You guys are right. It does look like the first decent snows are on the way for parts of the midwest and great plains. Most of the areas that will be affected haven't even seen a flurry yet, so that's sort of interesting. Ground temperatures are still a bit warm across much of the midwest and great plains, but how much of a factor that will be depends on where the snowband eventually sets up.

It will be interesting to track this over the next 4-6 days!

 

[Jeff Miller]

For those tracking:

Traditional flip flops of the model runs as the next run (00z) has this a lot farther south/east, more open and less intense - until it wraps up to a 988 low over SE Lower Michigan. (!)

A lot of variability in this for sure, and this is expected this far out. At this stage we'll be seeing a tremendous amount of variability and flip flops- looking forward to the morning run!

 

[Mike Hollingshead]

I've watched this on a few runs of the gfs. I actually joked about it with another chaser when it was out there around 372hr, lol. Always cool when things are even "seen" that far out. Seems like I've seen 2 more split flow runs(eeewww) before this 3rd one(tonights). I hope it goes back to something closer to the 12z run.

For what it is worth the 12z ecmwf didn't bring it out till next Saturday.

 

[Dan Robinson]

The models (particularly the GFS) have been overzealous on low temps and QPF the past two potential snowfall events here, during the last week or so. They've been as much as 5-8 degrees too low on the temps, with the GFS being the biggest offender. And that's been just two or three days out, much less seven.

I got to see a couple of flakes tonight and a little sleet earlier - so at least the ptype was right!

 

[Jeff Miller]

I'm just curious as to how it's going to handle the long awaited arctic intrusion. I know it's been very aggressive and like you said - overzealous on it - and I know that can impact a lot on winter storm situations (that's an understatement).

I'm waiting to see if the ensembles stick with their solution or get more aggressive.

 

[Robert Dewey]

Certainly worth watching if you're anywhere from NE to PA, in terms of winter weather. As of right now, I'm betting on a track further west - probably near LOT. For areas not affected by near-blizzard conditions, it looks like it could be quite a wind storm with +50knts at 925MB and a very tight pressure rise/fall.

Way too far out, but dreaming is fun.

 

[Brandon Sullivan]

Interesting to note that many models this morning, are bringing favorable winter storm materials in on the thanksgiving area, over much of the area. ECMWF is slower than the other models. Oz Canadian doesn't show this potential as well, and is an out lier.

If severe thunderstorms are gonna be done for the year. Bring on the heavy snow and snow days!!!!

 

[Robert Dewey]

Oz Canadian doesn't show this potential as well, and is an out lier.

In actuality, most of the ensembles aren't nearly as strong; favoring a fast moving open wave like what was shown on the GFS before this monster storm appeared. Even the GEM ensembles from 00Z are absent a strong storm.

The outlier here is actually the GFS, and with each run it has been pushing the system further east (with the 06Z not nearly as strong).

There's still plenty of time for changes, but after seeing the trends and ensembles, I'm containing myself.

 

[Adam Lucio]

Ive been eyeing this for a couple days now and have already warned my family. This could be a major rain maker before the winter precip takes over, locally Ive been keeping a close eye on the 'warm sector' as latest runs seem to bring in the southerly flow earlier and earlier...thunder snow might even be a possibility.

Previous GFS runs had this at only 1004mb but todays I see has it at 990. With a High at 1034 near the rockies thats quite a strong pressure gradient, better put some bricks on the grarbage cans. Just looking at the cold air behind it made the hair on my arm stand up...

Something for us weather finatics to be thankfull for I guess, at leaste we've got something to track/monitor for the next week.

 

[MatthewCarman]

This will not be good if it hits on the holiday weekend. You guys are expecting this to hit next Tuesday into Wensday if anything does form correct?

 

[Robert Dewey]

...and the 12Z GFS is a no-show with the system deepening to a whopping 1002MB. Damn those ensembles!

 

[Brandon Sullivan]

This will not be good if it hits on the holiday weekend. You guys are expecting this to hit next Tuesday into Wensday if anything does form correct?

I do believe in the Tues/Wednesday frame, it could pose a threat in the MO/IA area. and back into KS. For us in IL, it doesnt appear that thermal profile will support snow, until later on Thursday. I have not got to look at the 12z GFS yet though. The ECMWF and UKMET continue to take the system quicker further east. Thanksgiving could be white this year!!

I should have been more specific earlier. I meant the Canadian model is the only model that does bring a low close enough to support precip for me!

Edit: Rdewey Said IT!! 1002.. yuck!

 

[Jeff Miller]

LOL...if THIS trend continues I *Should* have waited to post this thread!

Nothing worse than model trends from a strong winter storm to nothing, but it's not like it wasnt expected with ensembles not picking up on it. Let's hope for a magical reappearance but I doubt it with everything lining up to ensembles.