June 26th-July 1st Severe Potential

[Minnesota Meso]

My thoughts in detail can be found at the Minnesota Forecaster site. The 12/28 0z run of the Nam has dropped south some more, albeit not much, I think that trend will continue.

 

I'm known there as randyinchamplin

 

http://www.minnesotaforecaster.com/2014/06/more-rain-and-severe-storms-this-weekend.html#comment-form

[Jim Marusak]

Yes, I realize that, but with strong surface highs to our NE or strong surface lows to our north/north west  I have seen this many times as westerly or easterly wind have shut us down..  The last time I saw it was last fall when many of us compared the set up to the St Peter tornado, but a strong high pressure system over northern lake Superior with it's easterly winds shut down MN.  I see the same thing happening only with the cyclonic flow this time compared to anti cyclonic flow last fall.

i could see what you're saying with a bubble-high developing between the main developing low in Manitoba/NW Ontario and the next wave along the boundary coming up from eastern NE/NW IA. but i'm not totally sure that bubble holds, given the next weaker but still significant moisture plume later on Sunday. definitely one where the SFC and UA analysis will have to be kept an eye on real closely. 20-30 miles could make the biggest of difference here.

[andyhb]

Yes, I realize that, but with strong surface highs to our NE or strong surface lows to our north/north west  I have seen this many times as westerly or easterly wind have shut us down..  The last time I saw it was last fall when many of us compared the set up to the St Peter tornado, but a strong high pressure system over northern lake Superior with it's easterly winds shut down MN.  I see the same thing happening only with the cyclonic flow this time compared to anti cyclonic flow last fall.

 

This kind of speculation goes mostly out the window when it is not even the same season.

 

If you have a strong surface low to your northwest, that means you are in the warm sector most of the time. Seriously, if the WF ends up draped across the metro on Sunday, there's a chance for a big problem there.

[Jim Marusak]

as for the flash flooding concerns today/tomorrow here in the 612/651/952, some of these numbers are troubling given the PW's currently.
 

1/3/6 hr ffg listed

Ramsey (STP) : 0.8/1.2/1.6

Hennepin (MSP/MIC): 1.2/1.4/1.8

Anoka (ANE): 1.8/2.25/2.5

Washington (21D/Stillwater/Cottage Grove): 1.4/1.6/2.0

Dakota (LVN/SGS): 1.4/1.6/2.0

Scott (Prior Lake/Jordan): 1.4/1.8/2.0

 

 

general PW's for the area attm are ~1.4", forecasted to be between 1.7 and 2" with a real good moisture feed today and tonight. tomorrow may not quite be as bad, but these type of numbers will be headling with the wrong type of storm rainfall.

 

http://www.srh.noaa.gov/rfcshare/ffg.php?location=MN&zoom_map=state&duration=1

[andyhb]

Omaha in another moderate eh? Man their CWA has been raked this year, by far the most active I can remember across eastern NE.

[MCS_hunter]

I was concerned last night that the greatest tornado potential could shift south and, sure enough, it has.  I don't think its worth the drive down from central MN anymore.

[andyhb]

I was concerned last night that the greatest tornado potential could shift south and, sure enough, it has.  I don't think its worth the drive down from central MN anymore.

 

Famous last words.

[MCS_hunter]

Haha I know and I will probably regret them...

[EricHaley]

Looks like things might quiet down around here (Lincoln, NE) after this weekend. Maybe a good thing since my fiancée is getting tired of me always watching the weather...

[Thunder Road]

SPC's Moderate is hitting the hail/wind really.  As the discussion mentions, greatest tornado risk will (obviously) be along the warm front, which will probably lie on the northern edge of the Moderate or even slightly north of there, along the IA/MN border (although we'll know for sure tomorrow afternoon).

 

It's already late in the season, what are the odds of another big trough like this after July starts?  I say, chase!

[andyhb]

SPC's Moderate is hitting the hail/wind really.  As the discussion mentions, greatest tornado risk will (obviously) be along the warm front, which will probably lie on the northern edge of the Moderate or even slightly north of there, along the IA/MN border (although we'll know for sure tomorrow afternoon).

 

It's already late in the season, what are the odds of another big trough like this after July starts?  I say, chase!

 

See, the problem with this is the GFS still appears to be ahead of the other models by several hours. The parameter space the NAM suggests would clearly support significantly tornadic supercells from 18z (or earlier) to 00z Monday across E NE and then pushing into IA and not just near the WF.

[Jim Marusak]

btw, severe t-storm watch now out. most of central and eastern MN, including the Twin Cities,Mankato/Rochester/St Cloud but not Lacrosse; and in central IA (Mason City, Des Moines, Fort Dodge, Waterloo, Knoxville).

 

risks are gusts to 70 and hail to 1.5"

 

http://www.spc.noaa.gov/products/watch/ww0365.html

[thewxmann]

Omaha in another moderate eh? Man their CWA has been raked this year, by far the most active I can remember across eastern NE.

 

This year's NE activity reminds me of last year's OK activity (thankfully over more rural areas this year). While most of the country remains below avg, that one area keeps getting hammered.

[andyhb]

This year's NE activity reminds me of last year's OK activity (thankfully over more rural areas this year).

 

Scratch what I said to abosmet, those are famous last words.

[thewxmann]

Scratch what I said to abosmet, those are famous last words.

 

Thus far*

 

Needless to say, hope that trend continues.

[nwburbschaser]

I'm wondering what impact the possible mid morning convection is going to have tomorrow.  It does look like parts of southwest Iowa into Nebraska will destabilize later in the day, but I don't see anything firing up in that area, at least on the 18z NAM. 

 

Edit: 4km NAM paints a different picture and does light up parts of E Nebraska into Iowa later in the day. 

[Thunder Road]

Just to be different, here's the 12z RGEM:

 

At 21z, the 3-hr precip tendency actually shows what looks to be tracks of two discrete cells from central NE eastward into IA:

 

 

Then by 03z, it looks like the model is trying to resolve a supercell between Omaha and Lincoln:

 

 

Kind of backs up the NAM in suggesting that there may be two targets tomorrow: Norfolk-Sioux City-Storm Lake and Grand Island-Lincoln-Omaha.  LCLs don't get really high until you get into KS.

[andyhb]

I'm wondering what impact the possible mid morning convection is going to have tomorrow.  It does look like parts of southwest Iowa into Nebraska will destabilize later in the day, but I don't see anything firing up in that area, at least on the 18z NAM. 

 

Edit: 4km NAM paints a different picture and does light up parts of E Nebraska into Iowa later in the day. 

 

Regular NAM has been absolutely atrocious at diagnosing convective initiation lately.

[nwburbschaser]

Regular NAM has been absolutely atrocious at diagnosing convective initiation lately.

It is something to watch though.  Even the 4km is somewhat iffy on anything sustaining itself in the NE/IA area after 21z and I'm not quite sure why. 

[andyhb]

Kind of backs up the NAM in suggesting that there may be two targets tomorrow: Norfolk-Sioux City-Storm Lake and Grand Island-Lincoln-Omaha.  LCLs don't get really high until you get into KS.

 

Deja vu.

[andyhb]

Good discussion from OAX regarding tomorrow.

 

THE AFTERNOON SHOULD PROVE A DIFFERENT STORY. WEAK FRONTAL BOUNDARY
IN NORTHEAST NEBRASKA THIS EVENING IS FORECAST TO SETTLE SOUTHEAST
SUNDAY...AND LIE SOMEWHERE CLOSE TO A SIOUX CITY TO COLUMBUS LINE BY
THE AFTERNOON. STRONG INSTABILITY IS FORECAST TO DEVELOP AHEAD OF
THE FRONT AS TEMPERATURES WARM INTO THE LOWER 90S AND DEW POINTS
INTO THE LOWER 70S...YIELDING OVER 3000 J/KG OF SURFACE-BASED CAPE.
FORECAST SOUNDINGS SUGGEST SOME CONVECTIVE INHIBITION WILL HAVE TO
BE OVERCOME EARLY IN THE AFTERNOON...BUT MOST OF THAT CAP IS ERODED
BY ABOUT 4 PM. A WEAK SHORTWAVE IN THE 700MB TO 500MB LAYER IS
SUGGESTED BY GFS HEIGHT FIELDS...HELPING TO TRIGGER CONVECTION IN
THE AFTERNOON. LAYER SHEAR PROFILES ARE SUPPORTIVE OF ROTATING
STORMS AS 40 TO 45KT OF WESTERLY 0-6KM BULK SHEAR ALIGNS AT A STEEP
ANGLE TO FRONT AND INSTABILITY AXIS. THUS ALL MODES OF SEVERE APPEAR
POSSIBLE...ESPECIALLY INITIALLY WHEN LOOPING HODOGRAPHS ARE MOST
PREVALENT. HAIL AND WIND THREAT SHOULD CONTINUE WELL INTO THE
EVENING AS COMPLEX DEVELOPS AND SHIFTS SOUTHEAST INTO SOUTHEAST
NEBRASKA AND SOUTHWEST IOWA. AFTER MIDNIGHT...MOST OF THIS ACTIVITY
SHOULD BE MOVING OUT OF OUR CWA. HOWEVER SURFACE LOW IN NORTHWEST
KANSAS IS FORECAST TO RIDE NORTHEAST ALONG REMNANT FRONTAL BOUNDARY
ENHANCING LIFT AS IT HEADS TOWARD OUR CWA. THUS WILL KEEP FAIRLY
HIGH POPS GOING AFTER MIDNIGHT INTO MONDAY MORNING FOR A GOOD PART
OF OUR AREA BEFORE THIS SURFACE LOW AND UPPER WAVE PASS TO THE EAST.
LINGERING STORMS MAY PERSIST INTO MONDAY AFTERNOON AS WELL BUT WILL
BE MORE SPOTTY.

[bdgwx]

Both 12Z HRW flavors (NMMB and ARW) have strongest UH tracks just to the east of Omaha between 18 and 21Z tomorrow. The 4km NAM nest has the strongest UH tracks closer to Des Moines. The regular NAM is showing widespread 50 kts of 0-6 km shear, but only isolated pockets of low level shear. Helicity values are still pretty respectable though. Unless I'm missing something it looks like a scenario with initiation closer to Des Moines would be along a boundary that is more east-west oriented and could mitigate the discrete nature, but if initiation is further west closer to Omaha then initiation would along a north-south oriented shortwave where shear vectors would be more perpendicular. Thoughts?

 

[Jim Marusak]

interesting setup here on the northern fringes of all this mess tomorrow in the twin cities. the recovery in the energy and moisture will be key for sure. here's a comparison between the NAM, GFS, GEM, and RAP soundings for 4pm (21z) sunday according to bufkit. all of them are only showing 1 to 1.5" of liquid. but they're also fatter with lower tops (CAPES near 1500, and helicities below 175). but the RAP is quite disappointing compared to the others (CAPE below 800, helicities also meager).

 

NAM

 

GFS

 

RAP

 

and the canadian regional.

http://meteocentre.com/models/gemreg_amer_00/skewt/skewt_Minneapolis_021.png

 

Redwood Falls (RWF) follows a similar pattern, and Rochester (RST) as well as LaCrosse (LSE) is as expected more unstable on all models and more consistent than the others. 

 

I understand from Reed Timmer's twitter/FB feeds that he's sticking mainly in IA with maybe a crossover into the i-90 corridor in MN east of 35 later on, which makes sense. but what I'm wondering here in St Paul is, am I close enough to all of this to actually see some nasty t-storms, or like minnesota meso was saying will we be just 20-40 miles too far north???

 

what's everyone's guess on what the analyses will show in the morning and how it'll setup?

[Thunder Road]

When I remember/feel like it, I play the storm chase game.  I (mostly randomly) put in Guthrie Center, IA for tomorrow, which is roughly along I-80 west of Des Moines.

 

SPC WRF is a mess with a big complex moving through eastern NE at 12z and it looks like that kills off the rest of the day.  NMM/ARW both hold off initiation in IA until ~22z but resolve a broken line of cells after that, as does the 4 km nest of the NAM.  Signals are there for something worth the drive in the northwest 1/4 or thereabouts of IA, and I would think that if the low-level backing that the NAM has advertised right under the LLJ verifies, it could be an interesting day before coagulation.

[thewxmann]

Jim Marusak,

 

Ignore the RAP output. It tends to unrealistically mix out the moisture during the day, which is what is causing the CAPE to disappear in this case.

[Jim Marusak]

I could see that as a real good starting spot t-road. if anything, I like central and eastern IA a ton for real serious chasing tomorrow, if I had the cash to do so.

[Jim Marusak]

Jim Marusak,

 

Ignore the RAP output. It tends to unrealistically mix out the moisture during the day, which is what is causing the CAPE to disappear in this case.

 that is definitely true, given how big that V is. but as for the NAM and GFS output, it does make for an interesting quandary up here. decent speed-shear but not much directional shear at all. almost says to me a day where if anything, we see good size gusts and some hail, but tornadoes aren't really on the board unless you get a rogue cell away from the flow from one of the remnant boundaries that may lay out there.

[Thunder Road]

Getting a pretty meh feeling about today - especially with how much convection is already ongoing in Nebraska.  That said, I'll probably head down to Atlantic, IA or thereabouts and see what happens.

 

My hope is that outflow from the complex over northern IA energizes the boundary that's already draped across IA, and that the stuff in NE either dissipates or lifts north all while the stratus that's currently socking in SW IA mixes out.  A tall order, I suppose.

 

But hey, you've got 45 kts just off the surface on the morning OAX sounding.  So that's something, I guess.

[Jim Marusak]

Getting a pretty meh feeling about today - especially with how much convection is already ongoing in Nebraska.  That said, I'll probably head down to Atlantic, IA or thereabouts and see what happens.

 

My hope is that outflow from the complex over northern IA energizes the boundary that's already draped across IA, and that the stuff in NE either dissipates or lifts north all while the stratus that's currently socking in SW IA mixes out.  A tall order, I suppose.

 

But hey, you've got 45 kts just off the surface on the morning OAX sounding.  So that's something, I guess.

good luck.

[Quincy]

The 12z HRRR dissipates the current convection fairly quickly by midday, but the caveat is that there isn't much air-mass recovery. As a result, it shows a messy storm mode this afternoon without much in the way of discrete supercells. I'm a bit suspect of this, but it shows the most impressive cell firing across north-central Iowa by early afternoon and tracks it into northeast sections after that.

 

It's getting to crunch time, as we'll see how the radar and observational trends look over the next few hours. I also feel like we'll be on the low end of expectations today. I'm staying put in Lincoln, NE for a bit since I stayed here last night. I'll make my way northeast later on, but I'm in no rush to leave with so much uncertainty at this point.