May 8 - 13 Severe Weather

[MNstorms]

Looking more like a June weather pattern than a May one over the northern plains. There was an area highlight for Sunday but that was taken off today. Jet stream is really constant with trough ejections.

Medium-range guidance is in good agreement that the overall upper
   pattern amplifies significantly on D4/Sunday and D5/Monday as
   western CONUS troughing deepens and upper ridging along the MS
   Valley builds. Position of the upper trough leads to deep
   southwesterly flow aloft across the Plains. At the same time, strong
   moisture advection will occur, with mid 60s dewpoints reaching
   eastern KS by D4/Sunday and into much of IA by D5/Monday. By
   D6/Tuesday, a large area of 70+ dewpoints may exist from the
   Arklatex north into IA. 

   This low-level moisture, coupled with the EML fostered by the deep
   southwesterly flow aloft, is forecast to result in strong
   instability across at least some portion of the Plains and/or
   Upper/Mid MS Valley from D4/Sunday through at least D6/Tuesday. The
   somewhat stagnant upper pattern and lack of progressive surface
   features leads to dearth of forcing for ascent for D4/Sunday,
   leading to predictability issues. Some elevated thunderstorms are
   possible across the northern Plains, but uncertainty on location and
   overall severity merit precluding any outlook areas. Somewhat more
   discernible/predictable surface features are expected on D5/Monday,
   with a front moving into the upper MS Valley. Given the forecast
   buoyancy and shear, any storms that do develop will likely be
   severe. 

   Some severe potential may persist across the Upper/Mid MS Valley on
   D6/Tuesday, but guidance varies crucially on the position of various
   surface features, limiting predictability. Additionally, guidance
   indicates that upper ridging will build west across more of the
   Plains on D6/Tuesday and D7/Wednesday, likely shifting the potential
   for storms back west towards the High Plains.

 

 

 

 

[MNstorms]

NAM isn't even close to agreement with other models for Monday.

[Quincy]

Sunday the 8th looks like it will mostly remain capped, but maybe there will be isolated severe storms.

Monday appears to have the most apparent potential through this period. Most likely in or near Iowa.

The 10-13th is forecast to be an odd pattern for early/mid May. Pronounced ridging across the central U.S. and a cutoff low across the Southeast. I’m not sure there will be much overlap between appreciable forcing, shear and instability. Still, I could see a few severe storms, somewhere between the central High Plains and Upper Midwest. 

[MNstorms]

Well that's an interesting decrease in chances.

[CheeselandSkies]

That stupid cutoff (remnants of the previous trough that produced the severe weather Wednesday through yesterday) is what will ruin this next few days of would-be setups by preventing the next trough from ejecting across the Plains properly.

[MNstorms]

Both RAP and HRRR have insane ingredients but barely storms developing.

 

 

[MNstorms]

SPC still thinking Iowa to Wisconsin.

 

 

[MNstorms]

Big hailers tonight and tomorrow just going to miss me.

[MNstorms]

Tornado watch likely. I don't remember the last time I've seen a dry line this far north.

Probability of Watch Issuance...95 percent

   SUMMARY...The airmass across southern MN into northern IA is rapidly
   destabilizing and severe potential is increasing. A tornado watch
   will likely be needed by 20-21z.

   DISCUSSION...The airmass across southern MN into far northern IA is
   rapidly recovering from morning convection and quickly
   destabilizating. Mid to upper 60s F surface dewpoints are now
   widespread across northern IA to near the MN state line as
   temperatures have warmed into the upper 60s to mid 70s. This is
   resulting in rapidly eroding MLCIN. Towering cumulus have been noted
   across southwest MN over the past hour or so as a north to south
   oriented surface boundary/dryline quickly progresses eastward. A
   warm front is extending southeast from a surface low near Fargo ND
   toward southeast MN. The warm front is forecast to lift northward
   into central MN/west-central WI over the next few hours. 

   While large-scale ascent is forecast to remain rather weak, strong
   vertical shear, both effective and in the 0-1 km layer, steep lapse
   rates and strong instability will support organized supercells.
   Weaker forcing will likely limit the number of storms, but one or
   two intense cells are expected to develop over the next few hours.
   Current VWP data from the KMPX 88-D near the warm frontal zone
   already indicated enlarged, favorably curved hodographs with 0-1 km
   SRH greater than 450 m2/s2. Any cell that develops withing the
   northward retreating warm frontal zone will have enhanced tornado
   potential in addition to large hail and damaging gusts.

 

MCD is farther west than I would have thought.

[yoda]

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 194
   NWS Storm Prediction Center Norman OK
   250 PM CDT Mon May 9 2022

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Eastern Minnesota
     Western Wisconsin

   * Effective this Monday afternoon and evening from 250 PM until
     1000 PM CDT.

   * Primary threats include...
     A few tornadoes possible
     Scattered large hail and isolated very large hail events to 2.5
       inches in diameter possible
     Scattered damaging wind gusts to 70 mph possible

   SUMMARY...Supercell thunderstorms are expected across portions of
   eastern Minnesota and western Wisconsin this afternoon and evening
   amid a strongly unstable air mass. All severe hazards are possible
   with these storms, including tornadoes and very large hail.

https://www.spc.noaa.gov/products/watch/ww0194.html

[MNstorms]

Wednesday looks interesting. I wonder if we'll see in upgrade for Day2.

RAP model is uhh, interesting...

8000+ CAPE anyone? 

[MNstorms]

I don't remember the last time I saw back to back 10% tornado risks in Minnesota. 

 

 

Day 1

 

...SUMMARY...
   Severe thunderstorms are expected this afternoon/evening over the
   north-central states. Very large hail, wind, and a threat for
   tornadoes is expected. Additionally, widely scattered severe
   thunderstorms are anticipated across the southern High Plains.
   Wind/hail are the primary threats.

   ...North-Central States...

   Weak mid-level short-wave trough that translated across northern
   Mexico into the southern High Plains Tuesday afternoon has
   contributed to a substantial MCS over the eastern TX Panhandle into
   western OK. This convection is expected to propagate slowly east and
   gradually weaken by sunrise. However, latest diagnostic data
   suggests an MCV has evolved over the northeastern TX Panhandle along
   the northern fringe of the MCS. HREF members appear to have sampled
   this feature well, and subsequent movement should track
   north-northeast across KS into southeast NE by 18z, then into
   southern MN by 12/00z. As the mid-level feature lifts northeast, LLJ
   should respond and strengthen across western IA into western MN.
   This will encourage the warm front draped across IA/southeast NE to
   retreat into southern MN prior to the aforementioned short wave. 

   Surface dew points are quite high across the warm sector south of
   this boundary and moderate/high buoyancy is expected to develop by
   mid day. Maximum surface heating/steepest surface-3km lapse rates
   are forecast across NE into extreme western IA.  As a result, there
   is increasing concern that supercells will develop ahead of the
   short wave/MCV by 19-20z over eastern NE, then spread northeast
   along the warm front. Ample shear/buoyancy will be present for very
   large hail with this activity, along with a tornado threat. Have
   increased severe probabilities for this corridor to account for more
   pronounced supercell threat ahead of this MCV.

 

Day2

 ...SUMMARY...
   Well-organized severe storms are expected to evolve from the eastern
   Dakotas and Minnesota southward into the central Plains Thursday. 
   Very large hail and damaging winds are expected, along with
   potential for a couple of tornadoes.

   ...Synopsis...
   While an upper low retrogrades westward out of the western Atlantic
   into the Southeast, a vigorous, increasingly negatively tilted
   trough will advance rapidly northeastward from the Rockies
   into/across the northern and central Plains Thursday.

   As this occurs, rapid surface cyclogenesis will occur across the
   Dakotas during the afternoon and evening, with the low becoming
   occluded overnight as it retrogrades northwestward into northwestern
   North Dakota through the end of the period.  Meanwhile, a warm front
   will shift northward across the upper Mississippi Valley, while a
   cold front advances eastward across the northern and central Plains
   through the period.

   ...Eastern Dakotas east to the Upper Mississippi Valley and south
   across the Mid Missouri Valley...
   Lingering/elevated convection -- and possible/low-end severe
   potential -- may be spreading across Lake Superior/western Upper
   Michigan/northern Wisconsin at the start of the period.

   Meanwhile, diurnal heating of a moist airmass across the
   north-central U.S. will commence.  While warm-sector capping will
   inhibit storm initiation well into the afternoon, increasing ascent
   ahead of the advancing upper system -- focused near the surface cold
   front -- will result in storm development within a zone from
   central/eastern South Dakota southward into northern Kansas.  

   Given increasing flow aloft supporting favorable shear for organized
   storms, updrafts will likely acquire rotation rather quickly.  Very
   large hail and locally damaging winds can be expected, with a couple
   of tornadoes also possible -- particularly near a northward-moving
   warm front expected to extend from an eastern South Dakota surface
   low, eastward across the central Minnesota vicinity during the
   afternoon and early evening.

   With time, upscale growth/linear organization of the convection is
   expected, possibly evolving into one or more small-scale bowing
   MCSs.  Along with continued hail potential and some risk for a
   tornado or two embedded within the line, damaging wind risk would
   increase/expand into the evening hours, assuming this upscale
   evolution.  Risk will likely continue into the overnight hours,
   though a general/gradual weakening of storms with time is expected.

[Quincy]

Localized supercell potential evident today in the front right quadrant of an MCV, which is moving into Nebraska late this morning. 

The threat should maximize between far northeastern Nebraska and southwestern Minnesota, where supercell wind profiles impinge on large/locally extreme instability late this afternoon. 

The main limiting factor I see is that there may be some subtle veer-back signatures in the wind profiles, due to the MCV moving NNE (southerly component to 500mb flow). Wind fields should improve toward 00z and especially with northward extent, with a lifting warm front, moving north across southern Minnesota. 

I’d expect an arc of semi-discrete supercells to intensify and tend to cluster, as they track across the NE/IA/SD border area. There is certainly a window for a few tornadoes, but storm mode may limit this from being a higher end localized event. If any isolated cells form ahead of the main arc of storms, they could pose a somewhat greater tornado risk across southern Minnesota.

[MNstorms]

This is after 25 minutes. Already a solid supercell.

[Quincy]

Relatively messy storm mode so far. Keeping an eye on an arc of semi-discrete cells around the Sioux City area. Those may have the least disrupted inflow environment to work with. Storms farther north appear to be clustering and interacting with cooler outflow, while storms to the west near the MCV center are likely elevated. 

[MNstorms]

 SUMMARY...A severe hail, wind, and tornado risk persist mainly from
   southeast South Dakota into southwest Minnesota. Hail may eventually
   occur north of the tornado watch.

   DISCUSSION...An MCV continues to move rapidly north, now crossing
   the MO River out of northeast NE, with arcing line of storms
   extending southeastward along the valley.  Meanwhile, other storms
   currently extend from west of FSD north and eastward into southwest
   MN near the warm front.

   Surface observations show a cool boundary layer along the warm
   front, which has recently become reinforced by outflows. In
   addition, dewpoints continue to fall in the well-mixed air across
   IA. The result is a relatively narrow zone of tornado potential over
   the next few hours, from southeast SD eastward along the front into
   southern MN. Any supercells in this zone may produce a brief
   tornado, but meridional flow aloft near the MCV may push cells
   quickly north of the boundary where they will become elevated.

[MNstorms]

Tornado watch expanded. 

[MNstorms]

Multiple tornado warnings now. 

[MNstorms]

Well I'm centered in this.

SUMMARY...The threat of severe thunderstorms including tornadoes
   appears to be increasing across southern Minnesota and northern
   Iowa.

   DISCUSSION...Latest surface analysis continues to show a surface low
   associated with a well-defined MCV over southeast SD.  A warm front
   extends eastward from the low along the MN/IA border.  Relatively
   strong heating has been occurring along and north of the warm front
   over southern MN, where backed low-level winds and dewpoints in the
   upper 60s to lower 70s are resulting in a very favorable environment
   for supercell development.  Recent CAM and WoFS solutions also
   indicate this potential.  A compact low-level jet is expected to
   strengthen in the next few hours in this area as well, enhancing
   low-level shear and suggesting a heightened risk for a few
   tornadoes.  Large hail and damaging winds would also be possible
   with storms along/north of the warm front.

   Farther west, radar suggests a developing bowing complex over
   Murray/Cottonwood/Nobles/Jackson counties MN.  This activity will
   likely accelerate eastward along the warm front during the next 2-3
   hours, posing an enhanced risk of damaging wind gusts and transient
   QLCS spinups.

[MNstorms]

Interesting that they are issuing tornado warnings well ahead of the line. 

[mob1]

25 minutes ago, MNstorms said:

Interesting that they are issuing tornado warnings well ahead of the line. 

A couple of confirmed tornadoes embedded in that line now. It's hard to stay on top of it given how fast they spin up and disappear, which is probably why they're doing this. 

[MNstorms]

Highest possible wind speed so far. I've only ever seen 80+ in 2008.

[Witness Protection Program]

Tornado warnings on track to include the Twins-Astros game soon.

[MNstorms]

Just now, Witness Protection Program said:

Tornado warnings on track to include the Twins-Astros game soon.

I'm shocked they didn't postpone the game before the start. Not safe to send people back out onto the road.

[Witness Protection Program]

As an Astros fan, we need to get 5 innings in now...

Seems like that line will move through, so maybe a 1 to 2 hour delay?  Not sure I'd want to wait out a tornado in a public area under a stadium, do they have parking garages near the stadium?

[MNstorms]

So many warnings so far for non existent rotation but not for this.

[Quincy]

Day 1 wind-driven moderate risk issued today for parts of the eastern Dakotas and western Minnesota. Based on wind profiles and model simulations, looks like storm mode will go linear very fast. This definitely has the feel of a summer setup, but it should help usher in somewhat cooler temperatures for the north-central states. 

[mob1]

SPC added an significant tornado contour in northeastern SD despite expecting things to grow upscale very quickly. Even with a messy storm mode, backed surface winds and eye-raising instability can lead to a couple of significant embedded tornadoes. Here's a cherry-picked sounding in SD from the latest HRRR. 

[Chinook]

A squall line is already getting going at Broken Bow, Nebraska. Dew points up to 70 at Huron, SD and Sioux Falls, SD. 

this probably needs a severe storm watch right now

Quote

  Areas affected...far north-central Kansas across much of central
   Nebraska and toward southeast South Dakota

   Concerning...Severe potential...Watch likely 

   Valid 121839Z - 122115Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Storms are likely to increase in coverage and intensity
   over the next several hours, with damaging winds and hail expected.

 

[MNstorms]

Early convection has seems to keep the warm front south, even moving it more south. I don't know if that was expected.