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Quincy

June 18th-21st Severe Events

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This time frame has been tracked for a while and although some of the more amplified model solutions from last week have faded, several severe weather threats should unfold in the coming days.

 

The pattern looks fairly zonal through the third quarter of June. A building ridge to the south will result in a jet steam across the northern tier of the country to southern Canada. This is not any surprise, especially since this season as a whole has behaved fairly well with respect to climo. The setup looks to include several high CAPE days with strong to locally extreme instability possible. Increased flow in the upper levels should be accompanied by several ripples and weak disturbances pinwheeling from the northern Plains to the upper Midwest.

 

Threats begin as far west as eastern Montana on Thursday the 18th and should focus predominantly on the Dakotas, portions of Nebraska and possibly as far east as Iowa/Minnesota. Although some of the details continue to evolve on the models, the general model consensus supports at some some severe thunderstorm potential for virtually every day in the period through the 22nd.

 

Pros: Strong instability, increased upper level flow, good wind shear - particularly directional.

 

Cons: Capping and convective inhibition will probably limit the threat to relatively small areas on most of these days, timing is a bit off - such that some of the threats may not ramp up until after peak heating and limited overlap of best instability with more favorable speed shear.

 

While no larger-scale or particularly significant event is expected, I would think all or at least most of these days should at least become SLGT risks with all severe weather hazards possible. Large to very large hail may be the biggest threat, followed by continued wind/MCS threats. A few tornadoes appear probable too. In the end, mesoscale features, particularly outflow boundaries, should narrow the focus as setups approach. 

 

Edit: Any discussion pertaining to the western Great Lakes threat on Monday the 22nd should be directed to the Lakes/Ohio Valley subforum.

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NAM soundings on Sharppy show that Aberdeen, South Dakota maxes out at an SCP value of 20, and and STP value of 3 on Friday night. In any case, June days on the Plains with 55kts of shear with dew points in the low 70's are generally pretty dangerous. (SREF shows 55 knots of shear at the North Dakota/South Dakota border on Friday.)

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Lol only 2015 could have an enhanced jet like this in June and no day that looks particularly interesting.

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NAM soundings on Sharppy show that Aberdeen, South Dakota maxes out at an SCP value of 20, and and STP value of 3 on Friday night. In any case, June days on the Plains with 55kts of shear with dew points in the low 70's are generally pretty dangerous. (SREF shows 55 knots of shear at the North Dakota/South Dakota border on Friday.)

Friday has some significant severe potential, even though the cap may be tough to bust until late afternoon or more likely early evening. SPC used some stronger wording in their latest day 2 update, mentioning a possible derecho and that they may upgrade to moderate risk in later outlooks.

As mentioned, strong instability is still projected to overlap with 45-55+ knots of bulk shear by 00z SAT over much of South Dakota, creating a relatively volatile environment. The kinematic forcing and resultant severe indices really light up at night, highlighting the very strong wind potential as storms quickly grow upscale.

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00z SPC WRF brings a strong derecho across SD tomorrow evening/overnight, looks like some initial supercells INVOF the Black Hills and westward as well.

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We could very well be looking at a setup for a derecho late Friday night into Saturday morning, particularly across South Dakota. At the very least, probably an intense MCS with fairly widespread damaging winds.

 

Capping during the day should really keep warm sector storm development to a minimum. Wouldn't be surprised if nothing really fires at all through 00z Saturday outside of Montana and the far western Dakotas. With little to disruption of daytime heating, there should be strong instability in place over western to central South Dakota, likely 3000+ J/kg MUCAPE into early Saturday evening. The NAM is likely a bit overdone with a sizable area of 4000+ J/kg MUCAPE. Even the GFS is on the order of 2500+ J/kg. 

 

As storms do eventually fire in eastern Montana and shift eastward, they should move into an increasingly volatile kinematic environment. The 850mb jet is forecast to increase to 50-60+ knots in northern Nebraska and advect into central South Dakota in the overnight. The GFS and NAM are in good agreement with the placement and strength of the LLJ progs. As storms merge and develop upscale, they'll have more than ample MUCAPE and moderate shear to sustain an MCS/derecho. The NAM forecast sounding for 05z SAT at PIR has 3312 J/kg MUCAPE with 57kts of effective shear. The 0-6km mean wind is 38kts. It appears that support is there both kinematically and instability-wise, with moderate to strong elevated CAPE continuing downstream into early Saturday morning.

post-533-0-65083100-1434692212_thumb.png

 

Just saw the SPC update and they held back without ramping up the probabilities really from the previous outlook. Can't say that's a bad idea, as there are multiple updates to see how the short-term environment is trending. The NAM hasn't been so hot with MCS development/placement lately, so the HRRR will be critical once it gets into range.

 

I could post a ton of graphics, but won't get carried away. FWIW, the 21z SREF derecho probabilities (I haven't really analyzed this index to see how it performs - we know the sig tor ingredients one is flawed and not all that reliable) increase to AOA 50% for about half of South Dakota by 06z SAT.

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HRRR has some rather potent looking supercells in W SD later on today.

15Z HRRR verbatim showed a pair of isolated supercells in W SD with impressive 2-5KM UH tracks approaching 200m2/s2... Very impressive environment will be in place, very supportive of all facets of SVR. HRRR shows 3000J/KG SBCAPE juxtaposed to 60-80kts of 0-6KM Shear.. Seems to be over doing the wind profile, with all other high-res guidance showing 50-60kts... Also, Forecast soundings from the HRRR/4KNAM/12KNAM across W/C SD show very impressive directional shear in place, and consequently ellongated curved hodographs, seems like any isolated cell would produce tornadoes just basing off of the veering wind profile and strong thermodynamic profile

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There have been some storms that have stalled in central South Dakota, and produced 2-4" of rain, and one instance of 2" hail. That's quite impressive for an area that had capping as per SPC mesoanalysis.

 

edit:

 

--

0215 PM     HEAVY RAIN       11 N REE HEIGHTS        44.68N  99.20W  06/19/2015  M2.00 INCH       HAND               SD   TRAINED SPOTTER                 2 INCHES OF RAIN HAS FALLEN IN APPROXIMATELY 90               MINUTES...STILL RAINING HEAVY  

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Tornado watch is likely in northern Wyoming and southern Montana.

 

This is the first moderate risk that has been issued in a while

 

--

DAY 1 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0300 PM CDT FRI JUN 19 2015   VALID 192000Z - 201200Z   ...THERE IS A MDT RISK OF SVR TSTMS OVER WRN/CNTRL SD...

---

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Tornado watch is likely in northern Wyoming and southern Montana.

 

This is the first moderate risk that has been issued in a while

 

--

DAY 1 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0300 PM CDT FRI JUN 19 2015   VALID 192000Z - 201200Z   ...THERE IS A MDT RISK OF SVR TSTMS OVER WRN/CNTRL SD...

---

MESOSCALE DISCUSSION 1073

NWS STORM PREDICTION CENTER NORMAN OK

0304 PM CDT FRI JUN 19 2015

AREAS AFFECTED...SOUTHERN AND SOUTHEASTERN MONTANA...AND ADJACENT

PARTS OF NORTHEASTERN WYOMING...AND NORTHWESTERN SOUTH DAKOTA

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 192004Z - 192200Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...A FEW THUNDERSTORMS HAVE DEVELOPED IN SOUTHWESTERN MONTANA

IN THE PAST HOUR...WITH MORE DEVELOPMENT EXPECTED ACROSS WESTERN

PARTS OF THE MD AREA IN THE NEXT HOUR OR TWO. A TORNADO WATCH IS

LIKELY WITHIN THE NEXT 1-2 HOURS.

DISCUSSION...A FEW THUNDERSTORMS HAVE DEVELOPED OVER SOUTHWESTERN

MONTANA WITHIN THE LAST 1-2 HOURS...WITH ADDITIONAL CUMULUS NOTED

FARTHER EAST ACROSS SOUTH CENTRAL MONTANA AND NORTHWESTERN WYOMING.

OBSERVATIONS AND MODEL GUIDANCE SUGGEST THAT A GRADUAL INCREASE IN

COVERAGE AND INTENSITY OF THUNDERSTORMS WILL COMMENCE IN THE

DISCUSSION AREA COINCIDENT WITH 1500-3000 J/KG MLCAPE...SUFFICIENT

DEEP SHEAR DUE TO 45-50 KNOT FLOW ALOFT...AND GLANCING INFLUENCE OF

SHORTWAVE CENTERED OVER BRITISH COLUMBIA. LARGE HAIL AND DAMAGING

WINDS ARE THE PRIMARY THREATS WITH INITIAL ACTIVITY...BUT THE

SUPERCELL/TORNADO AND SIGNIFICANT HAIL THREAT SHOULD INCREASE WITH

TIME AS LOW-LEVEL SOUTHEASTERLY FLOW STRENGTHENS ALONG WITH

INCREASED BOUNDARY LAYER MOISTENING/ADVECTION...ESPECIALLY IN

CENTRAL/EASTERN PARTS OF THE DISCUSSION AREA. NOCTURNAL

STRENGTHENING OF THE LOW-LEVEL JET MAY ALSO INCREASE TORNADO THREAT

TOWARD/JUST AFTER 00Z...ALTHOUGH THIS THREAT WILL BE DEPENDENT

SOMEWHAT ON HOW LONG STORMS CAN REMAIN DISCRETE AS UPSCALE GROWTH

INTO A CONVECTIVE COMPLEX IS EXPECTED TOWARD EVENING. TRENDS ARE

BEING MONITORED...AND A TORNADO WATCH MAY BE NEEDED PRIOR TO 21Z.

..COOK/GUYER.. 06/19/2015

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RAP.gifSpecial 18Z KRAP sounding.. pretty meh except for the 2500+ J/KG MUCAPE and 50+ kt 0-6KM SHR. Looks like mixing is a problem, but surface moisture should only continue to increase I believe.. Doesn't matter much anyways since KRAP is a tad south of the main threat area, which currently has DP's in the upper sixties. Seems as though this severe cluster/MCS and the associated cloud cover over central SD could prevent a more long-lived eastward progression of the MCS later tonight, and this is supported by the 18Z RAP which shows a general weakness in instability across this area later on tonight around the time the complex would be moving through. Also FWIW, the 18Z HRRR continues to show isolated supercells developing over NE WY/SW SD this evening... Which has also gained support from the 4KM NAM which shows an intense lone ranger moving across the area with a strong 0-1KM UH track approaching 300m2/s2. 

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HRRR is grossly over-estimating convection across eastern Wyoming already. Barely anything on satellite, except for up near the Montana border. We'll see how long capping wins out and if it's detrimental to initiation or beneficial by keeping any few cells mainly discrete. Not bad to see dew-points up to 70 at Philip. Very favorable shear to advect east and we'll pump up the LLJ from fhe south later on. I think western South Dakota has a narrow window around to shortly after 00z, but if a storm stays isolated, a strong tornado wouldn't surprise me. Climo has very few sig tors that far northwest, but at the same time it's a high-end environment compared to past tornado events.

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HRRR is grossly over-estimating convection across eastern Wyoming already. Barely anything on satellite, except for up near the Montana border. We'll see how long capping wins out and if it's detrimental to initiation or beneficial by keeping any few cells mainly discrete. Not bad to see dew-points up to 70 at Philip. Very favorable shear to advect east and we'll pump up the LLJ from fhe south later on. I think western South Dakota has a narrow window around to shortly after 00z, but if a storm stays isolated, a strong tornado wouldn't surprise me. Climo has very few sig tors that far northwest, but at the same time it's a high-end environment compared to past tornado events.

One reasoning for the lack of archived sig tors could deal with the sparsity of population/buildings in the area as well. To get Sig Tor in climo you need buildings to hit.

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Apparently there was a brief tor with the supercell SE of Broadus, MT a short time ago.

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89mph gust just recorded at a SDDot asos nw of Belle Fourche, SD and 82mph gusts at Bismarck, ND airport. and in the Black Hills has several cells with decent circulation signatures. and those clusters are headed ESE. yikes..  hopefully they get here in the twin cities weaker than that, or this could be big trouble.

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89mph gust just recorded at a SDDot asos nw of Belle Fourche, SD and 82mph gusts at Bismarck, ND airport. and in the Black Hills has several cells with decent circulation signatures. and those clusters are headed ESE. yikes.. hopefully they get here in the twin cities weaker than that, or this could be big trouble.

Seeing >120mph velocities at a beam height of 2200 feet with the eastern SW SD supercell.

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Good grief!

 

SEVERE WEATHER STATEMENT  
NATIONAL WEATHER SERVICE RAPID CITY SD  
838 PM MDT FRI JUN 19 2015  
 
SDC019-093-200315-  
/O.CON.KUNR.SV.W.0085.000000T0000Z-150620T0315Z/  
MEADE SD-BUTTE SD-  
838 PM MDT FRI JUN 19 2015  
 
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 915 PM MDT  
FOR SOUTHWESTERN MEADE AND SOUTHEASTERN BUTTE COUNTIES...  
 
AT 838 PM MDT...A SEVERE THUNDERSTORM WAS LOCATED 11 MILES EAST OF  
BEAR BUTTE STATE PARK...OR 15 MILES EAST OF STURGIS...MOVING  
SOUTHEAST AT 45 MPH.  
 
THIS IS A VERY DANGEROUS STORM.  
 
HAZARD...90 MPH WIND GUSTS AND GRAPEFRUIT SIZE HAIL.  
 
SOURCE...RADAR INDICATED.  
 
IMPACT...YOU ARE IN A LIFE-THREATENING SITUATION. FLYING DEBRIS MAY  
BE DEADLY TO THOSE CAUGHT WITHOUT SHELTER. MOBILE HOMES  
WILL BE HEAVILY DAMAGED OR DESTROYED. HOMES AND BUSINESSES  
WILL HAVE SUBSTANTIAL ROOF AND WINDOW DAMAGE. EXPECT  
EXTENSIVE TREE DAMAGE AND POWER OUTAGES.  

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SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE RAPID CITY SD
914 PM MDT FRI JUN 19 2015

SDC093-200330-
/O.CON.KUNR.TO.W.0007.000000T0000Z-150620T0330Z/
MEADE SD-
914 PM MDT FRI JUN 19 2015

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 930 PM MDT FOR SOUTH
CENTRAL MEADE COUNTY...

AT 914 PM MDT...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO WAS
LOCATED NEAR HEREFORD...OR 29 MILES NORTHEAST OF RAPID CITY...MOVING
EAST AT 50 MPH.

THIS IS A PARTICULARLY DANGEROUS SITUATION.

HAZARD...DAMAGING TORNADO.

SOURCE...RADAR CONFIRMED TORNADO.

IMPACT...YOU ARE IN A LIFE THREATENING SITUATION. FLYING DEBRIS MAY
BE DEADLY TO THOSE CAUGHT WITHOUT SHELTER. MOBILE HOMES
WILL BE DESTROYED. CONSIDERABLE DAMAGE TO
HOMES...BUSINESSES AND VEHICLES IS LIKELY AND COMPLETE
DESTRUCTION IS POSSIBLE.

LOCATIONS IMPACTED INCLUDE...
ELM SPRINGS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINFALL MAY HIDE THIS TORNADO. DO NOT WAIT TO SEE OR HEAR THE
TORNADO. TAKE COVER NOW.

&&

LAT...LON 4433 10286 4437 10284 4442 10239 4414 10255
TIME...MOT...LOC 0314Z 282DEG 46KT 4434 10277

TORNADO...OBSERVED
TORNADO DAMAGE THREAT...CONSIDERABLE
HAIL...4.00IN

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VWP from KUDX is very impressive, no wonder this storm is a beast.

EDIT: Also per mesoanalysis the long-lived tornadic supercell over Meade and Pennington counties will move into an increasing favorable environment for low-level mesocyclones it seems. Recent VWP samplings from KUDX show impressive veering with height and strong backed LLVL shear, SPC mesoanalysis shows 0-1KM shear values 25-35kts and increasing, effective shear of 70kts and CAPE values of 3000-4000J/KG all downstream and with the relatively slow cooling of the boundary layer, the tornado threat could persist for several more hours, pending the continue discrete/ semi-discrete nature of the supercell. 

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Still on the ground per RAP tor warning...

THE NATIONAL WEATHER SERVICE IN RAPID CITY HAS ISSUED A

* TORNADO WARNING FOR...
SOUTH CENTRAL MEADE COUNTY IN WEST CENTRAL SOUTH DAKOTA...
EAST CENTRAL PENNINGTON COUNTY IN WEST CENTRAL SOUTH DAKOTA...

* UNTIL 1015 PM MDT

* AT 926 PM MDT...A CONFIRMED LARGE AND EXTREMELY DANGEROUS TORNADO
WAS LOCATED NEAR ELM SPRINGS...OR 32 MILES NORTHEAST OF RAPID
CITY...MOVING SOUTHEAST AT 40 MPH.

THIS IS A PARTICULARLY DANGEROUS SITUATION.

HAZARD...DAMAGING TORNADO.

SOURCE...RADAR CONFIRMED TORNADO.

IMPACT...YOU ARE IN A LIFE THREATENING SITUATION. FLYING DEBRIS
MAY BE DEADLY TO THOSE CAUGHT WITHOUT SHELTER. MOBILE
HOMES WILL BE DESTROYED. CONSIDERABLE DAMAGE TO
HOMES...BUSINESSES AND VEHICLES IS LIKELY AND COMPLETE
DESTRUCTION IS POSSIBLE.

* THE TORNADO WILL BE NEAR...
ELM SPRINGS AROUND 935 PM MDT.
CREIGHTON AROUND 1000 PM MDT.

THIS INCLUDES INTERSTATE 90 IN SOUTH DAKOTA BETWEEN MILE MARKERS 93
AND 110.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINFALL MAY HIDE THIS TORNADO. DO NOT WAIT TO SEE OR HEAR THE
TORNADO. TAKE COVER NOW.

&&

LAT...LON 4423 10277 4435 10268 4426 10202 4396 10227
TIME...MOT...LOC 0326Z 294DEG 35KT 4429 10266

TORNADO...OBSERVED
TORNADO DAMAGE THREAT...CONSIDERABLE
HAIL...4.00IN

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Possible PDS SVR watch coming soon....

MESOSCALE DISCUSSION 1079
NWS STORM PREDICTION CENTER NORMAN OK
1031 PM CDT FRI JUN 19 2015

AREAS AFFECTED...W-CNTRL INTO CNTRL AND SERN SD

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 200331Z - 200430Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...THE POTENTIAL FOR AN UPPER-TIER SEVERE WIND EVENT
/POSSIBLE DERECHO/ IS INCREASING THIS EVENING. A NEW
WATCH...POSSIBLY A PARTICULARLY DANGEROUS SITUATION SEVERE
THUNDERSTORM WATCH...BE COORDINATED AND ISSUED WITHIN THE NEXT 30
MINUTES.

DISCUSSION...RADAR MOSAIC AT 0325Z SHOWS A HP SUPERCELL 25 MI N OF
RAP WITH AN ELONGATED COLD POOL EXTENDING WWD NEAR THE
LAWRENCE/PENNINGTON COUNTY LINE. ADDITIONAL SEVERE STORMS OVER
CROOK AND BUTTE COUNTIES MAY EVENTUALLY MERGE WITH THE ACTIVITY
FARTHER E AND ESTABLISH INTENSE UPDRAFTS ON THE LEADING EDGE OF THE
GUST FRONT. IT APPEARS THIS STORM-SCALE EVOLUTION OR FURTHER
DEVELOPMENT INVOF THE SUPERCELL WILL BE NECESSARY FOR THE CONVECTIVE
MODE TRANSITION FROM HP SUPERCELL TO SEVERE BOW ECHO.

THE MOIST LOW-LEVELS /UPPER 60S DEWPOINTS/ DOWNSTREAM COMBINED WITH
THE STRENGTHENING OF A SLY 50+ KT LLJ WILL MAINTAIN A STRONG
LOW-LEVEL MASS FLUX IN THE AREA. THE STRONG DEEP-LAYER WLY
MID-UPPER TROPOSPHERIC FLOW /REFERENCE THE KUDX VAD/ COUPLED WITH
STRONG BUOYANCY ARE RESULTING IN AN ENVIRONMENT VERY FAVORABLE FOR
SEVERE STORMS. A RESIDUAL BOUNDARY DRAPED ACROSS S-CNTRL SD AND
INTERSECTING THE MEADE COUNTY HP SUPERCELL WILL PROBABLY SERVE TO
FOCUS A PREFERRED CORRIDOR FOR AN UPPER-TIER SEVERE WIND GUST EVENT
/POSSIBLE DERECHO/ THIS EVENING INTO THE OVERNIGHT. SEVERE WIND
GUSTS 60-80 MPH WILL BECOME PROBABLE WITH THE MORE INTENSE
DOWNDRAFTS. LOCALIZED WIND SWATHS OF 80-100 MPH ARE POSSIBLE...IN
ADDITION TO TORNADOES WITH THE MORE PERSISTENT CIRCULATIONS.

..SMITH/HART.. 06/20/2015

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RGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 315
NWS STORM PREDICTION CENTER NORMAN OK
1055 PM CDT FRI JUN 19 2015

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
SOUTHWEST AND SOUTH CENTRAL SOUTH DAKOTA

* EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 1055 PM
UNTIL 400 AM CDT.

...THIS IS A PARTICULARLY DANGEROUS SITUATION...

* PRIMARY THREATS INCLUDE...
WIDESPREAD DAMAGING WINDS AND SCATTERED SIGNIFICANT GUSTS TO 90
MPH EXPECTED
WIDESPREAD LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 3
INCHES IN DIAMETER LIKELY
A FEW TORNADOES POSSIBLE

SUMMARY...FAST-MOVING INTENSE SUPERCELL STORMS OVER WESTERN SOUTH
DAKOTA WILL TRACK ACROSS THE WATCH AREA TONIGHT...WITH THE POTENTIAL
OF WIDESPREAD AND EXTREMELY DAMAGING WINDS ALONG WITH LARGE HAIL AND
ISOLATED TORNADOES.

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