CHASE CASE 1

I've just arrived at my target of Plankinton, SD and realize I might've over estimated the low level winds pushing the front this far E. A quick glimpse at the 18z models has really got me second guessing my forecast. What to do? Initiation appears to be imminent further W than I'd have liked but then again, by the time cells get this far E they might've matured to the point of producing? Maybe I should u-turn and head back W on I-90? Nope, I finally decide to stick it out here in Plankinton, SD and will adjust back W if I absolutely have to. I'm hoping my patience will pay off when cells move into a rapidly destabilizing environment where I'm sitting now. The waiting game begins...
 
At 18 Z the WF has made some nice ground and now sits draped along the ND/SD border. Gonna stay in the Warm Sector and use I-90 as my E-W pipeline. Gonna sit in Murdo, SD and see what the new convection off to the west is doing. May start to trickle west if I get too antsy.
 
Still in Murdo, SD with a nice cu field developing overhead and to the north. The boundary still looks to be sitting on I90.
 
20Z SEVERE WEATHER UPDATE

MESOSCALE DISCUSSION #1:

n53itc.gif


MESOSCALE DISCUSSION
NWS STORM PREDICTION CENTER NORMAN OK


AREAS AFFECTED...CENTRAL/SERN MN AND WCENTRAL WI

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID

ISOLATED SVR STORMS CAPABLE OF PRODUCING LARGE HAIL/DAMAGING WINDS
MAY DEVELOP IN THE NEXT HOUR. STRENGTH OF VERTICAL SHEAR COMBINED
WITH MODERATE INSTABILITY WILL FAVOR AN ORGANIZED SVR THREAT. A WW
MAY BE NEED SHORTLY.

SFC ANALYSIS INDICATES A TROUGH/OUTFLOW BOUNDARY EXTENDING FROM A
SFC LOW NEAR STC SEWD TO NEAR LSE. 18Z MPX SOUNDING INDICATE
MODERATE INSTABILITY WITH MUCAPES AROUND 3000 J/KG AND STEEP MID
LEVEL LAPSE RATES AROUND 7.5 DEG C/KM. SWLY WINDS TO THE WEST OF THE
SFC TROUGH WERE AIDING IN MIXING DOWN OF DRIER 850 MB AIR AND DEWPTS
HAVE SLOWLY FALLEN INTO THE LOWER 60S. GIVEN FOCUSED LIFT AHEAD OF
APPROACHING SHORTWAVE TROUGH...AND MODERATE LOW LEVEL /100-150 J/KG
FROM 0-1 KM/ SHEAR ALONG THE OUTFLOW BOUNDARY WILL SUPPORT THE
THREAT FOR ISOLATED TORNADOES IN ADDITION TO LARGE HAIL AND DAMAGING
WINDS WITH ANY STORMS THAT MOVE SEWD ALONG THE BOUNDARY.


MESOSCALE DISCUSSION #2:

2dbqjio.gif


MESOSCALE DISCUSSION
NWS STORM PREDICTION CENTER NORMAN OK


AREAS AFFECTED...WRN/CENTRAL SD INTO NWRN-NORTH CENTRAL NEB

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID

WW WILL BE REQUIRED SOON.

19Z SURFACE ANALYSIS SHOWED A PRIMARY SURFACE LOW OVER SRN WY
ASSOCIATED WITH THE STRONG MID LEVEL SHORT WAVE TROUGH MOVING NEWD
ACROSS WY. A SECOND LOW WAS DEVELOPING ACROSS THE NEB PANHANDLE
WITH TWO ZONES OF CONVERGENCE EXTENDING EWD AND NEWD FROM THE NEB
LOW. ONE WAS LOCATED ALONG THE SD/NEB BORDER...AND THE SECOND
EXTENDED NEWD INTO CENTRAL...THEN NERN SD. SELY LOW LEVEL WINDS
WILL CONTINUE TO TRANSPORT MOISTURE WNWWD INTO WRN SD/WRN NEB WITH
THE 60 F SURFACE ISODROSOTHERM NOW EXTENDING FROM FAITH SD SWD INTO
NEB AT CDR TO OGA. THIS COMBINED WITH STEEPENING MID LEVEL LAPSE
RATES IS AIDING IN DESTABILIZATION WITH MODERATE INSTABILITY
EXTENDING WWD INTO SWRN SD/NWRN NEB.

VIS IMAGERY SHOWED CU/TCU CONTINUING TO DEVELOP ACROSS WRN SD AND
ALONG THE SD/NEB BORDER REGION. THUNDERSTORMS WILL CONTINUE TO
DEVELOP OVER WRN SD...WITH ADDITIONAL DEVELOPMENT SWD INTO NWRN-NRN
NEB AS LARGE SCALE ASCENT SPREADS EWD ATOP THE DESTABILIZING AIR
MASS.
 
Gonna head west from Presho, SD on I 90 and look for a tower. Some nice TCu going up to my W and SW. Another hours drive west to Kadoka so maybe something will go between now and then....
 
Can we get 20Z surface, sat, and radar?

I AM PUTTING TOGETHER 21Z DATA NOW

WILL POST 21Z DATA LATER TODAY TO GIVE THOSE WHO WORK A CHANCE TO CHIME IN. I'LL POST AROUND NOON, AND WE CAN WRAP UP THE CHASE TONIGHT WITH THE REST OF THE DATA, CLOSING WITH PHOTOS/VIDEO AND REPORTS.


I WILL DO SOME RESEARCH TO SEE IF I CAN THROW SOME TID BITS IN BEFORE THAT DATA GOES OUT.
 
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21Z CONVECTIVE OUTLOOK


DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK


VALID


...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF SD...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE PLAINS THROUGH THE
UPPER MS VALLEY...

...CNTRL THROUGH NRN PLAINS...

THIS AFTERNOON A QUASISTATIONARY FRONT EXTENDS FROM A WEAK SURFACE
LOW OVER THE NEB PANHANDLE NEWD THROUGH CNTRL SD TO A SECONDARY LOW
OVER CNTRL MN. THIS BOUNDARY CONTINUES EWD THROUGH NRN WI. A DRYLINE
EXTENDS SWD FROM THE LOW IN THE NEB PANHANDLE THROUGH NERN CO...WRN
KS AND W TX.

BOUNDARY LAYER DEWPOINTS IN THE LOW TO MID 60S EXIST IN VICINITY OF
THE STATIONARY BOUNDARY ACROSS SD. STRONG SURFACE HEATING CONTINUES
TO DESTABILIZE THE ATMOSPHERE WITH MLCAPE FROM 1500 TO 3000 J/KG
EXPECTED THIS AFTERNOON. STRONG TO SEVERE STORMS ARE CURRENTLY
DEVELOPING OVER THE HIGHER TERRAIN OF WY INTO WRN SD WITHIN A ZONE
OF INCREASING DEEP LAYER ASCENT DOWNSTREAM FROM SHORTWAVE TROUGH
LIFTING NEWD THROUGH SWRN WY. SOME OF THIS ACTIVITY MAY SPREAD INTO
ERN MT. FARTHER EAST INTO SD WHERE STRONGER INSTABILITY EXIST...THE
ATMOSPHERE IS STILL CAPPED. HOWEVER...CUMULUS IS INCREASING FROM
SWRN THROUGH S CNTRL SD IN VICINITY OF THE STATIONARY BOUNDARY.
STORMS MAY DEVELOP IN THIS AREA BY 21-22Z AS CAP WEAKENS.

INITIAL DEVELOPMENT APPEARS MORE LIKELY OVER SWRN SD WHERE FORCING
FOR ASCENT ASSOCIATED WITH EJECTING MID-UPPER JET WILL OVERSPREAD
THE REGION AND HELP TO WEAKEN CAP. ACTIVITY MAY DEVELOP EWD THROUGH
SD DURING THE EVENING AS LIFT AND WARM ADVECTION ASSOCIATED WITH
INTENSIFYING LOW LEVEL JET INCREASES. SUPERCELLS WITH VERY LARGE
HAIL APPEAR LIKELY GIVEN THE STRONG DEEP LAYER SHEAR ASSOCIATED WITH
APPROACHING MID LEVEL JET. A WINDOW MAY EXIST FOR A FEW
TORNADOES...ESPECIALLY NEAR THE BOUNDARY OVER SD AS THE LOW LEVEL
JET STRENGTHENS. HOWEVER...STORMS MAY CONSOLIDATE INTO AN MCS THIS
EVENING WITH A CONTINUED THREAT OF LARGE HAIL AND DAMAGING WIND AS
IT SPREADS EWD THROUGH SD.


...UPPER MS VALLEY AREA...

AN OUTFLOW BOUNDARY EXTENDS SEWD THROUGH WRN WI FROM A SURFACE LOW
IN E CNTRL MN. THE ATMOSPHERE HAS BECOME MODERATELY UNSTABLE S OF
THIS BOUNDARY WITH MLCAPE AROUND 2000 J/KG. STORMS HAVE RECENTLY
BEEN DEVELOPING NEAR THE TRIPLE POINT AT THE INTERSECTION OF THE
OUTFLOW BOUNDARY AND STATIONARY FRONT. BEST TORNADO POTENTIAL SHOULD
BE IF STORMS CAN MOVE SEWD ALONG OR JUST N OF THE OUTFLOW BOUNDARY
WHERE THE LOW LEVEL FLOW REMAINS BACKED TO SELY AND WHERE IT APPEARS
THAT ADDITIONAL RECOVERY WILL OCCUR WITH CONTINUED SURFACE HEATING.
OTHERWISE LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS.


...SRN PLAINS...

THREAT REMAINS CONDITIONAL IN THIS AREA DUE TO PRESENCE OF CAP AND
UNCERTAINTIES REGARDING INITIATION. HOWEVER...MODEST DRYLINE
CONVERGENCE AND TEMPERATURES CLIMBING INTO THE 90S MAY PROVE
SUFFICIENT FOR ISOLATED STORMS TO DEVELOP ALONG PORTIONS OF THE
DRYLINE. THE DRYLINE MAY MIX EWD AND MERGE WITH A WEAK OUTFLOW
BOUNDARY ACROSS PORTIONS OF SWRN TX...AND THIS MAY ENHANCE POTENTIAL
FOR INITIATION IN THAT AREA. OTHER STORMS MAY DEVELOP OVER THE DAVIS
MOUNTAINS. WHERE STORMS DEVELOP...ISOLATED SUPERCELL STRUCTURES WILL
BE POSSIBLE WITH LARGE HAIL THE MAIN THREAT
 
18z update: Just now checking back on this thread and seeing that 18z data came out last night. Looking it over, am content to sit in Winner, SD for the time being, and grab some lunch. Will proceed through the thread to see if addt'l data is out.
 
Think it's time to drift north towards the NE/SD border. Cap is just too stout to expect any sfc based supercells down this way. Put me down for Martin SD for my
afternoon target. Hope I did not take off too late.
 
Looks like I cap busted. I'm slinking back to Omaha after 30 gallons of gas and a hotel stay, probably watch the towers up north and maybe just maybe something will break the cap in E Nebr.
 
leaving Presho, SD and heading west on I-90, scanning the vis sat for signs of initiation. Seeing a thickening CU field off to my west...
 
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