Mesoscale Discussion 1821

Issued

Aug 8, 2009, 2:18 AM MDT (08:18 UTC)

Expired

Aug 8, 2009, 4:15 AM MDT

In force

117 min

Issued by

the Storm Prediction Center

The Rapid City radar (KUDX), 114 km from the middle of the area, began a volume at 08:21 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

000 
ACUS11 KWNS 080818
SWOMCD
SPC MCD 080818 
SDZ000-NEZ000-MTZ000-WYZ000-081015-

MESOSCALE DISCUSSION 1821
NWS STORM PREDICTION CENTER NORMAN OK
0318 AM CDT SAT AUG 08 2009

AREAS AFFECTED...PORTIONS CENTRAL/ERN WY...EXTREME SERN MT...WRN
SD...NWRN NEB.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 080818Z - 081015Z

CONVECTIVE COVERAGE....AND AT LEAST CONDITIONAL SVR POTENTIAL...MAY
INCREASE DURING NEXT SEVERAL HOURS ACROSS DISCUSSION AREA AND
SPREAD/SHIFT SEWD.

STG SFC COLD FRONT WAS ANALYZED AT 08Z FROM SWRN ND SWD ACROSS NWRN
SD TO NEAR SRN BLACK HILLS...CURVING WWD ACROSS NRN LARAMIE RANGE. 
STRONGER FRONT SHOULD CONTINUE MOVING SEWD ACROSS E-CENTRAL/SERN WY
AND WRN SD...REINFORCING PRE-EXISTING/OUTFLOW-AUGMENTED BAROCLINIC
ZONE THAT EXTENDS SWD FROM LOW NEAR 9V9 ACROSS ANW-OGA-GXY AREAS. 
CLUSTER OF TSTMS HAS BEEN GROWING ON NW SIDE OF FRONT ACROSS NERN
WY...SERN MT...AND EXTREME WRN SD...WITH ADDITIONAL/NEWER
DEVELOPMENT UNDERWAY NEAR FRONT FROM CPR EWD TOWARD DGW AREA AND S
OF FRONT OVER NRN NEB PANHANDLE.  ADDITIONAL DEVELOPMENT IS LIKELY
ALMOST ANYWHERE IN THIS REGION...PRIMARILY ROOTED WITHIN LAYER OF
FAVORABLE DEEP-LAYER/EFFECTIVE SHEAR AND ELEVATED CAPE.
COUNTERBALANCING THERMODYNAMIC FACTOR WILL BE STG
POST-FRONTAL/LOW-LEVEL CAA...WHICH WILL DEEPEN AND INTENSIFY LAYER
OF STATIC STABILITY NEAR SFC.  850 MB FLOW AT RAP HAS TURNED TO
NLY...AND STG SFC PRESSURE RISES ARE NOTED ACROSS MUCH OF NERN
WY...NWRN SD AND SERN MT.  

STILL...STEEP MIDLEVEL LAPSE RATES ARE EXPECTED TO CONTINUE ABOVE
FRONTAL SURFACE WITHIN ABOUT 150 NM BEHIND WRN FRONT...WITH
SUFFICIENT FRONTOGENETIC FORCING...LARGE SCALE ASCENT AND ELEVATED
MOISTURE TO SUPPORT CONTINUED CONVECTIVE INITIATION.  REGIME SHOULD
SHIFT SWD AND SEWD AT PACE OF WRN FRONT DURING NEXT SEVERAL
HOURS...AS BUOYANCY/MOISTURE CONTINUE TO INCREASE WITH EWD EXTENT. 
ISOLATED STG-SVR GUST CANNOT BE RULED OUT...EXPECIALLY OVER HIGHER
TERRAIN...BUT MAIN SVR CONCERN SHOULD BE HAIL.

..EDWARDS.. 08/08/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ABR...LBF...UNR...CYS...BYZ...RIW...

LAT...LON   42430638 43400675 44300596 45100413 45700271 45770151
            44790084 43600132 42240249 41910484 42230591 42430638

Mesoscale Discussions in South Dakota, 2009Mesoscale Discussions in Wyoming, 2009Mesoscale Discussions in Nebraska, 2009Every mesoscale discussion in 2009

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.