Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS11 KWNS 302349
SWOMCD
SPC MCD 302349
SDZ000-NDZ000-NEZ000-MTZ000-WYZ000-310115-

MESOSCALE DISCUSSION 1641
NWS STORM PREDICTION CENTER NORMAN OK
0649 PM CDT SAT AUG 30 2014

AREAS AFFECTED...SERN MT...SWRN ND...WRN SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 302349Z - 310115Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...AT LEAST A SMALL WINDOW OF OPPORTUNITY STILL APPEARS TO
EXIST FOR SEVERE STORM DEVELOPMENT INCLUDING ISOLATED SUPERCELLS
THROUGH THE 01-03Z TIME FRAME.  IT REMAINS UNCERTAIN WHETHER A
SEVERE WEATHER WATCH IS NEEDED...BUT TRENDS CONTINUE TO BE MONITORED
FOR THIS POSSIBILITY.

DISCUSSION...LATEST OBSERVATIONAL DATA AND RAPID REFRESH OUTPUT
SUGGEST THAT THE ENVIRONMENT HAS BECOME INCREASINGLY SUPPORTIVE OF
SUPERCELL DEVELOPMENT ACROSS THE REGION DURING THE PAST COUPLE OF
HOURS... NORTH THROUGH EAST OF A DEVELOPING SURFACE LOW NEAR THE
BLACK HILLS.  BOUNDARY LAYER MOISTENING IN A NARROW CORRIDOR EAST
THROUGH NORTH OF THE BLACK HILLS APPEARS TO BE CONTRIBUTING TO
SIZABLE MIXED LAYER CAPE IN EXCESS OF 2000 J/KG...BENEATH MODEST
SOUTHWESTERLY MID-LEVEL FLOW WHICH MAY CONTINUE TO STRENGTHEN TO
AROUND 40 KT OR SO DURING THE NEXT FEW HOURS.

SCATTERED THUNDERSTORM ACTIVITY HAS BEEN INCREASING TO THE WEST...
ACROSS EASTERN WYOMING INTO THE BLACK HILLS AREA...AND NEW
DEVELOPMENT STILL SEEMS LIKELY ACROSS PARTS OF SOUTHEASTERN
MONTANA...NORTHWESTERN SOUTH DAKOTA...AND SOUTHWESTERN NORTH
DAKOTA...IN RESPONSE TO INCREASING LARGE-SCALE FORCING FOR UPWARD
VERTICAL MOTION.  THIS WILL BE ASSOCIATED WITH LOW-LEVEL WARM
ADVECTION ON THE NOSE OF A STRENGTHENING LOW-LEVEL JET /30-50 KT AT
850 MB/...AND AN AREA OF MID/UPPER FORCING NOW SPREADING ACROSS THE
EASTERN MONTANA/WYOMING BORDER TOWARD THE CENTRAL DAKOTAS.

BEFORE THE UNSTABLE BOUNDARY LAYER BEGINS TO STABILIZE WITH THE LOSS
OF DAYTIME HEATING...A WINDOW OF OPPORTUNITY STILL APPEARS FOR
SEVERE STORM DEVELOPMENT...INCLUDING A COUPLE OF SUPERCELLS.
UPSCALE CONVECTIVE GROWTH INTO A CONSOLIDATING/GROWING CONVECTIVE
CLUSTER PROBABLY WILL OCCUR THIS EVENING...BUT THE EXTENT OF ANY
CONTINUING SEVERE THREAT REMAINS UNCLEAR WITH ACTIVITY SEEMING
LIKELY TO BECOME INCREASINGLY ROOTED ABOVE A COOLER/MORE STABLE
BOUNDARY LAYER AS IT SPREADS NORTHEASTWARD INTO/THROUGH THE CENTRAL
DAKOTAS.

..KERR/EDWARDS.. 08/30/2014

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

ATTN...WFO...BIS...LBF...UNR...BYZ...

LAT...LON   45740481 46520416 47080353 46310278 45610210 44120129
            42980263 44130348 44470392 44950510 45740481



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