DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 061950
SWODY1
SPC AC 061948

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0248 PM CDT FRI SEP 06 2013

VALID 062000Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR WRN/CNTRL MT...

...SRN/WRN AZ...
A 5 PERCENT WIND DELINEATION HAS BEEN INTRODUCED FOR SRN/WRN AZ.
ENVIRONMENT IS SOMEWHAT MOIST WITH SURFACE DEWPOINTS IN THE 50S TO
NEAR 60...AND PW VALUES /PER SATELLITE DERIVED GUIDANCE/ AOA 1.30
INCHES. THIS AIRMASS IS CONTRIBUTING TO MLCAPE VALUES NEAR 1000
J/KG...AND WITH WINDS IN THE MIDLEVELS OUT OF THE E...MAY SUSTAIN
THUNDERSTORM CLUSTERS AS THEY MOVE WWD OFF OF THE HIGHER TERRAIN.
HOT SURFACE TEMPERATURES AND STEEP LOW-LEVEL LAPSE RATES WILL
FURTHER SUPPORT A MARGINAL THREAT FOR STRONG/SEVERE WIND GUSTS.

...WRN/CNTRL MT THIS AFTERNOON INTO TONIGHT...
PREVIOUS OUTLOOK FOR WRN/CNTRL MT APPEARS TO BE ON TRACK. REF MCD
1847 FOR ADDITIONAL SHORT-TERM DETAILS.

...FL PENINSULA...
EXPANDED THE 5 PERCENT WIND DELINEATION NWD IN ORDER TO INCLUDE
ONGOING STRONG/SEVERE PULSE STORMS. OTHERWISE...PREVIOUS FORECAST IS
ON TRACK. REF MCD 1846 FOR ADDITIONAL SHORT-TERM DETAILS.

..GARNER.. 09/06/2013

.PREV DISCUSSION... /ISSUED 1107 AM CDT FRI SEP 06 2013/

...SYNOPSIS...

A MID TO UPPER-LEVEL ANTICYCLONE WILL REMAIN ANCHORED OVER THE CNTRL
HIGH PLAINS WITH THE PRIMARY BELT OF POLAR WESTERLIES CONFINED TO
CANADA. A SEPARATE RIBBON OF HIGHER MOMENTUM MID TO
UPPER-TROPOSPHERIC FLOW WILL PREVAIL ACROSS THE NRN ROCKIES IN
CONJUNCTION WITH AN UPPER LOW WHICH WILL SLOWLY PROGRESS NEWD ACROSS
THE PACIFIC NW INTO SRN BRITISH COLUMBIA. SEVERAL LOW-AMPLITUDE
VORTICITY MAXIMA WILL PROGRESS THROUGH THE BROADER SYNOPTIC
PATTERN...ONE OF WHICH WILL MOVE FROM THE PACIFIC NW THROUGH THE NRN
INTERMOUNTAIN REGION...AND AT LEAST ONE OTHER WHICH WILL CREST THE
RIDGE AXIS OVER THE NRN PLAINS BEFORE SHIFTING SEWD INTO THE UPPER
MIDWEST.

IN THE LOW LEVELS...MID-MORNING MESOANALYSIS INDICATED A WEAK FRONT
FROM CNTRL MANITOBA SWWD TO LOW PRESSURE OVER CNTRL SD AND THEN INTO
CNTRL WY. ANOTHER BOUNDARY EXTENDED FROM THE INTERSECTION WITH THE
FORMER OVER CNTRL MANITOBA SWWD INTO NWRN MT. LATEST MODEL GUIDANCE
SUGGESTS THAT THE SRN BOUNDARY MAY WEAKEN WITH TIME WHILE SAGGING
SLOWLY SEWD AHEAD OF THE NRN BAROCLINIC ZONE WHICH WILL INTENSIFY
WHILE PROGRESSING INTO THE NRN PLAINS.

...WRN/CNTRL MT THIS AFTERNOON INTO TONIGHT...

MIDLEVEL HEIGHT FALLS/DCVA AHEAD OF THE PACIFIC NW SYSTEM WILL
AUGMENT LOW-LEVEL CONVERGENCE ALONG THE NRN-MOST FRONT AND
TERRAIN-INDUCED CIRCULATIONS TO FOSTER SCATTERED TSTMS THIS
AFTERNOON. CURRENT SATELLITE-DERIVED PW IMAGERY INDICATES THAT A
DRIER AIR MASS RESIDES ACROSS THE SWRN PORTION OF THE STATE WITH AN
AXIS OF HIGHER MOISTURE CONTENT /I.E. 1.0-1.3 INCH PW/ ACROSS NRN MT
INTO THE DAKOTAS. THIS MOISTURE WILL COMBINE WITH STEEP LAPSE RATES
TO PROMOTE A MODERATELY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE
APPROACHING 1000 J/KG.

THE STRONGEST MID AND HIGH-LEVEL FLOW --AND RESULTANT VERTICAL
SHEAR-- WILL RESIDE ACROSS WRN MT WHERE A FEW SUPERCELLS APPEAR
LIKELY WITH LARGE HAIL AND DAMAGING WINDS BEING THE PRIMARY HAZARDS.
WITH TIME...STORMS MAY GROW UPSCALE INTO ONE OR MORE
FORWARD-PROPAGATING CLUSTERS WITH THE THREAT FOR DAMAGING WINDS AND
HAIL PERSISTING INTO TONIGHT...MAINLY ACROSS N-CNTRL MT.

...NRN PLAINS INTO UPPER GREAT LAKES THIS AFTERNOON AND EVENING...

WIDELY SCATTERED ELEVATED TSTMS ACROSS THE WRN DAKOTAS APPEAR TO BE
ASSOCIATED WITH A WEAK MIDLEVEL PERTURBATION CRESTING THE MEAN RIDGE
AXIS. A SUBSET OF THIS ACTIVITY MAY PERSIST INTO AFTERNOON WITH
ADDITIONAL STORMS POSSIBLE ALONG EITHER OF THE TWO SURFACE
BOUNDARIES MENTIONED IN THE SYNOPSIS. GIVEN THE PRESENCE OF MODEST
AMOUNTS OF INSTABILITY AND VERTICAL SHEAR...A LOW-PROBABILITY RISK
FOR DAMAGING WINDS AND HAIL WILL EXIST WITH THE MOST INTENSE TSTMS
INTO THIS EVENING.

...CNTRL/SRN FL THIS AFTERNOON INTO EARLY EVENING...

12Z REGIONAL SOUNDINGS INDICATE THE PRESENCE OF SEASONABLY COOL
MIDLEVEL TEMPERATURES ATOP A VERY MOIST BOUNDARY LAYER WHICH WILL
PROMOTE A MODERATE TO STRONGLY UNSTABLE AIR MASS BY AFTERNOON WITH
MLCAPE VALUES OF 2000-3000 J/KG. WHILE LARGE-SCALE FORCING FOR
ASCENT WILL REMAIN NEGLIGIBLE THROUGH THE PEAK OF THE DIURNAL
HEATING CYCLE...LATEST CONVECTION-ALLOWING MODEL GUIDANCE REMAINS
CONSISTENT WITH PRIOR RUNS IN SUGGESTING THE DEVELOPMENT OF NUMEROUS
STORMS BY AFTERNOON ALONG THE EVOLVING SEA BREEZE CIRCULATIONS.
GIVEN THE MAGNITUDE OF INSTABILITY...LOCALLY DAMAGING WET
MICROBURSTS AND PERHAPS SOME SMALL HAIL MAY ACCOMPANY THE STRONGEST
STORMS INTO EARLY EVENING.

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