DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191632
SWODY1
SPC AC 191630

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT WED JUN 19 2013

VALID 191630Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
CENTRAL/NRN MT INTO NW ND...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR
PARTS OF THE CENTRAL/SRN HIGH PLAINS...

...MT/NW ND THROUGH TONIGHT...
A DEEP CLOSED LOW OVER THE PAC NW WILL PROGRESS INLAND AS A
PRONOUNCED SHORTWAVE TROUGH OVER NV ROTATES NEWD TO ID BY THIS
EVENING AND MT OVERNIGHT. AT THE SURFACE...STRONG CYCLOGENESIS IS
EXPECTED IN THE LEE OF THE NRN ROCKIES MOUNTAINS ACROSS S CENTRAL MT
AND NRN WY...IN ADVANCE OF THE EJECTING SHORTWAVE TROUGH. THE
PRESSURE FALLS ACROSS MT AND THE REST OF THE NRN HIGH PLAINS WILL
INDUCE STRONG SELY LOW-LEVEL FLOW INTO MT THROUGH TONIGHT...IN
ADVANCE OF THE SURFACE LOW AND A COLD FRONT WHICH WILL CROSS WY/MT
IN ASSOCIATION WITH THE MIDLEVEL TROUGH. REGIONAL 12Z SOUNDINGS
REVEALED RATHER MODEST BOUNDARY LAYER MOISTURE FROM NEB TO MT WITH
100 MB MEAN MIXING RATIOS OF 8-10 G/KG...WHICH TRANSLATES TO
DEWPOINTS MOSTLY IN THE MID-UPPER 50S AT ABOUT 2500 FT MSL. THE
ONLY LIKELY INCREASE IN MOISTURE TODAY INTO MT WILL BE THROUGH
EVAPOTRANSPIRATION...GIVEN SIMILAR MOISTURE OBSERVATIONS UPSTREAM
ACROSS THE CENTRAL/NRN HIGH PLAINS. THUS...MODERATE INSTABILITY
/MLCAPE OF 1500-2500 J PER KG/ IS EXPECTED BY MID-LATE AFTERNOON AS
SURFACE TEMPERATURES WARM INTO THE 85-90 F RANGE ACROSS CENTRAL/ERN
MT...BENEATH 8-9 C/KM MIDLEVEL LAPSE RATES.

THUNDERSTORM DEVELOPMENT IS FIRST EXPECTED BY EARLY-MID AFTERNOON
OVER THE HIGHER TERRAIN OF SW/S CENTRAL MT...AND THIS CONVECTION
WILL SPREAD NNEWD TOWARD N CENTRAL MT THIS EVENING. SUPERCELLS WITH
LARGE HAIL WILL BE POSSIBLE INITIALLY...THOUGH UPSCALE GROWTH INTO
CLUSTERS/LINE SEGMENTS APPEARS LIKELY THIS EVENING. THE UPSCALE
GROWTH WILL BE DRIVEN BY STORM/OUTFLOW INTERACTIONS IN AN
ENVIRONMENT WITH RATHER MODEST DEEP-LAYER SHEAR IN THE WARM SECTOR
/EFFECTIVE BULK SHEAR OF 25-30 KT DUE TO BACKED FLOW ALOFT/...AS
WELL AS TEMPERATURE-DEWPOINT SPREADS NEAR 30 F AND STRONG LINEAR
FORCING FOR ASCENT ALONG THE SURGING COLD FRONT. THE GREATER RISK
FOR MORE PERSISTENT SUPERCELLS...WITH AN ACCOMPANYING RISK FOR MORE
SIGNIFICANT HAIL AND PERHAPS A COUPLE OF TORNADOES...WILL BE ALONG
AND ON THE IMMEDIATE COOL SIDE OF THE BAROCLINIC ZONE ACROSS CENTRAL
MT /FROM ABOUT HVR-LWT-GTF-CTB TO CTB/...WHERE LOW-LEVEL SHEAR AND
MOISTURE WILL BE MAXIMIZED. OTHERWISE...EXPECT CONVECTION TO EXPAND
EWD OVERNIGHT ALONG THE COLD FRONT INTO ERN MT...WITH THE POTENTIAL
FOR ISOLATED DAMAGING WINDS/HAIL.

...CENTRAL/SRN HIGH PLAINS THROUGH TONIGHT...
AN MCS CONTINUES TO MOVE SEWD ACROSS THE SE TX PANHANDLE INTO NW TX
AS OF 16Z. THERE WILL BE SOME POTENTIAL FOR RE-INVIGORATION OF THE
STORMS ALONG THE LEADING EDGE OF THE COLD POOL THIS AFTERNOON AS THE
BOUNDARY LAYER DESTABILIZES. ALSO...ISOLATED THUNDERSTORM
DEVELOPMENT WILL BE POSSIBLE FARTHER W ALONG THE OUTFLOW BOUNDARY
INTO W CENTRAL TX/E CENTRAL NM. FARTHER N...THE FOCUS FOR STORM
INITIATION IS UNCERTAIN GIVEN THE TENDENCY FOR SLOW HEIGHT RISES
ACROSS THE HIGH PLAINS. SURFACE HEATING/MIXING ALONG THE EXTENSIVE
LEE TROUGH COULD SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT FOR A FEW
HOURS LATE THIS AFTERNOON/EVENING FROM ERN CO/WRN KS SWD INTO NE
NM/NW TX PANHANDLE IN THE ZONE OF INCREASING LOW-LEVEL MOISTURE...TO
THE W-NW OF THE MORNING TX PANHANDLE MCS. THIS ZONE WILL HAVE
SUFFICIENT INSTABILITY AND VERTICAL SHEAR FOR SUPERCELLS...WITH A
RISK FOR AT LEAST ISOLATED LARGE HAIL AND DAMAGING WINDS. FARTHER
N...THE FOCUS FOR STORM DEVELOPMENT IS LESS CLEAR...OTHER THAN THE
OROGRAPHIC INFLUENCE OF THE BLACK HILLS.

..THOMPSON/SMITH.. 06/19/2013

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