DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 202002
SWODY1
SPC AC 202000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT THU JUN 20 2013

VALID 202000Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS THROUGH TONIGHT FOR PARTS OF
THE NRN/CENTRAL PLAINS AND UPPER MS VALLEY...

...DAKOTAS/UPPER MIDWEST ...
LITTLE CHANGES TO FORECASTING REASONING/RISK AREAS...ALTHOUGH
CORRIDOR OF HIGHER /30 PERCENT/ WIND PROBABILITIES WERE ADJUSTED A
BIT SOUTHWARD ACROSS THE REGION FOR EXPECTED MCS DEVELOPMENT LATER
THIS EVENING. OTHERWISE...SEE PRIOR DISCUSSION BELOW...AND FOR
ADDITIONAL NEAR-TERM INFORMATION THIS AFTERNOON...SEE MESOSCALE
DISCUSSION 1141.

...SOUTHERN HIGH PLAINS...
SEE PRIOR OUTLOOK DISCUSSION IN ADDITION TO MESOSCALE DISCUSSION
1140.

..GUYER.. 06/20/2013

.PREV DISCUSSION... /ISSUED 1135 AM CDT THU JUN 20 2013/

...NRN PLAINS THROUGH TONIGHT...
A CLOSED MIDLEVEL LOW WILL PERSIST OVER THE NRN ROCKIES THROUGH THE
PERIOD WITH LITTLE EWD PROGRESSION ANTICIPATED. AN INITIAL EMBEDDED
SHORTWAVE TROUGH IS ROTATING NWD INTO SRN
ALBERTA/SASKATCHEWAN...WHILE OTHER MORE SUBTLE SPEED MAXIMA ROTATE
NEWD FROM THE GREAT BASIN/CENTRAL ROCKIES TO THE NRN PLAINS...AROUND
THE SERN PERIPHERY OF THE CLOSED LOW. AT THE SURFACE...A LOW NEAR
SD/ND BORDER AS OF 15Z WILL WEAKEN AND THE COLD FRONT WILL SLOW ITS
EWD MOTION AS THE PRIMARY SHORTWAVE TROUGH ROTATES INTO THE CANADIAN
PRAIRIES. FARTHER S...A SECONDARY LEE CYCLONE WILL CONTINUE TO
DEVELOP IN NE CO ALONG THE SRN EXTENSION OF THE COLD FRONT. WITHIN
THE WARM SECTOR...A SWATH OF UPPER 60S TO LOWER 70S DEWPOINTS WILL
CONTINUE TO SURGE NWD FROM THE SRN/CENTRAL PLAINS...WITH THE NE EDGE
OF THE GREATER INSTABILITY DEMARCATED BY AN OUTFLOW-ENHANCED WARM
FRONT ACROSS SW MN/NE SD.

VISIBLE SATELLITE IMAGERY SHOWS SOME CLOUD BREAKS ACROSS S CENTRAL
ND INTO CENTRAL SD IMMEDIATELY IN ADVANCE OF THE SURFACE LOW/COLD
FRONT...WHERE BOUNDARY LAYER DEWPOINTS WILL CONTINUE TO INCREASE
THROUGH THE MID 60S THIS AFTERNOON AS SURFACE TEMPERATURES WARM INTO
THE UPPER 70S-LOWER 80S. STEEP MIDLEVEL LAPSE RATES PRESENT IN 12Z
SOUNDINGS ACROSS THE NRN PLAINS...IN COMBINATION WITH THE LOW-LEVEL
WARMING/MOISTENING...WILL RESULT IN A CORRIDOR OF MODERATE-STRONG
INSTABILITY /MLCAPE VALUES NEAR 2500 J PER KG/ AND MINIMAL
CONVECTIVE INHIBITION BY EARLY AFTERNOON. THUS...EXPECT
THUNDERSTORM DEVELOPMENT BY EARLY AFTERNOON ACROSS CENTRAL/S CENTRAL
ND /POSSIBLY EVOLVING FROM THE ONGOING ELEVATED CONVECTION IN N
CENTRAL ND/...AND ADDITIONAL DEVELOPMENT FARTHER S-SE INTO SD LATER
THIS AFTERNOON. VERTICAL SHEAR WILL BE SUFFICIENT FOR SUPERCELLS
WITH LARGE HAIL AND POSSIBLY A TORNADO OR TWO THIS
AFTERNOON...THOUGH THE STRONGER MID-UPPER FLOW WILL REMAIN A LITTLE
W OF THE SURFACE WARM SECTOR. THE MODEST FLOW ALOFT OVER THE ERN
DAKOTAS/MN...COMBINED WITH WEAKENING CONVECTIVE INHIBITION AND STEEP
LAPSE RATES...WILL PROMOTE STORM INTERACTIONS AND UPSCALE GROWTH
INTO ONE OR MORE MCS/S THAT WILL MOVE ESEWD INTO MN LATE THIS
AFTERNOON THROUGH TONIGHT WITH A RISK FOR DAMAGING WINDS...POSSIBLY
REACHING NE NEB AND IA OVERNIGHT.

...CENTRAL HIGH PLAINS LATE THIS AFTERNOON THROUGH TONIGHT...
LOW-LEVEL MOISTURE WILL INCREASE BENEATH STEEP MIDLEVEL LAPSE RATES
TO THE IMMEDIATE E-NE OF THE DEVELOPING LEE CYCLONE IN NE CO. THE
STEEP LAPSE RATES ARE PART OF A WARM ELEVATED MIXED LAYER WITH 700
MB TEMPERATURES OF 14-16 C...BUT STRONG SURFACE HEATING/MIXING AND
LIFT ALONG THE SURFACE FRONT SHOULD BE SUFFICIENT TO WEAKEN THE CAP
AND ALLOW THUNDERSTORM DEVELOPMENT BY LATE AFTERNOON ACROSS SW NEB
AND VICINITY. LARGE HAIL AND DAMAGING WINDS WILL BE THE MAIN SEVERE
RISKS.

...SRN HIGH PLAINS THIS AFTERNOON...
STRONG SURFACE HEATING/MIXING ALONG THE LEE TROUGH/DRYLINE SHOULD
SUPPORT SCATTERED THUNDERSTORM DEVELOPMENT AGAIN THIS AFTERNOON FROM
SE NM INTO THE TX PANHANDLE. THE WEAK 500 MB FLOW NOTED IN THE 12Z
SOUNDINGS FROM MAF/AMA REFLECT THE WEAK VERTICAL SHEAR THAT IS
EXPECTED THIS AFTERNOON. ISOLATED MARGINALLY SEVERE HAIL AND STRONG
OUTFLOW GUSTS WILL BE POSSIBLE...THE RISK FOR PERSISTENT/ ORGANIZED
SEVERE STORMS APPEARS LOW AND WILL MAINTAIN LOW HAIL/WIND
PROBABILITIES.

...INTERIOR CENTRAL/S FL THIS AFTERNOON...
WEAK LOW-MIDLEVEL FLOW WILL PROMOTE INLAND MOVEMENT OF BOTH THE E
AND W COAST SEA BREEZES THIS AFTERNOON. THUNDERSTORM DEVELOPMENT IS
EXPECTED ALONG BOTH COASTS WITH OUTFLOWS AUGMENTING THE INLAND
MOVEMENT OF THE EACH SEA BREEZE BOUNDARY. GIVEN THE POTENTIAL FOR
MODERATE INSTABILITY INLAND WITH SEASONABLY COOL MIDLEVEL
TEMPERATURES...STORM MERGERS COULD SUPPORT ISOLATED STRONG/SEVERE
DOWNBURSTS AND SOME HAIL.

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