Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 101731
SWODY2
SPC AC 101730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU JUL 10 2014

VALID 111200Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN AND CENTRAL HIGH
PLAINS TO WRN AND CENTRAL IA...

...SUMMARY...
A FEW STRONG TO SEVERE STORMS ARE EXPECTED OVER PORTIONS OF THE
CENTRAL AND NORTHERN PLAINS...A PART OF THE NORTHERN ROCKY MOUNTAIN
AND HIGH PLAINS AREAS INTO THE UPPER MISSISSIPPI VALLEY REGION
FRIDAY INTO FRIDAY NIGHT.

...SYNOPSIS...
STRONG HIGH PRESSURE ALOFT WILL BE CENTERED OVER THE SRN PLAINS
DURING THIS FORECAST PERIOD...AND SHOULD BECOME MORE ELONGATED WEST
TO EAST ACROSS THE SRN HALF OF THE CONUS.  THIS WILL MAINTAIN A
CORRIDOR OF THE STRONGEST WLY MID-UPPER LEVEL WINDS FROM ALONG AND
NORTH OF THE U.S. CANADIAN BORDER EWD TO THE UPPER GREAT LAKES...
WITH W/NWLY FLOW EXTENDING FROM THERE TO THE CENTRAL APPALACHIANS
AND MID-ATLANTIC STATES.  MIDLEVEL IMPULSES...1/ EMANATING FROM THE
MONSOONAL REGIME IN THE SWRN STATES/GREAT BASIN AREA AND 2/ ANOTHER
SHORTWAVE TROUGH TRACKING ESEWD FROM SRN BRITISH COLUMBIA FRIDAY
MORNING WILL MOVE ACROSS THE NRN ROCKIES/HIGH PLAINS AND EWD WITHIN
SRN EXTENT OF WLY FLOW AIDING IN TSTM DEVELOPMENT FRIDAY/FRIDAY
NIGHT.

A COLD FRONT ASSOCIATED WITH A SHORTWAVE TROUGH MOVING THROUGH WRN
ONTARIO WILL CONTINUE THROUGH THE UPPER MIDWEST/UPPER MS VALLEY.
THE TRAILING PORTION OF THE FRONT IS EXPECTED TO STALL OVER SD.
MEANWHILE...A QUASI-STATIONARY FRONT IS FORECAST TO EXTEND FROM A
LOW OVER WRN KS NEWD THROUGH SRN NEB INTO SRN/CENTRAL IA.

...NRN/CENTRAL HIGH PLAINS TO IA/SRN MN AND SRN WI/NRN IL...
A MOIST ENVIRONMENT GIVEN A RESERVOIR OF RICHER LOW-LEVEL MOISTURE
/MID-UPPER 60S DEWPOINTS/ AND PW VALUES EXCEEDING 1.5-1.75 INCHES
WILL EXIST BENEATH STEEP MIDLEVEL LAPSE RATES ALONG AND NORTH OF THE
QUASI-STATIONARY FRONT FROM NEB INTO SD...AND EWD INTO THE UPPER MS
VALLEY.  DIABATIC WARMING IS EXPECTED OVER THE HIGHER TERRAIN INTO
PORTIONS OF THE GREAT PLAINS...CONTRIBUTING TO FURTHER
DESTABILIZATION WITH MLCAPE FROM 2000 TO 2500 J/KG...AND LOCALLY UP
TO 3000 J/KG POSSIBLE.  MOST OF THIS AREA WILL RESIDE SOUTH OF THE
STRONGER WLYS...BUT EFFECTIVE BULK SHEAR OF 25-40 KT IS EXPECTED.

STORMS SHOULD INITIATE OVER THE HIGHER TERRAIN...POSSIBLY AS FAR WWD
AS SWRN MT...AND SPREAD EWD INTO THE HIGH PLAINS FRIDAY
EVENING/NIGHT AS ONE OR TWO MCS/S.  OTHER STORMS COULD DEVELOP
ALONG/NORTH OF STATIONARY FRONT ACROSS NEB INTO IA...AND INVOF THE
COLD FRONT IN SD...WHILE FURTHER DEVELOPMENT IS POSSIBLE FROM SERN
SD INTO SRN MN PER FORCING FOR ASCENT WITH A LEAD PROGRESSIVE
IMPULSE.  STORM DEVELOPMENT SHOULD BE MORE LIKELY ACROSS NEB/SD TO
THE UPPER MS VALLEY FRIDAY EVENING/NIGHT AS A SWLY LLJ STRENGTHENS.
MULTICELLS AND A FEW SUPERCELLS WILL BE LIKELY WITH EARLY
INITIATION...BUT STORMS WILL LIKELY GROW UPSCALE INTO MCS CLUSTERS
OVERNIGHT FROM THE AFOREMENTIONED NRN HIGH PLAINS AND NORTH OF THE
QUASI-STATIONARY BOUNDARY. LARGE HAIL AND DAMAGING WIND GUSTS WILL
BE THE MAIN THREATS THROUGH THE PERIOD.

THIS OUTLOOK HAS EXPANDED THE SLIGHT RISK/SVR PROBABILITIES TO
INCLUDE MORE OF WRN SD PER POTENTIAL MCS DEVELOPMENT FRIDAY NIGHT AS
WEAK HEIGHT FALLS WITH THE SRN BRITISH COLUMBIA TROUGH MOVE INTO
THIS REGION...AIDING IN UPSCALE GROWTH.  THERE WILL ALSO BE SOME
SEVERE THREAT INTO SRN WI/NRN IL...EITHER WITH AFTERNOON DEVELOPMENT
AND/OR AS STORM CLUSTERS MOVE INTO THIS REGION FROM SRN MN/IA FRIDAY
NIGHT.  FOR THESE REASONS...THE 5% SEVERE PROBABILITIES HAVE BEEN
EXPANDED EWD.

...CENTRAL/NERN MN...
ELEVATED STORMS WILL LIKELY BE ONGOING OVER THE
MID-UPPER MS VALLEY IN ASSOCIATION WITH WARM ADVECTION
ACCOMPANYING A PROGRESSIVE SHORTWAVE TROUGH. LOW-LEVEL WINDS WILL
VEER AND WEAKEN AS THIS MIDLEVEL SYSTEM SHIFTS EWD...WITH TSTM
ACTIVITY SUBSEQUENTLY TENDING TO DIMINISH IN COVERAGE/INTENSITY
FRIDAY MORNING.  SOME BOUNDARY LAYER DESTABILIZATION SHOULD OCCUR
DURING THE AFTERNOON IN THE WAKE OF THE MORNING TSTMS...BUT THERE
REMAINS UNCERTAINTY IN THE DEGREE OF DESTABILIZATION WITH MUCAPE OF
500-1000 J/KG POSSIBLE INTO CENTRAL AND NERN MN BY PEAK HEATING.
DEEPER FORCING FOR ASCENT SHOULD REMAIN FARTHER NORTH IN CANADA.
THEREFORE...THESE FACTORS SUGGEST STORM COVERAGE ALONG THE FRONT
COULD REMAIN LIMITED AND THUS...WILL MAINTAIN 5% SEVERE
PROBABILITIES.  GIVEN 40+ KT EFFECTIVE SHEAR...ANY STORMS THAT DO
DEVELOP WILL LIKELY BECOME ORGANIZED AND...AT LEAST...POSE A SEVERE
THREAT.  THEREFORE...IF IT BECOMES APPARENT THAT STORM COVERAGE WILL
BE MORE THAN CURRENTLY ANTICIPATED...THEN AN UPGRADE TO SLIGHT
RISK/HIGHER PROBABILITIES MAY BE NEEDED IN LATER OUTLOOKS.

..PETERS.. 07/10/2014




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