Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 060457
SWODY2
SPC AC 060455

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CDT SUN JUL 05 2015

VALID 071200Z - 081200Z

...THERE IS A MRGL RISK OF SVR TSTMS TUESDAY AFTERNOON AND EVENING
ACROSS PARTS OF THE LOWER GREAT LAKES AND OHIO VALLEY...

...SUMMARY...
WIDELY SCATTERED STRONG TO SEVERE STORM DEVELOPMENT IS POSSIBLE
TUESDAY ACROSS PARTS OF THE LOWER GREAT LAKES REGION AND OHIO
VALLEY.

...SYNOPSIS...
THE MID-LATITUDE WESTERLIES MAY REMAIN AT LEAST BROADLY CYCLONIC
EAST OF THE CANADIAN ROCKIES THROUGH THE REMAINDER OF CANADA AND
ADJACENT NORTHERN U.S. BORDER AREAS TUESDAY AND TUESDAY NIGHT.
WITHIN THIS REGIME...AT LEAST A COUPLE OF SHORT WAVE PERTURBATIONS
WILL REMAIN PROGRESSIVE...INCLUDING ONE THAT IS STILL EXPECTED TO
GRADUALLY PIVOT EAST NORTHEAST OF THE UPPER GREAT LAKES REGION.
THIS FEATURE MAY BE ACCOMPANIED BY A SLOWLY DEEPENING SURFACE LOW.
A TRAILING COLD FRONT IS EXPECTED TO ADVANCE ACROSS AND EAST OF THE
LOWER GREAT LAKES REGION...WHILE STALLING ACROSS THE OHIO/MIDDLE
MISSISSIPPI VALLEYS AND SOUTH CENTRAL PLAINS AFTER ADVANCING INTO
THOSE REGIONS.  THE FRONT MAY BE PRECEDED BY CONSIDERABLE CONVECTIVE
OUTFLOW...PARTICULARLY ACROSS PARTS OF THE SOUTH CENTRAL PLAINS INTO
THE OZARK PLATEAU.

IN LOWER LATITUDES...THE EASTERN PERIPHERY OF A BROAD CLOSED
LOW...EMERGING FROM AN IMPULSE OF SUBTROPICAL EASTERN PACIFIC
ORIGINS...IS FORECAST TO GRADUALLY SPREAD INLAND ACROSS CALIFORNIA.
WITHIN THE DOWNSTREAM SUBTROPICAL WESTERLIES...WEAK MID/UPPER
TROUGHING MAY EVOLVE ACROSS THE SOUTH CENTRAL PLAINS... BUT
LOWER/MID TROPOSPHERIC WAVE AMPLIFICATION MOST EVIDENT IN THE
DETERMINISTIC MODEL OUTPUT MAY BE ASSOCIATED WITH CONVECTIVE
FEEDBACK.  MEANWHILE...FARTHER EAST...SUBTROPICAL RIDGING CENTERED
OFF THE SOUTH ATLANTIC COAST MAY BEGIN TO BUILD WESTWARD...WITH
MODEST STRENGTHENING ACROSS MUCH OF THE SOUTH ATLANTIC AND GULF
COAST STATES.

...LOWER GREAT LAKES/OHIO VALLEY REGION...
THERMODYNAMIC PROFILES WITHIN A PRE-FRONTAL CORRIDOR OF SEASONABLY
HIGH MOISTURE CONTENT /PRECIPITABLE WATER NEAR 2 INCHES AND 70+ F
SURFACE DEW POINTS/ ARE EXPECTED TO BE CHARACTERIZED BY RELATIVELY
WARM MID-LEVELS...WITH GENERALLY WEAK LOWER/MID TROPOSPHERIC LAPSE
RATES.  ONLY SEASONABLY MODEST BOUNDARY LAYER HEATING IS
EXPECTED...AND THIS STILL SEEMS LIKELY TO LIMIT MIXED LAYER CAPE TO
AROUND 1000-2000 J/KG.  FURTHERMORE...STRONGER WESTERLY MID/UPPER
FLOW FIELDS ARE EXPECTED TO REMAIN TO THE COOL SIDE OF THE SURFACE
FRONT TO THE SOUTH OF THE CANADIAN BORDER.  DESPITE THESE
LIMITATIONS... DESTABILIZATION AND FORCING FOR ASCENT ARE EXPECTED
TO BE SUFFICIENT TO SUPPORT CONSIDERABLE THUNDERSTORM DEVELOPMENT
TUESDAY AFTERNOON AND EVENING.  AND IT IS POSSIBLE THAT HEAVY
PRECIPITATION LOADING...AND DOWNWARD MIXING OF 20-30+ KT PRE-FRONTAL
SOUTHWESTERLY 850 MB FLOW...COULD CONTRIBUTE TO THE RISK FOR
POTENTIALLY DAMAGING SURFACE GUSTS IN THE STRONGER CONVECTION.

..KERR.. 07/06/2015




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