DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 252000
SWODY1
SPC AC 251958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT TUE JUN 25 2013

VALID 252000Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN PLAINS TO NEW
ENGLAND...

...MIDWEST/OH VALLEY INTO THE NORTHEAST...
PRIMARY CHANGES WERE TO ADJUST PROBABILITIES BASED ON WHERE
SCATTERED TO NUMEROUS TSTMS ARE PRESENT ATTM AND EXPECTED TO EVOLVE
THROUGH THE EVENING. A MIX OF SEVERE HAIL AND DAMAGING WINDS IS
ANTICIPATED ACROSS NEW ENGLAND DOWNSTREAM OF AN MCV IN ERN NY.
FARTHER WEST ACROSS THE MIDWEST/OH VALLEY...SEVERAL CLUSTERS APPEAR
PROBABLE TO DEVELOP ALONG WARM SECTOR CONFLUENCE BANDS EVIDENT IN
VISIBLE SATELLITE IMAGERY...WITHIN A MODERATE TO STRONGLY UNSTABLE
AIR MASS. PRIMARY RISK SHOULD BE DAMAGING WINDS ALONG WITH SOME
SEVERE HAIL.

...NRN PLAINS INTO THE MID/MO-MS VALLEYS...
MOST PROBABLE CORRIDOR OF TSTM INITIATION NEAR-TERM EXISTS IN
S-CNTRL ND /SEE MCD 1221/. HERE...SEVERE HAIL SHOULD BE THE PRIMARY
THREAT WITH A SEMI-ORGANIZED TSTM CLUSTER GIVEN STRONG INSTABILITY
BUT MODEST DEEP-LAYER SHEAR. UNCERTAINTY REMAINS OVER HOW CONVECTION
WILL DEVELOP/EVOLVE ACROSS THE MID-MO TO AREAS W OF THE MS VALLEY.
MORNING CONVECTION-ALLOWING WRF GUIDANCE ARE HIGHLY CONSISTENT THAT
INITIATION SHOULD BE IMMINENT OVER NWRN IA WITH UPSCALE GROWTH INTO
A SUBSTANTIAL MCS. HOWEVER...SATELLITE/SURFACE DATA SUGGEST
SUSTAINED INITIATION WOULD PROBABLY OCCUR TOWARDS EARLY EVENING
EITHER ACROSS ERN NEB OR ALONG THE NERN IA/SERN MN BORDER. AS THE
LLJ STRENGTHENS COUPLED WITH APPROACH OF A WEAK MID-LEVEL
TROUGH...SETUP WILL PROBABLY YIELD AN MCS AT SOME POINT TONIGHT WITH
ENHANCED RISKS FOR SEVERE HAIL/WIND.

..GRAMS.. 06/25/2013

.PREV DISCUSSION... /ISSUED 1118 AM CDT TUE JUN 25 2013/

...SYNOPSIS...
A STRONG MID-LATITUDE PACIFIC JET CONTINUES TO NOSE INLAND ACROSS
THE NORTH CENTRAL PACIFIC COAST AND NORTHERN INTERMOUNTAIN REGION.
THIS BELT OF FLOW HAS BEEN GENERALLY ZONAL...BUT MODELS SUGGEST
SIGNIFICANT AMPLIFICATION WITHIN THIS REGIME LATER TODAY INTO
TOMORROW. A SUBTROPICAL HIGH OVER THE NORTHERN MEXICAN AND SOUTHERN
U.S. PLATEAU REGION IS EXPECTED TO EXPAND...WITH RIDGING BUILDING
NORTHWARD THROUGH THE ROCKIES...WHILE UPPER TROUGHING DEEPENS
UPSTREAM...ACROSS THE EAST CENTRAL PACIFIC. EAST OF THE
PLAINS...MID/UPPER HEIGHT FALLS ARE EXPECTED TO COMMENCE...MOST
SUBSTANTIVELY...THOUGH STILL SOMEWHAT WEAK...ACROSS PARTS OF THE
GREAT LAKES AND UPPER OHIO VALLEY INTO THE NORTHEAST. WITHIN A
REGIME TRANSITIONING FROM BROADLY ANTICYCLONIC TO BROADLY
CYCLONIC...A NUMBER OF EMBEDDED SMALLER SCALE IMPULSES ARE EXPECTED
GRADUALLY DEVELOP EAST SOUTHEAST OF THE UPPER MIDWEST AND GREAT
LAKES REGION TODAY. A BELT OF STRONGER WESTERLY LOWER/MID
TROPOSPHERIC FLOW...ON THE ORDER OF 30-40+ KT...IS EXPECTED TO
ACCOMPANY THIS FEATURE ACROSS PARTS OF THE SOUTHERN GREAT LAKES
REGION AND UPPER OHIO VALLEY...THROUGH NORTHERN MID ATLANTIC COASTAL
AREAS AND SOUTHERN NEW ENGLAND.

VERY WARM AND STRONGLY CAPPING ELEVATED MIXED LAYER AIR WHICH HAS
ADVECTED EASTWARD ACROSS MUCH OF THE PLAINS...THE UPPER
MIDWEST...AND PARTS OF THE LOWER OHIO VALLEY DOES NOT APPEAR LIKELY
TO MAKE FURTHER EASTWARD PROGRESS TODAY. AND...IN FACT...CONVECTIVE
OVERTURNING AND MID-LEVEL COLD ADVECTION MAY BEGIN STABILIZING LAPSE
RATES ACROSS THE NORTHERN PLAINS LATE THIS AFTERNOON AND
TONIGHT...WHILE THE ELEVATED MIXED LAYER HOLDS FIRM ACROSS/SOUTH AND
WEST OF THE CENTRAL PLAINS AND MIDDLE MISSISSIPPI VALLEY.

GIVEN THE PRESENCE OF CONTINUING SEASONABLE MOISTURE...WEAK/
WEAKENING INHIBITION ACROSS MUCH OF THE GREAT LAKES/OHIO VALLEY AND
NORTHEAST PROBABLY WILL ALLOW FOR CONSIDERABLE THUNDERSTORM ACTIVITY
THIS AFTERNOON AND EVENING. THUNDERSTORM PROBABILITIES ALSO APPEAR
LIKELY TO BECOME RELATIVELY HIGH DURING THE PEAK AFTERNOON HEATING
ACROSS THE SOUTHEAST STATES...INCLUDING THE FLORIDA PENINSULA.

...GREAT LAKES/OHIO VALLEY INTO THE NORTHEAST...
MODERATELY LARGE MIXED LAYER CAPE...ON THE ORDER OF 1000-2000+ J/KG
...IS EXPECTED TO DEVELOP WITH DAYTIME HEATING ACROSS MUCH OF THE
REGION. HIGHEST VALUES ARE EXPECTED ACROSS THE OHIO VALLEY INTO THE
SOUTHERN/LOWER GREAT LAKES REGION...AND PORTIONS OF THE NORTHERN MID
ATLANTIC COAST STATES...WHERE THE AFOREMENTIONED BELT OF ENHANCED
LOW/MID-LEVEL FLOW MAY CONTRIBUTE TO SEVERAL STORM CLUSTERS WITH
COLD POOLS CAPABLE OF PRODUCING SWATHS OF POTENTIALLY DAMAGING WIND
GUSTS.

A BELT OF STRONGER MID/UPPER FLOW AND FORCING FOR UPWARD VERTICAL
MOTION...ASSOCIATED WITH A SHORT WAVE IMPULSE PROGRESSING ACROSS THE
EASTERN CANADIAN PROVINCES...MAY ALSO ENHANCE CONVECTIVE POTENTIAL
ACROSS PARTS OF CENTRAL/NORTHERN MAINE...WHERE ISOLATED SUPERCELLS
WITH THE RISK FOR LARGE HAIL AND LOCALIZED STRONG WIND GUSTS MAY NOT
BE OUT OF THE QUESTION.

...NORTHERN PLAINS INTO THE MID MO/MID MS VALLEYS...
DIFLUENT AND DIVERGENT HIGH LEVEL FLOW APPEARS LIKELY TO BECOME
FOCUSED ACROSS NORTH DAKOTA LATE THIS AFTERNOON OR EARLY EVENING.
THIS IS EXPECTED TO COINCIDE WITH THE NORTHEASTWARD PROGRESSION OF A
MID-LEVEL TROUGH OUT OF THE NORTHERN ROCKIES... BEFORE IT TURNS
EASTWARD...THEN SOUTHEASTWARD TOWARD THE UPPER MISSISSIPPI VALLEY.
IT SEEMS PROBABLE THAT THIS WILL WEAKEN INHIBITION SUFFICIENTLY FOR
CONVECTIVE DEVELOPMENT IN THE PRESENCE OF THERMODYNAMIC PROFILES
QUITE SUPPORTIVE OF SEVERE HAIL AND WIND POTENTIAL. MORE
UNCERTAINTY EXISTS CONCERNING THE STRENGTH OF VERTICAL SHEAR...BUT
THE EVOLUTION OF AN ORGANIZED STORM CLUSTER DOES NOT APPEAR OUT OF
THE QUESTION.

THE EXTENT AND LOCATION OF RELATIVELY HIGHER SEVERE PROBABILITIES
REMAIN MORE UNCLEAR ACROSS PARTS OF THE MID MISSOURI AND MIDDLE
MISSISSIPPI VALLEYS. THE PRIMARY FOCUS WOULD SEEM TO BE NORTHEAST
OF A SURFACE LOW...NEAR THE INTERSECTION OF A SURFACE TROUGH AND
REMNANTS OF CONVECTIVE OUTFLOW...JUST EAST OF THE MID MISSOURI
VALLEY AT EARLY EVENING. BUT MID-LEVEL INHIBITION COULD REMAIN
SUPPRESSIVE TO CONVECTIVE DEVELOPMENT THROUGH THE ONSET OF LATE
EVENING BOUNDARY LAYER COOLING/STABILIZATION.

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