DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 231954
SWODY1
SPC AC 231951

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT THU MAY 23 2013

VALID 232000Z - 241200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF NWRN TX...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
WEST TX INTO THE NRN TX PANHANDLE...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID
ATLANTIC INTO THE NORTHEAST...

...SOUTHERN PLAINS...

HAVE MADE A FEW CHANGES TO 1630Z OUTLOOK ACROSS THE SRN PLAINS.
REMNANTS OF DECAYED MCS HAVE MIGRATED INTO THE ARKLATEX AND WEAK
CONVERGENCE ALONG THE CONVECTIVE OUTFLOW BOUNDARY EXTENDS ACROSS
NCNTRL TX WHERE TEMPERATURES HAVE WARMED INTO THE MID 80S. ALTHOUGH
SIGNIFICANT MOISTURE/INSTABILITY RESIDE ACROSS THIS REGION THERE IS
LESSENING CONFIDENCE LOW LEVEL CONVERGENCE WILL PROVE SUFFICIENT FOR
MORE THAN A FEW TSTMS LATER TODAY.

ANOTHER AREA WHERE PROBABILITIES HAVE BEEN ADJUSTED ARE ACROSS THE
BIG BEND REGION OF WEST TX. TSTMS HAVE RECENTLY DEVELOPED AND ARE
INTENSIFYING WITHIN MOIST SELY LOW LEVEL FLOW. WHILE DEEP LAYER
SHEAR IS NOT PARTICULARLY STRONG...FLOW APPEARS ADEQUATE TO WARRANT
AT LEAST SLOW MOVING ORGANIZED MULTI-CELLS CAPABLE OF PRODUCING
LARGE HAIL.

FARTHER NORTH ACROSS THE MDT RISK...WWD MOVING OUTFLOW IS SURGING
ACROSS THE PANHANDLE AND SHOULD STALL SOON. STRONG HEATING NEAR THE
WIND SHIFT AND FAVORABLE UPSLOPE FLOW WILL LIKELY CONTRIBUTE TO
SIGNIFICANT TSTM DEVELOPMENT OVER THE NEXT FEW HOURS. LATEST VIS
IMAGERY SUPPORTS THIS WITH TOWER CU NEAR/JUST WEST OF THE I-27
CORRIDOR. AFTER INITIAL SUPERCELL DEVELOPMENT ONE OR MORE MCS/S
SHOULD EVOLVE OVER THE SOUTH PLAINS WITH SUBSEQUENT PROPAGATION
EXPECTED INTO PORTIONS OF NWRN TX.

...MID ATLANTIC STATES INTO THE NORTHEAST...

ONLY MINOR CHANGES HAVE BEEN MADE TO EARLIER PROBABILITIES...NAMELY
TO EXTEND 2 PERCENT TORNADO PROBS SOUTHWARD ACROSS THE DELMARVA TO
ACCOUNT FOR WEAK SUPERCELL STRUCTURES OVER THIS REGION.

..DARROW.. 05/23/2013

.PREV DISCUSSION... /ISSUED 1120 AM CDT THU MAY 23 2013/

...SYNOPSIS...
WHILE THE CURRENT BLOCKING PATTERN OVER NORTH AMERICA IS EXPECTED TO
BECOME A BIT LESS PROMINENT...LARGE-SCALE MID/UPPER FLOW OVER THE
U.S. IS EXPECTED TO REMAIN AMPLIFIED AND SLOW TO CHANGE. IN THE
EAST...THE TRANSITION OF A CLOSED LOW TO AN OPEN WAVE TROUGH
CONTINUES ACROSS THE GREAT LAKES AND LOWER OHIO VALLEY REGION...TO
THE SOUTH OF A SHORT WAVE TROUGH SLOWLY DIGGING SOUTHEAST OF THE
HUDSON/JAMES BAY REGION. BOTH THESE FEATURES WILL CONTINUE TO
GRADUALLY TURN EASTWARD/SOUTHEASTWARD TOWARD THE ATLANTIC SEABOARD
LATER TODAY AND TONIGHT. AT THE SAME TIME...A DEEP MID-LEVEL CLOSED
LOW WILL LINGER OVER THE PACIFIC NORTHWEST...WITH BROADER SCALE
UPPER TROUGHING ENCOMPASSING MUCH OF THE PACIFIC COAST STATES INTO
THE ROCKIES. A SIGNIFICANT MID-LEVEL IMPULSE IS EXPECTED TO
CONTINUE TO GRADUALLY PIVOT AROUND THE LOW...ACROSS THE NORTHERN
GREAT BASIN INTO THE NORTHERN ROCKIES BY LATE TONIGHT. THIS WILL
SUPPRESS MID-LEVEL HEIGHT RISES ACROSS PARTS OF THE NORTHERN
PLAINS...WHILE MID/UPPER RIDGING REMAINS OR BECOME MORE PROMINENT
ACROSS MUCH OF THE PLAINS INTO THE MISSISSIPPI VALLEY REGION. A
COUPLE OF WEAK IMPULSES PROGRESSING THROUGH THE CYCLONIC FLOW ACROSS
THE SOUTHERN PLATEAU INTO THE SOUTHERN ROCKIES REGION MAY HAVE AT
LEAST A GLANCING IMPACT ON PARTS OF THE SOUTHERN PLAINS...HOWEVER.

...MID ATLANTIC STATES INTO THE NORTHEAST...
AHEAD/EAST OF A COLD FRONT ADVANCING ACROSS THE LOWER GREAT LAKES
AND OHIO VALLEY REGION...MID-LEVEL LAPSE RATES APPEAR TO HAVE
STABILIZED CONSIDERABLY OVER THE PAST COUPLE OF DAYS. CONSIDERABLE
CLOUD COVER AND PRECIPITATION...SOME CONVECTIVE...IS ALREADY WELL
UNDERWAY...AND IT IS NOT CLEAR HOW MUCH DESTABILIZATION WILL TAKE
PLACE TODAY. THERE ARE BREAKS IN CLOUD COVER...WHICH WILL ALLOW FOR
AT LEAST POCKETS OF HEATING AND WEAK TO MODEST DESTABILIZATION...THE
STRONGEST OF WHICH SEEMS LIKELY TO TAKE PLACE ALONG THE LEE SURFACE
TROUGH...EAST OF THE APPALACHIANS. THIS MAY INCLUDE THE URBAN
CORRIDOR FROM WASHINGTON D.C./BALTIMORE INTO THE PHILADELPHIA AREA.

WHERE SUBSTANTIVE DESTABILIZATION IS ABLE TO TAKE PLACE...SHEAR AND
MOMENTUM ASSOCIATED WITH 20-40 KT SOUTHWESTERLY LOWER/MID
TROPOSPHERIC FLOW MAY ENHANCE CONVECTIVE DEVELOPMENT... CONTRIBUTING
TO STORM MOTION AND ORGANIZATION. STRONGEST ACTIVITY MAY BE CAPABLE
OF PRODUCING SEVERE WIND GUSTS...WITH SOMEWHAT LOWER POTENTIAL FOR
SEVERE HAIL OR A TORNADO.

...SOUTHERN PLAINS...
THE SEVERE STORM/SMALL STORM CLUSTER THAT EVOLVED FROM A LARGER
SCALE WARM ADVECTION REGIME OVER CENTRAL OKLAHOMA EARLIER THIS
MORNING IS CURRENTLY WEAKENING SOUTH OF THE RED RIVER...ACROSS PARTS
OF NORTHEAST TEXAS. IT MAY NOT BE OUT OF THE QUESTION THAT REMNANTS
OF THIS ACTIVITY COULD BE ASSOCIATED WITH NEW INTENSE STORM
DEVELOPMENT ACROSS PARTS OF EASTERN TEXAS INTO LOUISIANA LATER
TODAY...IN THE PRESENCE OF POTENTIALLY STRONG INSTABILITY.
HOWEVER...THE PRIMARY CONVECTIVE POTENTIAL IS EXPECTED TO BECOME
FOCUSED NEAR THE DRYLINE AND A DEVELOPING WARM FRONT ACROSS THE
SOUTHERN HIGH PLAINS LATER THIS AFTERNOON AND EVENING.

DESPITE THE TENDENCY FOR CONTINUING WEAK MID-LEVEL HEIGHT RISES
ACROSS THE SOUTHERN PLAINS TODAY...MODELS SUGGEST CONVECTIVE
INHIBITION WILL WEAKEN SUFFICIENTLY BY PEAK AFTERNOON HEATING FOR
STORM INITIATION ON THE DRYLINE. THE MOST INTENSE STORMS/GREATEST
STORM COVERAGE IS EXPECTED NEAR THE DRYLINE/WARM FRONT
INTERSECTION...EAST/SOUTHEAST OF LUBBOCK AND AMARILLO INTO AREAS OF
NORTHWEST TEXAS NEAR/SOUTH OF CHILDRESS. THIS IS WHERE
THERMODYNAMIC PROFILES WITH VERY STEEP MID-LEVEL LAPSE RATES AND
LARGE CAPE SHOULD BE SUPPORTIVE OF SUPERCELLS...BEFORE CONSIDERABLE
UPSCALE GROWTH OCCURS BY EARLY EVENING.

VERY LARGE HAIL IS POSSIBLE IN STRONGEST CELLS. A COUPLE OF
TORNADOES ARE ALSO POSSIBLE...BUT TORNADIC POTENTIAL MAY BE HINDERED
BY WEAKNESS IN MID-LEVEL FLOW...AND A TENDENCY FOR STORMS TO QUICKLY
GENERATE CONSIDERABLE OUTFLOW.

...NORTHERN ROCKIES...
ALTHOUGH MOISTURE APPEARS TO REMAIN LIMITED ACROSS THE BASINS
WEST/SOUTH OF THE LARAMIE AND BIG HORN MOUNTAINS OF WYOMING... THE
ENVIRONMENT APPEARS AT LEAST MARGINALLY CONDUCIVE TO ISOLATED
SUPERCELL DEVELOPMENT LATE THIS AFTERNOON/EVENING...SOME OF WHICH
COULD DEVELOP/SPREAD NORTH/EAST OF THE MOUNTAINS INTO PARTS OF
EASTERN WYOMING AND MONTANA.

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