VALID 031630Z – 041200Z

…THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL/ERN GULF COAST
INTO THE SRN APPALACHIANS…

…THERE IS A SLGT RISK OF SVR TSTMS SERN AZ INTO THE SRN ROCKIES…

…SYNOPSIS…

LITTLE CHANGE TO THE LARGE-SCALE PATTERN IS FORECAST DURING THE D1
PERIOD. A HIGH-AMPLITUDE RIDGE-TROUGH-RIDGE CONFIGURATION WILL BE
MAINTAINED FROM THE SWRN CONUS TO WRN ATLANTIC WITH THE POLAR BRANCH
OF WESTERLIES CONFINED TO CANADA. WITHIN THIS BROAD-SCALE
REGIME…THE SLIGHT WWD RETROGRESSION OF THE WRN ATLANTIC HIGH WILL
ENHANCE THE MIDLEVEL HEIGHT GRADIENT FROM THE GULF COAST STATES
THROUGH THE TN VALLEY INTO LOWER GREAT LAKES. IN THE LOW LEVELS…A
N-S BAROCLINIC ZONE WILL REMAIN QUASI-STATIONARY FROM THE OH VALLEY
TO CNTRL GULF COAST…WHILE FARTHER TO THE NW A COLD FRONT SETTLES
SEWD THROUGH THE NRN HIGH PLAINS.

…CNTRL/ERN GULF COAST INTO SRN APPALACHIANS THIS
AFTERNOON/TONIGHT…

A CONFLUENT LOW-LEVEL FLOW REGIME WILL INTERACT WITH A VERY MOIST
AND POTENTIALLY MODERATELY UNSTABLE AIR MASS TO FOSTER NUMEROUS
TSTMS BY AFTERNOON ACROSS THE REGION. ELY/SELY SURFACE WINDS
BENEATH A STEADILY STRENGTHENING SLY MIDLEVEL WIND FIELD WILL RESULT
IN A VERTICALLY VEERING WIND PROFILE WITH SUFFICIENT VERTICAL SHEAR
FOR DEEP UPDRAFT ROTATION. THIS SETUP WILL BE SUPPORTIVE OF
EMBEDDED SUPERCELL STRUCTURES WITH A RISK FOR A COUPLE TORNADOES
GIVEN THE VERY MOIST/LOW LCL PBL. LOCALLY DAMAGING WINDS WILL ALSO
BE POSSIBLE OWING TO WATER LOADING OF CONVECTIVE DOWNDRAFTS.

…SERN AZ INTO SRN ROCKIES THIS AFTERNOON/EVENING…

SIMILAR TO PAST DAYS…DIURNALLY ENHANCED TSTM DEVELOPMENT IS
ANTICIPATED THIS AFTERNOON WITHIN A RELATIVELY STEEP LAPSE RATE AND
MODESTLY UNSTABLE ENVIRONMENT. SUFFICIENT /35-45 KT/ DEEP-LAYER
SHEAR WILL EXIST FOR SUPERCELLS AS THE INITIAL STORM MODE WITH A
RISK FOR HAIL AND LOCALLY DAMAGING WINDS. COALESCING COLD POOLS MAY
SUPPORT THE UPSCALE GROWTH OF STORMS BY THIS EVENING WITH AN
INCREASING RISK FOR DAMAGING WINDS.

…OH VALLEY INTO THE GREAT LAKES THIS AFTERNOON/EVENING…

A SURFACE LOW OVER NERN IL/NWRN IND WILL DEVELOP NWD TODAY IN TANDEM
WITH A VORTICITY MAXIMUM PIVOTING AROUND THE ERN PERIPHERY OF THE
PARENT UPPER LOW. THIS WILL CONTRIBUTE SCATTERED TSTM DEVELOPMENT
ACROSS THE NRN EXTENSION OF THE WARM SECTOR THIS AFTERNOON. GIVEN
THE COMBINATION OF MODEST AMOUNTS OF VERTICAL SHEAR AND
INSTABILITY…THE SETUP WILL BE SUPPORTIVE OF MULTICELL AND MARGINAL
SUPERCELLS CAPABLE OF SOME HAIL…LOCALLY DAMAGING WINDS…AND
PERHAPS A BRIEF TORNADO.

…NRN HIGH PLAINS THIS EVENING/TONIGHT…

LOW-LEVEL UPLIFT ALONG THE COLD FRONT COUPLED WITH THE GLANCING
INFLUENCE OF A SHORT-WAVE TROUGH AMPLIFYING OVER THE CANADIAN
PRAIRIE PROVINCES INTO NRN HIGH PLAINS WILL SUPPORT ISOLATED TO
WIDELY SCATTERED TSTM DEVELOPMENT MAINLY AFTER 04/00Z. SOME HAIL
AND/OR LOCALLY DAMAGING WINDS WILL ACCOMPANY THE STRONGEST STORMS.

…NRN SIERRAS INTO NRN ROCKIES THIS AFTERNOON/EVENING…

THE TRAILING EXTENSION OF THE PACIFIC COLD FRONT SETTLING SEWD
THROUGH THE PACIFIC NW IN CONJUNCTION WITH TERRAIN-INDUCED
CIRCULATIONS WILL FOSTER SCATTERED AFTERNOON TSTMS ON THE NRN
PERIPHERY OF GREAT BASIN MIDLEVEL ANTICYCLONE. LOCALLY DAMAGING
WIND GUSTS WILL BE POSSIBLE OWING TO STRONG EVAPORATIONAL COOLING
POTENTIAL WITHIN THE DEEP WELL-MIXED SUB-CLOUD LAYER.

..MEAD/HART.. 07/03/2013