SWODY2
SPC AC 011730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU JUL 01 2010
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF MT/NWRN ND...
...SYNOPSIS...
HEIGHT RISES ARE EXPECTED INTO BC/WA/ORE DURING THE DAY 2 PERIOD
WITH THE APPROACH OF STRONG WLY MID-UPPER LEVEL FLOW INTO THE NERN
PACIFIC. THIS WILL SUPPORT AN EWD SHIFT OF AT LEAST THE NRN EXTENT
OF THE LONGWAVE TROUGH CENTERED ALONG THE U.S. WEST COAST...WITH
DOWNSTREAM HEIGHT RISES INTO THE ERN U.S. AS A LONGWAVE TROUGH MOVES
OFF THE EASTERN SEABOARD. SEVERAL WEAK IMPULSES WILL TRACK NEWD
ACROSS THE GREAT BASIN...CENTRAL ROCKIES AND THE NRN HIGH
PLAINS/DAKOTAS WITHIN INCREASING SWLY FLOW ALOFT ALONG ERN EXTENT OF
WRN TROUGH.
IN THE LOW LEVELS...A COLD FRONT ATTENDANT TO THE NRN EXTENT OF THE
WRN TROUGH IS FORECAST TO SPREAD EWD FROM WRN MT/NRN INTERMOUNTAIN
REGION FRIDAY MORNING...REACHING THE WRN DAKOTAS TO CENTRAL WY BY
12Z SATURDAY. THE TRAILING PORTION OF THIS BOUNDARY WILL SHIFT
SSEWD THROUGH THE GREAT BASIN.
...NORTHERN ROCKIES/NORTHERN HIGH PLAINS...
STRONGEST H5 HEIGHT FALLS /60 METERS/ ON FRIDAY SHOULD OCCUR FROM
THE NRN INTERMOUNTAIN WEST INTO WRN/CENTRAL MT...AS A PAIR OF MORE
PROMINENT SHORTWAVE TROUGHS TRACK E/NEWD ACROSS THE PAC NW AND NRN
ROCKIES. SURFACE DEWPOINTS IN THE MID-UPPER 50S SHOULD ALREADY BE
IN PLACE ACROSS CENTRAL MT EARLY FRIDAY MORNING...WITH DEWPOINTS IN
THE 60S ACROSS NWRN ND. THIS MOISTURE COMBINED WITH DIABATIC
HEATING AHEAD OF THE COLD FRONT AND BENEATH PLUME OF VERY STEEP
MIDLEVEL LAPSE RATES /7-8 C PER KM/ WILL RESULT IN A MODERATELY
UNSTABLE AIR MASS /MLCAPE 1500-2500 J PER KG/.
AT 12Z FRIDAY...TSTMS MAY BE ONGOING ACROSS PARTS OF NRN MT AND ND
WITH ACTIVITY TENDING TO WEAKEN FRIDAY MORNING AS IT SPREADS NEWD.
AIR MASS ACROSS WRN/CENTRAL MT MAY DESTABILIZE FAIRLY EARLY IN THE
DAY AS FORCING FOR ASCENT AND COOLING MIDLEVEL TEMPERATURES SPREAD
ACROSS THESE AREAS WITH THE INITIAL PAC NW SHORTWAVE TROUGH TO TRACK
NEWD FRIDAY. THIS WOULD SUPPORT TSTM DEVELOPMENT...WITH SOME SEVERE
POTENTIAL...POSSIBLY AS EARLY AS 18Z ALONG THE COLD FRONT FROM EAST
OF MSO TO NRN MT. ADDITIONAL STORMS WILL DEVELOP/SPREAD EWD ACROSS
MT THIS FORECAST PERIOD ALONG AND AHEAD OF THE COLD FRONT. STRONG
EFFECTIVE BULK SHEAR WILL EXCEED 50 KT AS STRONG SWLY FLOW ALOFT
SHIFTS EWD FROM THE NRN ROCKIES. SHEAR VECTORS ORIENTED PARALLEL TO
THE COLD FRONT AND STRONG FORCING FOR ASCENT SPREADING ACROSS THE
FRONT SHOULD RESULT IN A MORE LINEAR MODE TO THE CONVECTION.
HOWEVER...GIVEN THE DEGREE OF THE SHEAR...EMBEDDED SUPERCELLS WILL
BE POSSIBLE. LEAD ACTIVITY SHOULD REACH NERN MT/NWRN ND BY LATE
AFTERNOON WITH STORMS CONTINUING ACROSS NWRN/NRN ND FRIDAY NIGHT
WITH ATTENDANT SEVERE WEATHER THREAT GIVEN MODERATE INSTABILITY AND
STRONG DEEP LAYER SHEAR.
...CENTRAL HIGH PLAINS...
ISOLATED TO SCATTERED TSTMS SHOULD DEVELOP FRIDAY AFTERNOON ALONG
THE SRN FRINGE OF STRONGER SWLY FLOW ALOFT. MARGINAL-MODERATE
INSTABILITY /MLCAPE 500-1000 J PER KG/ IS EXPECTED TO EXTEND SWD
INTO NERN CO WHERE THE WRN EXTENT OF LOW LEVEL MOISTURE RETURN WILL
BE JUXTAPOSED WITH THE ERN EXTENT OF MIDLEVEL STEEP LAPSE RATES.
EFFECTIVE BULK SHEAR OF 25-30 KT WITHIN THIS ENVIRONMENT SUGGEST A
FEW SUSTAINED MULTICELLS CAPABLE OF SEVERE HAIL/WIND WILL BE
POSSIBLE LATE FRIDAY AFTERNOON/EARLY EVENING.
...EASTERN GREAT BASIN/CENTRAL ROCKIES...
WITH AN INCREASING PRECIPITABLE WATER ENVIRONMENT AHEAD OF THE GREAT
BASIN COLD FRONT...MODELS CONTINUE TO SUGGEST THE DEVELOPMENT OF
STORMS ACROSS ERN UT/WRN CO. EFFECTIVE BULK SHEAR 25-30 KT AND WEAK
INSTABILITY WILL SUPPORT A FEW MULTICELLS CAPABLE OF MARGINALLY
SEVERE HAIL/GUSTY WINDS FRIDAY AFTERNOON/ EARLY EVENING.
..PETERS.. 07/01/2010
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