SWODY2
SPC AC 180519
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 AM CDT TUE SEP 18 2007
VALID 191200Z - 201200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER NERN MT INTO WRN AND CNTRL
ND...
..SYNOPSIS...
UPPER LOW INITIALLY SITUATED ALONG THE PACIFIC NW COAST IS FORECAST
TO DIG SWD INTO CA DURING THE DAY TWO PERIOD. A SERIES OF WEAK
PERTURBATIONS EMANATING FROM THIS LOW WILL CONCURRENTLY EJECT NEWD
THROUGH DOWNSTREAM RIDGE INTO THE NRN PLAINS. IN THE LOW
LEVELS...CYCLOGENESIS IS EXPECTED OCCUR OVER N-CNTRL WY/S-CNTRL MT
WITH THIS FEATURE DEVELOPING EWD INTO SERN MT BY THURSDAY MORNING.
MEANWHILE...ATTENDANT WARM FRONT WILL LIFT NWD THROUGH THE NRN HIGH
PLAINS.
..CNTRL/ERN MT AND THE DAKOTAS...
CONSIDERABLE AIR MASS DESTABILIZATION IS FORECAST TO OCCUR NAMELY
DURING THE LATTER HALF OF THE PERIOD AS DEVELOPING 40-50 KT SSELY
LLJ ENHANCES THE TRANSPORT OF AN INCREASINGLY MOIST LOW-LEVEL AIR
MASS BENEATH A PLUME OF STEEP MID-LEVEL LAPSE RATES. LATEST MODEL
GUIDANCE SUGGESTS THAT ISOLATED...DIURNAL STORM DEVELOPMENT WILL BE
POSSIBLE LATE WEDNESDAY AFTERNOON INTO EVENING OVER PORTIONS OF WRN
SD WHERE STRENGTHENING LLJ WILL ENHANCE CONVERGENCE ALONG WARM
FRONT. FORECAST SOUNDING INDICATE VERY STRONG VERTICAL SHEAR AND
STEEP LAPSE RATES...SUPPORTIVE OF SUPERCELLS. HOWEVER...
BOUNDARY-LAYER MOISTURE /AND RESULTANT CONVECTIVE INSTABILITY/ WILL
REMAIN SOMEWHAT MARGINAL WITH THE POTENTIAL FOR THE ENVIRONMENT TO
REMAIN CAPPED. GIVEN THE UNCERTAINTIES IN WHETHER SURFACE-BASED
STORMS CAN DEVELOP AND BECOME SUSTAINED...ONLY LOW SEVERE
PROBABILITIES WILL BE INCLUDED IN THIS FORECAST.
A GREATER LIKELIHOOD OF MAINLY ELEVATED TSTMS WILL EXIST LATE
WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING FROM PORTIONS OF NERN MT
EWD ACROSS WRN AND CNTRL ND. ENVIRONMENT WILL CONTINUE TO MOISTEN
/NAMELY IN THE 850-750 MB LAYER/ ALONG STRONG...SSELY LLJ. THIS
MOISTENING COUPLED WITH THE STEEP MID-LEVEL LAPSE RATES WILL RESULT
IN THE DEVELOPMENT OF MODERATE ELEVATED INSTABILITY N OF SURFACE
WARM FRONT WITH MUCAPES OF 1000-1750 J/KG. MOREOVER...CLOUD BEARING
SHEAR WILL BE QUITE SUFFICIENT FOR UPDRAFT ROTATION WITH EFFECTIVE
BULK SHEARS OF 40-50 KT. LARGE HAIL WILL BE THE PRIMARY SEVERE
THREAT WITH THE MOST INTENSE STORMS DEVELOPING DURING THE OVERNIGHT
HOURS.
.MEAD.. 09/18/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write chris@lib.siu.edu.
No comments:
Post a Comment