Tornado and Flash Flooding in Utah, October 5 to 7, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
510 AM MDT TUE OCT 5 2010

.SYNOPSIS...AN UPPER LOW OVER SOUTHERN CALIFORNIA WILL REMAIN IN
PLACE THROUGH MID WEEK BEFORE IT STARTS MOVING EAST. THIS WILL
KEEP A MOIST AND COOLER SOUTHERLY FLOW OVER UTAH THROUGH THURSDAY.

&&

.DISCUSSION...THE LARGE CLOSED LOW OVER CENTRAL/SOUTHERN CA IS
BECOMING CUT OFF THIS MORNING AS THE PARENT TROF SLIDES EAST THRU
SRN CANADA. THIS LEAVES THE LOW IN PLACE THRU WED UNTIL THE NEXT
DEEP PAC TROF BEGINS TO APPROACH THE WEST COAST AND KICKS OUT THE
LOW ON THU.

UNTIL THEN...VERY MOIST SLY FLOW TO CONTINUE WITH DECENT DYNAMIC
AND OROGRAPHIC SUPPORT FOR WIDESPREAD SHOWERS AND SCT TSTMS ACROSS
SRN UT. SHOWERS WILL TEND TO WEAKEN AS THEY MOVE INTO THE NORTH
BUT SHOULD REMAIN WIDESPREAD ENOUGH TO WARRANT LIKELY POPS MOST
AREAS. ALTHO INDIVIDUAL STORMS ARE NOT ALL THAT STRONG...THE
CUMULATIVE EFFECT WILL BE TO GENERATE RATHER LARGE PRECIP TOTALS
ACROSS THE SOUTH BY LATE WED. RIVERS ARE ALREADY RESPONDING THIS
MORNING WITH MODEST RISES ON THE VIRGIN AND THE PARIA AND ALL THE
SMALLER DRAINAGES ARE LIKELY RUNNING TOO. WILL KEEP EXISTING FLASH
FLOOD WATCH UNCHANGED.

THE SOUTH FINALLY STARTS TO DRY SOMEWHAT THU AS THE LOW BEGINS TO
EJECT ACROSS THE CWA AND THE VEERING FLOW CUTS OFF THE MOISTURE
FEED. SHOWERS SHOULD PERSIST FOR A TIME ACROSS THE NORTH FRI IN
THE COOL MOIST NORTHWEST FLOW THEN TAPER OFF. MODELS HAVE NOT BEEN
CONSISTENT ON THE WEAK SHORT WAVE TROFS THAT FOLLOW THE EJECTING
LOW OVER THE WEEKEND SO HAVE LEFT SOME TOKEN POPS IN THE GRIDS BUT
CONFIDENCE IS LOW.

THE NEXT SHORT WAVE TO AFFECT THE CWA IS FORECAST TO SLIDE BY
MAINLY TO THE NORTH LATE MON THRU TUE BUT THIS TOO HAS NOT BEEN
A VERY STABLE FEATURE RUN TO RUN AND HAVE VERY LOW CONFIDENCE IN
FORECAST BEYOND SUN.

&&

.AVIATION...THE SLC TERMINAL WILL SEE MOSTLY CLOUDY SKIES WITH A
FEW SHOWERS THIS MORNING. WINDS SHOULD REMAIN SOUTHERLY THROUGH THE
PERIOD. INCREASING RAIN SHOWERS CAN BE EXPECTED THROUGH THE
AFTERNOON AND EVENING HOURS. THE MOST LIKELY IMPACT WILL BE PERIODS
OF CEILINGS NEAR 5000 TO 6000 FEET AGL. THERE IS ALSO A 30 PERCENT
CHANCE THAT STRONGER STORMS WILL CAUSE GUSTY ERRATIC WINDS AND
LIGHTNING WITHIN 5 MILES OF THE TERMINAL.

&&

.FIRE WEATHER...A DEEP LOW REMAINS OVER SOUTHERN CALIFORNIA.
A MOIST SOUTHERLY FLOW OVER THE GREAT BASIN WILL BE THE RESULT.
THE LOW WILL SLIDE NORTHEAST ACROSS THE GREAT BASIN
THURSDAY...WITH DRYING DEVELOPING FROM THE SOUTHWEST IN ITS WAKE
FRIDAY. IN THE MEANTIME...SCATTERED TO NUMEROUS THUNDERSTORMS CAN
BE EXPECTED THROUGH THURSDAY...WITH INCREASING HUMIDITIES...GOOD
CHANCES OF WETTING RAINS...AND DECREASING THREAT OF NEW LIGHTNING
STARTS.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...FLASH FLOOD WATCH THROUGH WEDNESDAY EVENING FOR
     UTZ013-016-019>021-518.

WY...NONE.
&&

WILENSKY/YOUNG

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
558 AM MDT TUE OCT 5 2010

UTZ001>016-019>021-517-518-WYZ021-061200-
CACHE VALLEY/UTAH PORTION-NORTHERN WASATCH FRONT-
SALT LAKE AND TOOELE VALLEYS-SOUTHERN WASATCH FRONT-
GREAT SALT LAKE DESERT AND MOUNTAINS-WASATCH MOUNTAIN VALLEYS-
WASATCH MOUNTAINS I-80 NORTH-WASATCH MOUNTAINS SOUTH OF I-80-
WESTERN UINTA MOUNTAINS-WASATCH PLATEAU/BOOK CLIFFS-
WESTERN UINTA BASIN-CASTLE COUNTRY-SAN RAFAEL SWELL-
SANPETE/SEVIER VALLEYS-WEST CENTRAL UTAH-SOUTHWEST UTAH-
UTAHS DIXIE AND ZION NATIONAL PARK-SOUTH CENTRAL UTAH-
GLEN CANYON RECREATION AREA/LAKE POWELL-CENTRAL MOUNTAINS-
SOUTHERN MOUNTAINS-SOUTHWEST WYOMING-
558 AM MDT TUE OCT 5 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN TWO THIRDS OF
UTAH AND FAR SOUTHWEST WYOMING.

.DAY ONE...TODAY AND TONIGHT

A MOIST SOUTHERLY FLOW WILL CONTINUE ACROSS THE OUTLOOK AREA
THROUGH TONIGHT AS A LARGE UPPER LOW REMAINS STALLED OVER SOUTH
CENTRAL CALIFORNIA.

SHOWERS AND THUNDERSTORMS WILL CONTINUE TO BE WIDESPREAD ACROSS
MOST OF THE AREA AND WILL PRODUCE LOCALLY HEAVY RAIN ACROSS
PORTIONS OF THE SOUTH. FLASH FLOODING IS POSSIBLE ACROSS SOUTHERN
UTAH PARTICULARLY IN SLOT CANYONS AND NORMALLY DRY WASHES. THE
LARGER STREAMS AND RIVERS WILL EXPERIENCE HIGHER FLOWS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE UPPER LOW WILL REMAIN OVER CENTRAL CALIFORNIA THROUGH
WEDNESDAY WITH A PERSISTENT MOIST SOUTHERLY FLOW OVER THE OUTLOOK
AREA. SCATTERED TO NUMEROUS RAIN SHOWERS ALONG WITH A CHANCE OF
THUNDERSTORMS WILL CONTINUE ACROSS THE AREA THROUGH WEDNESDAY.

LOCALLY HEAVY RAIN AND THE THREAT OF FLASH FLOODING WILL CONTINUE
THROUGH WEDNESDAY AS WELL...WITH THE GREATEST THREAT ACROSS THE
SOUTH.

THE UPPER LOW WILL START TO MOVE EAST ON THURSDAY THEN SHIFT PAST
THE OUTLOOK AREA FRIDAY. SHOWERS WILL CONTINUE IN MOST AREAS
THURSDAY AND ACROSS THE NORTH FRIDAY WHILE THEY BEGIN TO TAPER
OFF ACROSS THE SOUTH. A FEW SHOWERS COULD PERSIST THROUGH THE
WEEKEND.

TEMPERATURES WILL CONTINUE TO COOL OFF THROUGH WEDNESDAY THEN
REMAIN NEAR OR A LITTLE BELOW SEASONAL LEVELS THROUGH THE END OF
THE WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)