Tornado and Flash Flooding in Utah, July 24 to 26, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
939 AM MDT SAT JUL 24 2010

.SYNOPSIS...HIGH PRESSURE CENTERED OVER NEVADA WILL KEEP A DRY
NORTHERLY FLOW OVER ALL BUT FAR SOUTHERN UTAH THROUGH SUNDAY. THE
HIGH WILL SHIFT EAST MONDAY...ALLOWING DEEPER MOISTURE TO RETURN
TO THE AREA FROM THE SOUTH. THIS MOISTURE WILL REMAIN IN PLACE
THROUGH THE FIRST PART OF NEXT WEEK.

&&

.DISCUSSION...MOISTURE CONTINUES TO DECREASE ACROSS THE CWA AS DRY
NORTHERLY FLOW CONTINUES TO WRAP AROUND INTO THE AREA. PW IN THE
12Z SLC SOUNDING IS AT 0.39 INCHES...DOWN FROM THE HALF INCH
OBSERVED YESTERDAY. ADDITIONALLY THE BLENDED TOTAL PRECIP WATER
PRODUCT SHOWS PW VALUES DECREASING ACROSS THE SOUTH...WITH PW
VALUES AT AROUND 0.8 INCHES...SLIGHTLY LOWER THAN THE INCH OF PW
OBSERVED IN THE SAME AREA YESTERDAY. STILL...THESE ARE MODEST PW
VALUES FOR THE SOUTHERN UTAH...AND AFTERNOON CONVECTION IS
EXPECTED ONCE AGAIN TODAY. WITH VERY WEAK FLOW...THE POSSIBILITY
STILL EXISTS FOR FLASH FLOODING IF THUNDERSTORMS FORM OVER THE
MOST PRONE AREAS. HOWEVER...RAINFALL ASSOCIATED THESE STORMS WILL
BE EVEN LESS INTENSE THAN YESTERDAY...AND THE FLASH FLOOD THREAT
IS LOWER THAN IT HAS BEEN FOR THE PAST FEW DAYS.

MOISTURE WILL CONTINUE TO DECREASE ACROSS THE CWA THROUGH TOMORROW
AS HIGH PRESSURE MOVES SQUARELY OVERHEAD. HOWEVER...AS THIS HIGH
PRESSURE BEGINS TO MOVE EASTWARD MONDAY...SOUTHERLY FLOW WILL
DEVELOP. THIS WILL SPREAD MOISTURE NORTHWARD THROUGH
MIDWEEK...RESULTING IN AN UPTICK IN AFTERNOON CONVECTION. THIS
MOISTURE WILL STAY IN PLACE THROUGH AT WEDNESDAY...WITH MODEL
DISAGREEMENT AS TO HOW QUICKLY DRY AIR RETURNS TO THE REGION.

CURRENT FORECAST LOOKS GOOD...NO UPDATES PLANNED.

&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGHOUT THE
DAY WITH MOSTLY CLEAR SKIES. LIGHT SOUTHEAST WINDS ARE EXPECTED TO
SHIFT TO THE NORTHWEST BETWEEN 17Z AND 19Z.

&&

.FIRE WEATHER...HIGH PRESSURE ALOFT WILL REMAIN CENTERED ACROSS THE
AREA THROUGH THE WEEKEND MAINTAINING A DRY AIRMASS ACROSS NORTHERN
AND CENTRAL UTAH. MEANWHILE MOISTURE REMAINS IN PLACE ACROSS THE
SOUTHERN AND SOUTHEASTERN PORTION OF THE STATE...WHICH SHOULD ALLOW
FOR A FEW AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS THROUGH
SUNDAY.

BY MONDAY THIS HIGH PRESSURE WILL MOVE EAST ALLOWING MOISTURE TO
SURGE NORTHWARD ACROSS MUCH OF UTAH...BRINGING AN INCREASED THREAT
FOR THUNDERSTORMS THROUGH THE UPCOMING WEEK. WITH THE INITIAL SURGE
OF MOISTURE INTO THE NORTHERN HALF OF THE STATE REMAINING HIGH BASED
MONDAY THUNDERSTORMS LOOK TO REMAIN DRY ACROSS NORTHERN AND CENTRAL
UTAH...WITH THE POTENTIAL FOR AN OUTBREAK OF DRY LIGHTNING AND
MICROBURST WINDS LATE MONDAY AFTERNOON INTO MONDAY EVENING. THESE
STORMS SHOULD QUICKLY TRANSITION TO WET BY TUESDAY AS MOISTURE
RAPIDLY INCREASES. THIS DEEPER MOISTURE LOOKS TO REMAIN IN PLACE
ACROSS THE STATE THROUGH MUCH OF THE UPCOMING WEEK.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

PUBLIC...HOSENFELD
FIRE WEATHER...SEAMAN
AVIATION...TRAPHAGAN

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
601 AM MDT SAT JUL 24 2010

UTZ001>016-019>021-517-518-WYZ021-251200-
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-
601 AM MDT SAT JUL 24 2010

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

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP
AGAIN THIS AFTERNOON ACROSS THE FAR SOUTHERN PORTIONS OF THE
OUTLOOK AREA AND CONTINUE INTO TONIGHT BEFORE ENDING. A FEW OF
THESE COULD PRODUCE LOCALLY HEAVY RAIN.

THE CENTRAL AND NORTHERN PORTIONS WILL REMAIN WARM AND DRY.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE MOIST AIRMASS WILL REMAIN IN PLACE ACROSS THE SOUTH ON SUNDAY
THEN SPREAD NORTH MONDAY. THIS WILL RESULT IN A CHANCE OF SHOWERS
AND THUNDERSTORMS OVER THE ENTIRE OUTLOOK AREA BY MONDAY EVENING
AND AN INCREASED THREAT OF HEAVY RAIN ACROSS THE SOUTH.

MOISTURE WILL INCREASE EVEN MORE ON TUESDAY BRINGING A THREAT OF
HEAVY RAIN TO THE ENTIRE AREA...CONTINUING INTO WEDNESDAY.

GRADUAL DRYING FROM THE WEST IS FORECAST TO START THURSDAY WITH
THE DRYING TREND SPREADING ACROSS MORE OF THE AREA FRIDAY.

.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)

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
312 PM MDT SAT JUL 24 2010

UTZ019-020-518-242200-
SOUTH CENTRAL UTAH UT-SOUTHERN UTAH MOUNTAINS UT-UTAH'S DIXIE AND
ZION NATIONAL PARK UT-
312 PM MDT SAT JUL 24 2010

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN KANE AND EASTERN
WASHINGTON COUNTIES UNTIL 400 PM MDT...

AT 302 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 9 MILES EAST OF ZION NP...OR 23 MILES NORTHWEST
OF KANAB...MOVING SOUTHWEST AT 5 MPH.

PEA SIZE HAIL IS POSSIBLE WITH THIS STORM...ALONG WITH VERY HEAVY
RAIN.

* LOCATIONS IMPACTED INCLUDE...
   ZION NP...

IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A
STURDY BUILDING.

THIS STORM IS CAPABLE OF PRODUCING PEA SIZE HAIL. IF THREATENING
WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING.

LAT...LON 3702 11281 3720 11316 3741 11285 3729 11263
TIME...MOT...LOC 2111Z 036DEG 5KT 3728 11280

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