Freeze Warning 1, NWS Salt Lake City, UT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
947 PM MDT SUN SEP 20 2009

.SYNOPSIS...A COOL UPPER TROUGH WILL DROP SOUTH THROUGH THE
NORTHERN ROCKIES INTO THE WESTERN PLAINS STATES TONIGHT THEN
STALL AS A CLOSED LOW OVER EASTERN COLORADO MONDAY NIGHT. THE
ASSOCIATED COLD FRONT WILL CROSS UTAH TONIGHT. THE COOL NORTHERLY
FLOW FOLLOWING THE FRONT WILL PERSIST THROUGH MID WEEK.

&&

.DISCUSSION...A COOL UPPER TROF IS DROPPING SOUTH THRU THE
NORTHERN ROCKIES TONIGHT AS A RIDGE AMPLIFIES ALONG THE WEST
COAST. THE INITIAL SURFACE FRONT IS ALMOST OUT OF THE CWA AND THE
REINFORCING COLD PUSH IS DROPPING SOUTH THRU NRN UT AT THIS TIME.

THE INCREASING NORTHWEST FLOW HAS PUSHED THE MOISTURE OUT OF THE
FORECAST AREA AND THE SECONDARY FRONT WILL COMPLETE THE DRYING
PROCESS OVERNIGHT. COLD ADVECTION...A DECENT PRESSURE GRADIENT AND
MODERATE TO STRONG 700 MB NELY FLOW WILL COMBINE TO PRODUCE A GAP
WIND EVENT IN WASHINGTON COUNTY OF SW UT. THE WINDS WILL START
LATE TONIGHT AND INCREASE THRU MON INTO TUE MORNING. LOCAL DECISION
TREE DOES INDICATE A POTENTIAL FOR AN ADVISORY OR BETTER EVENT BUT
THIS CAN BE ISSUED BY DAY SHIFT MON IF SITUATION DEVELOPS AS
FORECAST. DONT SEE MUCH THREAT OF CANYON WINDS FOR THE WASATCH
FRONT AS THE FLOW ALOFT HAS LITTLE EASTERLY COMPONENT AND THE
SURFACE GRADIENT IS VERY WEAK.

THE AIRMASS IS FORECAST TO GET COLD AND DRY ENOUGH FOR LOCAL FROST
MON NIGHT/TUE MRNG IN THE UINTA BASIN AND CACHE VALLEY. IT IS
POSSIBLE SOME OF THE NORMALLY COLDER SPOTS ELSEWHERE SUCH AS DELTA
THE EASTERN BASINS AROUND GREEN RIVER AND HANKSVILLE COULD ALSO
HAVE SOME FROST AS THE DRY AIRMASS SHOULD RADIATE OUT NICELY UNDER
THE CLEAR SKIES. CURRENT FREEZE WATCH WILL CONTINUE UNCHANGED.

18Z GFS STILL WANTS TO BRING THE CLOSED LOW FARTHER WEST DURING
THE WEEK THAN THE EC BUT IT HAS BEEN TRENDING TOWARDS THE EC IDEA
AND WILL LIKELY FALL IN LINE WITH THE VERY CONSISTENT EC WITHIN
THE NEXT RUN OR TWO. EITHER WAY...WE STAY IN A COOL DRY NORTHERLY
FLOW PAST MID WEEK BEFORE RIDGING SHIFTS EAST AND THE AIRMASS
WARMS BACK UP.

UPDATED EARLIER TO ADJUST POPS ACROSS SRN UT FOR EARLIER THIS
EVE. NO ADDITIONAL UPDATES PLANNED.

&&

.AVIATION...NORTHERLY WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH MOST OF THE OVERNIGHT HOURS. WINDS ARE EXPECTED TO BECOME
LIGHT AND VARIABLE NEAR DAWN...THEN BECOME NORTHERLY AGAIN BETWEEN
13-15Z MONDAY. VFR UNDER CLEAR SKIES WILL PREVAIL.

&&

.FIRE WEATHER...A COLD FRONT WILL SWEEP OUT OF UTAH OVERNIGHT.
THE AIRMASS BEHIND THE COLD FRONT WILL DRY QUICKLY ON A BREEZY
NORTHWEST FLOW.

A RED FLAG WARNING HAS BEEN ISSUED MONDAY AFTERNOON AND EVENING
ACROSS MUCH OF SOUTHWEST AND SOUTHEAST UTAH DUE TO THE COMBINATION
OF GUSTY NORTHERLY WINDS...A DRY AIRMASS AND CRITICAL FUELS.

DRY AND COOL CONDITIONS ARE EXPECTED THRU MID WEEK AS STABLE HIGH
PRESSURE DOMINATES THE REGION WITH CONTINUED BREEZY NORTH WINDS.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...RED FLAG WARNING FROM NOON MONDAY TO 9 PM MONDAY FOR UTZ435-
     437-439-445>447-449.

     FREEZE WATCH FROM 2 AM TUESDAY TO 8 AM TUESDAY FOR UTZ001-UTZ011.

WY...NONE.

&&

WILENSKY

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

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
200 PM MDT SUN SEP 20 2009

UTZ001>016-019>021-517-518-WYZ021-211200-
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-
200 PM MDT SUN SEP 20 2009

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

.DAY ONE...TONIGHT

A COLD FRONT ACROSS CENTRAL UTAH THIS EVENING IS FORECAST TO SAG
SOUTH TO THE ARIZONA STATE LINE BY MONDAY MORNING. STRONG
NORTHERLY CANYON WINDS ARE ANTICIPATED ALONG INTERSTATE 15 SOUTH OF
CEDAR CITY AND ACROSS WASHINGTON COUNTY LATE TONIGHT AND EARLY
MONDAY MORNING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SUNDAY

THE COLD FRONT WILL EXIT SOUTHERN UTAH ON MONDAY. COOLER AND MUCH
DRIER AIR WILL EXIST BEHIND THE FRONT. THE COMBINATION OF GUSTY
NORTHERLY WINDS AND LOW RELATIVE HUMIDITY VALUES WILL LEAD TO THE
DEVELOPMENT OF SEVERE FIRE WEATHER CONDITIONS ACROSS MUCH OF
SOUTHWEST AND SOUTHEAST UTAH MONDAY AFTERNOON AND EVENING.

FAVORABLE CONDITIONS WILL EXIST OVER EXTREME SOUTHWEST UTAH TO
PRODUCE STRONG CANYON WINDS IN WASHINGTON COUNTY MONDAY NIGHT THROUGH
TUESDAY MORNING. BREEZY CANYON WINDS ARE ALSO A POSSIBILITY ALONG
THE WASATCH FRONT OF NORTHERN UTAH...THOUGH THESE WINDS ARE NOT
EXPECTED TO BE AS STRONG AS THOSE OVER SOUTHWEST UTAH.

THE MUCH DRIER AND COOLER AIRMASS WILL LEAD TO AREAS OF FREEZING
TEMPERATURES IN SOME OF THE NORTHERN UTAH GROWING AREAS. PORTIONS
OF THE CACHE VALLEY AND THE WESTERN UINTA BASIN CAN EXPECT
FREEZING TEMPERATURES LATE MONDAY NIGHT THROUGH EARLY TUESDAY
MORNING.

HIGH PRESSURE ALOFT WILL RETURN TO THE GREAT BASIN AROUND
MIDWEEK. GENERALLY DRY CONDITIONS AND ABOVE NORMAL TEMPERATURES
WILL DEVELOP FOR THE END OF THE WEEK THROUGH THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

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

ROGOWSKI

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