Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

000
FXUS65 KSLC 270242
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
742 PM MST THU FEB 26 2015

.SYNOPSIS...A WEATHER DISTURBANCE WILL CONTINUE TO TRACK SOUTHEAST
ACROSS UTAH INTO TONIGHT. A DEVELOPING STORM SYSTEM WILL AFFECT
MUCH OF THE SOUTHERN AND CENTRAL GREAT BASIN THIS WEEKEND. A THIRD
STORM WILL IMPACT THE ENTIRE AREA THE FIRST HALF OF NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A DISTURBANCE CROSSING
NORTHERN ARIZONA AS THE NEXT ARRIVES ON THE PACIFIC NORTHWEST
COAST. AMDAR 400-250MB WIND OBSERVATIONS INDICATE A NORTHWESTERLY
100-130KT JET FROM THE PACIFIC NORTHWEST INTO ARIZONA.
GOES/GPS/RAP/00Z RAOB INDICATE THE PRECIPITABLE WATER VALUE RANGES
BETWEEN 0.10-0.15" MOUNTAINS...TO 0.30-0.40" MOST VALLEYS. BLENDED
TOTAL PRECIPITABLE WATER PRODUCT INDICATES AN ABNORMALLY MOIST
AIRMASS OVER THE GREAT BASIN AND PACIFIC NORTHWEST WHERE A PACIFIC
MOISTURE TAP WAS NOSING IN.

WITH A DECREASE IN DIURNAL INSTABILITY...SHOWERS WILL LIKELY
CONTINUE TO GRADUALLY DECREASE OVERNIGHT...BUT PROBABLY NOT
COMPLETELY. UPDATED TO MASSAGE POPS A BIT...BUT OVERALL MESSAGE IS
STILL ISOLATED IN THE VALLEYS AND SCATTERED IN THE MOUNTAINS. SNOW
RATES TOO WILL BE ON THE DECLINE. CHANGED WEATHER WORDING TO
COVERAGE TERMINOLOGY.

SAW NO NEED TO MAKE CHANGES TO OVERNIGHT LOWS...JUST UPDATED THE
TEMPERATURE CURVE WITH OBSERVATIONS AND LAMP GUIDANCE INTO THE
OVERNIGHT HOURS. REST UNCHANGED.

PREVIOUS DISCUSSION FOLLOWS...
A MOIST AND SOMEWHAT UNSTABLE CYCLONIC NORTHWEST FLOW IS IN PLACE
OVER UTAH THIS AFTERNOON AS A WEAK SHORTWAVE TROUGH CONTINUES TO
CROSS THE AREA. SCATTERED SHOWERS...SNOW IN THE MOUNTAINS AND
HIGHER VALLEYS/BENCHES AND RAIN/SNOW IN THE LOWER VALLEYS...WILL
CONTINUE THROUGH THIS EVENING...THEN BECOME MORE ISOLATED AND
MOSTLY CONFINED TO THE NORTH AFTER SUNSET. A SLIGHTLY COOLER NIGHT
THAN LAST NIGHT IS EXPECTED ACROSS MANY AREAS DUE TO THE COLD AIR
ADVECTION TODAY AND SOME BREAKS IN THE CLOUDS TONIGHT.
OTHERWISE...A NORTHEASTERLY PRESSURE GRADIENT EXISTS OVER
SOUTHWEST WYOMING AND IS ASSOCIATED WITH A BOUNDARY PUSHING IN
FROM THE NORTHEAST. HOWEVER...THIS PUSH IS RELATIVELY SHALLOW AND
THE BULK OF THE COLD AIR WILL REMAIN IN WYOMING.

WEAK SHORTWAVE RIDGING WILL DEVELOP TOMORROW AFTERNOON AS THE AREA
WILL BE BETWEEN SYSTEMS. HOWEVER...STRENGTHENING H7 WARM AIR
ADVECTION TOMORROW WILL DRIVE SOME ADDITIONAL PRECIPITATION
TOMORROW.

THE NEXT STORM SYSTEM WILL DROP IN FROM THE PACIFIC NORTHWEST ON
FRIDAY AND CARVE SOUTH ALONG THE WEST COAST. THIS WILL THEN DEVELOP
INTO AN ELONGATED TROUGH WITH AXIS EXTENDING NORTHEAST TO SOUTHWEST
BY SATURDAY. PRECIPITATION WILL INCREASE ACROSS SOUTHERN UTAH FRIDAY
NIGHT AHEAD OF THIS SYSTEM AND CONTINUE AT TIMES THROUGH THE
WEEKEND...SPREADING INTO AT LEAST CENTRAL UTAH. SOME UNCERTAINTY
REGARDING THE NORTHERN EXTENT OF HEAVY PRECIPITATION STILL EXISTS AS
IT DEPENDS ON THE LOCATION OF THE DEFORMATION AXIS DRIVING SOME OF
THE HEAVIER PRECIP...BUT BULK OF THIS IS EXPECTED TO OCCUR ACROSS
MOST OF THE SOUTH AS WELL AS SOME EASTERN VALLEYS. SNOW LEVELS
ACROSS SOUTHEAST UTAH MAY BE A BIT HIGHER THAN LAST WEEKENDS
SOUTHERN UTAH STORM...DUE TO A MILD SOUTHWEST FLOW...AT LEAST
THROUGH SATURDAY. AS A RESULT...ACCUMULATIONS IN MOST SOUTHERN UTAH
VALLEYS RIGHT NOW...WHILE STILL RELATIVELY SIGNIFICANT...ARE
FORECAST IN THE ADVISORY RANGE SO DO NOT HAVE ANY WINTER WEATHER
HIGHLIGHTS OUT AT THIS TIME. HOWEVER...HIGHER ELEVATION
AREAS...ESPECIALLY ABOVE 5500-6000FT COULD SEE SIGNIFICANT TOTALS
AND A WINTER STORM WATCH HAS BEEN ISSUED FOR THE SOUTHERN AND
CENTRAL MOUNTAINS AND INCLUDES HIGHER THE PASSES ALONG I-15/I-70
ACROSS SOUTHERN UTAH.

GIVEN THE ORIENTATION OF THE TROUGH...ANOTHER CONCERN WILL BE
EASTERLY CANYON WINDS ACROSS NORTHERN UTAH. THIS COULD OCCUR AS
EARLY AS FRIDAY NIGHT WITH A STRENGTHENING SURFACE GRADIENT...BUT
WITH NO SUPPORT AT 700MB THIS WILL BE SHALLOW WITH SOME ENHANCED
WINDS CONFINED LOCALLY TO THE CANYONS. HOWEVER...H7 WINDS AND
ASSOCIATED COLD ADVECTION LOOKS TO STRENGTHEN ACROSS THE TERRAIN
SATURDAY NIGHT SO STRONGER AND MORE WIDESPREAD EASTERLIES WILL BE
POSSIBLE DURING THIS TIMEFRAME.

AN ELONGATED TROUGH AXIS IS EXPECTED TO BE LOCATED FROM THE WESTERN
GREAT BASIN TO OFFSHORE SOUTHERN CALIFORNIA AT THE BEGINNING OF THE
LONG TERM FORECAST PERIOD. ANOTHER SHORTWAVE IS EXPECTED TO BE
PROGRESSING AROUND THE EAST SIDE OF THE EASTERN PACIFIC HIGH DOWN
THE PACIFIC COAST. THIS UPSTREAM SHORTWAVE IS EXPECTED TO DISLODGE
THE FIRST TROUGH WHICH WILL CROSS ARIZONA INTO NEW MEXICO THROUGH
LATE MONDAY. PRECIPITATION IS LIKELY TO BE ONGOING AT THE START OF
THE LONG TERM FORECAST ACROSS PORTIONS OF SOUTHERN UTAH...WITH MORE
SPOTTY PRECIPITATION ASSOCIATED WITH THE DEFORMATION AXIS ACROSS
PORTIONS OF CENTRAL AND SOUTHERN UTAH.

THE UPSTREAM SHORTWAVE IS EXPECTED TO QUICKLY PROGRESS ACROSS THE
DESERT SOUTHWEST TUESDAY. NEXT UP IN THE TRAIN OF SYSTEMS IMPACTING
UTAH...ANOTHER SHORTWAVE DIVING SOUTH FROM INTERIOR CANADA IS
EXPECTED TO BRING A SIGNIFICANT COLD FRONT THROUGH THE AREA TUESDAY.
BOTH THE 12Z GFS AND EC DEPICT 700MB TEMPERATURES FALLING TO BELOW
-20C BY TUESDAY NIGHT BEHIND THIS COLD FRONT ACROSS NORTHERN AND
CENTRAL UTAH. WHILE THE GLOBAL MODELS HAVE BEEN TRENDING FURTHER
EAST WITH THIS SYSTEM...FEEL THERE IS ENOUGH CONFIDENCE IN A COLDER
AIRMASS ACROSS THE STATE TO DECREASE TEMPERATURES SIGNIFICANTLY
BELOW NORMAL FROM ROUGHLY WEDNESDAY ONWARD. MOST OF THE MODEL
GUIDANCE INDICATES THERE IS A THREAT OF PRECIPITATION NEAR AND

&&

.AVIATION...ISOLATED TO SCATTERED SNOW SHOWERS WILL CONTINUE TO
IMPACT THE VICINITY OF THE SLC TERMINAL THROUGH THE EVENING.
EXPECT OCCASIONAL CEILINGS NEAR 2000-3000 FEET AGL NEAR ANY
SHOWERS THROUGH AT LEAST 04Z...AFTERWARDS A DECREASING COVERAGE
TREND IS FORECAST. NORTH TO NORTHWESTERLY WINDS WILL CONTINUE
THROUGH 04Z...WITH A 30 PERCENT CHANCE THE SOUTHEAST DRAINAGE
WINDS DONT MATERIALIZE UNTIL AFTER 07Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SUNDAY EVENING
     FOR UTZ517-518.

WY...NONE.
&&

$$

PUBLIC...ROGOWSKI/CHENG/KRUSE
AVIATION...ROGOWSKI

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)



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.