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 50

000
FXUS65 KSLC 311048
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
448 AM MDT MON AUG 31 2015

.SYNOPSIS...WEAK HIGH PRESSURE ALOFT WILL BUILD BACK INTO THE
AREA LATE TODAY AHEAD OF ANOTHER STORM SYSTEM APPROACHING THE
PACIFIC NORTHWEST. A DRIER AND WARMER SOUTHWEST FLOW ALOFT WILL
DEVELOP AHEAD OF THE ADVANCING STORM SYSTEM EARLY THIS WEEK.

&&

.SHORT TERM (UNTIL 06Z FRIDAY)...AN AREA OF WEAK CONVERGENCE
STRETCHED WEST-TO-EAST ACROSS NORTHERN UTAH INTERACTING WITH
SUFFICIENT MOISTURE AND INSTABILITY HAS MAINTAINED WEAK CONVECTION
OVERNIGHT. THIS CONVECTION EXTENDS FROM NEAR WENDOVER THROUGH THE
SALT LAKE CITY AREA AND THEN EAST INTO SOUTHWEST WYOMING. THIS
ACTIVITY WILL LIKELY SHIFT OFF TO THE EAST WITH THE MODEST MID-
LEVEL COLD POOL EARLY THIS MORNING...EXITING THE FORECAST AREA BY
AROUND MID-MORNING.

THE DEEP LAYER MOISTURE PLUME CURRENTLY OVER SOUTH-CENTRAL THROUGH
NORTHEAST UTAH WILL GRADUALLY SHIFT EAST AS THE UPPER TROUGH OVER
THE NORTHERN ROCKIES MOVES EAST INTO THE NORTHERN PLAINS/SOUTHERN
CANADA LATER THIS MORNING. GOES IMAGERY SHOWS A RATHER EXTENSIVE
AREA OF DRIER AIR JUST TO THE WEST AND NORTH OF UTAH EARLY THIS
MORNING. THE EXITING UPPER TROUGH WILL DRAG THIS DRIER AIR ACROSS
MUCH OF WESTERN/NORTHERN UTAH...BRINGING AN END TO ANY REAL THREAT
OF CONVECTION OVER THOSE AREAS FOR THE NEXT COUPLE OF DAYS. AREAS
OF SOUTHERN/EASTERN UTAH WILL LIKELY SEE TERRAIN-BASED CONVECTION
AGAIN TODAY...WITH SOME ORGANIZED ACTIVITY NEAR THE BOUNDARY
BETWEEN THE ADVANCING DRY AIR AND THE EXISTING MOISTURE PLUME.

THE NEXT UNSEASONABLY STRONG UPPER TROUGH WILL DIG SOUTH THROUGH
WESTERN CANADA TONIGHT/TUESDAY...THEN MAINTAIN A PRESENCE OVER THE
PACIFIC NORTHWEST/NORTHERN ROCKIES THROUGH THE BALANCE OF THE
WEEK. A SERIES OF ENERGETIC SHORTWAVES WILL EJECT EAST-NORTHEAST
OUT OF THE MEAN TROUGH POSITION...WITH THESE FEATURES IMPACTING
MAINLY THE NORTHERN THIRD OF UTAH DURING THE LATTER HALF OF THE
WEEK. AHEAD OF THESE EJECTING SHORTWAVES BREEZY AND WARM
CONDITIONS ARE ANTICIPATED...WITH ISOLATED TERRAIN-BASED
CONVECTION POSSIBLE FOR MAINLY THE SOUTHERN/CENTRAL AND NORTHEAST
MOUNTAINS. TEMPERATURES WILL RUN CLOSE TO OR A LITTLE ABOVE NORMAL
FOR EARLY SEPTEMBER. THE FIRST SIGNIFICANT CHANCE AT PRECIP WILL
LIKELY HOLD OFF UNTIL THURSDAY AFTERNOON/EVENING AND WILL BE
CONFINED TO THE AREA ALONG AND BEHIND A COLD FRONT OVER NORTHWEST
UTAH. THIS PRECIP WILL LIKELY BE ISOLATED IN AREAL COVERAGE AND
LIGHT AS THE BEST LIFT WILL REMAIN TO THE NORTH OF THE FORECAST
AREA.

.LONG TERM (AFTER 06Z FRIDAY)...MODEL SPREAD WITHIN THE 00Z GLOBAL
MODEL GUIDANCE SUITE IS QUITE LARGE...HINDERING FORECAST CONFIDENCE
FOR MUCH OF THE LONG TERM FORECAST PERIOD.

A LARGE...RELATIVELY STRONG PACIFIC TROUGH IS EXPECTED TO POSITION
ITSELF ACROSS THE PACIFIC NORTHWEST FOR AN EXTENDED PERIOD. SEVERAL
SHORTWAVES ARE FORECAST TO ROTATE AROUND THE TROUGH THROUGH EARLY
SATURDAY. SEVERAL GLOBAL MODELS INDICATE THE SECOND MAIN SHORTWAVE
ROTATING THROUGH THE TROUGH WILL INDUCE A CLOSED CIRCULATION THAT
WILL SLOWLY MEANDER ACROSS THE PACIFIC NORTHWEST AND INTO THE
NORTHERN INTERMOUNTAIN REGION THROUGH THE WEEKEND AND INTO EARLY
MONDAY. SEVERAL OTHER GLOBAL MODELS..MAINLY THE 00Z GFS...INDICATE A
MUCH MORE PROGRESSIVE SYSTEM...WITH THE SECOND SHORTWAVE QUICKLY
EJECTING ACROSS THE NORTHERN INTERMOUNTAIN REGION. WITH SUCH A LARGE
DIFFERENCE IN THE EVOLUTION OF THIS SYSTEM BETWEEN VARIOUS GLOBAL
MODELS...CONFIDENCE IN ANY ONE SOLUTION IS LOW AT THIS POINT.

FOR UTAH...ONE OF THE MAIN IMPACTS OF THIS VARIATION IS HOW MUCH
MOISTURE WILL BE ADVECTED NORTHWARD WITH THE SOUTHERLY FLOW AHEAD OF
THE TROUGH SATURDAY. THE EC IS THE MOST PROGRESSIVE...WITH A RATHER
SIGNIFICANT MOISTURE SURGE SETTING UP ACROSS PORTIONS OF
SOUTHEASTERN UTAH SATURDAY. THE GFS TRENDS TOWARDS A DRIER
SOLUTION...BUT STILL INDICATES A SEMBLANCE OF A MOISTURE SURGE.
STARTED TO BUMP UP POPS A BIT ACROSS SOUTHEASTERN UTAH
SATURDAY...BUT GIVEN THE MODEL SPREAD...CONFIDENCE IS LOW AT THIS
TIME.

WITH THE DEEPER SOLUTION...THE EC BRINGS A MUCH STRONGER COLD FRONT
THROUGH THE CWA SATURDAY...WITH 700MB TEMPERATURES AS LOW AS -3C
ALONG THE UTAH/IDAHO BORDER BY SUNDAY MORNING. THOUGH THIS IS LIKELY
TO CHANGE IN FUTURE RUNS...KEPT THE TREND OF THE PREVIOUS FORECAST
AND LOWERED TEMPERATURES A BIT SATURDAY AND SUNDAY.

&&

.AVIATION...NORTHWEST WINDS ARE EXPECTED TO CONTINUE AT THE SLC
TERMINAL THROUGH THE REMAINDER OF THE NIGHT AND INTO THE DAY MONDAY.
A FEW SHOWERS ARE POSSIBLE EARLY THIS MORNING THROUGH ABOUT
12Z...WHICH MAY CAUSE BRIEF ERRATIC WINDS.

&&

.FIRE WEATHER...A DRIER AND MORE STABLE AIRMASS WILL MOVE BACK IN
FOR THE EARLY PART OF THE WEEK. A PACIFIC TROUGH WILL APPROACH THE
PACIFIC NORTHWEST BY MIDWEEK. THIS WILL INCREASE SOUTHWEST WINDS
TUESDAY THROUGH AT LEAST FRIDAY. THIS MAY PRODUCE AREAS OF CRITICAL
FIRE WEATHER CONDITIONS WHERE FUELS ARE DRY...PARTICULARLY OVER
WESTERN UTAH.

&&

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

&&

$$

SHORT TERM...CONGER
LONG TERM/FIRE WEATHER/AVIATION...KRUSE

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.