705  
FXUS65 KSLC 222111  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
311 PM MDT TUE AUG 22 2017  
   
SYNOPSIS
 
AN UPPER LEVEL TROUGH WILL MOVE NORTH INTO SOUTHERN  
UTAH THIS MORNING, THEN TRACK SLOWLY NORTH ACROSS THE REGION  
THROUGH TONIGHT. SOMEWHAT DRIER AIR WILL FOLLOW THIS TROUGH,  
WITH THIS DRIER AIR COVERING THE ENTIRE AREA BY THE END OF THE  
WEEK.  
 

 
   
SHORT TERM (THROUGH 00Z FRIDAY)
 
 
WATER VAPOR SATELLITE SHOWS A CLOSED LOW OFF THE CENTRAL CALIFORNIA  
COAST, WITH RIDGING OVER NORTHERN UTAH FROM THE EAST SOUTHEAST.  
400MB-200MB MDCARS WIND OBSERVATIONS PLACE A 45KT-65KT  
SOUTHWESTERLY JET FROM SOUTHERN CALIFORNIA INTO THE FOUR CORNERS.  
GOES/SLC 12Z RAOB/HRRR INDICATE THAT PRECIPITABLE WATER VALUES  
VARY FROM 0.25"-0.50" NORTHERN MOUNTAINS, 0.75"-1.25" ACROSS MOST  
VALLEYS.  
 
EJECTED WAVE PIVOTING NORTHEAST FROM THE AFOREMENTIONED CLOSED  
LOW CONTINUES TO PROPAGATE NORTHWARD OVER UTAH, EVENTUALLY  
WEAKENING AS IT RUNS INTO THE RIDGE AXIS WHICH RETREATS TO THE  
NORTHEAST OVER TIME. THIS FEATURE IS RESPONSIBLE FOR A CORRIDOR OF  
COPIOUS CLOUD COVER, SCATTERED TO NUMEROUS SHOWERS AND AFTERNOON  
THUNDERSTORMS.  
 
PRETTY GOOD DESTABILIZATION THIS AFTERNOON DESPITE CLOUD COVER  
PER SREF WITH DCAPE VALUES NEAR 1000 J/KG. BIGGEST THREAT FROM  
STORMS CENTRAL AND NORTHERN UTAH WILL BE GUSTY/ERRATIC WINDS  
MAINLY IN THE 35-45 MPH RANGE THOUGH SOME CAMS ARE A LITTLE MORE  
AGGRESSIVE. WENT AGAINST THAT NOTION DUE TO THE CLOUD COVER  
LIMITING HEATING.  
 
THIS FEATURE PIVOTS TO AND NORTH OF THE IDAHO BORDER LATE TONIGHT  
THROUGH TOMORROW MORNING, WHERE THE FOCUS OF CLOUD COVER AND  
PRECIPITATION WILL BE. MEANWHILE IT WILL BE DRYING OUT ACROSS THE  
SOUTH.  
 
HEIGHT FALLS BEGIN TOMORROW AS THE AFOREMENTIONED CLOSED LOW  
EASES INLAND. MOST OF THE FORECAST AREA EXCEPT IDAHO BORDER REGION  
PERHAPS WILL DESTABILIZE DUE TO RESIDUAL LOW LEVEL MOISTURE AND  
COOLING ALOFT. CONVECTION WILL BECOME MORE RELEGATED TO THE  
MOUNTAINS AND TO THEIR EAST-NORTHEAST BASED ON STEERING FLOW.  
 
UPPER LEVEL TROUGH PASSES TOMORROW NIGHT, WITH HEIGHT RISES  
THURSDAY. DUE TO THIS AND DRYING CONDITIONS, HAVE LOWER POPS THAN  
WEDNESDAY. ANY STORMS THAT DO FORM ON THE TERRAIN WILL DRIFT EAST  
SOUTHEAST GIVEN THE POST TROUGH STEERING FLOW.  
 
GRADUAL WARMING/DRYING TREND STARTED TODAY ACROSS THE SOUTH AND  
WILL SPREAD ACROSS THE REMAINDER OF THE REGION THROUGH THURSDAY  
AS HEIGHTS RISE.  
   
LONG TERM (AFTER 00Z FRIDAY)
 
 
A FLAT RIDGE IS IN PLACE OVER THE GREAT BASIN HEADING INTO  
THURSDAY NIGHT AND FRIDAY, WITH A BROAD TROUGH MOVING THROUGH THE  
PACIFIC NORTHWEST. AS THAT TROUGH SLIDES EASTWARD, IT COULD BRING  
SOME SHOWERS TO SOUTHERN IDAHO/NORTHERN UTAH ON FRIDAY, THOUGH A  
SIMPLE INCREASE IN CLOUD COVER CURRENTLY LOOKS MORE LIKELY.  
OTHERWISE, CONVECTION FRIDAY SHOULD LARGELY BE LIMITED TO THE  
HIGHER TERRAIN, AS A SLOW DRYING TREND CONTINUES.  
 
THE RIDGE OVER THE SOUTHWESTERN CONUS IS FORECAST TO AMPLIFY OVER  
THE WEEKEND, LEADING TO A MORE SIGNIFICANT WARMING AND DRYING TREND.  
THIS SHOULD PRODUCE ABOVE NORMAL TEMPERATURES HEADING INTO THE FINAL  
WEEK OF METEOROLOGICAL SUMMER, WITH ISOLATED CONVECTION AT BEST OVER  
THE MOST PRONE HIGHER TERRAIN LOCATIONS.  
 

 
   
AVIATION
 
 
SHOWERS/THUNDERSTORMS WILL CONTINUE TO INCREASE ACROSS  
NORTHERN UTAH LATER TODAY, WITH A 50 PERCENT CHANCE OF GUSTY AND  
ERRATIC WINDS AT THE SLC TERMINAL BETWEEN 22Z AND 04Z. OTHER  
POTENTIAL IMPACTS INCLUDE LIGHTNING AND BRIEF PERIODS OF CEILINGS  
BELOW 7000 FEET UNDER MODERATE-TO-HEAVY RAINFALL. SHOWERS MAY ALSO  
CONTINUE INTO THE OVERNIGHT HOURS.  
 

 
   
FIRE WEATHER
 
 
ERC VALUES ARE BELOW THE 50TH PERCENTILE ACROSS SOUTHERN AND  
PORTIONS OF EASTERN UTAH. ELSEWHERE VALUES ARE HIGHER, VARYING  
FROM 50TH THROUGH 79TH PERCENTILE MOST LOCATIONS. NEAR DUGWAY ERC  
VALUES ARE IN THE 80TH THROUGH 96TH PERCENTILE.  
 
A WAVE PROPAGATING NORTHWARD OVER UTAH TODAY INTO TONIGHT WILL  
BRING INCREASED CLOUD COVER AND CHANCES FOR WETTING RAINS. ACROSS  
SOUTH CENTRAL SOME MAY BE LOCALLY HEAVY, WHILE ACROSS MAINLY NORTH  
CENTRAL UTAH DRY MICROBURSTS MAINLY IN THE 35-45 MPH RANGE ARE  
FORECAST.  
 
PERIODS OF CLOUDS AND COOLING TEMPERATURES TODAY THROUGH  
REMAINING FAIRLY DRY RH-WISE. WILL HAVE TO WATCH FOR NEW LIGHTNING  
STARTS WHERE FUELS ARE PARTICULARLY DRY, BUT FEEL AREAL EXTENT  
AND OTHER PARAMETERS NOT WHERE I WANT TO SEE THEM FOR ANY  
HEADLINES AT THIS TIME.  
 
THE COVERAGE OF SHOWERS AND STORMS WILL DIMINISH THROUGH THE  
WEEK BECOMING MORE CONFINED TO THE MOUNTAINS. A RIDGE BUILDS IN  
FOR THE UPCOMING WEEKEND DRYING OUT THE STATE WITH ABOVE NORMAL  
TEMPERATURES.  
 

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

 
 

 
 
SHORT TERM/FIRE WEATHER...ROGOWSKI  
LONG TERM/AVIATION...SCHOENING  
 
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...  
HTTP://WEATHER.GOV/SALTLAKECITY  
 
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION  
VISIT...  
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP  
 
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