060  
FXUS65 KSLC 240234  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
834 PM MDT FRI JUN 23 2017  
   
SYNOPSIS
 
A GENERALLY DRY WEST TO NORTHWEST FLOW ALOFT WILL EXIST  
ACROSS UTAH TONIGHT AND TOMORROW. STRONG HIGH PRESSURE ALOFT WILL  
RETURN TO THE REGION LATE IN THE WEEKEND. A BRIEF SURGE OF  
MOISTURE WILL MOVE THROUGH THE AREA MONDAY.  
 

 
   
DISCUSSION
 
 
WATER VAPOR SATELLITE SHOWS RIDGING FROM CALIFORNIA INTO NEW  
MEXICO AND NORTHERN MEXICO, WHILE NORTHWESTERLY FLOW ALOFT  
RESIDES FROM THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES.  
400-200MB MDCARS WIND OBSERVATIONS PLACE A CYCLONIC 75-105KT JET  
FROM BRITISH COLUMBIA INTO THE NORTH CENTRAL PLAINS. GOES/SLC 00Z  
RAOB/HRRR INDICATE THAT PRECIPITABLE WATER VALUES VARY FROM  
0.10"-0.25" MOUNTAINS TO 0.33"-0.60" VALLEYS.  
 
WITH HIGH PRESSURE IN PLACE, BENIGN WEATHER ONCE AGAIN TONIGHT.  
GOING FORECAST IN FANTASTIC SHAPE. JUST TWEAKED THE HOURLY DIURNAL  
T/RH CURVE BASED ON LATEST OBSERVATIONS AND FORECAST DATA. ALSO  
MASSAGED THE WINDS DUE TO THE NORTHERLY PRESSURE GRADIENT WITH  
HIGH PRESSURE BUILDING IN. WINDS OUTSIDE OF ST GEORGE WILL BE  
LIGHTER THAN LAST NIGHT THOUGH.  
 

 
   
PREVIOUS DISCUSSION
 
 
MOUNTAIN CUMULUS CLOUDS HAVE DEVELOPED ACROSS FAR SOUTHERN UTAH  
THIS AFTERNOON, IN AND AROUND THE BRIAN HEAD FIRE. THE SMOKE PLUME  
FROM THE FIRE REMAINS VISIBLE ON SATELLITE AS THE PLUME DRIFTS TO  
THE SOUTHEAST. AS THE ATMOSPHERE HAS BECOME DESTABILIZED, THE  
SMOKE PLUME APPEARS TO BE GROWING. WINDS STATEWIDE LARGELY REMAIN  
NORTHWESTERLY THIS AFTERNOON AND SOME LOCALLY BREEZY CONDITIONS  
ARE OBSERVED.  
 
GOING IN TO THE WEEKEND, THE FLOW REMAINS MOSTLY UNCHANGED UNDER A  
BUILDING RIDGE AND NORTHWEST FLOW ALOFT. MOISTURE FIELDS ARE PRETTY  
MEAGER, WITH MIXING RATIO VALUES 3 G/KG OR LESS. TEMPERATURES ALSO  
CHANGE VERY LITTLE DAY TO DAY, AS 700MB TEMPS ACROSS THE NORTH RANGE  
FROM 10-12C AND ACROSS THE SOUTH 16-17C. AS THE HEAT CONTINUES  
ACROSS THE SOUTH, THE GOING EXCESSIVE HEAT WARNING REMAINS IN EFFECT  
FOR THE DIXIE AREA IN THE SOUTHWEST.  
 
THE RIDGE SLOWLY SHIFTS OVER UTAH AND SOUTHWEST WYOMING ON SUNDAY  
NIGHT AND MONDAY, AS A SHORTWAVE TROUGH PUSHES INTO NORTHERN  
CALIFORNIA. SOUTHWESTERLY FLOW WILL INCREASE OVER THE FORECAST  
AREA AHEAD OF THIS TROUGH, AND MONDAY WILL BRING A CONSIDERABLE  
WARMING TREND FOR MANY LOCATIONS, PARTICULARLY ACROSS THE NORTHERN  
HALF OF THE CWA.  
 
THIS INCREASED SOUTHERLY FLOW WILL HELP BRING IN SOME ADDITIONAL  
MID-LEVEL MOISTURE TO THE AREA, AND ISOLATED SHOWERS AND  
THUNDERSTORMS COULD INITIATE OVER THE HIGHER TERRAIN OF UTAH AND  
EASTERN NEVADA ON MONDAY, WITH THE LATTER STORMS POTENTIALLY  
DRIFTING INTO NORTHWEST UTAH MONDAY AFTERNOON/EVENING. HAVE  
INCREASED POPS SLIGHTLY FOR THIS POSSIBILITY, PARTICULARLY ACROSS  
THE FAR NORTHWEST. THAT SAID, ANY STORMS THAT DO DEVELOP MONDAY  
WILL BE HIGH BASED, AND THE DRY LOW LEVEL AIRMASS WILL MAKE GUSTY  
WINDS MUCH MORE LIKELY THAN SIGNIFICANT RAINFALL.  
 
THE WEAK SHORTWAVE PASSES THROUGH IDAHO AND NORTHERN UTAH LATE  
MONDAY INTO TUESDAY. THIS IS JUST THE BEGINNING OF A PATTERN  
CHANGE, WITH A MEAN TROUGH SETTING UP OVER THE PACIFIC NORTHWEST.  
WHILE MOST OF THE MOISTURE AND INSTABILITY GENERALLY REMAINS NORTH  
OF THE AREA THROUGH TUESDAY AND EARLY WEDNESDAY, ENOUGH LOW LEVEL  
COOL AIR DOES LOOK TO FILTER INTO UTAH TO DROP TEMPS A BIT,  
INCLUDING ENDING THE LONG STRING OF VERY HOT TEMPERATURES IN FAR  
SOUTHERN UTAH. (THAT SAID, TEMPERATURES TUESDAY GENERALLY  
DECREASE FROM "VERY HOT" TO SIMPLY "HOT".)  
 
TIMING DIFFERENCES IN THE GLOBAL MODELS BEGIN TO BECOME MORE  
EVIDENT WEDNESDAY THROUGH FRIDAY, THOUGH THE GENERAL IDEA IS THAT  
A SERIES OF WEAK WAVES AND SURFACE COLD FRONTS COULD PUSH THROUGH  
THE NORTHERN HALF OF THE CWA THROUGH THE LATTER HALF OF THE WEEK.  
HAVE GENERALLY DECREASED TEMPS A BIT AND RAISED POPS FOR THE NORTH  
WEDNESDAY AND THURSDAY. LEANED A BIT MORE TOWARD THE GFS TIMING  
FOR NOW, WHICH HAS A COLD FRONT WITH DECENT MOISTURE ASSOCIATED  
WITH IT ON WEDNESDAY AFTERNOON.  
 

 
   
AVIATION
 
VFR WITH CLEAR SKIES OVERNIGHT AT THE SLC TERMINAL.  
NORTH WINDS WILL BECOME LIGHT AND VARIABLE AS THE NIGHT PROGRESSES.  
 

 
   
FIRE WEATHER
 
NORTHWEST WINDS WILL CONTINUE TO WEAKEN ACROSS THE  
SOUTH AND EAST THIS EVENING, BECOMING MUCH LIGHTER SATURDAY. HOT AND  
DRY CONDITIONS REMAIN IN PLACE AREA WIDE AND WILL CONTINUE INTO THE  
WEEKEND. A MORE STABLE AIR MASS ACROSS NORTHERN UTAH WILL CREATE  
POOR MIXING AND CLEARING INDICES WHILE THE SOUTH REMAINS GOOD TO  
EXCELLENT FOR CLEARING.  
 
HIGH PRESSURE IS BUILDING BACK ACROSS THE REGION WHICH WILL RESULT  
IN MORE WIDESPREAD HAINES VALUES OF 6 AS THE AIRMASS BECOMES WARMER  
INTO NEXT WEEK. A WEAK SYSTEM HAS THE POTENTIAL TO BRING ISOLATED  
SHOWERS AND THUNDERSTORMS MAINLY ACROSS THE NORTH MONDAY INTO  
TUESDAY, AND LIGHTNING IS POSSIBLE AS WELL WITH THESE STORMS.  
 

 
   
SLC WATCHES/WARNINGS/ADVISORIES
 
 
UT...EXCESSIVE HEAT WARNING UNTIL 10 PM MDT SUNDAY FOR UTZ019.  
 
WY...NONE.  

 
 

 
PUBLIC...ROGOWSKI/DEWEY/SCHOENING  
AVIATION...ROGOWSKI  
FIRE WEATHER...DEWEY  
 
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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