603  
FNUS21 KWNS 200719  
FWDDY1  
 
DAY 1 FIRE WEATHER OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0219 AM CDT SAT JUL 20 2024  
 
VALID 201200Z - 211200Z  
   
..SYNOPSIS
 
 
A LARGE UPPER RIDGE WILL DOMINATE THE WESTERN US THROUGH THE  
FORECAST PERIOD WITHIN A RELATIVELY STAGNANT MID-LEVEL FLOW PATTERN.  
A BROAD PACIFIC TROUGH WILL MOVE ONSHORE TO THE WEST OF THE RIDGE,  
BRINGING ISOLATED THUNDERSTORMS TO PORTIONS OF THE NORTHWEST. TO THE  
EAST, NORTHWESTERLY FLOW ALOFT WILL CONTINUE OVER THE NORTHERN  
ROCKIES AND INTERMOUNTAIN WEST WITH SEASONABLE MONSOON MOISTURE.  
WIDELY SCATTERED THUNDERSTORMS ARE LIKELY THROUGH THE AFTERNOON.  
   
..NORTHERN GREAT BASIN AND NORTHWEST
 
 
TO THE WEST OF THE UPPER RIDGE, SUBTLE ASCENT WILL GRADUALLY  
OVERSPREAD PORTIONS OF THE NORTHERN GREAT BASIN AND PACIFIC  
NORTHWEST AHEAD OF THE ADVANCING UPPER TROUGH. PWAT VALUES ARE  
FORECAST TO INCREASE THROUGH THE DAY, REACHING 0.8 TO 1 INCHES BY  
THIS EVENING. CONTINUED MOISTURE ADVECTION SHOULD ALLOW FOR GRADUAL  
MID-LEVEL DESTABILIZATION AND DRY THUNDERSTORM DEVELOPMENT ALONG THE  
HIGHER TERRAIN BY MID AFTERNOON.  
 
ISOLATED THUNDERSTORMS OVER THE NORTHERN GREAT BASIN SHOULD SLOWLY  
EXPAND IN COVERAGE TO THE NORTHWEST FROM LATE IN THE AFTERNOON AND  
INTO THE OVERNIGHT PERIOD. ENHANCED FLOW ALOFT WILL ALLOW FOR  
MODERATE STORM MOTIONS OF 20-25 KT ATOP RELATIVELY DRY BOUNDARY  
LAYER. THIS WILL LIKELY SUPPORT DRY THUNDERSTORM POTENTIAL THROUGH  
THE OVERNIGHT HOURS DESPITE INCREASING MID-LEVEL MOISTURE. GIVEN THE  
POTENTIAL FOR LIGHTNING OVER VERY RECEPTIVE FUELS (95TH PERCENTILE  
ERCS), THE ISODRYT AREA WAS EXPANDED WESTWARD INTO PORTIONS OF  
WEST/SOUTHWEST OR.  
   
..NORTHERN ROCKIES
 
 
EAST OF THE RIDGE, CONFIDENCE IN DRY STORMS IS LOWER, AS FLOW ALOFT  
WILL BE WEAKER AND DEEPER MONSOONAL MOISTURE IS EXPECTED TO BE IN  
PLACE. THE COMBINATION OF SLOWER SPEEDS AND HIGHER PWATS SUGGESTS  
STORMS MAY HAVE GREATER RAINFALL EFFICIENCY. STILL, THE POTENTIAL  
FOR LIGHTING OUTSIDE OF THE WETTER CORES FROM SCATTERED STORM  
COVERAGE, AND THE POSSIBILITY OF A FEW DRIER STORMS, SUGGEST SOME  
THREAT FOR LIGHTNING IGNITIONS. HOWEVER, THE BEST STORM COVERAGE  
APPEARS DISPLACED TO THE EAST, AWAY FROM THE MORE RECEPTIVE FUELS.  
 
..LYONS.. 07/20/2024  
   
..PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT
 
 

 
 
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