594  
FXUS65 KGJT 202318  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
418 PM MST THU FEB 20 2020  
   
SHORT TERM
 
(TONIGHT THROUGH FRIDAY NIGHT)  
ISSUED AT 153 PM MST THU FEB 20 2020  
 
A PROGRESSIVE RIDGE HAS BEGUN TO BUILD OVER THE REGION ALLOWING WARM  
AIR ADVECTION TO BECOME WELL ESTABLISHED. THERE IS NOT A CLOUD IN  
THE SKY AT THIS NOON HOUR AND INDICATIONS ARE THAT SKIES SHOULD BE  
MOSTLY CLEAR TONIGHT. THE MAIN CHALLENGE WILL BE HOW MUCH THE  
WARMING ALOFT TRANSLATES TO THE SURFACE. THE NORTHERN VALLEYS ENDED  
UP AROUND -25 F LAST NIGHT, WHICH WAS MUCH COLDER THAN EXPECTED. THE  
700 MB TEMPERATURES INCREASE BY 10 C OVER THOSE LOCATIONS SO TRIED  
TO FOLLOW THAT TREND IN THE FORECAST. TOMORROW SOME MOISTURE IN THE  
SOUTHWEST FLOW MIGHT REACH THE SAN JUANS IN THE FORM OF CLOUDS  
OTHERWISE MOSTLY SUNNY AGAIN. HIGH TEMPERATURES WILL BE RIGHT  
AROUND NORMAL FOR TOMORROW. THE NEXT STORM FOR THIS WEEKEND WILL  
BE A CLOSED LOW PRESSURE LOCATED JUST OFF THE COAST OF SOUTHERN  
CALIFORNIA.  
   
LONG TERM
 
(SATURDAY THROUGH THURSDAY)  
ISSUED AT 153 PM MST THU FEB 20 2020  
 
ON EARLY SATURDAY THE STORM SYSTEM COMES ASHORE AND THE ASSOCIATED  
PRECIPITATION BEGINS TO SPREAD NORTHEASTWARD THROUGH ARIZONA. THE  
MODELS ARE IN FAIRLY GOOD AGREEMENT THAT THE ABAJOS, LA SALS AND SAN  
JUANS WILL SEE SHOWERS BY THE AFTERNOON. TEMPERATURES AHEAD OF THE  
SYSTEM BECOME MAXIMIZED SATURDAY AFTERNOON WITH MANY LOCATIONS ABOVE  
NORMAL. AS A RESULT THE SNOW LEVELS STILL APPEAR TO BE RELATIVELY  
HIGH WHEN THE PRECIPITATION MOVES IN FROM THE SOUTHWEST, WHICH ARE  
AROUND ROUGHLY 8500 FEET IN THE SOUTH AND 5000 FEET IN THE NORTH.  
 
THINGS GET INTERESTING AND COMPLICATED SATURDAY EVENING AS THE  
DYNAMICS REALLY INCREASE AND THE MIDLEVEL LOW PRESSURE TRACKS  
OVER NORTHERN ARIZONA. THE EXACT TRACK OVER OUR AREA IS STILL  
UNCERTAIN WITH VARIOUS SOLUTIONS FROM A TRACK OF THE MAIN LOW  
SOUTH OF OUR SOUTHERN BORDER, TO TWO CLOSED LOWS...ONE TRACKING  
NEAR OUR SOUTHERN BORDER AND THE OTHER NEAR I-70, OR THE MAIN LOW  
TRACKING IN BETWEEN I-70 AND OUR SOUTHERN BORDER. UNFORTUNATELY,  
CONFIDENCE HAS LOWERED AGAIN AS SIGNS OF A MIDLEVEL DRY SLOT ARE  
BEGINNING TO SHOW UP. IF THIS MATERIALIZES IT WOULD RUN INTO THE  
SOUTHERN AND CENTRAL AREAS AND REALLY DECREASE PRECIPITATION  
EFFICIENCY. ANOTHER CONCERNING TREND IS A DEFORMATION BAND THAT  
SETS UP ACROSS NORTHEASTERN UTAH AND FAR NORTHWEST COLORADO.  
TEMPERATURES SATURDAY NIGHT ARE EXPECTED TO BE COOLER UP NORTH  
RESULTING IN THE POTENTIAL FOR ENHANCED SNOWFALL TOTALS AROUND  
THE EASTERN UINTA BASIN AND MOUNTAINS. FOR AREAS ALONG AND SOUTH  
OF I-70 NOCTURNAL COOLING WILL BE LIMITED GIVEN WAA AND POSSIBLE  
CLOUD COVER, SO SNOW LEVELS MAY DROP TO 6000 FEET SOUTH AT BEST  
AND 3500 FEET NORTH.  
 
THE DRY SLOT COULD RESULT IN INSTABILITY, WHICH INTRODUCES THE  
POTENTIAL FOR GRAUPEL AND MORE SCATTERED COVERAGE. THIS  
INSTABILITY LOOKS TO FOCUS OVER THE SOUTHERN HALF OF THE FORECAST  
AREA. ON SATURDAY NIGHT THE SYSTEM TRACKS OVERHEAD AND FLOW  
GRADUALLY SHIFTS TO THE WEST ON SUNDAY MORNING. THE COLDEST AIR  
WITH THIS LOW MIGHT BE -10 C AT 700 MB, BUT MOST LIKELY WARMER. AS  
A RESULT THE SNOW RATIOS REMAIN AT OR BELOW 13:1 FOR THE ENTIRE  
EVENT. WITH THE SYSTEM LACKING CAA THE HIGHS ON SUNDAY ARE CLOSE  
TO NORMAL FOR MANY LOCATIONS. THE MOST FAVORED AREAS WILL BE THE  
SOUTHERN MOUNTAINS ESPECIALLY THE SOUTHWEST AND WEST FACING  
SLOPES. THE CENTRAL MOUNTAINS ARE LESS FAVORABLE, BUT MAY STILL  
SEE DECENT SNOWFALL IN SPOTS, WHILE THE NORTHERN MOUNTAINS ARE THE  
LEAST FAVORED. GIVEN THE AMOUNT OF UNCERTAINTIES AND HOW FAR OUT  
WE ARE FROM THE START DECIDED NOT TO ISSUE ANY HIGHLIGHTS. THE  
SNOWFALL AMOUNTS STILL APPEAR TO BE AROUND ADVISORY CRITERIA FOR  
NOW. THE POTENTIAL BANDING AND DRY SLOT WILL NEED TO BE WATCHED  
CLOSELY.  
 
THE NEXT SHORTWAVE TROUGH DROPS SOUTHEASTWARD OVER THE NORTHERN  
ROCKIES ON MONDAY BUT TIMING WILL BE KEY. THE MODELS ARE STARTING TO  
SHOW THE PREVIOUS SYSTEM OVER THE PLAINS AND THIS ONE TRYING TO  
INTERACT AND PARTIALLY PHASE. THIS WILL HAVE IMPLICATIONS ON WHERE  
THE NORTHERN WAVE TRACKS WITH THE NORTHERN MOUNTAINS BEING MORE  
FAVORED WITH A SOUTHERLY TRACK. THE RUN TO RUN CONSISTENCY IS MAKING  
IT TOUGH TO GET A HANDLE ON THIS SYSTEM, BUT IT COULD RESULT IN  
MORE MOUNTAIN SNOW MONDAY INTO TUESDAY. AN EXPANSIVE RIDGE LOOKS  
TO TAKE OVER THE WESTERN CONUS IN THE LATER HALF OF THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)  
ISSUED AT 418 PM MST THU FEB 20 2020  
 
WIDESPREAD VFR CONDITIONS WILL PREVAIL ACROSS EASTERN UTAH AND  
WESTERN COLORADO THROUGH THE TAF PERIOD UNDER HIGH PRESSURE ALOFT.  
WINDS WILL GENERALLY REMAIN LIGHT AND TERRAIN DRIVEN. HIGH-LEVEL  
CLOUDS WILL BEGIN TO INCREASE AFTER 16Z FRIDAY AS FLOW BEGINS TO  
SHIFT TO THE SOUTHWEST, THOUGH CIGS WILL REMAIN WELL ABOVE ILS  
BREAKPOINTS.  
 

 
   
GJT WATCHES/WARNINGS/ADVISORIES
 
 
CO...NONE.  
UT...NONE.  

 
 

 
 
SHORT TERM...KJS  
LONG TERM...KJS  
AVIATION...MMS  
 
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