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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