527
FXUS65 KGJT 221001
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
401 AM MDT SAT SEP 22 2018
SHORT TERM
(TODAY THROUGH SUNDAY)
ISSUED AT 401 AM MDT SAT SEP 22 2018
SKIES WERE AGAIN CLEAR OVER MOST OF THE FORECAST AREA OVERNIGHT AS
A LOW-AMPLITUDE RIDGE LINGERED OVER THE REGION. HOWEVER, AREAS OF
ALTOCUMULUS WERE EVIDENT IN IR IMAGERY OVER THE SOUTHWEST SAN
JUAN MOUNTAINS. MODELS INDICATED A WEAK DISTURBANCE MOVING OVER
THE SOUTH EARLY THIS MORNING WAS RESPONSIBLE FOR SUSTAINING THESE
CLOUDS. GFS SOLUTION NOT WITHSTANDING, THERE IS EXCEEDINGLY LITTLE
CHANCE THAT THESE CLOUDS WILL GENERATE PRECIPITATION DURING THE
REMAINDER OF THE NIGHT OR AFTER SUNRISE THIS MORNING. IN FACT,
IT'S UNCLEAR HOW THERE WILL BE SUFFICIENT MOISTURE TO FUEL ANY
MOIST CONVECTIVE ACTIVITY DURING THE AFTERNOON EITHER GIVEN THE
DRY WEST-SOUTHWEST FLOW ALOFT. THEREFORE, IGNORED GFS INPUT AND
LEFT OUT ANY MENTION OF PRECIPITATION TODAY, THOUGH THERE WILL BE
PARTLY CLOUDY SKIES OVER THE SAN JUAN MOUNTAINS DURING THE
AFTERNOON. ELSEWHERE, LOOK FOR ANOTHER SUNNY AND MILD/WARM DAY.
UNEVENTFUL WEATHER CONTINUES OVERNIGHT AND INTO SUNDAY MORNING AS
FLOW ALOFT SHIFTS TO THE SOUTHWEST IN RESPONSE TO A MID-LEVEL
TROUGH MOVING ASHORE OVER THE PACIFIC NORTHWEST. OVERNIGHT LOWS
WILL BE LESS CHILLY IN RESPONSE TO A MODEST INCREASE IN MID-LEVEL
MOISTURE.
THE TROUGH MENTIONED PREVIOUSLY WILL CONTINUE TO PUSH EASTWARD
ACROSS THE NORTHWEST AND THE WESTERN GREAT BASIN ON SUNDAY. THE
COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SHIFT TO NORTHERN
WYOMING AND EXTREME NORTHWEST UTAH SUNDAY AFTERNOON. THE PRE-
FRONTAL PRESSURE GRADIENT INCREASE ASSOCIATED WITH THIS MOVEMENT
WILL BRING BREEZY SOUTHWEST WINDS TO THE AREA FROM LATE MORNING
THROUGH THE AFTERNOON WITH THE FOCUS ALONG AND NORTH OF THE I-70
CORRIDOR. MODELS MIXED ON PRECIPITATION CHANCES SUNDAY AFTERNOON,
BUT CAN'T ENTIRELY RULE OUT ISOLATED HIGH BASED THUNDERSTORMS OVER
THE PEAKS. MEANWHILE, TEMPERATURES WILL CONTINUE TO RUN WARMER
THAN NORMAL FOR THIS TIME OF YEAR, AND HEWED AFTERNOON HIGHS
PRETTY CLOSE TO PERSISTENCE.
LONG TERM
(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 401 AM MDT SAT SEP 22 2018
FOLLOWING THE NICE WEATHER THIS WEEKEND, A FAST MOVING UPPER
LEVEL TROUGH AND SURFACE COLD FRONT WILL BRING CLOUDS AND LIGHT
PRECIPITATION. MODELS HAVE BEEN IN FAIRLY GOOD AGREEMENT DEPICTING
THE JET STREAM DROPPING DOWN FROM THE NORTH SUNDAY NIGHT THROUGH
MONDAY PROVIDING THE UPPER LEVEL SUPPORT FOR THIS SYSTEM. HOWEVER,
THE UPPER LEVEL SUPPORT IS RATHER WEAK WITH A JET CORE OF AROUND
75 KTS. THIS IS BORNE OUT BY MODELS SHOWING GENERALLY LIGHT
PRECIPITATION AMOUNTS. THE GFS IS A BIT MORE AGGRESSIVE WHILE THE
NAM HAS SCALED BACK SOME. AS THE UPPER LEVEL SUPPORT REMAINS ON
THE WEAK SIDE, THE NAM IS A BIT MORE BELIEVABLE AT THE MOMENT. THE
FRONT WILL JUST BE ENTERING THE CWA EARLY MONDAY MORNING AND WILL
REACH THE I-70 CORRIDOR AROUND NOON BEFORE MOVING THROUGH THE SAN
JUANS IN THE EVENING. A FEW SHOWERS AND AN ISOLATED THUNDERSTORM
WILL CERTAINLY BE POSSIBLE. SNOW LEVELS LOOK TO BE AROUND 11 TO
12 KFT SO SOME MINOR ACCUMULATION IS NOT OUT OF THE QUESTION FOR
THE HIGHER PEAKS. FALL IS HERE. AFTER THAT, NORTHWESTERLY FLOW
SETS UP BRINGING IN MORE SEASONABLE TEMPERATURES AS PIECES OF
ENERGY DROP DOWN FROM THE NORTH. WE'LL BE FAR ENOUGH WEST TO NOT
SEE ANY OF THESE DISTURBANCES AFFECT OUR WEATHER OUTSIDE OF SOME
INCREASED CLOUDS FROM TIME TO TIME.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1143 PM MDT FRI SEP 21 2018
VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS. SOME GUSTY
WINDS UP TO 20 TO 25 KTS ARE EXPECTED TOMORROW AFTERNOON BUT
SHOULDN'T POSE ANY THREATS TO AVIATION.
FIRE WEATHER
ISSUED AT 401 AM MDT SAT SEP 22 2018
EXPECT SOUTHWEST WINDS TO INCREASE OVER NORTHWEST COLORADO AND
PORTIONS OF NORTHEAST UTAH THIS WEEKEND AHEAD OF AN APPROACHING
PACIFIC TROUGH. VEGETATION REMAINS VERY DRY ACROSS THE REGION SO
GUSTY SOUTHWEST WINDS COMBINED WITH ABOVE NORMAL TEMPERATURES AND
LOW RELATIVE HUMIDITY COULD RESULT IN CRITICAL FIRE WEATHER
CONDITIONS.
THE FIRE WEATHER WATCH FOR NORTHWEST COLORADO FOR THIS AFTERNOON
AND EVENING FOR FIRE WEATHER ZONE 200 HAS BEEN UPGRADED TO A RED
FLAG WARNING. MODELS INDICATED JUST A BIT MORE WIND ACROSS THE
AREA TODAY AS COMPARED TO FRIDAY WHILE RH REMAINS QUITE LOW.
HOWEVER, HELD OFF UPGRADING THE FIRE WEATHER WATCH ON SUNDAY FOR
COLORADO FIRE WEATHER ZONE 200, THOUGH DID EXPAND THE WATCH TO
INCLUDE UTAH FIRE WEATHER ZONE 487. BOTH AREAS APPEARED BORDERLINE
IN LATEST MODEL RUNS, THOUGH THIS TIME WIND GUSTS SEEM MORE
CERTAIN TO EXCEED 25 MPH WHILE RH WILL BE HOVERING NEAR OR ABOVE
15 PERCENT.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING
FOR COZ200.
RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR
COZ200.
UT...FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING
FOR UTZ487.
SHORT TERM...NL
LONG TERM...TGR
AVIATION...TGR
FIRE WEATHER...TGJT
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