408
FXUS65 KGJT 190532
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1132 PM MDT WED SEP 18 2019
SHORT TERM
(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 400 PM MDT WED SEP 18 2019
THE MID-LEVEL PACNW LOW HAS MOVED INLAND THIS AFTERNOON,
TIGHTENING THE PRESSURE GRADIENT OVER EASTERN UTAH AND WESTERN
COLORADO. SOUTHWEST WINDS WILL CONTINUE TO INTENSIFY AS THE UPPER
LEVEL JET ROUNDING THE BASE OF THE TROUGH APPROACHES THE CWA.
STRONG MIXING WILL PREVENT TEMPERATURES FROM PLUNGING TONIGHT AND
CONTINUE TO MIX GUSTY WINDS DOWN TO THE SURFACE. EXPECT MOSTLY
CLEAR SKIES TONIGHT ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO,
HOWEVER, MOISTURE WILL CREEP INTO THE REGION FROM THE SOUTH.
ISOLATED TO SCATTERED SHOWERS ARE POSSIBLE ACROSS WESTERN COLORADO
BY THURSDAY AFTERNOON/EVENING FAVORING HIGHER TERRAIN IN SOUTHWEST
COLORADO AND ALONG THE DIVIDE. PW VALUES INCREASING TO AS HIGH AS
0.5 TO 0.75 INCHES ALONG THE UT/CO BORDER MAY KEEP RH LEVELS
ABOVE CRITICAL CONDITIONS. HOWEVER, DRY PERIODS AND STRONG WINDS
LEAVE BORDERLINE FIRE WEATHER CONDITIONS ACROSS SOUTHEAST UTAH.
CRITICAL CONDITIONS APPEAR SPOTTY IN TIMING AND LOCATION DUE TO
MOISTURE CONTENT, SO NO HIGHLIGHTS HAVE BEEN ISSUED, ALTHOUGH,
KEEP IN MIND, WINDY CONDITIONS WILL PERSIST. EXPECT TEMPERATURES
TO CLIMB A FEW DEGREES WARMER THURSDAY AS WE MIX THROUGH A DEEPER
LAYER IN THE ATMOSPHERE WHILE INCREASED CLOUD COVER THURSDAY NIGHT
WILL KEEP TEMPERATURES MILD OVERNIGHT AS WELL.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 400 PM MDT WED SEP 18 2019
ON FRIDAY THE MID LEVEL CLOSE LOW PRESSURE WILL BE LOCATED OVER THE
NORTHERN GREAT BASIN, AND LIFTING NORTHEASTWARD THROUGH THE DAY. AS
IT DOES IT WILL WEAKEN INTO AN OPEN WAVE THEREFORE THE FORCING WILL
BE ON A DOWN TREND. THE CHALLENGE DURING THIS PERIOD IS THE COVERAGE
OF AFTERNOON SHOWERS AND THUNDERSTORMS. A JET STREAK MOVING THROUGH
THE AREA WILL PROVIDE MODEST OROGRAPHIC LIFT, BUT MODELS ARE ALSO
INDICATING A SYNOPTIC DRY SLOT. WITH DAYTIME HEATING THIS AIR WILL
MIXING TO THE SURFACE, WHICH MAY LIMIT STORM COVERAGE TO ISOLATED
AND PERHAPS SCATTERED. THE MORE MODEST LIFT SHOULD OCCUR IN
NORTHEAST UTAH AND NORTHERN COLORADO CLOSER TO THE MID LEVEL
DYNAMICS. A COLD FRONT APPEARS TO CLIP PORTIONS OF NORTHWEST
COLORADO FRIDAY AFTERNOON AND EVENING, WHICH COULD BE THE FOCUS
FOR STORMS. CRITICAL FIRE WEATHER CONDITIONS WILL BE POSSIBLE
MAINLY ACROSS SOUTHEAST UTAH ON FRIDAY AFTERNOON.
ON SATURDAY THE TROUGH AXIS FINALLY DRAGS THROUGH THE AREA AND DRY
AIR FILTERS IN FROM THE NORTHWEST. THE LINGERING PRESSURE GRADIENT
MAY KEEP CONDITIONS WINDY WITH AN OVERALL DECREASE LATER IN THE
WEEKEND. ON SUNDAY A WEAK MIDLEVEL RIDGE QUICKLY RACES OVER THE
REGION IN BETWEEN THE NEXT SYSTEM THAT MOVES ON SHORE OF THE PACIFIC
NORTHWEST. EARLY NEXT WEEK THE MODELS CONTINUE TO STRUGGLE WITH THE
EVOLUTION OF THE PACIFIC NORTHWEST SYSTEM. THE GFS IS RATHER
AGGRESSIVE WITH A CLOSED LOW DIVING SOUTHEASTWARD RIGHT INTO THE
FORECAST AREA, AND TO SOME DEGREE THE CANADIAN AGREES. THE ECMWF IS
CUTTING THE LOW OFF OVER THE GREAT BASIN AND DROPPING IT SOUTHWARD
TOWARDS SOUTHERN CALIFORNIA.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1128 PM MDT WED SEP 18 2019
BIGGEST CONCERN OVER THE NEXT 24 HOURS WILL BE GUSTY SURFACE WINDS
THANKS TO AN APPROACHING TROUGH AND SOME MIXING FROM THE JET
STREAM ALOFT. GUIDANCE SUGGESTING ALL TAF SITES WILL SEE SOME
GUSTS RANGING FROM 20 TO 30KTS FROM THE SOUTH FOR MUCH OF THE
DAY. WINDS SHOULD PICKUP FROM ABOUT 16 TO 17Z ONWARDS AND CONTINUE
THROUGH 00Z BEFORE LIGHTENING SOME. SOME MIDLEVEL BROKEN CEILINGS
WILL MOVE IN TOWARDS THE LATE AFTERNOON AND EARLY EVENING BUT
SHOULDN'T POSE ANY AVIATION THREATS. WITH WINDS LIKE THIS, SOME
WIND SHEAR IS POSSIBLE ALONG WITH SOME MOUNTAIN WAVE TURBULENCE.
GJT WATCHES/WARNINGS/ADVISORIES
CO...NONE.
UT...NONE.
SHORT TERM...ERW
LONG TERM...KJS
AVIATION...TGR
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