981
FXUS65 KGJT 211135
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
535 AM MDT THU OCT 21 2021
SHORT TERM
(TODAY THROUGH FRIDAY)
ISSUED AT 305 AM MDT THU OCT 21 2021
HIGH CLOUDS ARE BEGINNING TO ENCROACH UPON THE NORTHERN AND
CENTRAL CWA AS A WEAK SHORTWAVE TROUGH IS EJECTED ACROSS THE
SOUTHERN CANADIAN PRAIRIES AHEAD OF A PERSISTENT TROUGH SITTING
OFF THE PACIFIC NORTHWEST COAST. SKIES ARE EXPECTED TO CLEAR AND
BECOME MOSTLY SUNNY BY MID AFTERNOON AS THE RIDGE OF HIGH PRESSURE
RE-ESTABLISHES ITSELF ACROSS THE GREAT BASIN. HIGHS TODAY WILL BE
WARMER THAN YESTERDAY BUT STILL A FEW DEGREES BELOW NORMAL.
HIGH CLOUDS WILL MOVE ACROSS THE CWA FROM THE SOUTHWEST AS THE
PACIFIC TROUGH PUSHES ONSHORE BY FRIDAY AFTERNOON, ALLOWING THE
RIDGE AXIS TO ALSO SHIFT DIRECTLY OVERHEAD. A LEADING SHORTWAVE
WILL EJECT OUT AHEAD OF THIS PARENT TROUGH ACROSS THE
INTERMOUNTAIN WEST BY FRIDAY EVENING. OUR CWA WILL BARELY GET
CLIPPED BY THIS TROUGH, RESULTING IN PERHAPS SOME BREEZY
WINDS ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO. TEMPERATURES
WILL BUMP UP ON THE NORTH SIDE OF NORMAL DUE TO BETTER MIXING AS A
RESULT OF INCREASED SOUTHWEST FLOW ON FRIDAY.
LONG TERM
(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 305 AM MDT THU OCT 21 2021
THE FIRST IN A SERIES OF PACIFIC TROUGHS WILL MOVE ONSHORE AND
LIFT NORTHEAST ACROSS THE INTERMOUNTAIN WEST LATE FRIDAY AND INTO
SATURDAY. A SUBTLE SPLIT WILL SEE A WEAK VORT MAX QUICKLY TREK
ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO SATURDAY NIGHT AND
INTO SUNDAY. SOME GUIDANCE FEATURES A SHALLOWER TROUGH THAN
OTHERS WHICH WILL ULTIMATELY DETERMINE WHICH AREAS RECEIVE
PRECIPITATION. FOR NOW, FAVORING AREAS ALONG AND NORTH OF I-70 FOR
THE BEST CHANCE OF SHOWERS, THOUGH THE SOUTHERN MOUNTAINS LOOK TO
SEE AT LEAST ISOLATED SNOWFALL SATURDAY NIGHT. THIS FEATURE WILL
QUICKLY LIFT NORTHEAST TOWARDS THE FRONT RANGE SUNDAY MORNING WITH
LIGHT SNOW SHOWERS LINGERING OVER THE NORTHERN MOUNTAINS IN THE
FAVORED NORTHWESTERLY FLOW THROUGHOUT THE DAY. WHEN ALL IS SAID
AND DONE, A COUPLE UP TO A FEW INCHES OF SNOW WILL FALL IN THE
NORTHERN AND CENTRAL MOUNTAINS WITH A FEW TENTHS IN THE SAN JUANS
(UNLESS THIS SYSTEM DRIFTS FURTHER SOUTH, RESULTING IN SLIGHTLY
BETTER SHOWER COVERAGE AND SUBSEQUENT ACCUMULATION). REGARDLESS,
AFTER THIS SUBADVISORY EVENT A RIDGE OF HIGH PRESSURE WILL BUILD
OVER THE REGION FOR MONDAY. TEMPERATURES LOOK TO RECOVER QUICKLY
AFTER BEING KNOCKED DOWN A COUPLE OF DEGREES IN RESPONSE TO
SUNDAY'S SYSTEM WITH HIGHS ON MONDAY TRENDING 5 TO 10 DEGREES
ABOVE NORMAL.
THE POWERHOUSE OF AN UPPER LEVEL TROUGH RESPONSIBLE FOR THE
PROLONGED ATMOSPHERIC RIVER EVENT ACROSS THE NORTHWESTERN CONUS
WILL FINALLY BEGIN TO SLOWLY PUSH INLAND ON MONDAY. ITS BASE WILL
ELONGATE AND EXTEND AS FAR SOUTH AS BAJA. THIS WILL RESULT IN A
PROMINENT SHIFT TO SOUTHWEST FLOW ACROSS EASTERN UTAH AND WESTERN
COLORADO (ACCOUNTING FOR THAT NOTABLE JUMP IN TEMPERATURES MONDAY
AFTERNOON). IN ADDITION TO THE WARMER TEMPERATURES, IT'LL BE A
BREEZY DAY AS THE UPPER LEVEL JET DIGS INTO THE GREAT BASIN
RESULTING IN A TIGHTENING GRADIENT OVERHEAD. UNFORTUNATELY, IT'S
FROM TUESDAY ONWARDS THAT CONFIDENCE BEGINS TO DEGRADE AS
DISCREPANCIES CONTINUE TO PLAGUE THE EXTENDED MODELS IN TERMS OF
HOW THE TROUGH WILL EVOLVE AS WELL AS HOW QUICKLY IT WILL PROGRESS
EAST. WHILE WE COULD SEE SHOWERS DEVELOP OVER THE WESTERN ZONES
AS EARLY AS MONDAY AFTERNOON, IT LOOKS LIKE THE BETTER PUSH WILL
COME LATE MONDAY NIGHT AND INTO TUESDAY. REGARDLESS, A WIDESPREAD
PRECIPITATION EVENT LOOKS LIKELY WITH THE PREVIOUS ESTIMATE OF A
QUARTER OF AN INCH AND UP TO OR EXCEEDING AN INCH OF QPF STILL ON
TRACK FOR MUCH OF THE REGION.
700MB TEMPERATURES WILL DROP FROM A MILD 6 TO 12 DEGREES C MONDAY
AFTERNOON TO -3 TO -6 DEGREES C AT THE MIDWEEK POINT. WITH THE
WARM ANTECEDENT CONDITIONS CONFIDENCE IS NOT HIGH ON SNOW REACHING
MANY VALLEYS AT THIS TIME OR IN NARROWING DOWN IMPACTS IN THE
HIGHER ELEVATIONS. STILL PLENTY OF TIME FOR THINGS TO CHANGE AND
FOR THE MODELS TO REACH A BETTER CONSENSUS (ESPECIALLY IN REGARDS
TO THE POTENTIAL CUTOFF LOW OVER THE FOUR CORNERS BEFORE THIS
SYSTEM DEPARTS). OVERALL THOUGH, THE END OF THE LONG TERM PERIOD
LOOKS TO REMAIN COOL AND UNSETTLED.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 534 AM MDT THU OCT 21 2021
HIGH CLOUDS WILL TRAVERSE THE CWA FROM WEST TO EAST THROUGH THE
MORNING HOURS WITH CLEARING BY MID TO LATE AFTERNOON. WINDS WILL
REMAIN LIGHT AND TERRAIN DRIVEN WITH OCCASIONAL BREEZY CONDITIONS
AT THE HIGHER ELEVATION TAF SITES. VFR CONDITIONS WILL PREVAIL.
GJT WATCHES/WARNINGS/ADVISORIES
CO...NONE.
UT...NONE.
SHORT TERM...MDA
LONG TERM...MMS/MDA
AVIATION...MDA
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