157
FXUS65 KGJT 151140
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
540 AM MDT MON AUG 15 2022
SHORT TERM
(TODAY THROUGH TUESDAY)
ISSUED AT 417 AM MDT MON AUG 15 2022
THE PLUME OF DEEPEST MONSOON MOISTURE SHIFTED OVER NORTHEAST UTAH
AND NORTHWEST COLORADO TODAY IN RESPONSE TO A MID-LEVEL SHORT WAVE
TROUGH WHICH TRACKED EASTWARD ACROSS UTAH. THIS DISTURBANCE
EXTENDED FROM KRWL SOUTHWEST TO A SHALLOW LOW CENTERED OVER KPGA
EARLY THIS MORNING. A FEW SHOWERS LINGERED BENEATH THE TROUGH IN A
BAND WHICH EXTENDED FROM KEEO SOUTHWEST TO KCNY WHICH INCLUDED A
PORTION OF THE GRAND VALLEY.
THE TROUGH CONTINUES TO TRACK SOUTHEASTWARD TODAY DRIVING THE HIGH
LOCATED OVER THE SOUTHERN PLAINS FARTHER SOUTH. THIS WILL CAUSE
THE PLUME OF DEEPEST MOISTURE TO SHIFT SOUTHWARD SHIFTING ITS AXIS
OVER SOUTHEAST UTAH AND WEST-CENTRAL COLORADO. ACCORDING TO
CLIMATOLOGICAL NORMS, MOISTURE LEVELS IN THE PLUME ARE PROJECTED
TO RANGE FROM 150 TO 200 PERCENT OF NORMAL, AND AT THOSE LEVELS
SUGGEST THE POTENTIAL FOR EXCESSIVE RAINFALL, ESPECIALLY IN AN
ENVIRONMENT WHERE STEERING WINDS ARE LIGHT. HOWEVER, ONE
SIGNIFICANT MITIGATING FACTOR IS CLOUD COVER, WHICH MODELS
SUGGESTED WILL BE PRETTY EXPANSIVE. THIS SEEMED REASONABLE GIVEN
THE MID-LEVEL TROUGH OVERHEAD AND THE MESOSCALE CONVECTIVE VORTEX
UPSTREAM OVER ARIZONA. GIVEN ANTECEDENT MOISTURE FROM YESTERDAY'S
RAIN COMBINED WITH PRECIPITABLE WATER LEVELS WELL ABOVE NORMAL,
GAVE CAREFUL CONSIDERATION TO ISSUING A FLOOD WATCH FOR SOUTHEAST
UTAH AND MUCH OF WEST-CENTRAL COLORADO. HOWEVER, JUST COULDN'T
FIND THE CONFIDENCE TO PULL THE TRIGGER GIVEN THE CLOUDIER
FORECAST. HOWEVER, DID HOIST A FLASH FLOOD WATCH FOR THE GRIZZLY
CREEK BURN SCAR AS RAIN GAUGES AROUND THE SITE PICKED UP FROM 1
TO 3 INCHES OF RAINFALL YESTERDAY, SO IT REALLY WOULDN'T TAKE MUCH
TO GET IT FLOWING TODAY. IN CONTRAST, DRYING FLOW FROM THE
NORTHWEST OVER THE NORTHERNMOST ZONES SHOULD BRING MORE ISOLATED
ACTIVITY TO THOSE AREAS.
DEEP MOISTURE AND PERSISTENT WEAK TROUGHINESS OVERHEAD FAVORS
SHOWERS AND THUNDERSTORMS LINGERING OVERNIGHT, MAINLY FOR THE
SOUTHERN TWO-THIRDS OF THE FORECAST AREA. LITTLE CHANGES ON
TUESDAY AS THE LARGE SCALE PATTERN CONTINUES TO FEATURE HIGH
PRESSURE OVER THE SOUTHERN PLAINS AND A RIDGE OF HIGH PRESSURE
OVER THE GREAT BASIN AND INTERMOUNTAIN WEST WITH A WEAK TROUGH
BETWEEN THE TWO STALLED OVERHEAD. AS RESULT, EXPECT ANOTHER ROUND
OF SHOWERS AND THUNDERSTORMS, FAVORING THE CENTRAL AND SOUTHERN
MOUNTAINS AND ADJACENT VALLEYS.
INCREASED CLOUDS ARE EXPECTED TO BRING COOLER TEMPERATURES TO THE
REGION TODAY AND TOMORROW. LATEST GUIDANCE SUGGESTED HIGHS WILL
DIP CLOSE TO 10 DEGREES FOR MOST LOCATIONS TODAY WITH READINGS
COMING IN ROUGHLY 3 TO 5 DEGREES BELOW NORMAL.
LONG TERM
(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 417 AM MDT MON AUG 15 2022
THE RIDGE OF HIGH PRESSURE WILL PERSIST OVER THE GREAT BASIN
REGION AT MIDWEEK. THE BEST MOISTURE WILL REMAIN SOUTH OF
INTERSTATE 70 WHICH WILL KEEP AN ELEVATED THREAT EXCESSIVE
RAINFALL FROM SCATTERED TO NUMEROUS THUNDERSTORMS. THERE WILL BE
A DECREASING TREND IN COVERAGE AND INTENSITY ON WEDNESDAY AS THE
MONSOONAL PLUME WEAKENS AND SHIFTS TO THE WEST OF THE FORECAST
AREA. ELSEWHERE, WEAK NORTHERLY FLOW WILL KEEP CONDITIONS DRIER
ACROSS THE NORTH WITH A SLIGHT CHANCE OF LATE-DAY SHOWERS AND
THUNDERSTORMS THROUGH THE MID-WEEK PERIOD. CONFIDENCE DECREASES BY
LATE IN THE WEEK AS ENSEMBLE FORECASTS SHIFT THE RIDGE OF HIGH
PRESSURE EAST ACROSS THE FORECAST AREA. DIVERGENCE IN ENSEMBLE
MEMBERS WAS EVIDENT REGARDING THE TIMING OF THIS EASTWARD
PROGRESSION. HOWEVER, THE TREND INDICATED AN UPTICK IN SHOWER AND
THUNDERSTORM COVERAGE AND INTENSITY AS THE PLUME OF MONSOONAL
MOISTURE SHIFTS BACK TO THE EAST AND ACROSS THE FORECAST AREA
LATER IN THE WEEK AND INTO THE WEEKEND. MEANWHILE, HIGH
TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY BELOW NORMAL THROUGH
THE LONG TERM FORECAST PERIOD.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 540 AM MDT MON AUG 15 2022
LINGERING MOISTURE WILL FUEL ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS WHICH BRINGS THE LIKELIHOOD OF SOME ACTIVITY MOVING
OVER ALL TAF SITES EXCEPT KVEL AND KHDN THIS AFTERNOON AND
EVENING. THERE'S A GOOD CHANCE THAT CELLS COULD DRIVE VISIBILITY
INTO THE MVFR RANGE AND CEILINGS MAY BRIEFLY FALL BELOW ILS
BREAKPOINTS AT KRIL, KEGE AND KASE. THERE'S LITTLE TO SUGGEST
THAT OVERNIGHT STORMS WON'T OCCUR AGAIN TONIGHT AT TAF SITES
ALONG AND SOUTH OF THE I-70 CORRIDOR.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLASH FLOOD WATCH FROM 1 PM MDT THIS AFTERNOON THROUGH THIS
EVENING FOR COZ008-010-013.
UT...NONE.
SHORT TERM...NL
LONG TERM...MPM/NL
AVIATION...NL
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