734
FXUS65 KGJT 201723
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1123 AM MDT TUE OCT 20 2026
KEY MESSAGES
- ISOLATED SHOWERS AND SEASONABLE TEMPERATURES CONTINUE TUESDAY.
- WIDESPREAD RAIN RETURNS WEDNESDAY THROUGH FRIDAY.
- THE POTENTIAL FOR FLOODING INCREASES THURSDAY AND FRIDAY
ESPECIALLY FOR PORTIONS OF SOUTHEAST UTAH AND SOUTHWEST
COLORADO.
- RAINFALL AMOUNTS IN THE SOUTHERN MOUNTAINS RANGE FROM 1-3
INCHES WITH LOCALLY HIGHER AMOUNTS POSSIBLE IN THE SAN JUANS.
DISCUSSION
ISSUED AT 1102 PM MDT MON OCT 19 2026
HIGH PRESSURE OVER THE GULF DRIFTING WEST INTO MEXICO AND A DEEP
LOW CURRENTLY OFF THE OREGON COAST DESCENDING SOUTH OFF THE WEST
COAST WILL DOMINATE THE WEATHER PATTERN THROUGH THE REST OF THE WEEK
AND POSSIBLY INTO EARLY NEXT WEEK. THE CURRENT SOUTHWESTERLY FLOW IS
PULLING PACIFIC MOISTURE UP THROUGH SOUTHERN CALIFORNIA AND THE
DESERT SOUTHWEST INTO THE REGION THAT SUPPORTED WEAK ISOLATED LIGHT
SHOWERS WITH A FEW THUNDERSTORMS TODAY, AND WILL AGAIN TOMORROW, BUT
COVERAGE DOES LOOK TO BE A LITTLE MORE ISOLATED. AS THE LOW BOTTOMS
OUT OFF THE SOUTHERN CALIFORNIA COAST BY WEDNESDAY MORNING, TURNING
TO THE NORTHEAST TO TRACK UP ACROSS THE GREAT BASIN AND UTAH BY
FRIDAY, THE HIGH PRESSURE MOVES IN OVER NORTHEASTERN MEXICO TO SET
UP A MORE SOUTHERLY FLOW THAN WE SAW WITH THE LAST TROPICAL SURGE OF
MOISTURE. THIS SCENARIO SETS THE DEEPER PLUME OF TROPICAL MOISTURE
FROM THE REMNANTS OF HURRICANE TRUDY TO PLOW INTO THE SOUTHERN
MOUNTAINS WHERE CURRENT GUIDANCE HAS THE BULK OF THE RAIN FALLING,
AND CASTING A RAIN SHADOW TO THE NORTH IN THE CENTRAL AND NORTHERN
MOUNTAINS. THIS BEING SAID, THERE IS STILL A LOT OF UNCERTAINTY
CREEPING INTO THE FORECAST AS EARLY AS WEDNESDAY. THE LATEST
GUIDANCE IS SLIDING THE MOIST PLUME TO THE WEST A BIT THAT WOULD
ALLOW MORE MOISTURE TO PUSH NORTH INTO SOUTHERN UTAH AND TO THE EAST
INTO THE CENTRAL AND NORTHERN COLORADO AREAS. THE ATMOSPHERIC RIVER
(AR) MODELS DO SUPPORT THIS SOLUTION WITH INTEGRATED VAPOR TRANSPORT
(IVT) VALUES UP TO 500 KG/M/S PUSHING INTO THE CENTRAL AND NORTHERN
AREAS. AS A RESULT, STORM TOTALS HAVE INCREASED TO ONE TO TWO INCHES
RAIN IN THE CENTRAL MOUNTAINS AND UP TO AN INCH FARTHER NORTH. MEAN
WHILE THE SOUTHERN FACE OF THE SAN JUAN AND ABAJO MOUNTAINS WILL SEE
TWO TO THREE INCHES RAIN WITH LOCALLY HIGHER AMOUNTS POSSIBLE. THIS
SYSTEM IS A VERY WARM SYSTEM WITH SNOW LEVELS REMAINING ABOVE 12K FT
THROUGH THURSDAY CREATING A RISK FOR RECEIVING RAIN ON SNOW THROUGH
THE SOUTHERN MOUNTAINS THAT CAN LEAD TO HIGH STREAM FLOWS ACROSS THE
SOUTHERN AREAS OF COLORADO AND UTAH. IN FACT, THE RIVER FORECAST
CENTER IS FORECASTING SOME OF THE RIVERS IN THIS AREA TO REACH FLOOD
STAGE WITH THIS SYSTEM. UNDERSTAND THAT THE FORECAST REMAINS FLUID
AT THIS TIME, AND KEY DETAILS WILL SHIFT OVER THE COMING DAYS. STAY
TUNED FOR UPDATES ON THIS. LOOK FOR THE HEAVIEST RAINS TO FALL
WEDNESDAY NIGHT INTO THURSDAY AS COOLER AIR AND STRONGER JET
DYNAMICS MOVE IN ALOFT SUPPORTING STRONGER THUNDERSTORMS WITH
PERIODS OF HEAVY RAIN. THESE STRONGER STORMS MAY LEAD TO LOCALIZED
FLASH FLOODING POSSIBLE ACROSS MUCH OF EASTERN UTAH AND WESTERN
COLORADO. STAY TUNED ON THIS TOO AS THE FORECAST DEVELOPS.
THE SHOWERS AND THUNDERSTORMS WILL TAPER OFF FRIDAY AS DRIER AIR
MOVES IN FROM THE SOUTHWEST. AS THE LOW PASSES TO THE NORTHWEST, IT
WILL DRAG A COLD FRONT ACROSS THE NORTHERN AREAS FRIDAY MOSTLY ALONG
AND NORTH OF I-70, DROPPING TEMPERATURES FROM THURSDAY'S HIGHS ABOUT
TEN DEGREES. RESIDUAL MOISTURE ACROSS THE REGION WILL SPAWN SHOWERS
MOSTLY OVER THE HIGHER TERRAIN SATURDAY AFTERNOON AND AGAIN SUNDAY
BEFORE THINGS ARE FINISHED.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1118 AM MDT TUE OCT 20 2026
VFR CONDITIONS WILL PERSIST THROUGH MUCH OF THIS PERIOD. SOME
LOW CLOUD DEBRIS IS STILL HANGING AROUND THE TERRAIN, BUT SHOULD
BE ON THE WANE THIS AFTERNOON. KEPT CEILINGS IN KEGE FOR A BIT
LONGER TO ALLOW TIME TO DISPERSE. TROPICAL MOISTURE INTRUSION
RETURNS LATE TONIGHT FROM THE SOUTHWEST. THIS WILL BRING SOME
CEILINGS AND SHOWERS LATE IN THE PERIOD FROM THE FOUR CORNERS
NORTHEAST TO ABOUT THE HIGHWAY 50 CORRIDOR, THEN SPREAD BEYOND
IN LATTER TAF PERIODS. BREAKPOINT CEILINGS WILL LIKELY IMPACT
TERMINALS WEDNESDAY MORNING AND CONTINUE BEYOND AS THE TROPICAL
MOISTURE DEEPENS IN THE ATMOSPHERE.
HYDROLOGY
ISSUED AT 300 PM MDT MON OCT 19 2026
STRONG SOUTHWESTERLY WINDS DEVELOP OVERHEAD ON WEDNESDAY, WHICH
WILL OPEN THE ATMOSPHERIC FLOOD GATES AND DRAW IN MOISTURE TIED
TO TROPICAL STORM TRUDY. YET ANOTHER DECAYING TROPICAL SYSTEM
WILL FUEL WIDESPREAD SHOWERS ACROSS THE DESERT SOUTHWEST AND
SOUTHERN COLORADO ROCKIES THROUGH THE END OF THE WEEK. RAINFALL
TOTALS ARE SUBJECT TO CHANGE, HOWEVER, CURRENT GUIDANCE SHOWS 1
TO 3 INCHES OF RAIN ACROSS THE FOUR CORNERS REGION, WITH LOCALLY
HIGHER AMOUNTS EXPECTED. THE WARM TROPICAL MOISTURE IS ALSO
THROWING A WRECKING BALL AT NORMAL SNOW LEVELS FOR THIS TIME OF
YEAR, WITH RAIN POSSIBLE ABOVE 12,000' THROUGH THURSDAY. SNOTEL
SITES ACROSS THE SAN JUANS INDICATE 1 TO 2 INCHES OF SWE
ACCUMULATED FROM LAST WEEK'S STORMS. IF THE THE WARM TROPICAL
MOISTURE ARRIVES AS RAIN UP HIGH, WE CAN ANTICIPATE ACCELERATED
RUNOFF DUE TO RAIN ON SNOW FOR OUR UPPER LEVEL BASINS.
IN ADDITION, CONVECTIVE STORMS ARE NOT OUT OF THE QUESTION,
PRECEDING AND FOLLOWING THE MAIN ATMOSPHERIC PLUME OF MOISTURE.
HEAVY RAINFALL RATES AHEAD OF THE SYSTEM (I.E. WEDNESDAY
AFTERNOON) MAY LOCALLY ENHANCE WATER LEVELS IN RIVERS AND
WASHES, OR AT LEAST, PRIME SOILS FOR MORE EFFICIENT RUNOFF COME
THURSDAY. CONFIDENCE IN THE DETAILS OF HEAVY PRECIPITATION RATES
AND COVERAGE ARE LOW AT THIS TIME, BUT CERTAINLY NOTEWORTHY FOR
THE EVENT'S ENTIRETY.
THE COMPLEXITY TRUDY BRINGS, IN TERMS OF PRECIPITATION RATES,
TOTALS AND TEMPERATURES, RAISES OUR CONCERN FOR ANOTHER ROUND OF
FLOODING AND FLASH FLOODING OF RIVERS, STREAMS, CREEKS AND
NORMALLY DRY ARROYOS. THE LATEST RIVER FORECASTS PROVIDED BY
CBRFC SUGGEST MINOR FLOODING FOR THE SAN JUAN RIVER, NEAR
PAGOSA SPRINGS, CO. IN ADDITION, RIVERS REACHING BANKFULL TO
NEAR MINOR FLOOD STAGE IS POSSIBLE FOR THE PIEDRA AND ANIMAS
BASINS, WITH A 1 TO 2 FOOT RISE EXPECTED IN NEARBY BASINS.
ALTHOUGH TIMING IS LIKELY TO CHANGE, EXPECT A RAPID RISE IN
RIVERS, CREEKS, AND DRY WASHES THURSDAY INTO FRIDAY.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY MORNING
FOR COZ019-021>023.
UT...FLOOD WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY MORNING
FOR UTZ022-027>029.
DISCUSSION...DB
AVIATION...TGJT
HYDROLOGY...ERW
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