088
FXUS65 KGJT 201902
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
102 PM 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 102 PM MDT TUE OCT 20 2026
HYDROLOGIC CONCERNS RAMP UP TOMORROW (WEDNESDAY), DUE TO THE
POTENTIAL FOR THUNDERSTORM DEVELOPMENT. ATMOSPHERIC MOISTURE
INCREASES UNDER STRONG SOUTH-SOUTHWESTERLY FLOW, LOFTING AN
ABUNDANCE OF WARM TROPICAL MOISTURE ACROSS THE FORECAST AREA.
WHILE BANDS OF SHOWERS EXPAND AS EARLY AS WEDNESDAY MORNING,
THUNDERSTORMS ARE EXPECTED TO MOVE INTO EAST/SOUTHEAST UTAH
TOMORROW AFTERNOON. SOUTHEAST UTAH AND LOWER VALLEYS ALONG THE
CO/NM BORDER SHOW THE HIGHEST POCKETS OF INSTABILITY, WHICH
FOCUSES THE BETTER CONFIDENCE FOR FLASH FLOODING ACROSS DESERT
FLOORS AND DRY WASHES. COVERAGE OF RAINFALL RATES EXCEEDING 0.5
INCHES IN AN HOUR REMAINS LOW EVEN 24 HOURS OUT. HOWEVER,
WHATEVER EMBEDDED THUNDERSTORMS THAT DEVELOP TOMORROW WILL ONLY
HELP SATURATE SOILS LEADING INTO THE MAIN SURGE OF MOISTURE
EXPECTED WEDNESDAY NIGHT THROUGH THURSDAY.
THE BULK OF PRECIPITATION REMAINS ON TRACK FOR THURSDAY, WITH
GENERALLY 1 TO 3 INCHES OF RAIN FALLING ACROSS THE SOUTHERN HALF
THE CWA WITHIN A 24 TO 36 HOUR WINDOW. BULLSEYE QPFS ARE
HIGHEST OVER THE SAN JUAN'S, WHERE LOCALLY HIGHER AMOUNTS OF 4
TO 5 INCHES ARE POSSIBLE. THIS SYSTEM CONTINUES TO TRACK
ANOMALOUSLY WARM, AS THE MAIN MOISTURE PLUME REMAINS WELL AHEAD
OF A COLD, CLOSED LOW DEEPENING ALONG THE PACIFIC COAST. THUS,
RAIN ON SNOW IS A VIABLE CONCERN. SNOW LEVELS ARE FORECAST ABOVE
12-13 KFT THROUGHOUT THE DAY THURSDAY, WHICH WILL LIKELY RESULT
IN MELTING MUCH OF THE EXISTING EARLY-SEASON SNOW PACK. THE
COMBINED RUNOFF FROM RAIN AND RAIN-ON-SNOW WILL RESULT IN A
RAPID RISE IN MANY OF OUR CREEKS, STREAMS AND RIVERS. MODELED
RESPONSES ALSO NUDGED UPWARD ACROSS MANY RIVER FORECAST POINTS
ACROSS SOUTHWEST COLORADO. WE HAVE THE HIGHEST CONFIDENCE IN
MINOR FLOODING AND IMPACTS ALONG THE SAN JUAN RIVER, PIEDRA,
ANIMAS, LA PLATA RIVERS AND ABOVE VALLECITO RESERVOIR. HOWEVER,
OTHER CREEKS AND TRIBUTARIES WITHIN THE FOUR CORNERS REGION
REMAIN SUSCEPTIBLE. ALL RIVER RESPONSES ARE HEAVILY DEPENDENT ON
WHERE THE HEAVIEST PRECIPITATION FALLS, SO PLEASE CONTINUE TO
MONITOR THE FORECAST AS THE WEEK UNFOLDS.
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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