143
FXUS65 KGJT 201941
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
141 PM MDT TUE OCT 20 2026
KEY MESSAGES
- WIDESPREAD RAIN IS EXPECTED WEDNESDAY THROUGH FRIDAY.
- STRONG TO SEVERE STORMS CANNOT BE RULED OUT NEAR THE FOUR
CORNERS ON WEDNESDAY AND THURSDAY.
- 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 HIGHER AMOUNTS OF 2-4" OR MORE POSSIBLE IN THE
SAN JUANS AND SOUTHERN FOOTHILLS.
DISCUSSION
ISSUED AT 136 PM MDT TUE OCT 20 2026
HAZARDOUS WEATHER POSSIBLE THROUGH FRIDAY:
REMNANT MOISTURE FROM A TROPICAL CYCLONE FORMERLY KNOWN AS
TRUDY WILL MOVE INTO THE FOUR CORNERS TOMORROW BEFORE TRACKING
NORTHEASTWARD ACROSS EASTERN UTAH AND WESTERN COLORADO THROUGH
FRIDAY MORNING. A PLETHORA OF WEATHER HAZARDS ARE POSSIBLE WITH
THIS SYSTEM INCLUDING FLOODING, FLASH FLOODING, STRONG TO SEVERE
THUNDERSTORMS, AND SNOW ABOVE 12,000-13,000 FEET. AS A RESULT,
A FLOOD WATCH HAS BEEN ISSUED FOR PARTS OF SOUTHEAST UTAH AND
SOUTHWEST COLORADO FROM 12 PM WEDNESDAY THROUGH 12 PM FRIDAY.
WEDNESDAY:
SHOWERS AND STORMS DEVELOP ALONG THE MOISTURE TRANSPORT
GRADIENT AS EARLY AS TOMORROW MORNING, WITH STORMS STRENGTHENING
THROUGHOUT THE AFTERNOON. THIS INITIAL PUSH OF CONVECTION
TOMORROW WILL POSE A LOCALIZED THREAT FOR HEAVY RAINFALL AND
FLASH FLOODING IF STRONGER STORMS DEVELOP, ESPECIALLY IF STORMS
BEGIN TO TRAIN OVER THE SAME AREAS. ISOLATED SEVERE STORMS ARE
POSSIBLE IN THE FOUR CORNERS REGION CAPABLE OF PRODUCING LARGE
HAIL, DAMAGING WIND, AND BRIEF TORNADOES AS WELL DUE TO THE
PRESENCE OF MODEST INSTABILITY AND STRONG SHEAR. HOWEVER, THE
HIGHEST POTENTIAL FOR SEVERE WEATHER WILL REMAIN OFF TO OUR
SOUTHWEST IN NORTHWEST INTO CENTRAL ARIZONA. STAY WEATHER AWARE
IF YOU HAVE OUTDOOR ACTIVITIES PLANNED! IF YOU EXPERIENCE ANY OF
THE HAZARDS NOTED ABOVE, PLEASE REPORT THEM TO NWS GRAND
JUNCTION.
WEDNESDAY NIGHT - THURSDAY NIGHT:
WITH AN ANOMALOUSLY MOIST TROPICAL AIRMASS OVERHEAD, WIDESPREAD
RAINFALL TAKES HOLD OF THE FORECAST AREA WEDNESDAY NIGHT.
PLEASE SEE THE HYDROLOGY SECTION BELOW FOR MORE INFORMATION
CONCERNING THE THREAT FOR FLOODING FROM THIS PERIOD OF MODERATE
TO WIDESPREAD RAINFALL.
ANOTHER ROUND OF STRONG TO SEVERE STORMS CANNOT BE RULED OUT ON
THURSDAY AFTERNOON/EVENING WITH MARGINAL INSTABILITY AND STRONG
WIND SHEAR PRESENT. HOWEVER, WIDESPREAD CLOUD COVER ADDS A
LAYER OF UNCERTAINTY TO THE FORECAST AND MAY INHIBIT SURFACE
HEATING. IF STRONGER STORMS DEVELOP, ISOLATED DAMAGING WIND,
LARGE HAIL, BRIEF TORNADOES ARE POSSIBLE. WE HAVE LOW CONFIDENCE
IN THIS ASPECT OF THE FORECAST.
FRIDAY:
MODELS HAVE CONTINUED TO KEY IN ON A DRY SLOT QUICKLY
EVACUATING THE TROPICAL MOISTURE FROM THE REGION ON FRIDAY
MORNING. EVEN AFTER IT STOPS RAINING, THE RISK FOR FLOODING AND
FLASH FLOODING WILL REMAIN ELEVATED ON FRIDAY MORNING AS WATER
CONTINUES TO WORK THROUGH THE SYSTEM. DO NOT LET YOUR GUARD DOWN
RIGHT AWAY! WE'LL HAVE A BETTER IDEA OF HOW LONG FLOODING MAY
CONTINUE TO CAUSE ISSUES AFTER WE GET A BETTER SENSE OF HOW MUCH
RAINFALL IS RECEIVED ON THURSDAY.
LOOKING AHEAD:
CHANCES FOR LIGHT PRECIPITATION (VALLEY RAIN, MOUNTAIN SNOW
ABOVE 10,000 FEET) CONTINUE THROUGH THE WEEKEND AS A LOW
PRESSURE SYSTEM, CURRENTLY SPINNING OFF THE CALIFORNIA COAST,
TRAVERSES THE INTERMOUNTAIN WEST. PLENTY OF UNCERTAINTY REMAINS
IN HOW THIS LOW WILL EVOLVE AS IT MOVES INLAND, BUT ENSEMBLE
GUIDANCE TENDS TO SHOW A WEAKENING SYSTEM BY THE TIME IT REACHES
OUR FORECAST AREA. REGARDLESS, THIS SYSTEM WILL PROVIDE ENOUGH
FORCING FOR SCATTERED TO WIDESPREAD PRECIPITATION AS IT MOVES
THROUGH, ALONGSIDE A BRIEF REDUCTION IN TEMPERATURES.
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...KAA
AVIATION...TGJT
HYDROLOGY...ERW
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