906
FXUS65 KGJT 220444
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1044 PM MDT WED OCT 21 2026
KEY MESSAGES
- WIDESPREAD RAIN CONTINUES TOMORROW THROUGH EARLY FRIDAY.
- STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE FAVORING
SOUTHEASTERN UTAH AND FAR WESTERN COLORADO GENERALLY FROM I-70
SOUTH THURSDAY AND THURSDAY NIGHT.
- 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 1038 PM MDT WED OCT 21 2026
A DEEP TROUGH OFF THE WEST COAST AND HIGH PRESSURE TO THE SOUTHEAST
NEAR BIG BEND IS KEEPING THE DESERT SOUTHWEST UNDER A STRONG SOUTH
TO SOUTHWESTERLY FLOW ALOFT ADVECTING DEEP SUBTROPICAL MOISTURE
NORTH THROUGH ARIZONA INTO EASTERN UTAH AND WESTERN COLORADO. MODELS
ARE IN GOOD AGREEMENT WITH SATELLITE IMAGERY SHOWING THE LOW JUST
TURNING THE CORNER IN THE BASE OF THE TROUGH OFF THE SOCAL COAST
BEFORE EJECTING TO THE NORTHEAST INTO THE GREAT BASIN THURSDAY
EVENING AND CONTINUING INTO MONTANA FRIDAY EVENING TAKING MOST OF
THE MOISTURE WITH IT. MEANWHILE, ANOTHER SHORTWAVE SYSTEM DESCENDING
INTO THE TROUGH FRIDAY CUTS OFF OVER SOCAL FRIDAY NIGHT TO EJECT
FARTHER EAST OVER THE REGION SATURDAY NIGHT INTO SUNDAY TO KEEP
UNSETTLED WEATHER IN THE FORECAST THROUGH THE WEEKEND. MODELS STAY
IN FAIRLY GOOD AGREEMENT THROUGH THE WEEKEND, BUT ARE DIVERGING ON
THE TIMING AND TRACK OF THE SECOND SYSTEM BY SUNDAY WITH SOME
SOLUTIONS TRACKING IT TO THE WEST OVER NORTHERN UTAH. THE MODELS DO
GENERALLY AGREE ON SETTING UP A DRY ZONAL FLOW ACROSS THE REGION
NEXT WEEK THAT COULD EXTEND INTO THE NEXT WEEKEND, BUT THAT A LONG
WAY OUT AND CONFIDENCE IS LOT ON THE EXTENDED PERIOD.
TODAY WE SAW QUIETER SHOWERS WITH RAIN RATES REMAINING ON THE LOW
SIDE ONLY AROUND A HALF INCH PER HOUR IN THE HEAVIER SHOWERS. EVEN
THOUGH WE HAD STRONG VERTICAL SHEER AND PLENTY MOISTURE ON HAND,
WITH ALL THE HEAVY CLOUD COVER AND THE WARM AIR ALOFT, WE JUST
DIDN'T HAVE ANY CAPE TO FEED STRONGER STORMS. BOTH THE 18Z AND 00Z
SOUNDINGS SHOWED A SATURATED ATMOSPHERE NEARLY UP TO 200MB FOR
EFFICIENT RAIN MAKING, BUT WITH ZERO CAPE THERE WASN'T THE STRONG
CONVECTION. THAT BEING SAID, MUCH OF THE SOUTHERN HALF OF THE REGION
STILL RECEIVED AN INCH OR MORE RAIN TODAY SATURATING THE SOIL WITH
WATER AND PRIMING THE AREA FOR FLASH FLOODING SHOULD HEAVIER SHOWERS
COME OVERNIGHT INTO TOMORROW.
THESE CONDITIONS LOOK TO CHANGE OVERNIGHT INTO TOMORROW AS WE COME
MORE UNDER THE INFLUENCE OF THE TROUGH TO THE WEST COOLING THE AIR
ALOFT TO PROVIDE SOME CAPE TO SUPPORT CONVECTION. ADDITIONALLY, UPPER-
LEVEL DYNAMICS INCREASE AS A 70-90 KT JET MOVES IN OVER THE REGION.
THE PRIMARY CONCERN WITH CONVECTION WILL BE STRONG WINDS OVER 60 MPH
POSSIBLE AS THE WINDS ALOFT MIX DOWN. THE ATMOSPHERE REMAINS
SATURATED THROUGH THE DAY, MAKING LOCALIZED HEAVY RAIN IN SHOWERS
AND THUNDERSTORMS MUCH MORE LIKELY LEADING TO FLASH FLOODING,
ESPECIALLY NEAR RECENT FIRE SCARS AND AREAS PRONE TO FLOODING LIKE
SLOT CANYONS AND STEEP TERRAIN. STAY TUNED TO THE FORECAST FOR
UPDATES AS WEATHER DEVELOPS THROUGH THE DAY. DRIER AIR STARTS MOVING
INTO THE REGION LATE TOMORROW WHICH LOOKS TO SCATTER OUT THE SHOWERS
AND THUNDERSTORMS, BUT ALSO LOOKS TO INCREASE THE POTENTIAL FOR
STRONGER THUNDERSTORMS OVERNIGHT INTO FRIDAY. MOST OF THE MOISTURE
IS SWEPT OUT OF THE REGION FRIDAY LIMITING CONVECTIVE ACTIVITY
THROUGH THE AFTERNOON, BUT HAS THE SECOND LOW STARTS MOVING IN FROM
THE WEST, SHOWERS AND THUNDERSTORMS WILL PICK UP AGAIN FRIDAY NIGHT
INTO SATURDAY FEEDING ON THE RESIDUAL MOISTURE AND CONTINUE THROUGH
SATURDAY NIGHT AND SUNDAY AS THE LOW TRACKS OVER THE REGION. THE
STORMS MOVE ON OFF TO THE EAST AS A ZONAL PATTERN SETS UP ACROSS THE
REGION SUNDAY NIGHT THROUGH MID NEXT WEEK.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 546 PM MDT WED OCT 21 2026
EXPECT WIDESPREAD LIGHT RAIN AND MODERATE RAIN SHOWERS ACROSS HE
REGION THROUGH THE TAF PERIOD. CURRENTLY SCATTERED EMBEDDED
THUNDERSTORMS ARE LIMITED TO THE SOUTHERN AREAS OF SOUTHEASTERN
UTAH AND SOUTHWESTERN COLORADO, BUT WILL SPREAD NORTH TO ALONG
AND WEST OF THE LINE FROM KVEL TO KCPW AFTER 12Z. WINDS WILL BE
GENERALLY LIGHT ACROSS THE REGION THROUGH THE TAF PERIOD, BUT EXPECT
OUTFLOW GUSTS TO 40 KTS ASSOCIATED WITH THUNDERSTORMS OVERNIGHT
INCREASING TO OVER 50 KTS AFTER 12Z. CONDITIONS WILL BE MOSTLY
MVFR TO IFR WITH THE SHOWERS AND THUNDERSTORMS, BELOW ILS
BREAKPOINTS FOR MOST MOUNTAIN TAF SITES FOR THE NEXT 24 HOURS.
HYDROLOGY
ISSUED AT 257 PM MDT WED OCT 21 2026
HYDROLOGIC CONCERNS REMAIN ELEVATED THROUGH FRIDAY DUE TO THE
INFLUX OF HIGHLY ANOMALOUS TROPICAL MOISTURE ACROSS THE 4
CORNERS AREA INTO THE CENTRAL ROCKIES. POTENTIAL HAZARDS
INCLUDE LOCALIZED FLASH FLOODING FROM THUNDERSTORMS PRODUCING
HEAVY RAINFALL RATES AND RIVER FLOODING DUE TO A PROLONGED
PERIOD OF WIDESPREAD MODERATE TO HEAVY RAINFALL.
SOUTHEAST UTAH AND THE LOWER VALLEYS ALONG THE CO/NM BORDER
WILL BE UNDER THE HIGHEST THREAT OF STRONG TO SEVERE
THUNDERSTORMS CAPABLE OF PRODUCING FLASH FLOODING ACROSS DESERT
FLOORS AND DRY WASHES THE THROUGH TOMORROW EVENING.
THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL LEADING TO
FLOODING ACROSS PORTIONS OF THE SAN JUANS AND ADJACENT SOUTHERLY
VALLEYS WHERE PRECIPITATION TOTALS OF 2 TO 4 INCHES WILL BE
POSSIBLE. THE BULK OF THIS PRECIPITATION WILL FALL OVERNIGHT
THROUGH EARLY FRIDAY MORNING. HIGHER PRECIPITATION TOTALS OVER
PORTIONS OF THE SOUTHERN SAN JUANS OF 4 TO 5 INCHES ARE
DEFINITELY POSSIBLE. AN ADDITIONAL CONCERN OF RAIN ON SNOW
LEADING TO ADDITIONAL RUNOFF MAKING IT INTO THE WATERWAYS. SNOW
LEVELS ARE FORECAST ABOVE 12-13 KFT THROUGHOUT THE DAY THURSDAY,
WHICH WILL LIKELY RESULT IN MELTING OF SOME 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 SUGGEST SEVERAL RIVERS
REACHING BANKFULL OR HIGHER AT RIVER FORECAST POINTS ACROSS
SOUTHWEST COLORADO AND SOUTHEAST UTAH. THE HIGHEST CONFIDENCE IN
MINOR FLOODING AND RELATED 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 THROUGH FRIDAY MORNING FOR COZ019-021>023.
UT...FLOOD WATCH THROUGH FRIDAY MORNING FOR UTZ022-027>029.
DISCUSSION...DB
AVIATION...DB
HYDROLOGY...ERW
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