951
FXUS65 KFGZ 201126
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
426 AM MST TUE OCT 20 2026
SYNOPSIS
NORTHERN ARIZONA WILL REMAIN IN AN ACTIVE WEATHER
PATTERN THROUGH THE WEEK. A FEW ISOLATED SHOWERS AND THUNDERSTORMS
ARE POSSIBLE ON TUESDAY, THEN A STRONG WEATHER SYSTEM WILL BRING
HIGH CHANCES FOR SHOWERS AND THUNDERSTORMS BEGINNING WEDNESDAY
MORNING AND CONTINUING THROUGH THURSDAY. THE PRIMARY CONCERNS ARE
FLOODING AND FLASH FLOODING, ESPECIALLY ACROSS EASTERN ARIZONA.
THERE IS A SECONDARY CONCERN FOR SEVERE THUNDERSTORMS, THOUGH
THERE IS LOWER CONFIDENCE IN THIS HAZARD.
DISCUSSION...TODAY
CURRENT MESOANALYSIS AND SATELLITE IMAGERY
REVEALS A SUBTLE SHORTWAVE AND A WEAK 40KT JET AT 500MB OVER
EASTERN ARIZONA. THIS HAS COMBINED WITH MARGINAL INSTABILITY (100
J/KG OF MUCAPE) TO ALLOW FOR VERY ISOLATED AND WEAKLY ROTATING
THUNDERSTORMS ACROSS THE WHITE MOUNTAINS AS OF 2 AM MST THIS
MORNING. THIS IS EXPECTED TO END WITHIN A FEW HOURS AS THE MID-
LEVEL PATTERN SHIFTS NORTHEASTWARD. INTO TODAY, A DEEP UPPER-LEVEL
LOW WILL CONTINUE TO RAPIDLY DIVE SOUTHWARD ALONG THE WEST COAST
WHILE RIDGING OVER THE CENTRAL CONUS AMPLIFIES. THIS WILL HELP
LIFT THE WEAK SHORTWAVE FULLY OUT OF ARIZONA, AND BRIEF SUBSIDENCE
ALOFT WILL LEAD TO SUPPRESSED DAYTIME SHOWER ACTIVITY. STILL A
FEW WEAK SHOWERS OR EVEN THUNDERSTORMS WILL REMAIN POSSIBLE
ESPECIALLY TOWARDS THE KAIBAB AND THE WHITE MOUNTAINS.
LATE TONIGHT THROUGH THURSDAY...BEGINNING LATE TONIGHT, THE WEST
COAST LOW WILL BEGIN TO PUSH EASTWARD AND CARRY A DEEP SURGE OF
SUBTROPICAL AND TROPICAL MOISTURE TO NORTHERN ARIZONA. THIS MOISTURE
SURGE IS SOMEWHAT ENHANCED DUE TO CONTINUED ACTIVE TROPICAL CYCLONE
ACTIVITY ACROSS THE EASTERN PACIFIC. PWAT VALUES (A MEASURE OF
ATMOSPHERIC MOISTURE) ARE FORECAST TO RISE UP TO 0.8-1.1 INCHES,
WELL ABOVE NORMAL FOR MID-OCTOBER. AS A RESULT, THERE WILL
WIDESPREAD SHOWERS AND THUNDERSTORMS BRINGING A PRIMARY HAZARD OF
FLOODING/FLASH FLOODING THROUGH THE PERIOD. THE CURRENT FORECAST
CALLS FOR THE HEAVIEST RAINFALL ACCUMULATIONS ALONG/SOUTH OF THE
MOGOLLON RIM, WITH A 1.0-3.0 INCHES EXPECTED. ANOTHER AREA OF
CONCERN WILL BE THE NAVAJO NATION, WHERE WIDESPREAD RAINFALL
ACCUMULATIONS OF 1.0-2.0 INCHES ARE FORECAST. LOCALIZED HEAVY
RAINFALL WILL REMAIN POSSIBLE EVEN OUTSIDE OF THE REGIONS. AS A
RESULT, A FLOOD WATCH HAS BEEN ISSUED FOR ALL OF NORTHERN AND
CENTRAL ARIZONA FROM 5 AM MST WEDNESDAY-11 PM MST THURSDAY (6 AM
MDT WEDNESDAY-12 AM MDT FRIDAY). HAVE A WAY TO RECEIVE FLASH FLOOD
WARNINGS AND BE PREPARED TO TAKE ACTION SHOULD WARNINGS BE
ISSUED.
THERE ALSO REMAINS A SEVERE THUNDERSTORM THREAT. A STRONG 500MB JET
STREAK MOVES OVERHEAD THROUGH THE PERIOD, AND 50+ KTS OF SHEAR ARE
LIKELY. THERE STILL IS A DEGREE OF UNCERTAINTY IN THE AVAILABLE
INSTABILITY, HOWEVER MESOSCALE MODELS REMAIN ADAMANT THAT WE WILL
SEE CAPE VALUES 500-1500 J/KG FROM HIGH SURFACE DEWPOINTS AND
STEEPENING MID-LEVEL LAPSE RATES. IF THE HIGHER INSTABILITY
MANIFESTS, THERE WILL BE SEVERE HAIL AND WIND THREATS. THE SHEAR
PROFILE ALSO SUGGESTS POTENTIAL FOR ROTATING STORMS, AND EVEN AN
ISOLATED TORNADO THREAT. THE SPC MAINTAINS A MARGINAL RISK (CATEGORY
1 OUT OF 5) OF SEVERE WEATHER ACROSS ALL OF NORTHERN AND CENTRAL
AZ ON WEDNESDAY AND THURSDAY, AND EVEN A SLIGHT RISK (2 OUT OF 5)
FOR SEVERE STORMS ACROSS THE EASTERN MOGOLLON RIM AND WHITE
MOUNTAINS ON WEDNESDAY. BESIDES HEAVY RAIN AND THUNDERSTORMS,
EXPECT GUSTY DAYTIME WINDS UP TO 30-40 MPH ON THURSDAY, THOUGH
LIKELY REMAINING BELOW ADVISORY CRITERIA.
FRIDAY AND ONWARD...ACTIVITY IS EXPECTED TO TREND DOWNWARD BY FRIDAY
INTO AFTER THE MAIN TROUGH AXIS PUSHES PAST NORTHERN AZ AND DRIER
AIR MOVES IN. SOME SLIGHT CHANCES FOR SHOWERS LOOK TO LINGER EACH
DAY, BUT THERE IS LOW CONFIDENCE DURING THIS PERIOD. EXPECT LIGHTER
WINDS AND TEMPERATURES REMAINING BELOW NORMAL OTHERWISE.
AVIATION...TUESDAY 20/12Z THROUGH WEDNESDAY 21/12Z
PRIMARILY
VFR, PERIODS OF MVFR/IFR IN HEAVIER SHOWERS AND STORMS. ISOLATED
SHOWERS AND THUNDERSTORMS POSSIBLE OVER THE WHITE MOUNTAINS AND
KAIBAB PLATEAU AFTER 18Z. NUMEROUS TO WIDESPREAD SHOWERS AND
THUNDERSTORMS BEGIN MOVING IN FROM THE SOUTH AFTER 06Z WEDNESDAY.
WINDS S-SW 5-15KTS GUSTS TO 20KTS DAYTIME TUESDAY, LIGHT AND VRB
OVERNIGHT. GUSTY AND ERRATIC WINDS EXPECTED NEAR STORMS.
OUTLOOK...WEDNESDAY 21/12Z THROUGH FRIDAY 23/12Z...WIDESPREAD
SHOWER AND THUNDERSTORM ACTIVITY BRINGING PERIODS OF MVFR/IFR
CONDITIONS. ACTIVITY DIMINISHES FROM WEST TO EAST LATE THURSDAY
EVENING/NIGHT. WINDS S 10-15KTS WITH GUSTS TO 25KTS WEDNESDAY,
S-SW 10-20KTS WITH GUSTS TO 30KTS THURSDAY.
FIRE WEATHER...TODAY THROUGH WEDNESDAY
ISOLATED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE DURING THE DAYTIME TODAY, THEN ACTIVITY
WILL INCREASE IN COVERAGE LATE TUESDAY AND BECOME WIDESPREAD ON
WEDNESDAY. SOME STORMS MAY PRODUCE VERY HEAVY RAINFALL LEADING TO
FLOODING OR FLASH FLOODING ON WEDNESDAY. WINDS ARE SOUTH 10-15 MPH
WITH GUSTS TO 25 MPH ON TUESDAY, THEN 10-20 MPH WITH GUSTS 25-35 MPH
ON WEDNESDAY. DAYTIME TEMPERATURES NEAR TO BELOW NORMAL.
THURSDAY THROUGH SATURDAY...WIDESPREAD SHOWERS AND THUNDERSTORMS
CONTINUE ON THURSDAY, BECOMING ISOLATED FOR FRIDAY AND SATURDAY.
SOME STORMS MAY PRODUCE VERY HEAVY RAINFALL LEADING TO FLOODING OR
FLASH FLOODING ON THURSDAY. SOUTH THROUGH SOUTHWEST WINDS 15-25 MPH
WITH GUSTS 30-40 MPH ON THURSDAY, BECOMING SOUTHWEST THROUGH WEST 10-
15 MPH WITH GUSTS TO 25 MPH ON FRIDAY, THEN LIGHT NORTHERLY WINDS 5-
15 MPH ON SATURDAY.
FGZ WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR
AZZ004>018-037>040.
PUBLIC...LEWANDOWSKI
AVIATION...LEWANDOWSKI
FIRE WEATHER...LEWANDOWSKI
FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF
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