556
FXUS65 KFGZ 202147
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
247 PM MST TUE OCT 20 2026
SYNOPSIS
AN ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH THE END
OF THE WEEK. A STRONG WEATHER SYSTEM WILL BRING WIDESPREAD SHOWERS
AND THUNDERSTORMS BEGINNING WEDNESDAY MORNING AND CONTINUING THROUGH
THURSDAY. THE PRIMARY CONCERNS ARE FLOODING AND FLASH FLOODING,
ALONG WITH THE POTENTIAL FOR SEVERE THUNDERSTORMS.
DISCUSSION
A VERY ACTIVE WEATHER PATTERN IS EXPECTED ACROSS THE
STATE THROUGH THE NEXT WEEK. A STRONG LOW PRESSURE SYSTEM JUST OFF
THE CALIFORNIA COAST TODAY, WILL MOVE INLAND AND THROUGH THE DESERT
SOUTHWEST THROUGH THURSDAY. THIS STORM IS UNUSUALLY STRONG FOR THIS
TIME OF YEAR AND WITH THAT WILL COME A VARIETY OF HAZARDS. THE LOW
EVENTUALLY LIFTS THROUGH THE GREAT BASIN ON THURSDAY, DRAGGING A
COLD FRONT THROUGH THE REGION LATE THURSDAY INTO FRIDAY. A PIECE OF
ENERGY BREAKS AWAY FROM THE DEPARTING LOW, THEN BECOMES A CLOSED LOW
OVER ARIZONA AND LINGERS THROUGH THE WEEKEND.
LATE TONIGHT THOUGH THURSDAY...A VERY ACTIVE COUPLE OF DAYS ARE
EXPECTED FOR WEDNESDAY AND THURSDAY ACROSS THE ENTIRE FORECAST AREA.
LET'S BREAK IT DOWN BY HAZARD.
RAINFALL: STRONG MOISTURE ADVECTION FROM THE SOUTH WILL CONTINUE
THROUGH THURSDAY. THERE IS A GOOD PLUME OF MOISTURE BEING BROUGHT UP
FROM THE WESTERN COAST OF MEXICO AND THROUGH THE GULF OF CALIFORNIA.
SOME OF THIS MOISTURE IS LEFT OVER FROM POST-TROPICAL CYCLONE TRUDY
AND IS ENHANCED BY THE CONTINUED ACTIVE TROPICAL ACTIVITY IN THE
EASTERN PACIFIC. SHOWERS AND THUNDERSTORMS WILL DEVELOP BY LATE
TONIGHT AND SPREAD NORTHWARD THROUGH THE STATE AND BECOME WIDESPREAD
IN COVERAGE ON WEDNESDAY AND THURSDAY. PWAT VALUES HAVE RISEN
SLIGHTLY OVER THE PAST SEVERAL MODEL RUNS AND RANGE FROM 0.8-1.25",
WHICH ARE ANOMALOUSLY HIGH AND ABOVE THE 95 PERCENTILE FOR THE
REGION THIS TIME OF YEAR. RAINFALL AMOUNTS WILL VARY ACROSS THE
REGION BUT EXPECT WIDESPREAD 1.0-3.0" AMOUNTS TO OCCUR. SOME LOCALLY
HIGHER AMOUNTS BETWEEN 3-5" ARE CERTAINLY POSSIBLE, ESPECIALLY IN
AREAS THAT SEE CONTINUED CONVECTIVE STORMS AND MULTIPLE ROUNDS OF
PRECIPITATION. MODELS CONTINUE TO SHOW THE HIGHEST AMOUNTS ALONG AND
SOUTH OF THE MOGOLLON RIM. ADDITIONALLY, AREAS ACROSS THE NAVAJO
NATION MAY SEE 1-2" OF RAINFALL.
FLOODING/FLASH FLOODING: THE EXPECTED RAINFALL COMBINED WITH THE
FACT THAT WE HAVE WET ANTECEDENT CONDITIONS, WILL RESULT IN A FLOOD
AND FLASH FLOOD RISK. THE CONVECTIVE NATURE OF STORMS OVER THE NEXT
TWO DAYS COULD RESULT FAIRLY HIGH PRECIPITATION RATES, WHICH MAY
LEAD TO FLASH FLOODING. BE ADVISED THAT AREA CREEKS AND STREAMS
ALONG WITH MAIN STEM RIVERS MAY SEE 2-3 FOOT RISES. THE FLOOD WATCH
IS IN EFFECT FOR THE ENTIRE FORECAST AREA FROM EARLY WEDNESDAY
MORNING THROUGH LATE TUESDAY EVENING.
SEVERE WEATHER: A STRONG MID-LEVEL JET IS EXPECTED TO MOVE OVER THE
REGION THROUGH THE NEXT COUPLE OF DAYS. STRONG SOUTHWESTERLY WINDS
WILL STRENGTHEN AND COMBINE WITH INCREASING MOISTURE THROUGH THE MID
LEVELS, WITH STEEPENING LAPSE RATES. SHEAR IS HIGH WITH THIS SYSTEM
(50+ KTS) AND CAPE VALUES ARE HIGHER THAN USUAL FOR MID/LATE OCTOBER
AND IN THE 500-1000 J/KG RANGE. A LIMITING FACTOR FOR STRONGER
STORMS WOULD BE THE INCREASING CLOUD COVER BUT WE LOOK TO HAVE
ENOUGH SHEAR AND LINGERING INSTABILITY TO KEEP STORMS PROPAGATING
THROUGH THE EVENING AND OVERNIGHT PERIODS. STORM RELATIVE HELICITY
REMAINS HIGH WITH MODELED HELICITY UPDRAFTS SHOWING SUPPORT FOR
SUPERCELL ACTIVITY AND ROTATING STORMS. THE STORM PREDICTION CENTER
HAS PLACED PARTS OF OUR AREA IN AN ENHANCED RISK (CATEGORY 3 OUT OF
5) OF SEVERE WEATHER FOR WEDNESDAY AND IN A SLIGHT RISK (CATEGORY 2
OUT OF 5) FOR THE MUCH OF EASTERN ARIZONA FOR THURSDAY. ALL SEVERE
HAZARDS (DAMAGING WINDS, LARGE HAIL, A FEW TORNADOES).
BE PREPARED AND HAVE A WAY TO RECEIVE WARNINGS!
FRIDAY AND ONWARD...THE MAIN LOW PULLS OFF TO THE EAST BUT SOME OF
ITS ENERGY SEPARATES FROM THE FLOW AND MAY BECOME A CLOSED LOW OVER
ARIZONA THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. FOR NOW,
SHOWER AND THUNDERSTORM ACTIVITY DECREASES BY LATE THURSDAY INTO
EARLY FRIDAY WITH ONLY ISOLATED COVERAGE FOR FRIDAY THROUGH THE
WEEKEND. COOLER TEMPERATURES ARE EXPECTED TO CONTINUE WITH GENERALLY
LIGHT WINDS.
AVIATION...TUESDAY 20/18Z THROUGH WEDNESDAY 21/18Z
A FEW
ISOLATED -SHRA/-TSRA ARE POSSIBLE TODAY, ESPECIALLY IN THE WHITE
MOUNTAINS. EXPECT SCATTERED TO NUMEROUS SHRA/TSRA TO DEVELOP
AFTER 06Z AND SPREAD NORTHWARD THROUGH WEDNESDAY MORNING. WINDS
TODAY WILL BE S TO SE AROUND 10-20 KTS. CONDITIONS SHOULD REMAIN
MOSTLY VFR TODAY, WITH AREAS OF MVFR DEVELOPING AFTER 06Z AND
EXPANDING THROUGH WEDNESDAY MORNING. THERE IS POTENTIAL THAT SOME
STORMS COULD BECOME SEVERE ON WEDNESDAY, PRODUCING LARGE HAIL OR
DAMAGING WIND, ESPECIALLY FROM KGCN - KINW SOUTHWARD.
OUTLOOK...WEDNESDAY 21/18Z THROUGH FRIDAY 23/18Z...EXPECT WIDESPREAD
SHOWER AND THUNDERSTORM ACTIVITY TO BRING PERIODS OF MVFR/IFR
CONDITIONS. SOME STORMS MAY BECOME SEVERE, PRODUCING LARGE HAIL
AND DAMAGING WINDS. ACTIVITY DIMINISHES FROM WEST TO EAST LATE
THURSDAY EVENING/NIGHT. WINDS OUTSIDE OF STORMS, S AT 10-15 KTS
WITH GUSTS TO 25 KTS WEDNESDAY, S-SW 10-20 KTS WITH GUSTS TO 30
KTS THURSDAY.
FIRE WEATHER...TONIGHT THROUGH THURSDAY
INCREASING SHOWERS AND
THUNDERSTORMS LATE TONIGHT BECOME WIDESPREAD ON WEDNESDAY AND
THURSDAY. SOME STORMS MAY PRODUCE VERY HEAVY RAINFALL LEADING TO
FLOODING OR FLASH FLOODING BOTH DAYS. SOME STRONGER STORMS MAY
PRODUCE STRONG WINDS AND HAIL. OUTSIDE OF STORMS, EXPECT SOUTH WINDS
10-20 MPH WITH GUSTS 30-40 MPH ON WEDNESDAY, BECOMING SOUTH THROUGH
SOUTHWEST ON THURSDAY. DAYTIME TEMPERATURES NEAR TO BELOW NORMAL.
FRIDAY THROUGH SUNDAY...ISOLATED SHOWERS AND THUNDERSTORMS ARE
EXPECTED FOR FRIDAY THROUGH SUNDAY. SOUTHWEST THROUGH WEST WINDS 10-
15 MPH WITH GUSTS TO 25 MPH ON FRIDAY, THEN LIGHT NORTHERLY WINDS 5-
15 MPH ON SATURDAY AND SUNDAY.
FGZ WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR
AZZ004>018-037>040.
PUBLIC...MEOLA
AVIATION...MCT
FIRE WEATHER...MEOLA
FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF
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