Severe Thunderstorm Warning 130, NWS Flagstaff, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
816 PM MST MON OCT 19 2015

.SYNOPSIS...PERSISTENT LOW PRESSURE SYSTEMS WILL LEAD TO CHANCES
FOR SHOWERS AND THUNDERSTORMS AND COOL CONDITIONS OVER NORTHERN
ARIZONA THROUGH THURSDAY. A DRYING TREND AND A RETURN TO NEAR
NORMAL TEMPERATURES ARE FORECAST FRIDAY THROUGH THE WEEKEND.

&&

.DISCUSSION...THOUGH THUNDERSTORM COVERAGE HAS BEEN RATHER
UNIMPRESSIVE THIS EVENING...WE HAVE SEEN ISOLATED SEVERE STORM
ACTIVITY IN YAVAPAI COUNTY. WE CAN SEE TWO DISTINCT SHORTWAVES ON
WATER VAPOR SATELLITE IMAGERY THIS EVENING (ONE JUST OFF THE
CA/BAJA COAST AND 2ND ALONG THE SAN FRANCISCO COASTLINE) WHICH
ARE BOTH ACTING TO DEEPEN THE WEST COAST TROUGH AS IT DROPS SOUTH
INTO THE SOUTHWESTERN UNITED STATES. THE PERIOD OF CONCERN FOR
SEVERE WEATHER WILL CONTINUE TO BE OVER THE NEXT 18 HRS AS THE LOW
DEEPENS AND FORMS A CLOSED LOW OVER THE LOWER COLORADO RIVER BY
NOON TUESDAY. THE OVERALL THINKING REMAINS UNCHANGED WITH THE BEST
POTENTIAL BETWEEN NOW AND TUESDAY MORNING FOR COCONINO AND YAVAPAI
COUNTIES...SHIFTING EAST INTO GILA/NAVAJO/APACHE COUNTIES FROM
TUESDAY MORNING THROUGH EARLY AFTERNOON.

&&

.PREV DISCUSSION /322 PM MST/ BY LATE TONIGHT THROUGH TUESDAY
MORNING, AN INCREASE IN STORM COVERAGE IS POSSIBLE AS A WEST COAST
TROUGH APPROACHES AND RESULTS IN COOLING ALOFT A WEAK LARGE SCALE
LIFT. THIS COULD BE ENOUGH TO TRIGGER OVERNIGHT CONVECTION, AND IN
THE PRESENCE OF STRONG DEEP-LAYER SHEAR, A FEW OF THESE STORMS
COULD BECOME SEVERE. THIS THREAT PERSISTS THROUGH THE MORNING
HOURS TUESDAY FOR MUCH OF NORTHERN ARIZONA, THEN SHIFTS TO MAINLY
EASTERN ARIZONA BY LATE MORNING AND AFTERNOON AS WIND SHEAR
DECREASES CLOSER TO THE CENTER OF THE LOW PRESSURE SYSTEM.

THE LOW PRESSURE SYSTEM IS FORECAST TO BE NEARLY STATIONARY
TUESDAY EVENING THROUGH WEDNESDAY WITH A GOOD CHANCE OF SHOWERS
AND THUNDERSTORMS CONTINUING OVER MOST OF NORTHERN ARIZONA. WIND
SHEAR VALUES DECREASE SO THE THREAT OF SEVERE THUNDERSTORMS IS
MUCH LOWER. A CHANCE OF SHOWERS AND A FEW STORMS CONTINUES
THURSDAY WITH ONLY A SLIGHT CHANCE BY FRIDAY. MODELS ARE IN GOOD
AGREEMENT THAT IMPROVING WEATHER FINALLY ARRIVES FOR THE WEEKEND.

&&

.AVIATION...FOR THE 06Z PACKAGE...EXPECT SCT SHRA/TSRA ALONG AND
WEST OF A KPGA-KFLG-KPAN LINE THROUGH 12Z TUESDAY WITH ISOLATED
MVFR/IFR IN +TSRA. THERE IS A MARGINAL THREAT OF ISOLATED SEVERE
STORMS PRODUCING HAIL AND STRONG WINDS. COVERAGE OF SHRA/TSRA IS
EXPECTED TO INCREASE TUESDAY AS LOW PRESSURE MOVES ACROSS THE
REGION. STRONGER STORMS WILL PRODUCE MVFR/IFR CONDITIONS...HAIL
AND GUSTY WINDS. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

PUBLIC...MCS/JJ
AVIATION...MCS

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1041 PM MST MON OCT 19 2015

AZZ004>018-037>040-201300-
KAIBAB PLATEAU-MARBLE AND GLEN CANYONS-GRAND CANYON COUNTRY-
COCONINO PLATEAU-YAVAPAI COUNTY MOUNTAINS-
NORTHEAST PLATEAUS AND MESAS HWY 264 NORTHWARD-CHINLE VALLEY-
CHUSKA MOUNTAINS AND DEFIANCE PLATEAU-
LITTLE COLORADO RIVER VALLEY IN COCONINO COUNTY-
LITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTY-
LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY-
WESTERN MOGOLLON RIM-EASTERN MOGOLLON RIM-WHITE MOUNTAINS-
NORTHERN GILA COUNTY-YAVAPAI COUNTY VALLEYS AND BASINS-
OAK CREEK AND SYCAMORE CANYONS-BLACK MESA AREA-
NORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264-
1041 PM MST MON OCT 19 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR APACHE...COCONINO...
NORTHERN GILA...NAVAJO...AND YAVAPAI COUNTIES IN NORTHERN
ARIZONA.

.DAY ONE...TONIGHT

AN APPROACHING TROUGH WILL BRING AN INCREASE IN THUNDERSTORM
COVERAGE OVER YAVAPAI COUNTY TONIGHT...AND POSSIBLY OVER COCONINO
AND NORTHERN GILA COUNTIES. A FEW THUNDERSTORMS COULD BECOME
SEVERE WITH LARGE HAIL AND STRONG WIND GUSTS. THERE IS ALSO A
CHANCE OF LOCALIZED FLASH FLOODING WITH THE STRONGEST STORMS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE THREAT OF A FEW SEVERE THUNDERSTORMS WILL CONTINUE TUESDAY
MORNING EAST OF A PRESCOTT TO FLAGSTAFF TO PAGE LINE...THEN THE
THREAT SHIFTS TO MAINLY NAVAJO AND APACHE COUNTY BY TUESDAY
AFTERNOON.

WEDNESDAY THROUGH THURSDAY...THUNDERSTORM CHANCES WILL CONTINUE
EACH DAY. HOWEVER...ANY THUNDERSTORMS THAT DEVELOP SHOULD REMAIN
BELOW SEVERE LIMITS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS TO THE NATIONAL WEATHER SERVICE FLAGSTAFF OFFICE AT
1-888-745-1637.