355
FXUS65 KFGZ 151617
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
917 AM MST MON JUL 15 2019
SYNOPSIS
DRIER WEST TO SOUTHWEST FLOW WILL PUSH MONSOON
MOISTURE AND STORM COVERAGE EASTWARD TODAY THROUGH WEDNESDAY.
GUSTY AFTERNOON WINDS WILL ACCOMPANY THIS PUSH ESPECIALLY TUESDAY
AND WEDNESDAY. HIGH PRESSURE WILL THEN BEGIN TO BOUNCE BACK
TOWARD THE FOUR CORNERS WITH A GRADUAL RETURN OF MOISTURE.
DAYTIME TEMPERATURES AT LOWER ELEVATIONS WILL BE VERY HOT OVER THE
NEXT FEW DAYS.
DISCUSSION
THE MAIN STORIES OVER THE NEXT COUPLE DAYS WILL BE
DECREASING THUNDERSTORM CHANCES, HOT TEMPERATURES, AND GUSTY
AFTERNOON WINDS. WEST TO SOUTHWEST FLOW IS ADVECTING A DRIER
AIRMASS INTO THE REGION WHICH WILL ACT TO DECREASE THUNDERSTORM
CHANCES ACROSS NORTHERN ARIZONA. EXPECT GENERALLY ISOLATED
COVERAGE TODAY, WITH THE HIGHEST CHANCES REMAINING OVER THE WHITE
MOUNTAINS. THUNDERSTORM CHANCES WILL BE LIMITED TO NAVAJO AND
APACHE COUNTIES ON TUESDAY AND WEDNESDAY. THE PRIMARY HAZARDS WITH
THESE STORMS WILL REMAIN GUSTY OUTFLOW WINDS AND LIGHTNING.
LOCALIZED HEAVY RAINFALL IS ALSO POSSIBLE.
VERY HOT TEMPERATURES WILL OCCUR THROUGH MID WEEK OVER THE LOWER
ELEVATIONS. AN EXCESSIVE HEAT WARNING REMAINS IN EFFECT THROUGH
8PM TUESDAY FOR PORTIONS OF THE LOW DESERT IN CENTRAL ARIZONA
(INCLUDING SOUTHERN YAVAPAI COUNTY) AS WELL AS LOWER ELEVATIONS IN
THE GRAND CANYON INCLUDING PHANTOM RANCH. TEMPERATURES OF THIS
NATURE WILL SUBSTANTIALLY INCREASE THE THREAT OF HEAT ILLNESS. BE
SURE TO STAY HYDRATED AND OUT OF THE SUN AS MUCH AS POSSIBLE.
THE TROUGH WHICH IS DRIVING THE WEST TO SOUTHWEST FLOW WILL ALSO
GENERATE GUSTY WINDS OF 25-35 MPH ACROSS THE REGION TUESDAY AND
WEDNESDAY. NEAR CRITICAL FIRE WEATHER CONDITIONS ARE POSSIBLE IN
WESTERN COCONINO/YAVAPAI COUNTIES ON TUESDAY AFTERNOON. AFTERNOON
WIND SPEEDS ARE EXPECTED TO WEAKEN THURSDAY THROUGH THE REMAINDER
OF THE WEEK.
THE CURRENT FORECAST HANDLES THIS WELL AND NO UPDATES ARE NEEDED
THIS MORNING.
PREV DISCUSSION /324 AM MST/
HIGH PRESSURE WAS IN THE PROCESS
OF SHIFTING SOUTHEASTWARD IN RESPONSE TO A WEST TO EAST MOVING
TROUGH ENTERING THE WESTERN STATES.
FOR TODAY THROUGH WEDNESDAY...THE WESTERN STATES TROUGH WILL
INTRODUCE A DRIER AIR MASS TO NORTHERN ARIZONA ALONG WITH A
VERTICAL WIND PROFILE UNFAVORABLE FOR MONSOON STORM DEVELOPMENT.
LINGERING MOISTURE WILL ALLOW FOR JUST ONE MORE DAY OF LIMITED
ACTIVITY BEFORE THUNDERSTORMS AND SHOWERS ARE CONFINED TO THE
WHITE MOUNTAINS AREA EAST-CENTRAL ARIZONA. IN ADDITION, ALONG THE
WITH THE DRIER AIR MASS, DAYTIME TEMPERATURES WILL BE ON THE
INCREASE. IN GENERAL IT WILL BE HOT WITH ELEVATIONS BELOW 3500
FEET CLIMBING TO TEMPERATURES RANGING FROM 107-112 DEGREES. AS A
RESULT AN EXCESSIVE HEAT WARNING IS IN EFFECT FOR POTIONS OF THE
LOW DESERT IN CENTRAL ARIZONA (INCLUDING SOUTHERN YAVAPAI COUNTY)
AS WELL AS LOWER ELEVATIONS IN THE GRAND CANYON INCLUDING PHANTOM
RANCH.
FROM THURSDAY ONWARD...HIGH PRESSURE BOUNCES BACK NORTHWARD AS THE
WESTERN STATES TROUGH MAKES IT'S WAY TO THE NORTHEAST. THE RESULT
WILL BE A GRADUAL RETURN OF MONSOON MOISTURE TO PORTIONS OF
NORTHERN ARIZONA. THERE ARE A COUPLE FACTORS THAT COULD SPEED UP
OR SLOW DOWN THE LATE WEEK UPWARD TREND IN MOISTURE. ONE, A
SECONDARY TROUGH COULD PUT THE NORTHWARD MOVEMENT OF MOISTURE IN
A HOLDING PATTERN. TWO, IF A THUNDERSTORM COMPLEX DEVELOPS OVER
NORTHWEST MEXICO OR SOUTHEAST ARIZONA A MOIST OUTFLOW BOUNDARY
COULD PUSH MOISTURE ACROSS THE AREA (REGARDLESS OF ANY SECONDARY
TROUGH). HOW IT WILL BALANCE OUT IS SIMPLY A GUESS AT THIS POINT
SO WE OPTED FOR A SLOW INCREASE IN MOISTURE AND STORM ACTIVITY
THROUGH THE PERIOD. CHECK BACK FOR UPDATES.
AVIATION...FOR THE 18Z PACKAGE
EXPECT VFR CONDITIONS OVER
NORTHERN ARIZONA THROUGH THE TAF PERIOD. SURFACE WINDS SOUTHWEST AT
5-10 KTS WITH STRONGER BREEZES AT 10 GUSTING 20 KTS OVER THE HIGHER
TERRAIN. WINDS WILL BECOME LIGHT AND VARIABLE AROUND SUNSET.
ISOLATED TO SCATTERED -TSRA WILL DEVELOP ALONG THE HIGHER TERRAIN OF
NORTHERN ARIZONA BETWEEN 19Z MON AND 03Z TUES. LOCAL MVFR CONDITIONS
AND GUSTY AND ERRATIC OUTFLOW WINDS WILL BE POSSIBLE NEAR
THUNDERSTORMS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
EXPECT ISOLATED TO SCATTERED HIGH-BASED
THUNDERSTORMS PRODUCING GUSTY AND ERRATIC OUTFLOW WINDS TODAY,
MAINLY ALONG THE HIGH TERRAIN. TUESDAY WILL HAVE NEAR CRITICAL
FIRE WEATHER CONDITIONS IN ZONES 104 AND 106-108. THUNDERSTORMS
WILL BE LIMITED TO THE HIGHER TERRAIN IN NAVAJO AND APACHE
COUNTIES.
WEDNESDAY THROUGH FRIDAY...WEDNESDAY WILL HAVE BREEZY WEST TO
SOUTHWEST WINDS AGAIN WITH AN INCREASE IN SURFACE RH. THUNDERSTORMS
WILL CONTINUE EACH DAY, MOSTLY IN THE WHITE MOUNTAINS, AND WITH A
SLIGHT CHANCE ALONG THE MOGOLLON RIM AND CHUSKA MOUNTAINS.
FGZ WATCHES/WARNINGS/ADVISORIES
EXCESSIVE HEAT WARNING UNTIL 8
PM MST TUESDAY FOR AZZ006-037.
PUBLIC...TPS/MCCOLLUM
AVIATION...DB
FIRE WEATHER...DB
FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF
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