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000
FXUS65 KFGZ 220403
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
900 PM MST TUE MAY 21 2013

.SYNOPSIS...
HIGH LEVEL CLOUDS WILL MOVE ACROSS ARIZONA THIS EVENING. ON
WEDNESDAY...A LOW PRESSURE SYSTEM WILL SETTLE OVER THE PACIFIC
NORTHWEST. THIS LOW WILL PRODUCE GUSTY WINDS ACROSS NORTHERN ARIZONA
AND BRING SEVERAL DAYS OF CRITICAL FIRE WEATHER CONDITIONS.
&&

.DISCUSSION...A BROAD PACIFIC LOW PRESSURE SYSTEM WILL SET UP OVER
PACIFIC NORTHWEST AND BECOME NEARLY STATIONARY THROUGH SUNDAY. THE
POSITION OF THIS LOW AND A HIGH PRESSURE RIDGE OVER THE PLAINS
STATES WILL BRING WARM TEMPERATURES...STRONG GUSTY WINDS AND DRY
HUMIDITY LEVELS TO ARIZONA. SMALLER SCALE SHORT WAVE TROUGHS MOVING
AROUND THIS BROAD LOW WILL BRING PERIODS OF STRONGER WINDS TO
NORTHERN ARIZONA. THE MAIN WEATHER IMPACTS THIS WEEK WILL BE AN
EXTENDED CRITICAL FIRE WEATHER PATTERN LASTING INTO THE MEMORIAL DAY
WEEKEND.

WEDNESDAY AND THURSDAY...STRONG WINDS WILL PICK UP IN THE AFTERNOON
HOURS ON WEDNESDAY WITH THE FIRST IN A SERIES OF RED FLAG WARNINGS
IN EFFECT. ON THURSDAY...A SHORT WAVE TROUGH WILL MOVE AROUND THE
SOUTHERN EDGE OF THE PACIFIC NORTHWEST LOW INCREASING OUR WIND
SPEEDS STARTING IN THE MID MORNING HOURS AND PRODUCING RED FLAG
WARNING CONDITIONS FOR A SECOND DAY ACROSS MUCH OF NORTHERN ARIZONA.

FRIDAY THROUGH SUNDAY...OUR LONGER RANGE MODEL SOLUTIONS ARE IN GOOD
AGREEMENT THAT THE BROAD LOW WILL REMAIN LOCKED IN PLACE OVER THE
PACIFIC NORTHWEST THROUGH SUNDAY. ADDITIONAL SHORT WAVE TROUGHS ARE
EXPECTED TO MOVE AROUND THIS BROAD LOW AND WILL LIKELY BRING PERIODS
OF STRONGER WINDS TO NORTHERN ARIZONA AS THEY PASS. THERE IS A GOOD
CHANCE FOR CONTINUED CRITICAL FIRE WEATHER CONDITIONS FOR SOME
LOCATIONS THROUGH SUNDAY. THE CHALLENGING PART TO THIS FORECAST WILL
BE THAT MANY OF OUR FIRE ZONES APPEAR TO BE EITHER APPROACHING OR
SLIGHTLY EXCEEDING OUR FIRE WEATHER THRESHOLDS. THE WIND SPEED
FORECASTS ARE HIGHLY DEPENDENT ON THE TIMING AND STRENGTH OF THESE
SMALLER SCALE TROUGH FEATURES. WE WILL PROBABLY NEED TO WAIT UNTIL
THE TIME PERIOD GETS INTO THE 24 TO 48 HOUR RANGE BEFORE WE CAN
ACCURATELY PIN DOWN WHERE THE MORE CRITICAL FIRE IMPACTS WILL
DEVELOP. PLEASE CONTINUE TO CLOSELY MONITOR OUR FORECASTS AND
WARNINGS FOR UPDATES AS OUR PRODUCTS WILL EVOLVE OVER TIME.

&&

.AVIATION...FOR THE 06Z PACKAGE...EXPECT VFR CONDITIONS WITH
STRONGER WINDS STARTING WEDNESDAY MORNING WITH PEAK AFTERNOON WIND
GUSTS RANGING FROM 35 TO 45 MPH.  AVIATION DISCUSSION NOT UPDATED
FOR AMENDMENTS.

&&

.FIRE WEATHER...A BROAD TROUGH OF LOW PRESSURE WILL DEVELOP ACROSS
THE WESTERN STATES BY WEDNESDAY AND REMAIN IN PLACE THROUGH THE
WEEKEND. PERIODS OF STRONG WINDS WILL COMBINE WITH LOW RELATIVE
HUMIDITIES TO CREATE CRITICAL FIRE WEATHER CONDITIONS FOR AN
EXTENDED PERIOD.

A RED FLAG WARNING IS IN EFFECT FOR WEDNESDAY AND THURSDAY FOR
MUCH OF NORTHERN ARIZONA. FIRE WEATHER CONDITIONS WILL BRIEFLY
IMPROVE WEDNESDAY NIGHT AS RELATIVE HUMIDITIES INCREASE AND WINDS
DECREASE. SOME LOCATIONS DOWNWIND OF HIGHER TERRAIN MAY CONTINUE
TO EXPERIENCE BREEZY OVERNIGHT WINDS. ON THURSDAY...VERY LOW
RELATIVE HUMIDITIES AND STRONG WINDS WILL ONCE AGAIN DEVELOP
ACROSS MUCH OF NORTHERN ARIZONA.

FRIDAY THROUGH SUNDAY...THE WEST COAST TROUGH WILL CONTINUE TO BRING
VERY DRY AND WINDY CONDITIONS TO NORTHERN ARIZONA. NEAR CRITICAL
FIRE WEATHER CONDITIONS CAN BE EXPECTED TO OCCUR THROUGH THE WEEKEND
AND INTO THE EARLY PART OF NEXT WEEK.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...

RED FLAG WARNING WEDNESDAY NOON TO 8 PM MST FOR FIRE WEATHER ZONES
AZZ104>117-138>140.

WIND ADVISORY WEDNESDAY NOON TO 8 PM MST FOR PUBLIC ZONES
AZZ004-006>008-012-013-015-016-040.

RED FLAG WARNING THURSDAY FROM NOON TO 8 PM MST FOR FIRE WEATHER
ZONES AZZ104>117-138>140.

&&
$$

PUBLIC.........BOHLIN
AVIATION.......BOHLIN
FIRE WEATHER...DB

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT WEATHER.GOV/FLAGSTAFF