613
FXUS65 KTWC 130917
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
217 AM MST TUE OCT 13 2026
SYNOPSIS
MOSTLY CLOUDY AND BREEZY AT TIMES THIS AFTERNOON
ACROSS THE MAJORITY OF SOUTHEAST ARIZONA WITH A CHANCE OF
SHOWERS TRACKING WEST TO EAST ACROSS THE AREA. TEMPERATURES WILL
REMAIN BELOW NORMAL THROUGH MOST OF THIS COMING WORK WEEK.
STRONG WINDS FROM THE EAST TO SOUTHEAST WILL IMPACT THE AREA
FRIDAY INTO THIS WEEKEND.
DISCUSSION
THE UPPER PATTERN THIS MORNING IS DEFINED BY A
HIGH AMPLITUDE TROUGH ACROSS THE WEST/GREAT BASIN AND ASSOCIATED
UPPER-LOW CENTERED OVER NORTHERN NEVADA, AND A HIGH AMPLITUDE
RIDGE UPSTREAM TO ITS WEST NEAR 135W IN THE EASTERN PACIFIC.
WATER VAPOR IMAGERY SHOWING THE TROUGH AXIS EXTENDS SOUTH
THROUGH SOUTHERN CALIFORNIA TOWARD THE SSW. A DISTINCT JET
STREAK OUT AHEAD OF THIS TROUGH AXIS EXTENDS FROM THE BAJA SPUR
NNE INTO TUCSON AND UP TO NW AZ THIS MORNING. GIVEN THE ELEVATED
PRECIPITABLE WATER VALUES FROM TUCSON WEST (GOES PWATS BETWEEN
0.80 AND 1.10 INCHES), THIS FEATURE IS RESPONSIBLE FOR THE
SCATTERED WEAK SHOWERS FLARING UP ACROSS EASTERN PIMA AND
EASTERN PINAL COUNTY EARLY THIS MORNING. THESE SHOWERS WILL
CONTINUE TO TRANSLATE EAST THIS MORNING AND WEAKEN, WITH THE
TROUGH AXIS EVENTUALLY SWINGING THROUGH EARLY THIS AFTERNOON
RESULTING IN ISOLATED WEAK SHOWERS. PRECIPITATION WITH THESE
SHOWERS ARE NOT EXPECTED TO BE IMPACTFUL, WITH GENERALLY BETWEEN
A TRACE TO TENTH INCH EXPECTED, AND LOCALLY HEAVIER AMOUNTS UP
TO A THIRD INCH POSSIBLE.
THE MAIN WEATHER STORY CONTINUES TO BE A SIGNIFICANT EASTERLY
WIND EVENT ACROSS SOUTHEAST ARIZONA FRIDAY INTO SATURDAY.
FORECAST MODELS REMAIN IN SOLID AGREEMENT WITH THE EVOLUTION OF
AN ANOMALOUSLY STRONG RIDGE OF HIGH PRESSURE ALOFT BUILDING
INTO THE GREAT BASIN AND NORTHERN INTERMOUNTAIN WEST DURING THE
LATTER HALF OF THE WEEK. THIS WILL DRIVE A STRONG SURFACE HIGH
SOUTHWARD ALONG THE SOUTHERN ROCKIES, RESULTING IN A VERY TIGHT
PRESSURE GRADIENT ACROSS SOUTHEAST ARIZONA. THE 13/00Z GFS AND
ECMWF ENSEMBLE GUIDANCE STILL SUPPORTS AN ANOMALOUSLY STRONG
SURFACE HIGH, WITH SFC PRESSURE ON THE ORDER OF 2.5 TO 3.5
STANDARD DEVIATIONS ABOVE NORMAL.
WHAT HAS INCREASED CONFIDENCE IN THIS WIND EVENT IS THE GOOD
RUN-TO-RUN CONSISTENCY IN BOTH THE STRENGTH AND PERSISTENCE
OF THE LOWER-LEVEL WIND. RECENT GUIDANCE CONTINUES TO INDICATE
850 MB WINDS OF 45-55 KTS ACROSS SOUTHERN AND EASTERN PORTIONS
OF OUR CWA BETWEEN 16/06Z-18Z FRIDAY, WITH WINDS REMAINING
ELEVATED BETWEEN 40-45 KTS THROUGH 17/18Z SATURDAY. THIS
PROLONGED PERIOD OF STRONG EASTERLY FLOW, COMBINED WITH A VERY
TIGHT SURFACE PRESSURE GRADIENT, INCREASES CONFIDENCE IN A
SIGNIFICANT AND POTENTIALLY LONG-DURATION WIND EVENT ACROSS
SOUTHEAST ARIZONA.
OF PARTICULAR INTEREST IS THE FORECAST VERTICAL STABILITY
PROFILE, WITH STRONG STATIC STABILITY NEAR AND IMMEDIATELY
ABOVE RIDGE-TOP LEVEL. THIS, COMBINED WITH THE PERSISTENT
STRONG EASTERLY CROSS-BARRIER FLOW APPEARS FAVORABLE FOR
MOUNTAIN-WAVE DEVELOPMENT...WITH POTENTIALLY SIGNIFICANT
DOWNSLOPE WIND ACCELERATION ALONG THE LEE SLOPES OF THE HIGHER
TERRAIN (WEST SIDE OF THE HIGHER TERRAIN IN THIS PARTICULAR
CASE). ALTHOUGH THE STRONGEST WINDS MAY BE FOCUSED IMMEDIATELY
DOWNSTREAM OF THE HIGHER TERRAIN, TERRAIN GAPS AND EAST-WEST
ORIENTED VALLEYS WILL ALSO BE SUSCEPTIBLE TO STRONG WINDS GIVEN
THE MAGNITUDE AND DURATION OF THE LOW-LEVEL PRESSURE GRADIENT.
CONFIDENCE IS HIGH THAT AT LEAST WIND ADVISORY CRITERIA WILL BE
MET FRIDAY AND SATURDAY, WITH SUSTAINED ELY/SELY WINDS OF 30-35
MPH AND GUSTS OF 50-60 MPH. HOWEVER, GIVEN THE MAGNITUDE AND
PERSISTENCE OF THE STRONG WINDS ALONG WITH THE POTENTIAL FOR
MOUNTAIN-WAVE AMPLIFICATION, THERE IS INCREASING CONCERN THAT
PORTIONS OF THE AREA COULD EXPERIENCE SUSTAINED WINDS EXCEEDING
40 MPH AND GUSTS IN EXCESS OF 60 MPH. ALTHOUGH CONFIDENCE IN
ADVISORY-LEVEL WINDS IS HIGH, UNCERTAINTY REMAINS REGARDING THE
MAGNITUDE AND AREAL EXTENT OF THE STRONGEST WINDS. A HIGH WIND
WATCH MAY BECOME NECESSARY AS WE GET CLOSER TO THE EVENT AND
CONFIDENCE IN WARNING-LEVEL WINDS INCREASES.
IN ANY EVENT, GIVEN THE INCREASING CONFIDENCE IN A PROLONGED
PERIOD OF ADVISORY-LEVEL WINDS, I DECIDED TO ISSUE A WIND
ADVISORY EARLY TO PROVIDE ADDITIONAL LEAD TIME FOR THE NUMEROUS
OUTDOOR ACTIVITIES PLANNED ACROSS SOUTHEAST ARIZONA THIS
WEEKEND. WE WILL CONTINUE TO CLOSELY MONITOR SUBSEQUENT MODEL
RUNS WITH REGARDS TO THE EVOLUTION OF THE LOW-LEVEL WINDS AND
VERTICAL STABILITY PROFILE TO SEE IF WE NEED TO ADDRESS
UPGRADING WIND HEADLINES.
AVIATION
VALID THROUGH 14/12Z. SCT-BKN CLOUDS 2-6K FT AGL
WITH SCATTERED -SHRA THIS MORNING WITH LOCALIZED 3-5SM IN -SHRA
BR. LOW CLOUDS MAY RESULT IN MOUNTAIN OBSCURATIONS ACROSS
SOUTHERN ARIZONA THIS MORNING. CLOUDS WILL THEN BECOME 5-8K FT
AGL THIS AFTERNOON WITH A SLIGHT CHANCE OF -SHRA INTO THE EARLY
EVENING. SUSTAINED SFC WIND SWLY LESS THAN 12 KTS THROUGH
13/19Z, THEN SWLY 10-15 KTS WITH GUSTS TO 25 KTS THIS AFTERNOON
INTO EARLY THIS EVENING. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.
FIRE WEATHER
MOSTLY CLOUDY AND OCCASIONALLY BREEZY WITH
GUSTS TO 30 MPH THIS AFTERNOON ACROSS THE MAJORITY OF SOUTHEAST
ARIZONA. THERE IS A CHANCE OF LIGHT SHOWERS TRACKING WEST TO
EAST ACROSS THE AREA TODAY. TEMPERATURES COOL WITH THE SYSTEM
PASSAGE TO AROUND 10 DEGREES BELOW NORMAL TODAY AND WEDNESDAY.
MINIMUM RELATIVE HUMIDITY REMAINS ABOVE 25-35 PERCENT THROUGH
THE WEEK. WINDY EAST TO SOUTHEAST WINDS WILL IMPACT THE AREA
FRIDAY INTO THE WEEKEND. THIS WIND EVENT HAS THE POTENTIAL TO
PRODUCE VERY STRONG EASTERLY WINDS. LOCATIONS ON THE LEE-SIDE
OF THE HIGHER TERRAIN, TERRAIN GAPS AND EAST-TO-WEST ORIENTED
VALLEYS WILL ALSO BE SUSCEPTIBLE TO STRONG WINDS FRIDAY MORNING.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
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