372
FXUS65 KTWC 141015
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 AM MST FRI NOV 14 2025
SYNOPSIS
HIGH TEMPERATURES WILL REMAIN 5 TO 10 DEGREES ABOVE
NORMAL TODAY AND SATURDAY. A LOW PRESSURE SYSTEM IS THEN EXPECTED
TO IMPACT THE REGION THIS WEEKEND, BRINGING CHANCES FOR LIGHT
SHOWERS, COOLER TEMPERATURES, AND BREEZY CONDITIONS. UNSETTLED
CONDITIONS ARE EXPECTED TO CONTINUE NEXT WEEK ALONG WITH BELOW
NORMAL TEMPERATURES.
DISCUSSION
ONE OF THE FORECAST CHALLENGES I HAVE FACED AS A
METEOROLOGIST OVER THE PAST FEW DECADES WITH REGARDS TO WINTER
WEATHER DISTURBANCES MOVING ACROSS SOUTHEAST ARIZONA DURING THE
MONTH OF NOVEMBER IS THAT MULTIPLE CONDITIONS SEEM TO BE REQUIRED
TO PERFECTLY FALL IN-LINE FOR US TO SEE AN UPPER-LOW SIGNIFICANTLY
IMPACT OUR NECK OF THE WOODS. THIS IS NOT TO SAY THAT WE DON'T
HAVE WINTER WEATHER IMPACTING SOUTHEAST ARIZONA THIS TIME OF YEAR,
IT'S JUST THAT MOST OF THE TIME WE SEE THE STRONGER UPPER-LOWS/TROUGHS
TO OUR WEST EJECT NORTHEAST ACROSS NORTHERN ARIZONA AND THE GREAT
BASIN. CASE IN POINT: WHAT WE WILL EXPERIENCE THE NEXT FEW DAYS.
THE UPPER PATTERN THIS MORNING IS DEFINED BY A TROUGH OF LOW
PRESSURE OFF THE CALIFORNIA COASTLINE, AN AMPLIFIED RIDGE OF HIGH
PRESSURE IN THE EASTERN PACIFIC WITH THE HIGH-CENTER NEAR
33N/115W, AND ANOTHER TROUGH FARTHER UPSTREAM NEAR THE ALEUTIAN
ISLANDS. AS THIS UPSTREAM FEATURE MOVES SE, IT WILL CONTINUE TO
FORCE THE UPPER RIDGE AXIS TO BECOME POSITIVELY TILTED AND IN TURN
FORCE THE TROUGH ALONG THE CALIFORNIA COAST TO CLOSE OFF AND
BECOME A CUTOFF-LOW JUST OFF THE SOUTHERN CALIFORNIA COASTLINE BY
18Z SATURDAY. THE FLATTENING RIDGE BEHIND THE CUTOFF WILL BEGIN
TO NUDGE/EJECT THIS CUTOFF NE INTO THE GREAT BASIN/NORTHERN
ARIZONA DURING THE DAY SUNDAY.
EVEN THROUGH THERE IS A DECENT SUBTROPICAL MOISTURE PLUME OUT
AHEAD OF THIS UPPER-LOW, WE WILL FAIL TO UTILIZE IT AS SOUTHEAST
ARIZONA WILL RESIDE ON THE SOUTHERN PERIPHERY OF THE EJECTING
TROUGH AND AWAY FROM THE BEST DYNAMICS. THIS IS NOT TO SUGGEST
THAT WE WON'T SEE SOME LIGHT SHOWERS AS IT TRACKS THROUGH, BUT
PRECIPITATION AMOUNTS ARE GENERALLY EXPECTED TO REMAIN LIGHT
THROUGH MONDAY. THE 14/07Z NBM PROBABILITY OF RAINFALL BETWEEN
0.50 AND 1.25 INCHES (VALUES THAT WOULD RESULT IN RUNNING WATER IN
NORMALLY DRY WASHES AND/OR PONDING OF WATER IN ROADWAY DIPS AND
OTHER LOW-LYING AREAS) REMAIN BELOW 5 PERCENT THROUGH MONDAY,
WITH THE EXCEPTION OF A 10-15 PERCENT PROBABILITY ACROSS SE PINAL
DURING THE DAY SUNDAY WITH THE TROUGH PASSAGE. SINCE THIS IS ONLY
A GLANCING BLOW, THE SNOW LEVELS WILL REMAIN ELEVATED WITH THIS
SYSTEM AS WELL (ABOVE 10K FEET SUNDAY MORNING, SLOWLY LOWERING TO
8500 FEET MONDAY). THE MAIN IMPACTS WITH THIS SYSTEM MAY ACTUALLY
BE THE 10 DEGREE DROP IN AFTERNOON HIGH TEMPERATURES BETWEEN
SATURDAY AND SUNDAY AND THE BREEZY CONDITIONS EXPECTED SUNDAY.
EXPECT BREEZY SOUTHWEST TO WEST WINDS 15 TO 25 MPH WITH GUSTS TO
30-40 MPH SUNDAY, ESPECIALLY EAST AND SOUTHEAST OF TUCSON IN
COCHISE COUNTY.
WITH THE FLAT RIDGE IN THE EASTERN PACIFIC, THAT SECOND TROUGH
RESPONSIBLE FOR EJECTING THE CUTOFF LOW WILL RAPIDLY MOVE IN
BEHIND IT, WITH THE OVERALL PATTERN BECOMING MORE PROGRESSIVE
WITHIN THE WESTERLY FLOW. THIS WILL HELP RESULT IN A MORE
UNSETTLED WEATHER FOR OUR NECK OF THE WOODS TUESDAY/WEDNESDAY AND
POTENTIALLY ANOTHER UPPER-LOW IMPACTING SOUTHEAST ARIZONA LATE
NEXT WEEK INTO NEXT WEEKEND. THESE SYSTEMS WILL BE COLDER SINCE
THE BULK OF THE COOLING WILL OCCUR WITH THE PASSAGE OF THE FIRST
SYSTEM AND MORE LIKELY TO RESULT IN VALLEY RAIN/MOUNTAIN SNOW. MY
CONFIDENCE THAT WE WILL SEE THESE FOLLOW-UP SYSTEMS IS HIGH, BUT
THE STRENGTH AND TIMING OF THESE FEATURES REMAINS IN QUESTION
WITH LOTS OF VARIANCE BETWEEN ENSEMBLE MEMBERS. IN ANY EVENT, THIS
SCENARIO MATCHES UP WELL WITH THE 6-10 DAY CPC OUTLOOK THAT
ADVERTISES BELOW NORMAL TEMPERATURES WITH A 60% CHANCE FOR ABOVE
NORMAL PRECIPITATION.
AVIATION
VALID THROUGH 15/12Z. SKC TO SCT CLOUDS 20-25K FT AGL.
SFC WINDS LIGHT AND TERRAIN DRIVEN LESS THAN 12 KTS THROUGH 14/19Z,
THEN GENERALLY WEST TO NORTHWEST LESS THAN 12 KTS. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
WARM AND DRY TODAY WITH LIGHT TERRAIN DRIVEN
WINDS UNDER 12 MPH. A LOW PRESSURE SYSTEM WILL BEGIN TO SLOWLY
MOVE INTO THE AREA FROM THE WEST SATURDAY AND ESPECIALLY SUNDAY
RESULTING IN COOLER TEMPERATURES, BREEZY SOUTHWEST WINDS AND
CHANCES FOR LIGHT SHOWERS. SHOWER CHANCES MAY ARRIVE AS EARLY AS
SATURDAY FOR AREAS WEST OF TUCSON, BUT GREATER CHANCES WILL BE
DELAYED ELSEWHERE UNTIL SUNDAY. MINIMUM RH VALUES 15-25 IN THE
VALLEYS AND 22-35 PERCENT IN THE MOUNATINS TODAY WILL INCREASE
SATURDAY AND ESPECIALLY SUNDAY TO 35-45 PERCENT IN THE VALLEYS
AND 50-65 PERCENT IN THE MOUNTAINS.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
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