229
FXUS65 KTWC 060940
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 AM MST TUE JAN 6 2026
SYNOPSIS
MILD TEMPERATURES TODAY WITH HIGH-CLOUDS THICKENING
THROUGH THE DAY. A LOW PRESSURE SYSTEM IS THEN EXPECTED TO MOVE
ACROSS SOUTHEAST ARIZONA WEDNESDAY RESULTING IN NUMEROUS VALLEY
RAIN AND HIGH-ELEVATION SNOW SHOWERS, FOLLOWED BY YET ANOTHER
COOLER WEATHER SYSTEM THURSDAY RESULTING IN SCATTERED VALLEY RAIN
AND MOUNTAIN SNOW. THIS SECOND SYSTEM WILL ALSO USHER IN
UNSEASONABLY COOL TEMPERATURES TO THE AREA, WITH A CHANCE FOR
FREEZING MORNING LOW TEMPERATURES ACROSS THE TUCSON METRO AREA
FRIDAY AND SATURDAY MORNINGS.
DISCUSSION
THE UPPER PATTERN THIS MORNING IS DEFINED BY HIGH
AMPLITUDE TROUGH OF LOW PRESSURE EXTENDING FROM NRN CALIFORNIA
TOWARD THE SSW, WITH A LOW CENTERED NEAR 34N/126W IN THE EASTERN
PACIFIC. THE LATEST GOES-W PRECIPITABLE WATER IMAGERY INDICATED A
DEEP PLUME OF SUB-TROPICAL MOISTURE WITH PWATS IN EXCESS OF 1.50
INCHES NEAR 22N/122W TO THE SSE OF THE UPPER TROUGH.
ANOTHER UPPER LOW IN THE GULF OF ALASKA THIS MORNING WILL RAPIDLY
DIVE SSE INTO THE MEAN TROUGH ALONG THE WEST COAST TODAY, WHICH
SHOULD FORCE THE TROUGH ALONG THE CALIFORNIA COAST TO INITIALLY
DIVE DOWN TOWARD THE NORTHERN BAJA TODAY, THEN EJECT EAST ACROSS
NORTHERN SONORA MEXICO AND SOUTHERN ARIZONA DURING THE DAY
WEDNESDAY. THE DEEP PLUME OF MOISTURE TO ITS SSE WILL SHIFT NE
INTO SOUTHEAST ARIZONA AHEAD OF THIS SYSTEM BEGINNING WEDNESDAY
MORNING. THE 06/00Z GEFS AND ECMWF RUNS INDICATE THIS PLUME WILL
GENERALLY BE BETWEEN 200-300 PERCENT OF NORMAL FOR THIS TIME OF
YEAR, WHICH SHOULD HELP IT PRIME THE PUMP FOR THE UPPER TROUGH
AXIS TO TRACK ACROSS OUR NECK OF THE WOODS WEDNESDAY AFTERNOON AND
EVENING. MODERATE MID-TO-UPPER LEVEL DEFORMATION IN THE FLOW ALOFT
AHEAD OF THE TROUGH AXIS WILL RESULT IN DECENT LIFT, ESPECIALLY
IN THE DENDRITIC GROWTH ZONE IN THE LATE AFTERNOON AND EARLY
EVENING HOURS. THIS SHOULD INCREASE THE OVERALL PRECIPITATION
EFFICIENCY OF THE SYSTEM. EXPECT THIS SYSTEM TO PRODUCE LIGHT-
MODERATE INTENSITY PRECIPITATION, WITH THE HEAVIEST QPF OCCURING
DURING WEDNESDAY AFTERNOON/EVENING.
OVERALL QPF AMOUNTS CONTINUE TO TICK UPWARDS AS MODELS CONTINUE
TO LATCH ON TO THE DEEPER PLUME OF MOISTURE. THIS FIRST SYSTEM
SHOULD PRODUCE BETWEEN 0.33-0.75 INCHES IN THE VALLEYS, WITH 3-6
INCHES OF SNOWFALL ACCUMULATION ABOVE 7500-8000 FEET. DUE TO THE
HIGHER MOISTURE CONTENT OF THE MOISTURE PLUME, SNOWFALL RATIOS
SHOULD BE LOW FOR THIS FIRST SYSTEM MAKING ACCUMULATIONS STRUGGLE.
ESPECIALLY GIVEN THE WET-BULB TEMPERATURES WILL BE AT OR SLIGHTLY
ABOVE FREEZING ABOVE 7000 FEET. THIS FIRST SYSTEM SHOULD ONLY
RESULT IN MINOR WEATHER IMPACTS TO SOUTHEAST ARIZONA, WITH POCKETS
OF MODERATE RAINFALL IN THE VALLEYS...RESULTING IN LOCALIZED
PONDING OF WATER IN ROADWAY DIPS AND OTHER LOW-LYING AREAS.
THAT SECOND UPPER-LOW RESPONSIBLE FOR KICKING THIS FIRST FEATURE
ACROSS US WEDNESDAY CONTINUES TO DIVE THROUGH THE GREAT BASIN
WEDNESDAY NIGHT AND EVENTUALLY INTO ARIZONA THURSDAY. THIS SYSTEM
IS MUCH COLDER, BUT ARRIVES A LITTLE TOO LATE TO WORK WITH THE
AVAILABLE MOISTURE FOR THE FIRST SYSTEM. IT WILL, HOWEVER, BE COLD
ENOUGH TO WRING OUT THE RESIDUAL MOISTURE...ENOUGH TO SUPPORT
SCATTERED VALLEY RAIN AND MOUNTAIN SNOW THURSDAY. THE BEST MID-
UPPER LEVEL LIFT IS EXPECTED TO MOVE ACROSS THE NORTHERN PORTIONS
OF GRAHAM AND GREENLEE COUNTY THURSDAY EVENING. THIS WILL BRING
ANOTHER 3-6 INCHES OF SNOWFALL ABOVE 6000 FEET, ESPECIALLY ACROSS
THE PINALENO AND WHITE MOUNTAINS. THIS WOULD RESULT IN THE HIGHEST
ELEVATIONS RECEIVING 6-12 INCHES OF STORM-TOTAL SNOW OVER THE 48
HOUR PERIOD. WE WILL HAVE TO KEEP A CLOSER EYE ON THE FORECAST
SNOWFALL AMOUNTS WITH FUTURE MODEL RUNS AS THESE AMOUNTS MAY
NECESSITATE WINTER WEATHER HEADLINES ABOVE 7000 FEET.
OTHERWISE, COLD AIR IN THE WAKE OF THIS SECOND SYSTEM WILL USHER
IN UNSEASONABLY COOL MORNING LOW TEMPERATURES TO THE AREA, WITH
FREEZING TEMPERATURES ACROSS THE VALLEYS FROM TUCSON EAST FRIDAY
AND SATURDAY MORNINGS. THE 06/05Z NBM PROBABILITY FOR MINIMUM
TEMPERATURES AT THE TUCSON INTERNATIONAL AIRPORT (KTUS) AT OR
BELOW FREEZING (32 DEGREE F) IS 21% FRIDAY MORNING, INCREASING
TO 58% SATURDAY MORNING. OTHERWISE, AFTERNOON TEMPERATURES ARE
FORECAST TO FALL BELOW NORMAL WILL THIS SYSTEM THURSDAY INTO THE
WEEKEND.
AVIATION
VALID THROUGH 07/12Z. SCT-BKN CIRRUS AOA 20K FT AGL
THRU 07/00Z THIS AFTERNOON, THEN FEW-SCT CLOUDS 12-15K FT AGL
BKN-OVC 20K FT AGL THIS EVENING THROUGH THE FORECAST PERIOD.
SFC WINDS LESS THAN 10 KTS AND TERRAIN DRIVEN THROUGH 06/18Z,
THEN WLY 10-12 KTS DURING THE AFTERNOON. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
MILD TEMPERATURES TODAY WITH HIGH-CLOUDS
THICKENING THROUGH THE DAY. A LOW PRESSURE SYSTEM IS THEN
EXPECTED TO MOVE ACROSS SOUTHEAST ARIZONA WEDNESDAY RESULTING IN
NUMEROUS VALLEY RAIN AND HIGH-ELEVATION SNOW SHOWERS. THESE STORMS
WILL BRING LIGHT-TO-MODERATE INTENSITY PRECIPITATION, WITH WINDS
GUSTING TO 30-35 MPH WITH THE STRONGER STORMS. ANOTHER COOLER
WEATHER SYSTEM WILL MOVE ACROSS THE AREA THURSDAY, RESULTING IN
SCATTERED VALLEY RAIN AND MOUNTAIN SNOW. THIS SECOND SYSTEM WILL
ALSO USHER IN UNSEASONABLY COOL MORNING LOW TEMPERATURES TO THE
AREA, WITH FREEZING TEMPERATURES ACROSS THE VALLEYS FROM TUCSON
EAST FRIDAY AND SATURDAY MORNINGS. OTHERWISE, AFTERNOON
TEMPERATURES ARE FORECAST TO FALL BELOW NORMAL WILL THIS SYSTEM
THURSDAY INTO THE WEEKEND. MINIMUM RHS BETWEEN 25-35 PCT IN THE
VALLEYS AND 35-45 PCT IN THE MOUNATINS TODAY, INCREASING TO 50-60
PCT VALLEYS AND 70-80 PCT MOUNATINS WEDNESDAY AND THURSDAY, BEFORE
LOWERING AGAIN FRIDAY INTO THE WEEKEND.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
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