662
FXUS65 KTWC 052128
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
228 PM MST MON JAN 5 2026
SYNOPSIS
MILD TEMPERATURES CONTINUE THROUGH TUESDAY WITH PARTLY CLOUDY
SKIES. A LOW PRESSURE SYSTEM IS EXPECTED TO CROSS THE REGION
WEDNESDAY AND THURSDAY, BRINGING INCREASING CHANCES FOR RAIN AND
MOUNTAIN SNOW. UNSEASONABLY COOL TEMPERATURES WILL LIKELY ARRIVE
THURSDAY INTO THE WEEKEND.
DISCUSSION
WATER VAPOR IMAGERY THIS AFTERNOON DEPICTED AN ACTIVE EASTERN
PACIFIC WITH DEEP TROUGHING AND AN EMBEDDED SHORTWAVE OFF THE
NORTHERN CALIFORNIA COAST. SOUTHWEST FLOW FROM THIS EASTERN
PACIFIC TROUGHING WILL CONTINUE TO STREAM HIGH LEVEL CLOUDS OVER
THE DESERT SOUTHWEST AND KEEP HIGH TEMPERATURES NEAR TO JUST ABOVE
NORMAL THROUGH TUESDAY.
WHILE THE AFOREMENTIONED SHORTWAVE WILL INITIALLY CLOSE AND STALL
OFF THE SOUTHERN CALIFORNIA COAST, IT IS EXPECTED TO OPEN BACK UP
AND CROSS NORTHERN MEXICO AND FAR SOUTHERN ARIZONA THROUGH THE
DAY WEDNESDAY. WITH MUCH OF SOUTHEASTERN ARIZONA SITTING UNDER THE
LEFT EXIT REGION OF THE ASSOCIATED JET STREAK WITHIN THIS WAVE,
PRECIPITATION CHANCES WILL INCREASE WEDNESDAY AS THIS WAVE
PASSES. THIS WAVE SHOULD BE ON ITS WAY OUT EARLY THURSDAY WITH
GREATEST RAIN AND MOUNTAIN SNOW CHANCES COMING LATER IN THE DAY
WEDNESDAY THROUGH THURSDAY MORNING. SNOW LEVELS WILL MOSTLY SIT
ABOVE 7000 FEET WITH THIS PACIFIC WAVE THROUGH EARLY THURSDAY
MORNING, WITH SNOW ACCUMULATIONS OF 2 TO 5 INCHES AND VALLEY RAIN
RANGING FROM 0.25 TO 0.75 INCHES. THESE PRECIPITATION FORECASTS
COME JUST FROM THIS PACIFIC WAVE HOWEVER, WHILE THE POSSIBILITY
OF A SECOND (AND COLDER) WAVE ORIGINATING FROM THE NORTHWEST ON
THURSDAY REMAINS. THERE IS A SPECTRUM OF POSSIBILITIES WITH HOW
DEEP THIS WAVE BECOMES, BRINGING FORECAST AND IMPACT UNCERTAINTY.
A DEEPER SOLUTION (SUCH AS THE 12Z ECMWF DETERMINISTIC AND MANY
OF ITS ENSEMBLE MEMBERS SHOW) WOULD BRING ADDITIONAL MOUNTAIN SNOW
AND LOWER SNOW LEVELS, POTENTIALLY NECESSITATING AN ADVISORY WITH
MOUNTAIN TOPS CLEARING AT LEAST 6 INCHES OF ACCUMULATION. GEFS
AND GEPS ENSEMBLES HOWEVER FAVOR A SHALLOWER SOLUTION WITH LESS OF
A COLD PUSH AND LESS PRECIPITATION. WRAPPING THIS UP THE CURRENT MESSAGE
REMAINS: INCREASING CHANCES FOR LOWER ELEVATION RAIN WEDNESDAY
THROUGH THURSDAY WITH ACCUMULATING SNOW ABOVE 7000 FEET LIKELY.
SNOW ACCUMULATIONS CURRENTLY RANGE FROM 2 TO 5 INCHES, MAINLY ON
MOUNTAIN TOPS FROM TUCSON NORTHEASTWARD THROUGH MOUNT GRAHAM AND
THE WHITE MOUNTAINS. THERE IS LOWER CONFIDENCE BUT A DISTINCT
POSSIBILITY OF A SECOND PUSH OF MOUNTAIN SNOW THURSDAY, WHICH MAY
NECESSITATE ADVISORIES.
COLD MORNING LOWS FOLLOWING THIS SERIES OF LOW PRESSURE WAVES ARE
LIKELY TO FOLLOW BEGINNING FRIDAY MORNING. A HARD FREEZE IS LIKELY
IN THE HISTORICALLY COOLER EASTERN VALLEYS, WHILE FURTHER WEST THE
TUCSON METRO MAY SEE ITS FIRST REAL RUN AT FREEZING MORNING LOWS.
LOWS IN THE 30S FRIDAY THROUGH SUNDAY MORNINGS ARE LIKELY IN THE
TUCSON METRO, WHILE THE POSSIBILITY OF SUB-FREEZING MORNING LOWS
WILL DEPEND ON THE DEPTH OF THE PREVIOUSLY DISCUSSED SECOND WAVE.
SATURDAY CURRENTLY IS THE MORE LIKELY DAY FOR A FREEZE WITH
NBM PROBABILITIES FOR A SUB-FREEZING MORNING LOW IN THE 30-60
PERCENT RANGE.
AVIATION
VALID THROUGH 07/00Z.
SCT-BKN CIRRUS THROUGH THE FORECAST PERIOD WITH FEW CIRRUS AT
4K-5K FEET THROUGH 06/00Z. SURFACE WINDS LIGHT AND TERRAIN DRIVEN.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
LIGHT WINDS AND MINIMUM RELATIVE HUMIDITIES ABOVE 30 PERCENT
THROUGH TOMORROW. A SYSTEM WILL CROSS THE REGION WEDNESDAY INTO
FRIDAY, BRINGING CHANCES FOR RAIN AND HIGH ELEVATION MOUNTAIN
SNOW ALONG WITH INCREASED WINDS ON THURSDAY. TEMPERATURES ARE
FORECAST TO FALL BELOW NORMAL WILL THIS SYSTEM THURSDAY INTO THE
WEEKEND.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
PUBLIC...EDWARDS
AVIATION...EDWARDS
FIRE WEATHER....EDWARDS
VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page