553
FXUS65 KTWC 201938
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
1238 PM MST SAT DEC 20 2025
SYNOPSIS
DRY AND WARM WEATHER CONTINUES, WITH POTENTIALLY RECORD
BREAKING HIGH TEMPERATURES AT SOME LOCALES INTO EARLY NEXT WEEK. A
PACIFIC SYSTEM APPROACHES DURING THE PERIOD FROM THE MIDDLE TO LATE
NEXT WEEK, BRINGING SOME CHANCES (20-40%) OF LIGHT SHOWERS AND
SLIGHTLY COOLER TEMPERATURES OVER THE HOLIDAYS.
KEY POINTS:
- ABNORAMLLY WARM TEMPERATURES CONTINUE TODAY AND THROUGH MUCH OF
THE FORECAST PERIOD, WITH TEMPERATURES PEAKING MONDAY.
TEMPERATURES SLOWLY TRENDING DOWNWARD BEGINNING TUESDAY WITH
ADDED CLOUD COVER, BUT SHOULD REMAIN ABOVE NORMALS THROUGH AT
LEAST THE END OF THE WEEK (DEC 26).
- PATTERN CHANGE IS ARRIVING TUESDAY, PRIMARILY IN THE FORM OF
CLOUD COVER AND BREEZY WINDS, BUT CANNOT RULE OUT SOME LIGHT
SHOWERS (20- 40%) TUESDAY AFTERNOON INTO WEDNESDAY.
- WE CONTINUE TO KEEP 20-40% RAIN CHANCES IN THE FORECAST LATE
WEDNESDAY/CHRISTMAS EVE INTO NEXT WEEKEND, THOUGH THERE IS UNCERTAINY
IN HOW FAR LIGHT RAIN CHANCES EXTEND INTO SOUTHEASTERN AZ, WITH
SCATTERED LIGHT RAIN SHOWERS POTENTIALLY REMAINING ALONG AND
WEST OF TUCSON OR JUST NORTHWEST OF THE TUCSON METRO.
DISCUSSION
WE WILL CONTINUE TO SEE DRY CONDITIONS AND ABNORMALLY WARM
TEMPERATURES (15-20 DEGREES ABOVE NORMALS) THROUGH MONDAY.
OUR ATTENTION THEN SHIFTS TO A WELCOMED PATTERN CHANGE TUESDAY.
THE BROAD RIDGE CURRENTLY POSITIONED OFF THE NORTHWESTERN COAST OF
MEXICO/BAJA CALIFORNIA, WILL SHIFT EASTWARD AS A VERY LARGE LOW
PRESSURE SYSTEM OFF THE WESTERN CONUS DEVELOPS/DIGS THE FULL
EXTENT OF THE WESTERN COAST. THIS WILL ALLOW A SUBTROPICAL
DISTRUBANCE TO BE BROUGHT UP AHEAD OF THE DEVELOPING SOUTHWEST
FLOW ACROSS SOUTHERN CA/AZ, BRINGING PRIMARILY DEEP MOISTURE AND
BREEZY WINDS WITH IT LATE TUESDAY INTO WEDNESDAY. THE PRESSURE
GRADIENT DOESN'T GET TOO IMPRESSIVE, AND LIKELY WILL ONLY RESULT
IN NOTICEABLY BREEZY WINDS (15-25 MPH). EVEN THOUGH THERE WILL BE
DEEP MOISTURE SURGED INTO SOUTHEASTERN AZ TUESDAY, IT WILL
PRIMARILY MATERIALIZE AS CLOUD COVER, DUE TO THE LITTLE FORCING
ASSOCIATED WITH IT AS IT LIFTS JUST WEST OF OUR AREA. EVEN SO,
EMBEDDED LIGHT SHOWERS (POTENTIALLY NOT PRODUCING MEASURABLE RAIN)
ARE POSSIBLE LATE TUESDAY/WEDNESDAY AS WE WILL BE ON THE FRINGES
OF WEAK LIFT/VORT MAX.
AS THE BROAD UPPER LOW OFF THE WESTERN COAST CONTINUES TO
CONSOLIDATE INTO A CLOSED LOW THROUGH MID/LATE WEEK, SOUTHEAST AZ
WILL REMAIN UNDER WEAK SOUTHWEST FLOW. WITH THE MOISTURE REMAINING
THROUGH LATE WEEK AND THE LACK OF ANY SIGNIFICANT SYNOPTIC LIFT
UNDER THIS REGIME, THE DEEP MOISTURE ACROSS SOUTHEAST AZ WILL
STRUGGLE TO PRODUCE MUCH MORE THAN SCATTERED LIGHT RAIN SHOWERS.
THIS CAN BE REALIZED WHEN LOOKING AT THE PRECIPITATION
PROBABILITIES AS WELL. PROBABILITIES OF RAIN AMOUNTS GREATER THAN
0.25" IN 24 HRS IS ONLY 10-20% LATE CHRISTMAS EVE THROUGH EARLY
NEXT SATURDAY. IF THE BETTER LIFT REMAINS WEST/NORTHWEST OF
TUCSON, AREAS SOUTHEAST WOULD LIKELY JUST SEE MOSTLY CLOUDS, WITH
A FEW SPRINKLES.
WITH THE ADDED CLOUD COVER, TEMPERATURES WILL TEMPER SOME THROUGH
THE HOLIDAY WEEK, BUT WILL REMAIN ABOVE SEASONAL NORMALS AT LEAST
THROUGH END THE OF THE WEEK (DEC 26).
GIVEN THE ORIGINS OF THE MOISTURE BEING SUBTROPICAL, SNOW LEVELS
REMAIN FAIRLY HIGH THROUGHOUT THE WEEK (9K-11K FEET). RESULTING IN
LITTLE TO NO SNOW CONCERNS WITH ANY PRECIPITATION.
BY NEXT WEEKEND, THE UPPER LOW LOOKS TO WEAKEN AS IT DIGS
SOUTHEAST INTO SOUTHERN CA AND INTO AZ. EVEN SO, IT SHOULD BRING
MORE LIFT WITH IT AS IT MORE DIRECTLY ENTERS SOUTHEASTERN AZ LATE
NEXT WEEKEND, POTENTIALLY RESULTING IN BETTER CHANCES FOR
PRECIPITATION, BUT THOSE DETAILS ARE FAR TOO UNCLEAR THIS FAR OUT.
AVIATION
VALID THROUGH 21/00Z.
GENERALLY LIGHT WINDS, REMAINING BELOW 10 KNOTS, WILL FOLLOW
TYPICAL DRAINAGE PATTERNS EXPECTED THROUGH THE WEEKEND. SKIES
MOSTLY CLEAR TO FEW AOA 25 KFT. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
WARM AND DRY CONDITIONS CONTINUE INTO EARLY NEXT
WEEK. HIGHS 15 TO 20 DEGREES ABOVE NORMAL THROUGH MONDAY WITH
GRADUAL COOLING MID TO LATE NEXT WEEK. MINIMUM RELATIVE HUMIDITY
VALUES OF 12-22 PERCENT EACH DAY THROUGH EARLY NEXT WEEK. 20-FOOT
WINDS LESS THAN 15 MPH AND TERRAIN DRIVEN. A PACIFIC SYSTEM
APPROACHES THE MIDDLE OF NEXT WEEK WITH BROAD BRUSHED 20 TO 40
PERCENT SHOWER CHANCES TUESDAY NIGHT INTO FRIDAY WITH INCREASING
MINIMUM HUMIDITY VALUES TO 30 TO 50 PERCENT.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...PETERS
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