721
FXUS65 KTWC 080927
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
227 AM MST THU JAN 8 2026
SYNOPSIS
A WINTER WEATHER SYSTEM WILL MOVE ACROSS SOUTHEAST
ARIZONA TODAY RESULTING IN ANOTHER ROUND OF VALLEY RAIN AND
MOUNTAIN SNOW SHOWERS...THIS TIME WITH EMBEDDED THUNDERSTORMS
POSSIBLE. THE BEST CHANCE FOR STORMS WILL OCCUR WITH THE PASSAGE
OF A COLD FRONT MOVING FROM THE NORTHWEST TO THE SOUTHEAST DURING
THE AFTERNOON INTO THE EVENING. COLD AIR ASSOCIATED WITH THIS
SYSTEM WILL USHER IN UNSEASONABLY COOL TEMPERATURES TO THE AREA,
WITH FREEZING MORNING LOW TEMPERATURES POSSIBLE ACROSS THE TUCSON
METRO AREA FRIDAY AND SATURDAY MORNINGS.
KEY MESSAGES
THE SECOND WINTER WEATHER SYSTEM WILL IMPACT SOUTHEAST ARIZONA
TODAY, WITH A STRONG COLD FRONT MOVING FROM THE NORTHWEST TO THE
SOUTHEAST THIS AFTERNOON INTO THIS EVENING.
1. WINTER WEATHER ADVISORIES:
A WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR THE MOUNTAINOUS
AREAS INCLUDING THE WHITE MOUNTAINS, GALIURO, PINALENO, CATALINA,
AND RINCON MOUNTAINS THROUGH 11 PM MST THIS EVENING.
2. MOUNTAIN SNOW ACCUMULATIONS:
ALTHOUGH SNOWFALL WILL OCCUR THIS MORNING IN BETWEEN THE TWO
WINTER STORM SYSTEMS, THE HEAVIER SNOWFALL WILL OCCUR DURING THE
AFTERNOON AND EARLY EVENING HOURS. SNOW LEVELS WILL START OFF
BETWEEN 6500-7000 FEET THIS MORNING, LOWERING TO 6000 FEET THIS
AFTERNOON, THEN RAPIDLY LOWERING TO 4500-5000 FEET THIS EVENING.
THIS SYSTEM IS COLDER AND WILL BE MORE EFFICIENT IN PRODUCING
SNOWFALL. EXPECT AN ADDITIONAL 4 TO 8 INCHES OF SNOWFALL ABOVE
6000 FEET. LOCALLY HIGHER AMOUNTS UP TO 10 INCHES MAY ACCOMPANY
THUNDERSTORMS THAT DEVELOP.
3. VALLEY RAINFALL:
WIDESPREAD RAIN SHOWERS FOR THE VALLEYS OF SOUTHEAST ARIZONA THIS
AFTERNOON AND THIS EVENING. THE HEAVIEST (MODERATE-INTENSITY)
RAINFALL WILL ALONG THE COLD FRONT PASSAGE LATE THIS AFTERNOON
INTO THE EARLY EVENING, ESPECIALLY NEAR THUNDERSTORMS. RAINFALL
AMOUNTS TODAY WILL BE LESS THAN WHAT WE EXPERIENCED WEDNESDAY
ACROSS THE AREA...GENERALLY BETWEEN 0.10 AND 0.33 INCHES. GIVEN
THE SATURATED SOILS FROM THE RAINFALL WEDNESDAY, THIS RAINFALL
RUNOFF MAY STILL RESULT IN SIGNIFICANT PONDING OF WATER IN
NORMALLY DRY WASHES, ROADWAY DIPS AND OTHER LOW-LYING AREAS.
4. STRONG AND GUSTY WINDS:
A STRONG COLD FRONT MOVING FROM THE NORTHWEST TOWARD THE SOUTHEAST
THIS AFTERNOON INTO THIS EVENING WILL RESULT IN BREEZY SOUTHWEST
TO WEST WINDS 15 TO 25 MPH WITH GUSTS BETWEEN 35-40 MPH.
5. FREEZING TEMPERATURES:
VERY COLD TO FREEZING TEMPERATURES ARE EXPECTED BOTH FRIDAY AND
SATURDAY MORNING FOR THE VALLEYS FROM TUCSON EAST. POTENTIAL FOR
ICY ROADS THURSDAY NIGHT TO FRIDAY MORNING.
DISCUSSION
SOUTHEAST ARIZONA THIS MORNING IS IN BETWEEN TWO
WINTER WEATHER STORM SYSTEMS. THAT FIRST ONE THAT IMPACTED THE
AREA WEDNESDAY WITH DECENT RAINFALL AND HIGH ELEVATION SNOW HAS
SINCE MOVED NE INTO NORTHEAST NEW MEXICO. HOWEVER, AS OF 2 AM MST,
ISOLATED TO SCATTERED LIGHT INSTABILITY SHOWERS STILL PERSIST TO
THE NORTH AND NORTHEAST OF TUCSON.
THE NEXT UPPER-LOW TO IMPACT OUR NECK OF THE WOODS IS CURRENTLY
POSITIONED ALONG THE NORTHERN CALIFORNIA AND NEVADA BORDER. AN
AMPLIFIED RIDGE IN THE EASTERN PACIFIC WILL DRIVE THIS FEATURE
SSE INTO CENTRAL ARIZONA BETWEEN 08/15-18Z THIS MORNING, THEN
THROUGH SOUTHEAST ARIZONA BETWEEN 08/21Z THIS AFTERNOON AND 09/03Z
THIS EVENING. MODEST MID-LEVEL DIVERGENCE/DEFORMATION IN THE FLOW
OUT AHEAD OF THIS SYSTEM, ALONG WITH THE PASSAGE OF A SURFACE COLD
FRONT WILL MAKE THIS SYSTEM A BIT BEEFIER AS IT MOVES THROUGH
TODAY. THESE DYNAMICS, CAPES AROUND 250 J/KG, MODEST MID-LEVEL
SHEAR AND LOWER-LEVEL LCLS WILL ALLOW FOR THUNDERSTORMS WITH SMALL
HAIL TO DEVELOP ALONG THE COLD FRONT AS IT TRACKS THRU THE AREA.
ALTHOUGH THIS SYSTEM IS MUCH COLDER WITH STRONGER DYNAMICS, IT
ARRIVES A LITTLE TOO LATE TO WORK WITH THE AVAILABLE MOISTURE THAT
WE HAD WITH THE FIRST SYSTEM. QPF AMOUNTS FOR THIS SECOND SYSTEM
SHOULD BE AROUND A TENTH TO THIRD INCH IN THE VALLEYS TO 0.75-1.00
INCHES IN THE MOUNATINS. DESPITE THE LOWER QPF AMOUNTS COMPARED TO
THE FIRST SYSTEM, THIS SYSTEM WILL BE MORE EFFICIENT THAN THE
FIRST SYSTEM IN PRODUCING SNOWFALL. EXPECT AN ADDITIONAL 4 TO 8 INCHES
OF SNOW TODAY ABOVE 6000 FEET. LOCALLY HIGHER AMOUNTS UP TO 10
INCHES MAY ACCOMPANY THUNDERSTORMS THAT DEVELOP. WE STILL HAVE A
WINTER WEATHER ADVISORY IN EFFECT FOR THE MOUNTAINOUS AREAS
INCLUDING THE WHITE MOUNTAINS, GALIURO, PINALENO, CATALINA, AND
RINCON MOUNTAINS THROUGH 11 PM MST THURSDAY EVENING.
THE ONE THING WE HAVEN'T BEEN ADVERTISING ARE THE BREEZY SOUTHWEST
TO WEST WINDS BETWEEN 15-25 MPH WITH GUSTS TO 35-40 MPH ALONG AND
NEAR THE COLD FRONT AS IT TRACKS THROUGH THIS AFTERNOON. THE
STRONGEST WINDS WON'T PERSIST THE ENTIRE DAY, BUT CAN BE PROBLEMATIC
FOR SEVERAL HOURS BEGINNING LATE THIS AFTERNOON INTO THE EARLY
EVENING.
THE COLD AIRMASS 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 08/08Z NBM PROBABILITY FOR MINIMUM
TEMPERATURES AT THE TUCSON INTERNATIONAL AIRPORT (KTUS) AT OR
BELOW FREEZING (32 DEGREE F) IS 39% FRIDAY MORNING, INCREASING TO
86% SATURDAY MORNING (WITH A 23% PROBABILITY OF A HARD FREEZE).
THIS MAY NECESSITATE FREEZE HEADLINES WITH THE NEXT FORECAST
PACKAGE.
OTHERWISE, THAT AMPLIFIED RIDGE IN THE EASTERN PACIFIC BEGINS TO
FLOP OVER INTO THE DESERT SOUTHWEST THIS WEEKEND, BECOMING MORE
ESTABLISHED ACROSS THE WEST COAST NEXT WEEK. THIS WILL RESULT IN A
GENERAL WARMING TREND.
AVIATION
VALID THROUGH 09/12Z. SCT-BKN 4-8K FT AGL BKN-OVC
8-10K FT AGL WITH ISOLATED TO SCATTERED VALLEY -SHRA AND
MOUNTAIN -SHSN THROUGH 08/20Z, INCREASING IN COVERAGE TO NUMEROUS
AS A COLD FRONT SWEEPS THROUGH SOUTHEAST FROM THE NORTHWEST TO THE
SOUTHEAST BETWEEN 08/20Z AND 09/06Z. CIGS 2-5K FT AGL DURING THE
LATE AFTERNOON AND EARLY EVENING WITH MTN OBSCURATIONS POSSIBLE. A
FEW EMBEDDED -TSRA WILL BE POSSIBLE NEAR THE COLD FRONT. SFC
WINDS SLY/SWLY 10-12 KTS THIS MORNING...INCREASING TO SWLY/WLY
18-22 KTS WITH GUSTS TO 30-35 KTS WITH THE PASSAGE OF THE COLD
FRONT THIS AFTERNOON AND EVENING. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.
FIRE WEATHER
A WINTER WEATHER SYSTEM WILL MOVE ACROSS SOUTHEAST
ARIZONA TODAY RESULTING IN ANOTHER ROUND OF VALLEY RAIN AND
MOUNTAIN SNOW SHOWERS...THIS TIME WITH EMBEDDED THUNDERSTORMS
POSSIBLE. THE BEST CHANCE FOR STORMS WILL OCCUR WITH THE PASSAGE
OF A COLD FRONT MOVING FROM THE NORTHWEST TO THE SOUTHEAST DURING
THE AFTERNOON INTO THE EVENING. BREEZY 20-FOOT WINDS FROM THE
SOUTHWEST TO WEST 15-20 MPH WITH GUSTS TO 35-40 MPH WILL BE
POSSIBLE ALONG THE COLD FRONT. THIS SYSTEM WILL BE MORE EFFICIENT
AT PRODUCING ACCUMULATING MOUNTAIN SNOWFALL THAN THE FIRST
SYSTEM. A WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR THE WHITE
MOUNTAINS, CATALINA AND PINALENO MOUNTAINS THROUGH 11 PM MST THIS
EVENING. 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.
MINIMUM RHS TODAY WILL BE BETWEEN 50-60 PCT IN THE VALLEYS AND
75-90 PCT IN THE MOUNATINS, LOWERING TO 25-35 PCT IN THE VALLEYS
AND 35-45 PCT IN THE MOUNTAINS FRIDAY INTO EARLY NEXT WEEK. GUSTY
EAST TO SOUTHEAST WINDS WILL DEVELOP LATE THIS WEEKEND.
TWC WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR AZZ510-
511-514.
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