Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 312136
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
235 PM MST SAT JAN 31 2015

.SYNOPSIS...A STORM SYSTEM CONTINUED TO BRING VALLEY RAIN AND
MOUNTAINTOP SNOW THIS AFTERNOON...BUT THIS ACTIVITY WILL DIMINISH
THIS EVENING AND TONIGHT. MINOR FLOODING AND ELEVATED FLOWS IN
WASHES AND STREAMS WILL REMAIN A CONCERN THROUGH TONIGHT. THE MOST
SIGNIFICANT SNOWFALL WILL BE ACROSS THE HIGHEST PEAKS...ABOVE 7500
FEET. EXPECT MUCH COOLER DAYTIME TEMPERATURES THIS WEEKEND. DRY
CONDITIONS WITH A WARMING TREND WILL THEN OCCUR DURING THE UPCOMING
WEEK.

&&

.DISCUSSION...A STORM SYSTEM TRACKING SOUTHEAST OVER NORTHERN BAJA
INTO NORTHWEST MEXICO WILL CONTINUE TO BRING PERIODS OF RAIN AND
HIGH ELEVATION SNOW TO SOUTHEAST ARIZONA THROUGH EARLY SUNDAY.
LATEST MODELS SUGGESTED THAT MUCH OF THIS PRECIPITATION WILL BE
DIMINISHING THIS EVENING INTO TONIGHT AS THE SYSTEM TRACKS FARTHER
SOUTHEAST OF THE AREA. THE HRRR SOLUTIONS INDICATE THAT THE
CONVECTIVE SHOWERS DEVELOPING EARLY THIS AFTERNOON WILL DISSIPATE
RAPIDLY AFTER SUNDOWN. THAT SAID...WILL KEEP RATHER HIGH POP VALUES
AND THE WINTER STORM WARNING GOING...THEN TAPER OFF POP VALUES AFTER
03Z SUNDAY THROUGH 12Z SUNDAY.

THE MAIN CONCERN WILL SHIFT FROM HEAVY MOUNTAINTOP SNOWFALL AND
ELEVATED FLOWS IN NORMALLY DRY WASHES AND STREAMS TO DEVELOPING FOG
LATER TONIGHT AND SUNDAY MORNING. DENSE FOG WAS REPORTED THIS
MORNING IN SPOTS...ESPECIALLY AROUND CASA GRANDE WHERE THE
VISIBILITY DROPPED TO 1/4 OF A MILE AT TIMES. A REPEAT OF THIS FOG
WILL LIKELY BE MORE WIDESPREAD TONIGHT AS SKIES BEGIN TO CLEAR FROM
NORTHWEST TO SOUTHEAST ACROSS THE AREA. NOT SURE HOW DENSE OR WHERE
THE FOG WILL BE AT THIS TIME...SO WILL NOT POST AN ADVISORY ON THE
AFTERNOON FORECAST PACKAGE.

MODELS TRACK THE STORM SYSTEM WELL SOUTH OF THE REGION BY SUNDAY
AFTERNOON WITH A RIDGE OF HIGH PRESSURE BUILDING INTO THE
SOUTHWESTERN UNITED STATES BEHIND IT. THE MEDIUM RANGE MODELS KEEP
THE STORM TRACK NORTH OF THE REGION THIS COMING WEEK. THAT
SAID...THE FORECAST WILL CALL FOR DRY CONDITIONS ALONG WITH A
WARMING TREND. HIGH TEMPERATURES WILL PEAK ABOUT 8 TO 10 DEGREES
ABOVE NORMAL BY THE MIDDLE OF THIS COMING WEEK. FOR TUCSON...THE
NORMAL HIGH THIS TIME OF YEAR IS AROUND 68 DEGREES.

&&

.AVIATION...VALID THRU 02/00Z.
PERIODS OF VALLEY RAIN AND HIGH ELEVATION MOUNTAIN SNOW ABOVE 7K FT
AGL WILL CONTINUE INTO THIS EVENING...BEFORE TAPERING OFF OVERNIGHT
INTO SUNDAY MORNING FROM NORTHWEST TO SOUTHEAST. THERE IS A SLIGHT
CHANCE OF -TSRA ACROSS MUCH OF THE AREA THIS AFTERNOON INTO EARLY
EVENING. CLOUD DECKS OF 2-3K FT AGL ARE LIKELY IN SHOWERS AND
THUNDERSTORMS. OUTSIDE OF PRECIPITATION...EXPECT BKN-OVC CLOUDS AT
3-6K FT AGL. WINDS WILL MAINLY BE LESS THAN 10 KTS. DEPENDING ON
CLOUD COVERAGE LATE TONIGHT...COULD SEE SOME PATCHY FOG BUT
CONFIDENCE TOO LOW TO INCLUDE IN TERMINAL FORECASTS.
OTHERWISE...IMPROVING CONDITIONS SUNDAY WITH DIMINISHING CLOUD
COVERAGE. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT PERIODS OF VALLEY RAIN AND MOUNTAIN SNOW INTO
THIS EVENING ALONG WITH WITH A FEW RUMBLES OF THUNDER AS A LOW
PRESSURE SYSTEM MOVES ACROSS THE AREA. A FEW LINGERING SHOWERS WILL
OCCUR MAINLY EAST TO SOUTH OF TUCSON EARLY SUNDAY. DRY CONDITIONS
WILL RETURN SUNDAY AFTERNOON AND LAST THROUGH THE UPCOMING WORK
WEEK. 20-FT WINDS THIS AFTERNOON WILL GENERALLY BE ELY-SLY AT 5-15
MPH. SOME EASTERLY WINDS ARE EXPECTED THURSDAY NIGHT INTO FRIDAY
WITH A FEW HIGHER GUSTS POSSIBLE. OTHERWISE...TYPICAL DIURNAL WIND
TRENDS FOR MUCH OF THE UPCOMING WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
     WINTER STORM WARNING UNTIL 5 PM MST TODAY FOR AZZ510>512-514.

&&

$$

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