Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 302221
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
320 PM MST FRI JAN 30 2015

.SYNOPSIS...A STORM SYSTEM WILL BRING VALLEY RAIN AND MOUNTAIN SNOW
INTO SATURDAY. MINOR FLOODING WILL OCCUR DUE TO PERIODS OF HEAVY
RAINFALL. THE MOST SIGNIFICANT SNOWFALL WILL BE ACROSS THE HIGHEST
PEAKS. EXPECT MUCH COOLER DAYTIME TEMPERATURES THIS WEEKEND. DRY
CONDITIONS WITH A WARMING TREND WILL THEN OCCUR DURING THE UPCOMING
WEEK.

&&

.DISCUSSION...UPPER LEVEL TROUGH WILL REMAIN QUASI-STATIONARY OVER
THE SWRN CONUS INTO SAT. A SERIES OF IMPULSES ALOFT IN COMBINATION
WITH ABUNDANT MOISTURE WILL MAINTAIN WIDESPREAD SHOWER COVERAGE. A
POTENTIAL PERIOD OF ENHANCED RAINFALL WILL LIKELY OCCUR INTO SAT
MORNING. THIS ENHANCED RAINFALL WILL LEAD TO MINOR FLOODING. THERE
IS ALSO A SLIGHT CHANCE OF THUNDERSTORMS THIS EVENING AND SAT
AFTERNOON DUE TO A WEAK CAPE ENVIRONMENT. SNOW LEVELS LATER THIS
EVENING ARE FORECAST TO ONLY LOWER TO AROUND 8500 FEET...THEN SNOW
LEVELS ARE EXPECTED TO LOWER TO NEAR 7500 FEET BY MIDDAY SATURDAY.

30/12Z GFS/ECMWF WERE IN GOOD AGREEMENT THAT A 559 DM LOW WILL
CONSOLIDATE OVER THE NRN GULF OF CALIFORNIA SAT AFTERNOON. THIS
UPPER LOW WILL THEN FILL AND MOVE SEWD INTO SONORA MEXICO BY EARLY
SUN MORNING. SCATTERED SHOWERS WILL CONTINUE SAT NIGHT FROM TUCSON
EWD/SWD WITH LESSER PRECIP CHANCES NW OF TUCSON. A SLIGHT CHANCE OF
SHOWERS WILL CONTINUE SUN MORNING FROM TUCSON EWD/SWD...AND A SLIGHT
CHANCE OF SHOWERS SUN AFTERNOON WILL BE CONFINED TO LOCALES EAST-TO-
SOUTH OF TUCSON.

DRY CONDITIONS WILL THEN PREVAIL AREA-WIDE SUN NIGHT UNDER NLY FLOW
ALOFT. THEREAFTER...A HIGH PRESSURE RIDGE ADJACENT THE WEST COAST
MON IS PROGGED TO GRADUALLY MOVE EWD INTO THE INTERMOUNTAIN WEST
BY THE LATTER PART OF THE UPCOMING WEEK. THIS PATTERN WILL MAINTAIN
DRY CONDITIONS UNDER CLEAR SKIES OR MOSTLY CLEAR SKIES.

HIGH TEMPS SAT WILL AVERAGE ABOUT 5-10 DEGS F BELOW NORMAL. A
WARMING TREND WILL THEN OCCUR SUN-FRI.

&&

.AVIATION...VALID THRU 01/00Z.
WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW WILL OCCUR INTO SATURDAY AS
A LOW PRESSURE SYSTEM MOVES OVER THE AREA. THERE IS A SLIGHT CHANCE
OF -TSRA ACROSS MUCH OF THE AREA THIS EVENING AND SATURDAY
AFTERNOON. CLOUD DECKS OUTSIDE OF PRECIPITATION WILL GENERALLY BE
4-8K FT AGL. HOWEVER...WIDESPREAD MVFR CONDITIONS AND LOCAL IFR
CONDITIONS WILL OCCUR DUE TO SHOWERS. SURFACE WIND INTO SATURDAY
MORNING WILL GENERALLY BE ELY/SELY AT 5-15 KTS. SURFACE WIND
SATURDAY AFTERNOON WILL BE SLY/SWLY AT 5-15 KTS. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW WILL
CONTINUE INTO SATURDAY AS A STORM SYSTEM MOVES ACROSS THE AREA. THE
MOST SIGNIFICANT SNOWFALL WITH THIS SYSTEM WILL OCCUR ACROSS THE
HIGHEST PEAKS OF THE WHITE MOUNTAINS...MOUNT GRAHAM...AND THE
CATALINA AND RINCON MOUNTAINS NEAR TUCSON. A FEW LINGERING SHOWERS
WILL PREVAIL MAINLY EAST TO SOUTH OF TUCSON SUNDAY...THEN DRY
CONDITIONS WILL RETURN SUNDAY NIGHT AND CONTINUE THROUGH FRIDAY.
20-FOOT WINDS WILL GENERALLY BE LESS THAN 10 MPH THROUGH MIDWEEK.
LOCALLY GUSTY 20-FOOT WINDS MAY OCCUR LATE THURSDAY INTO FRIDAY.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    WINTER STORM WARNING UNTIL NOON MST SATURDAY FOR AZZ510-511-514
    ABOVE 7000 FEET.

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

FRANCIS




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