Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 310445
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
945 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...WIDESPREAD RAIN EVENT TODAY ACROSS SOUTHEAST ARIZONA
WITH VALLEY RAINFALL TOTALS RANGING WIDELY FROM 0.25" TO 2.50" WHILE
IN THE MOUNTAINS TOTALS RANGED FROM 2"-5" WITH LOCALIZED SPOTS
AROUND 6". SNOW LEVELS HAVE BEEN SLOWLY FALLING WITH THE WHITES
FIRST SEEING ACCUMULATING SNOW TODAY. PER LATEST SNOTEL REPORT FROM
HANNAGAN MEADOW BETWEEN 15"-17" HAS FALLEN THERE. SNOW STARTED AT MT
GRAHAM ABOUT 6 PM AND BASED ON CAMERA UP TO 2" HAS OCCURRED SO FAR
THERE. TEMPERATURE AT MT LEMMON WAS BOUNCING BETWEEN 34 AND 36
DEGREES.

AS OF 9 PM DOPPLER RADAR SHOWED SHOWER ACTIVITY ACROSS THE EASTERN
2/3RDS OF THE FORECAST AREA. WATER VAPOR IMAGERY THIS EVENING SHOWED
TWO UPPER LEVEL CENTERS...ONE NEAR LAS VEGAS WITH THE SECOND ONE OFF
NRN BAJA COAST. ISOLATED THUNDERSTORMS THAT DEVELOPED OVER CENTRAL
BAJA MOVED ACROSS THE GULF OF CALIFORNIA AND HAVE MOVED INLAND SOUTH
OF HERMOSILLO. AS THIS SECOND LOW MOVES INTO CENTRAL BAJA OVERNIGHT
THE DEFORMATION ZONE INCREASES ACROSS SONORA MEXICO AND LIFTS NORTH
INTO PIMA/SANTA CRUZ AND COCHISE COUNTIES. WITH THE SNOW LEVEL
LOWERING ACROSS THE SOUTHERN MOUNTAINS I HAVE DECIDED TO ADD THEM
INTO THE WINTER STORM WARNING. POPS AND QPF VALUES HAVE ALSO BEEN
INCREASED OVERNIGHT INTO SATURDAY MORNING. UPDATE OUT SHORTLY. MY
CHANGES TO QPF VALUES STILL MAY NOT BE HIGH ENOUGH. TO ADD SOME
UNCERTAINTY IS THAT THE FEATURE UP NEAR LAS VEGAS WILL DROP SOUTH
ALONG THE COLORADO RIVER BRINGING ADDED LIFT INTO THE WESTERN AREAS.

ALL OF THIS RAIN THAT HAS OCCURRED HAS CAUSED SOME RISES IN
WASHES...CREEKS AND RIVERS AND FURTHER RISES EXPECTED OVERNIGHT INTO
SATURDAY. WILL HAVE TO KEEP WATCH OF LEVELS NEXT 24 HOURS.

&&

.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.
  WINTER STORM WARNING FROM MIDNIGHT SATURDAY UNTIL NOON SATURDAY
   FOR AZZ512-513 ABOVE 8000 FEET.

&&

$$

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