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000
FXUS65 KTWC 301645
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
945 AM 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 ABOVE 8000 FEET...OR
ACROSS THE HIGHEST PEAKS. EXPECT MUCH COOLER DAYTIME TEMPERATURES
INTO THIS WEEKEND. DRY CONDITIONS WITH A WARMING TREND WILL THEN
OCCUR EARLY NEXT WEEK.

&&

.DISCUSSION...KEMX WSR-88D DETECTED A BAND OF 30-55 DBZ ECHOES JUST
EAST OF THE TUCSON METRO AREA...OR MOSTLY ACROSS WESTERN/CENTRAL
COCHISE COUNTY EXTENDING NWD INTO SRN GRAHAM COUNTY. OTHER MUCH
WEAKER ECHOES WERE WEST OF TUCSON...OR ACROSS THE TOHONO O`ODHAM
NATION AND SRN PINAL COUNTY. MOVEMENT OF THESE ECHOES WAS TO THE NE
AT 20-30 MPH.

THERE HAVE BEEN SOME IMPRESSIVE RAINFALL AMOUNTS THUS FAR...
ESPECIALLY ACROSS THE HIGHER TERRAIN. NEARLY 4.25 INCHES HAS BEEN
OBSERVED AT PARK TANK...OR ON THE NRN PORTION OF THE RINCON MTNS.
ALSO...MOUNT LEMMON HAS MEASURED 3.58 INCHES...AND NRN GREENLEE
COUNTY NORTH OF CLIFTON HAD RECEIVED 2.64 INCHES. FINALLY...ABOUT 2
INCHES OF RAIN HAS FALLEN ACROSS THE DRAGOON MOUNTAINS AND HUACHUCA
MOUNTAINS IN WRN COCHISE COUNTY.

30/12Z KTWC SOUNDING TOTAL PRECIP WATER VALUE OF 1.18 INCHES IS THE
HIGHEST PRECIP WATER VALUE ON RECORD FOR JANUARY...BREAKING THE
PREVIOUS RECORD OF 1.12 INCHES SET ON JANUARY 9, 2009.

UPPER LEVEL TROUGH OVER THE GREAT BASIN/SWRN CONUS WITH 563 DM LOW
CENTERED NEAR SAN DIEGO WILL REMAIN QUASI-STATIONARY INTO SAT. FOR
THE REMAINDER OF TODAY...SEVERAL RUC HRRR SOLUTIONS AS WELL AS RADAR
TRENDS SUGGEST THAT THE MOST SIGNIFICANT RAINFALL WILL OCCUR ACROSS
COCHISE/GREENLEE/GRAHAM COUNTIES EAST OF TUCSON. HOWEVER...THE RUC
HRRR AS WELL AS THE UNIV OF AZ WRF-NAM AND WRF-GFS SOLUTIONS
INDICATE THAT ADDITIONAL SHOWERS WILL DEVELOP DURING THE NEXT
SEVERAL HOURS WEST TO SOUTHWEST OF TUCSON. THIS ACTIVITY THEN HOLDS
THE POTENTIAL TO PRODUCE THUNDERSTORMS GIVEN SUFFICIENT INSTABILITY.
SNOW LEVELS WILL REMAIN QUITE HIGH TODAY...ESSENTIALLY ABOVE 8000
FEET.

ONLY VERY MINOR ADJUSTMENTS WILL BE MADE TO THE INHERITED OFFICIAL
FORECAST. WIDESPREAD VALLEY RAIN WILL OCCUR INTO SAT...WITH
SIGNIFICANT SNOW ACCUMULATIONS LIMITED TO LOCALES ABOVE 8000 FEET.
THE AWIPS PRODUCT PHXWSWTWC /WMO HEADER WWUS45 KTWC/ CONTAINS MORE
INFORMATION. PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER
DETAIL.

&&

.AVIATION...VALID THRU 31/18Z.
WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW WILL OCCUR INTO SATURDAY
MORNING AS LOW PRESSURE SYSTEM MOVES OVER THE AREA. THERE IS A
SLIGHT CHANCE OF THUNDERSTORMS ACROSS MUCH OF THE AREA THIS
AFTERNOON. CLOUD DECKS OUTSIDE OF PRECIPITATION WILL GENERALLY BE
4-8K FT AGL. HOWEVER...WIDESPREAD MVFR CONDITIONS AND LOCAL IFR
CONDITIONS MAINLY FROM LOW CEILINGS WILL OCCUR DUE TO SHOWERS.
SURFACE WIND INTO SATURDAY MORNING WILL GENERALLY BE ELY/SELY AT
5-15 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW
TODAY THROUGH SATURDAY WITH A STRAY LIGHTNING STRIKE OR TWO NOT OUT
OF THE QUESTION. THE MOST SIGNIFICANT SNOWFALL 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 OCCUR MAINLY EAST TO SOUTH OF TUCSON SUNDAY WITH DRY CONDITIONS
EXPECTED AREA-WIDE EARLY NEXT WEEK. 20-FOOT WINDS INTO SATURDAY
MORNING WILL GENERALLY BE FROM THE EAST TO SOUTHEAST AT 5-15 MPH.
EXPECT DIURNAL WIND TRENDS TO RESUME THIS WEEKEND THROUGH EARLY NEXT
WEEK.

&&

.PREV DISCUSSION...SURFACE HIGH OVER THE GREAT PLAINS HAS SETTLED IN
A LITTLE FURTHER EAST THAN PREVIOUSLY PROGGED...WHICH HAS LIMITED
THE TIGHTENING OF THE PRESSURE GRADIENT OUT EAST. THAT BEING SAID...
OVER THE LAST SEVERAL HOURS THE AREA HAS SEEN SOME TIGHTENING OF THE
GRADIENT AND IT/S RESULTANT WIND INCREASE. THESE WINDS SHOULD STAY
PRESENT THROUGH THE AFTERNOON WHEN THE GRADIENT RELAXES.

UPPER TROUGH/LOW CENTERED NEAR SOUTHERN CALIFORNIA THIS MORNING
WILL CONTINUE TO DEEPEN AS IT MOVES ONSHORE TODAY. THIS WILL KEEP
A STEADY STREAM OF MOISTURE MOVING INTO THE AREA TODAY AND
TOMORROW. TOMORROW AFTERNOON THE LOW WILL BEGIN TO SLIDE SOUTHEAST
WHICH WILL SHUT THIS MOISTURE TAP OFF...THOUGH THERE WILL BE
ENOUGH REMNANT MOISTURE IN PLACE FOR CONTINUAL SHOWERS ACROSS THE
AREA THROUGH THE EVENING HOURS. THEN THE AREA SHOULD SEE SOME
DISSIPATION FROM NORTHWEST TO SOUTHEAST/EAST THROUGH SUNDAY EARLY
EVENING.

FOR THIS MORNING GUIDANCE HAS SHOWN A LITTLE MORE WARM AIR ADVECTION
THAN PREVIOUSLY PROGGED...WHICH THE 00Z SOUNDING SUPPORTS.
THEREFORE...HAVE UPPED SNOW LEVELS SOME THOUGH THIS REALLY DIDN/T
IMPACT THE SNOW ACCUMULATIONS THAT MUCH. IT STILL LOOKS LIKE SNOW
LEVELS WILL BEGIN TO LOWER TO ABOUT 8500 FEET THIS AFTERNOON...8000
FEET BY THIS EVENING...AND 7000 FEET BY SATURDAY MORNING.

THOUGH THIS STORM WILL CONTINUALLY BRING WIDESPREAD RAIN/SNOW TO THE
AREA...ONE CONCERN IS THE DRY SLOT PROGGED FOR THIS MORNING AND
EARLY AFTERNOON ACROSS THE CENTRAL ZONES. THIS COULD IMPACT QPF
VALUES THOUGH DIDN/T HAVE THE CONFIDENCE TO LOWER THEM TOO MUCH AS
INSTABILITY INCREASES DURING THIS TIME FRAME AS WELL. LATEST HRRR
SOLUTION DOES SHOW A LULL IN SHOWER ACTIVITY OUT WEST DURING THIS
TIME...THOUGH THIS IS MAINLY IN COVERAGE. THE IMPACT OF THE DRY SLOT
WILL LESSEN THROUGHOUT THE DAY AND ESPECIALLY DURING THE OVERNIGHT AS
THE LOW WOBBLES SOUTHEAST SOME. THIS WILL ALSO DECREASE THE
EFFICIENCY OF THESE SHOWERS DURING THE DAY SATURDAY.

GENERALLY SPEAKING HAVE CONTINUED THE QPF/SNOW TOTALS ADVERTISED
THE LAST COUPLE OF DAYS...AS WELL AS TIMING. THE ONE EXCEPTION IS
AN INCREASE OVER MT GRAHAM TO ACCOUNT FOR TODAY/S EXPECTED
CONVECTIVE ENHANCEMENT.

&&

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

    WINTER STORM WARNING FROM 11 AM THIS MORNING TO NOON MST
    SATURDAY FOR AZZ514 ABOVE 7000 FEET.

&&

$$

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DISCUSSION...FRANCIS
PREVIOUS DISCUSSION...MEADOWS
AVIATION/FIRE WEATHER...FRENCH