Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 300939
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
239 AM MST FRI JAN 30 2015

.SYNOPSIS...A STORM SYSTEM WILL CONTINUE TO BRING VALLEY RAIN AND
MOUNTAIN SNOW INTO SATURDAY. MINOR FLOODING MAY 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 FRIDAY INTO THIS WEEKEND. DRY CONDITIONS WITH
A WARMING TREND WILL THEN OCCUR EARLY NEXT WEEK.

&&

.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 LESS 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 EXPECT
CONVECTIVE ENHANCEMENT.

&&

.AVIATION...VALID THRU 31/00Z.
SCATTERED TO WIDESPREAD VALLEY RAIN AND MOUNTAIN SNOW WILL OCCUR
OVER SOUTHEASTERN ARIZONA TODAY. THERE IS ALSO A SLIGHT CHANCE OF
THUNDERSTORMS ACROSS MUCH OF THE AREA THIS AFTERNOON. CEILINGS OF
6-10K FT AGL WILL LOWER TO AROUND 2-3K FT AGL AS PRECIPITATION
BECOMES MORE WIDESPREAD. MVFR VSBYS AND MT OBSCURATIONS ARE LIKELY
BEFORE DAYBREAK AND ESPECIALLY NEAR HEAVIER PRECIPITATION. EASTERLY
WINDS AT 12-18 KTS WILL DIMINISH THROUGHOUT THE DAY TODAY...
GENERALLY BECOMING SELY/SLY AT 5-15 KTS BY THIS EVENING. 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. EASTERLY WINDS TODAY WILL PEAK
DURING THE MID-MORNING HOURS AT 15-20 MPH...GRADUALLY WEAKENING AND
BECOMING MORE SOUTHERLY/SOUTHEASTERLY BY THIS EVENING. EXPECT
DIURNAL WIND TRENDS TO RESUME THIS WEEKEND THROUGH EARLY NEXT
WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 11 AM THIS MORNING TO NOON MST
SATURDAY FOR AZZ514 ABOVE 7000 FEET.

WINTER STORM WARNING FROM 5 AM EARLY THIS MORNING TO NOON MST
SATURDAY FOR AZZ510-511 ABOVE 7000 FEET.

&&

$$

DISCUSSION...MEADOWS
FIRE WEATHER/AVIATION...81

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