Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 281015
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 AM MST SAT FEB 28 2015

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM DEVELOPING ALONG THE WEST
COAST WILL BRING STRONG AND GUSTY WINDS TO THE AREA TODAY AND AGAIN
MONDAY. THIS WIND WILL BE FOLLOWED BY PERIODS OF VALLEY RAIN AND
MOUNTAIN SNOW LATER THIS WEEKEND INTO THE MIDDLE OF NEXT WEEK. THE
BEST CHANCE FOR PRECIPITATION WILL BE MONDAY AND MONDAY NIGHT. AS
THIS OCCURS...A WARM WEEKEND WILL GIVE WAY TO COOLER TEMPERATURES
THE FIRST HALF OF NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY SHOWS AN UPPER LOW CURRENTLY
SPINNING IN THE GENERAL VICINITY OF COASTAL OREGON AND MAKING ITS
WAY DOWN THE WEST COAST. IR IMAGERY SHOWS SIGNIFICANT CLOUDINESS AND
PRECIPITATION CONTINUING TO DEVELOP AHEAD OF THIS SYSTEM OVER MUCH
OF THE GREAT BASIN...AS WELL AS NORTHERN PARTS OF ARIZONA AND INTO
NEW MEXICO AND COLORADO. CLOSER TO HOME...SKIES ARE MOSTLY CLEAR
THIS FAR SOUTH OVER SOUTHEAST ARIZONA WITH THE EXCEPTION OF SOME MID
LEVEL CLOUDS OVER THE NORTHERN FRINGES OF MY FORECAST AREA...
SPECIFICALLY PARTS OF PINAL...GRAHAM AND GREENLEE COUNTIES.

LATEST SURFACE OBSERVATIONS INDICATE THAT SOUTHERLY WINDS REMAIN
FAIRLY ELEVATED FOR THIS TIME OF NIGHT WITH SUSTAINED SPEEDS RANGING
FROM 10 TO 15 MPH WITH GUSTS TO NEAR 20 MPH. SPEEDS HIGHER OVER
HIGHER TERRAIN WHERE SOME GUSTS OF AROUND 35 MPH HAVE OCCURRED.
THESE WINDS HAVE BEEN TRANSPORTING MOISTURE INTO THE REGION WITH THE
LATEST SATELLITE DERIVED BLENDED TOTAL PRECIPITABLE WATER IMAGE
SHOWING VALUES HAVING INCREASED THROUGHOUT THE DAY AND ARE NOW IN
THE 0.50 - 0.70 INCH RANGE TO THE SOUTHWEST...WHILE VALUES ARE STILL
AROUND 0.30 - 0.50 INCHES ACROSS THE EXTREME EASTERN PART OF MY
FORECAST AREA...SPECIFICALLY NEAR THE NEW MEXICO BORDER. IN
ADDITION...SURFACE DEWPOINTS ARE RUNNING 3 TO 7 DEGS WARMER/WETTER
VERSUS 24 HOURS AGO OVER EASTERN AREAS...AND 10 TO 20 DEGS
WARMER/WETTER VERSUS 24 HOURS AGO FOR CENTRAL AND WESTERN AREAS.
MOISTURE SHOULD CONTINUE TO INCREASE THROUGHOUT THE DAY WITH THE
THREAT OF PRECIPITATION ALSO INCREASING A TAD. STILL ONLY LOOKING AT
SLIGHT CHANCES MAINLY FOR MOUNTAIN TOP LOCATIONS AND AREAS TO THE
WEST AND NEAR THE INTERNATIONAL BORDER. IN ADDITION...THE WINDS WILL
ALSO CONTINUE TO INCREASE TODAY WITH BREEZY TO LOCALLY WINDY
CONDITIONS EXPECTED. COULD SEE A FEW LOCATIONS FLIRT WITH ADVISORY
CRITERIA...BUT FOR NOW IT DOESN`T LOOK LIKE THESE CONDITIONS WILL BE
WIDESPREAD...MAINLY CONFINED TO AREAS NEAR THE BORDER WITH MEXICO IN
COCHISE AND PERHAPS SANTA CRUZ COUNTIES.

AS THE AFOREMENTIONED UPPER LOW MAKING ITS WAY SOUTH CONTINUES TO
MOVE DOWN THE WEST COAST...THE ORIENTATION OF THE LOW WILL SHIFT AS
THE ASSOCIATED TROUGH AXIS BECOMES MORE NORTH TO SOUTH AS OPPOSED TO
EAST TO WEST...WHICH IS THE CURRENT SCENARIO OVER THE PACIFIC
NORTHWEST. AS THIS OCCURS THE SHOWER ACTIVITY WILL DEVELOP OUT AHEAD
OF THE TROUGH AXIS AND EXTEND FROM PARTS OF COLORADO...NORTHERN NEW
MEXICO...UTAH AND INTO NORTHERN ARIZONA AND SOUTHWEST ARIZONA AND
SOUTHERN CALIFORNIA BY LATE SUNDAY AFTERNOON...WITH MOSTLY DRY
WEATHER OVER EXTREME SOUTHEAST ARIZONA...WITH THE EXCEPTION OF THE
MOUNTAIN TOPS. THE MODELS CONTINUE TO SLOW THE SYSTEM DOWN AS
COMPARED TO MODEL RUNS FROM JUST A FEW DAYS AGO...WHEN IT LOOKED
LIKE SUNDAY WOULD BE AN ACTIVE DAY. NOW IT LOOKS LIKE PRIME TIME
WILL BE MONDAY INTO MONDAY NIGHT. HOWEVER...CONFIDENCE IS NOT HIGH
REGARDING THE TIMING OF THE PRECIPITATION GIVEN THE WAY THE MODELS
KEEP SLOWING IT DOWN. I MADE SOME MINOR ADJUSTMENTS TO THE POP
FORECAST THROUGH LATE MONDAY TO REFLECT RECENT MODEL RUNS...BUT I
STILL SHOW THE BULK OF SHOWER ACTIVITY MOVING THROUGH MY FORECAST
AREA MONDAY AND MONDAY NIGHT AS THE MAIN SYSTEM SWINGS EAST OF THE
AREA...THEN SLOWLY TAPERING OFF TUESDAY THROUGH WEDNESDAY AS A
SECONDARY LOW BEHIND THE FIRST LOW EXITS THE REGION ON
WEDNESDAY.

SNOW LEVELS ARE NOT ANTICIPATED TO BE VERY LOW WITH THIS FIRST
SYSTEM...GENERALLY REMAINING FAIRLY HIGH THROUGH THE WEEKEND...
TYPICALLY AROUND 8-9K FT. BY MONDAY EVENING SNOW LEVELS EXPECTED TO
LOWER TO AROUND 6-7K FT AND AROUND 5500-6K FT BY LATE TUESDAY. QPF
AMOUNTS STILL EXPECTED TO BE RESPECTABLE WITH TOTAL LIQUID AMOUNTS
IN DESERT VALLEY LOCATIONS RANGING FROM A THIRD OF AN INCH ACROSS
EXTREME SOUTHEAST PORTIONS OF ARIZONA TO AROUND A HALF TO THREE
QUARTERS OF AN INCH FOR MOST REGIONS. HIGHER AMOUNTS OF AN INCH OR
MORE COULD OCCUR MAINLY ALONG THE NORTHERN FRINGES OF MY FORECAST
AREA...SINCE IT LOOKS LIKE AREAS TOWARD PHOENIX WILL SEE MORE
ACTIVITY THAN WE WILL. SNOW AMOUNTS FOR THE ENTIRE PERIOD STARTING
TODAY AND CONTINUING THROUGH EARLY WEDNESDAY COULD SEE SNOW AMOUNTS
FOR THE WHITE MOUNTAINS OF NORTHERN GREENLEE COUNTY RANGING FROM 18
TO 24 INCHES WITH LESSER AMOUNTS FARTHER SOUTH. MOUNT GRAHAM AND THE
CATALINAS PERHAPS 10 TO 14 INCHES ARE POSSIBLE. I HELD OFF ON
ISSUING ANY HEADLINE PRODUCTS SINCE THE CONFIDENCE IN THE EXACT
TIMING OF THE ONSET OF PRECIPITATION AND WHEN IT WILL END IS NOT
HIGH. IN ADDITION...SURROUNDING OFFICES HAVE NOT INDICATED ANY
THOUGHTS OF WINTER WEATHER PRODUCTS AT THIS TIME EITHER. SO...AS NEW
MODEL RUNS SHED MORE LIGHT ON HOW THIS SYSTEM WILL EVOLVE...WE MAY
END UP WITH HEADLINE PRODUCTS IN THE NEAR FUTURE...SO STAY TUNED.

FOR TUCSON...HIGH TEMPS SLIGHTLY ABOVE NORMAL TODAY AND SUNDAY...
THEN BELOW NORMAL MONDAY THROUGH THURSDAY...BUT THE COOLEST DAYS
WILL OCCUR TUESDAY AND WEDNESDAY WHEN HIGHS WILL BE AROUND 10 DEGS
BELOW NORMAL. NEAR NORMAL HIGHS EXPECTED FOR FRIDAY. LOW TEMPS
AROUND 10 DEGS ABOVE NORMAL SUNDAY AND MONDAY MORNINGS...THEN NEAR
NORMAL TUESDAY FOLLOWED BY LOWS 3 TO 5 DEGS BELOW NORMAL FOR
WEDNESDAY AND THURSDAY. NEAR NORMAL LOWS AGAIN FOR FRIDAY MORNING.

&&

.AVIATION...VALID THRU 01/12Z.
CLOUDS GENERALLY INCREASING TODAY WITH SCT TO OCCASIONALLY BKN
CLOUDS AOA 20K FT AGL THRU 28/16Z THEN ADDING SCT-BKN CLOUDS 5-7K FT
THEREAFTER.  AS THE LOWER CLOUDS DEVELOP THERE IS ALSO A SLIGHT CHC
OF -SHRA TO THE NORTH AND WEST OF KTUS AS WELL AS OVER THE MOUNTAINS
AFT 28/16Z.  WINDS GENERALLY SOUTH AT 8-15 KTS BECOMING SWLY AND
INCREASING TO 15-25 KTS WITH GUSTS TO 35 KTS THROUGH 01/02Z THEN
EASING TO SOUTH 6-14 KTS OVERNIGHT.  AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.  CERNIGLIA

&&

.FIRE WEATHER...A STRENGTHENING STORM SYSTEM WEST OF THE AREA WILL
PRODUCE GUSTY WINDS TODAY MAINLY SOUTH OF I-10...GENERALLY AROUND 5
MPH STRONGER THAN YESTERDAY AND WITH HIGHER GUSTS.  EXPECT SUSTAINED
WINDS TO PEAK AROUND 18-28 MPH THIS AFTERNOON WITH GUSTS 40+ MPH
SOUTH OF I-10 AND ACROSS HIGHER TERRAIN.  WINDS WILL BE SOMEWHAT
LIGHTER SUNDAY THEN INCREASE AGAIN ON MONDAY...POTENTIALLY BEING THE
WINDIEST DAY OF THIS STRETCH.

AS THE SYSTEM APPROACHES...ISOLATED SHOWERS ARE EXPECTED TODAY NORTH
AND WEST OF TUCSON...THEN SCATTERED SHOWERS ACROSS THE SAME AREA
TONIGHT AND SUNDAY.  THE THREAT OF SHOWERS WILL SPREAD TO ALL AREAS
SUNDAY NIGHT THROUGH TUESDAY BEFORE DIMINISHING WEDNESDAY WITH DRY
CONDITIONS THEREAFTER.  THE SHOWERS WILL BE SNOW ABOVE 8000 FT
THROUGH MONDAY THEN DROPPING TO AROUND 6000 FEET LATE MONDAY THROUGH
WEDNESDAY.  CERNIGLIA

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

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MOLLERE





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