Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 282116
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
216 PM 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 INTO THIS
EVENING AND ONCE AGAIN MONDAY. PERIODS OF VALLEY RAIN AND MOUNTAIN
SNOW ARE POSSIBLE THIS EVENING AND SUNDAY MAINLY TO THE NORTH OF
TUCSON...THEN BECOMING WIDESPREAD MONDAY INTO MONDAY NIGHT.
PRECIPITATION CHANCES WILL LESSEN DURING THE MIDDLE OF NEXT WEEK.
EXPECT COOLER TEMPERATURES FOR THE FIRST HALF OF NEXT WEEK.

&&

.DISCUSSION...LATEST IR/WV SATELLITE IMAGERY SHOWS CLOSED UPPER LOW
NOW MOVING SOUTHWARD NEAR SACRAMENTO. A TIGHT PRESSURE GRADIENT DUE
TO STRONG WESTERLY FLOW ALOFT IS RESULTING IN WINDY CONDITIONS THIS
AFTERNOON. GUSTS HAVE BEEN AS HIGH AS 45 TO 50 MPH IN THE SIERRA
VISTA AREA...AIDED LOCALLY THERE BY THE MOUNTAINS. MOST OF THE
REMAINDER OF THE AREA IS SEEING SUSTAINED WINDS OF 20 TO 30 MPH WITH
GUSTS TO ABOUT 40 MPH. WE CAN`T RULE OUT A SPOT OR TWO OF BLOWING
DUST BUT WE`VE YET TO HAVE ANY REPORTS. MEANWHILE...SKIES ARE PARTLY
TO MOSTLY CLOUDY ACROSS THE FORECAST AREA WITH QUITE AN EXTENSIVE
LOWER LEVEL STRATOCUMULUS FIELD. LATEST REGIONAL RADAR IMAGERY SHOWS
A FEW SHOWERS OVER NORTHEAST PINAL COUNTY WITH THE REST OF THE
FORECAST AREA PRECIPITATION FREE. AS A WEAK DISTURBANCE ALOFT MOVES
THROUGH INTO THIS EVENING...WE DO EXPECT A FEW SHOWERS MAINLY FROM
PINAL COUNTY INTO GRAHAM AND GREENLEE COUNTY. PRECIPITATION AMOUNTS
WILL REMAIN LIGHT AND SNOW LEVELS REMAINING HIGH AT ABOUT 8000-9000
FEET. A COUPLE OF INCHES OF SNOW IS POSSIBLE FOR THE HIGHEST TERRAIN
OF THE WHITE MOUNTAINS IN NORTHERN GREENLEE COUNTY.

FOR SUNDAY...AS THE UPPER LOW CONTINUES TO DIG SOUTH AND THE TROUGH
AXIS TAKES ON A MORE NORTH-SOUTH ORIENTATION...THAT WILL LIKELY
FOCUS THE DEEP MOISTURE PLUME TO THE NORTH AND WEST OF THE AREA WITH
HEIGHTS ACTUALLY SLIGHTLY INCREASING ACROSS SOUTHEAST ARIZONA DUE TO
THE AMPLIFICATION OF THE TROUGH. THE BEST PRECIPITATION CHANCES WILL
REMAIN ACROSS THE WHITE MOUNTAINS WITH ENHANCED UPSLOPE FLOW. MUCH
OF THE REMAINDER OF SOUTHEAST ARIZONA AND ESPECIALLY FROM TUCSON
SOUTH AND EAST WILL STAY COMPLETELY DRY WITH BREEZY CONDITIONS
EXPECTED AGAIN SUNDAY AFTERNOON. THE WINDS WILL NOT BE AS STRONG ON
SUNDAY AND THE SNOW LEVELS WILL REMAIN HIGH.

ON MONDAY...THE TROUGH AXIS...ASSOCIATED COLD FRONT AND DEEP LAYER
ASCENT WILL GRADUALLY SHIFT FROM WEST TO EAST BRINGING THE BEST
CHANCE OF RAIN AND MOUNTAIN SNOW TO SOUTHEAST ARIZONA. THE LATEST
TRENDS FROM THE 12Z NUMERICAL GUIDANCE DEPICT THE COLD FRONT
MOVING THROUGH MOSTLY DURING THE AFTERNOON INTO THE EVENING. HAVE
NOTED THAT THE HIGHEST QPF WILL REMAIN ACROSS THE NORTHERN HALF OF
THE STATE INCLUDING THE MOGOLLON RIM CLOSEST TO THE STRONGEST JET
DYNAMICS AS THE TROUGH SHIFTS EAST WITH LESSER AMOUNTS IN OUR
FORECAST AREA. THE MOUNTAINS WILL CONTINUE TO SEE FAVORABLE UPSLOPE
FLOW ENHANCING PRECIPITATION TOTALS FOR THOSE AREAS BUT VALLEY QPFS
HAVE BEEN LOWERED A BIT AND ARE NOW GENERALLY A QUARTER TO HALF AN
INCH. SNOW LEVELS WILL FINALLY LOWER TO 6000-7000 FEET FOLLOWING THE
FRONTAL PASSAGE. WITH LOWER QPF AND SNOW AMOUNTS AS THE MAIN CORE OF
THE PRECIPITATION MOVES THROUGH MONDAY INTO MONDAY NIGHT...IT IS
STARTING TO LOOK MORE LIKE AN ADVISORY LEVEL EVENT FOR THE MOUNTAINS
WITH 6 TO 12 INCHES DURING THIS PERIOD. WILL WAIT FOR ADDITIONAL
SHIFTS TO CONTINUE TO TWEAK THE FORECAST AND GAIN HIGHER CONFIDENCE
BEFORE ISSUING ANY WINTER WEATHER PRODUCTS. THE OTHER BIG STORY ON
MONDAY WILL BE THE GUSTY WINDS...ESPECIALLY SOUTH AND EAST OF
TUCSON. WITH THE SYSTEM BEING A BIT SLOWER...THIS WILL ALLOW DEEPER
MIXING ESPECIALLY TO THE SOUTH AND EAST OF TUCSON. SOME OF THESE
AREAS MIGHT SEE WINDS EXCEEDING ADVISORY THRESHOLDS.

THERE WILL REMAIN A CHANCE OF SHOWERS AND MOUNTAIN SNOW SHOWERS ON
TUESDAY INTO TUESDAY NIGHT AS A SECONDARY TROUGH AXIS SHIFTS SOUTH
AND EAST. HOWEVER...CONFIDENCE REMAINS QUITE LOW AS PORTIONS OF THE
AREA MAY END UP BEING IN A DRY SLOT BETWEEN THE INITIAL DEPARTING
DISTURBANCE AND DIGGING SECONDARY LOW NEAR OR JUST OFF NORTHERN
BAJA. THERE ARE MORE CONSIDERABLE DIFFERENCES STARTING WEDNESDAY
WITH HOW FAST TO EJECT THE UPPER LOW EASTWARD. IN FACT...SOME OF THE
GUIDANCE IS NOW DEPICTING THE UPPER LOW TO REMAIN IN THE AREA IN A
WEAKENED STATE THROUGH THE END OF THE WEEK. WILL STILL MAINTAIN
SLIGHT CHANCE POPS ON WEDNESDAY WITH DRY CONDITIONS FOR THE END OF
THE WORK WEEK. TEMPERATURES WILL BE AT THEIR COOLEST TUESDAY INTO
WEDNESDAY WITH HIGHS ABOUT 10 DEGREES BELOW NORMAL FOR THIS TIME OF
YEAR.

&&

.AVIATION...VALID THRU 02/00Z.
SCT-BKN CLOUDS 5-7KFT AGL. ISOLD -SHRA MNLY W AND N KTUS WITH MTN
TOPS OBSCD. WINDS GENERALLY S-SW TO 10-25 KTS WITH LCL GUSTS TO 35
KTS THRU 01/02Z THEN EASING TO S 6-14 KTS OVERNIGHT. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SUSTAINED S-SW WINDS OF 10-25 MPH WITH GUSTS 20-40
MPH...HIGHER IN THE TERRAIN...WILL GRADUALLY DIMINISH OVERNIGHT.
WIND SPEEDS WILL BE A LITTLE LIGHTER ON SUNDAY BEFORE INCREASING
AGAIN ON MONDAY. THESE WINDS ARE ASSOCIATED WITH AN APPROACHING
SYSTEM CURRENTLY MOVING DOWN THE WEST COAST. A FEW LIGHT SHOWERS
WEST AND NORTH OF TUCSON...BECOMING SCATTERED IN THIS SAME AREA ON
SUNDAY. SHOWERS WILL SPREAD ACROSS 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.

&&

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

&&

$$

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

GL





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