Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 221559
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 AM MST SUN FEB 22 2015

.SYNOPSIS...EXPECT GUSTY SOUTHWEST WINDS TODAY WITH A FEW SHOWERS
EAST OF TUCSON. PERIODS OF GUSTY WINDS WILL CONTINUE MONDAY INTO
TUESDAY ALONG WITH A CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW SHOWERS
AS A LOW PRESSURE SYSTEM MOVES NORTH OF THE AREA. MUCH COOLER
TEMPERATURES TUESDAY AND TUESDAY NIGHT WILL BE FOLLOWED BY DRY
CONDITIONS WITH A WARMING TREND WEDNESDAY AFTERNOON INTO FRIDAY.
PRECIPITATION CHANCES WILL INCREASE NEXT WEEKEND AS A STORM SYSTEM
DEVELOPS ACROSS THE REGION.

&&

.DISCUSSION...WE`VE SEEN A MODEST MOISTURE INCREASE OVER THE PAST 12
HOURS WITH OUR PRECIPITABLE WATER LEVELS NOW AROUND 2/3 OF AN INCH
AND SURFACE DEW POINTS IN THE 30S AND 40S. PATCHY MID CLOUD WITH
MAINLY VIRGA ACROSS SOUTHEAST ARIZONA. HOWEVER, SPRINKLES OR LIGHT
SHOWERS ARE REACHING THE GROUND IN A FEW SPOTS (MAINLY HIGHER
TERRAIN). THE INCREASING SOUTHWESTERLY FLOW HAS APPEARED ON CUE THIS
MORNING AS THE GRADIENT TIGHTENS UNDER THE ENERGY ERODING THE
EASTERN FLANK OF THE RIDGE. BREEZY FROM TUCSON WESTWARD AND WINDY IN
EASTERN AREAS, BUT BELOW ADVISORY LEVELS EXCEPT PERHAPS IN A FEW
WIND PRONE LOCATIONS. THE CURRENT FORECAST COVERS ALL OF THIS WELL.
PLEASE SEE THE PREVIOUS DISCUSSION FOR ADDITIONAL DETAILS.

&&

.AVIATION...VALID THRU 23/18Z.
A FEW SHOWERS MAY OCCUR MAINLY NEAR THE HIGHER TERRAIN EAST OF KTUS
INTO THIS EVENING. THERE IS A SLIGHT CHANCE OF -SHRA WEST TO NORTH
OF KTUS LATE TONIGHT INTO MONDAY MORNING. OTHERWISE...EXPECT A FEW
TO SCATTERED CLOUDS AROUND 6-10K FT AGL AND SCT-BKN CLOUDS ABOVE 12K
FT AGL THRU THE PERIOD. GUSTY SURFACE WIND UNTIL AROUND 23/03Z
THIS EVENING...SWLY AT 12-22 KTS WITH GUSTS OF 25-35 KTS. THE
STRONGEST WIND WILL BE SOUTH TO SOUTHEAST OF KTUS IN THE VICINITY OF
THE KOLS/KDUG TERMINALS. OTHERWISE...SURFACE WIND WILL BE MAINLY
LESS THAN 12 KTS FOR MOST LOCALES. AVIATION DISCUSSION NOT UPDATED
FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A FEW SHOWERS MAY OCCUR ACROSS THE HIGHER TERRAIN
EAST OF TUCSON TODAY. HOWEVER...THE MAIN IMPACT ASSOCIATED A
DEEPENING LOW PRESSURE SYSTEM NORTH OF THE AREA WILL BE STRONG AND
GUSTY SOUTHWEST WINDS FROM LATE THIS MORNING INTO EARLY THIS
EVENING. WINDS WILL DIMINISH ACROSS MUCH OF THE AREA AROUND OR
SHORTLY AFTER SUNSET THIS EVENING. THE CHANCE OF VALLEY RAIN AND
MOUNTAIN SNOW WILL INCREASE LATE MONDAY INTO TUESDAY AS A STORM
SYSTEM MOVES NORTH OF THE AREA. PRECIPITATION AMOUNTS WILL GENERALLY
BE QUITE LIGHT. COOLER TEMPERATURES WILL OCCUR TUESDAY FOLLOWED BY
DRY CONDITIONS WITH A WARMING TREND WEDNESDAY INTO FRIDAY. GUSTY
AFTERNOON WINDS WILL PREVAIL MAINLY EAST OF TUCSON TUESDAY THROUGH
THURSDAY. THE FAVORED AREA FOR THE STRONGEST WIND WILL BE ACROSS THE
UPPER GILA VALLEY INCLUDING SAFFORD. THEREAFTER...PRECIPITATION
CHANCES ARE FORECAST TO INCREASE NEXT WEEKEND AS THE NEXT STORM
SYSTEM DEVELOPS NORTH OF THE AREA.

&&

.PREV DISCUSSION...UPPER LEVEL RIDGE AXIS WAS OFF THE WEST COAST
NEAR 130W AND A SHORTWAVE TROUGH WAS OVER THE GREAT BASIN EARLY THIS
MORNING. THE SHORTWAVE TROUGH WILL DEVELOP INTO A CLOSED UPPER LOW
AND BE CENTERED OVER WRN NEVADA/CENTRAL CALIFORNIA BY MON MORNING.
GUSTY SOUTH WINDS WILL DEVELOP MID TO LATE MORNING...THEN SOUTHWEST
WINDS WILL REACH BREEZY TO WINDY CRITERIA THIS AFTERNOON IN RESPONSE
TO A TIGHT MID-LEVEL GRADIENT SE OF THIS SYSTEM ACROSS SE AZ. WINDS
WILL DIMINISH ACROSS MUCH OF THE AREA AROUND SUNSET THIS EVENING.
HAVE MAINTAINED A SLIGHT CHANCE OF SHOWERS ACROSS THE HIGHER TERRAIN
EAST OF TUCSON INTO THIS EVENING. HOWEVER...THE LACK OF
SYNOPTIC-SCALE ASCENT WILL LIMIT ANY AMOUNTS OF SIGNIFICANCE FROM
OCCURRING.

A 551-552 DM LOW IS PROGGED VIA THE 22/00Z GFS/ECMWF/CMC TO BE
CENTERED JUST SE OF SAN FRANCISCO MIDDAY MON. THIS UPPER LOW WILL
MOVE NEWD INTO NWRN AZ MON NIGHT...THEN WILL MOVE ESEWD INTO NWRN
NEW MEXICO BY MIDDAY TUE. BLENDED TOTAL PRECIP WATER IMAGERY VALID
0903Z AMOUNTS GENERALLY RANGING FROM 1.00 - 1.25 INCHES FROM CENTRAL
SONORA SWWD ACROSS SRN BAJA CALIFORNIA. THUS...SOME MOISTURE WILL
OCCUR ACROSS SE AZ STARTING MON AND CONTINUE INTO TUE AS THE UPPER
LOW MOVES NORTH OF THE AREA.

A CHANCE OF SHOWERS EXISTS MON ACROSS THE WHITE MOUNTAINS...AND A
SLIGHT CHANCE OF SHOWERS FURTHER SW ACROSS SRN PINAL COUNTY INTO WRN
PIMA COUNTY. DRY CONDITIONS SHOULD CONTINUE MON FOR TUCSON AND FOR
MOST LOCALES SOUTH TO SOUTHEAST OF TUCSON. BASED ON THE VARIOUS
22/00Z NWP SOLUTIONS...POPS WERE THEN INCREASED MON NIGHT INTO TUE
MORNING. THESE NWP SOLUTIONS WERE QUITE SIMILAR WITH DEPICTING THE
BEST CHANCE OF SHOWERS FOR THE TUCSON METRO AREA TO OCCUR 06Z-18Z
TUE...OR LATE MON NIGHT INTO TUE MORNING...ASSOCIATED WITH A SURFACE
COLD FRONT THAT WILL MOVE EWD ACROSS THE AREA.

ISOLATED TO SCATTERED SHOWERS SHOULD CONTINUE MAINLY NE OF TUCSON
TUE AFTERNOON...AND HAVE MAINTAINED A SLIGHT CHANCE OF SNOW SHOWERS
ACROSS THE WHITE MOUNTAINS TUE EVENING. LIQUID AMOUNTS ASSOCIATED
WITH THIS SYSTEM WILL GENERALLY RANGE FROM A FEW HUNDREDTHS OF AN
INCH TO PERHAPS AS MUCH AS TWO TENTHS OF AN INCH. THE BULK OF ANY
MEASURABLE PRECIP WILL BE ABOVE 5000 FEET. SNOW ACCUMULATIONS TO
AROUND 2 INCHES ARE FORECAST TO OCCUR IN THE WHITE MOUNTAINS...AND
ONLY TRACE AMOUNTS SHOULD OCCUR ELSEWHERE.

GUSTY NORTHWEST WINDS WILL ALSO OCCUR TUE AFTERNOON...ESPECIALLY
EAST OF TUCSON. IN FACT...THE UPPER GILA RIVER VALLEY INCLUDING
SAFFORD MAY BRIEFLY APPROACH WIND ADVISORY CRITERIA TUE AFTERNOON.
DRY CONDITIONS WILL PREVAIL WED-FRI UNDER GENERALLY NWLY FLOW ALOFT.

THEREAFTER...THE OFFICIAL FORECAST DEPICTS A SLIGHT CHANCE OF
SHOWERS MAINLY FROM TUCSON NWD NEXT SAT. 22/00Z GFS/ECMWF PROGGED AN
UPPER TROUGH TO DEEPEN OVER THE WRN CONUS EARLY NEXT WEEKEND. THE
BULK OF PRECIP ASSOCIATED WITH THIS SYSTEM SHOULD REMAIN NORTH OF
THIS FORECAST AREA SAT. PRECIP CHANCES MAY IMPROVE DURING THE LATTER
PART OF NEXT WEEKEND AS THE UPPER TROUGH CONTINUES TO DEEPEN.
FORECAST CONFIDENCE IS QUITE LOW AT THIS TIME...ESPECIALLY GIVEN THE
TIME PERIOD...AND THE DIFFERENCES OF QPF/S EXHIBITED VIA THE
GFS/ECMWF.

A GRADUAL COOLING TREND WILL OCCUR TODAY INTO MON...THE MORE
PRONOUNCED COOLING WILL PREVAIL TUE. EXPECT WARMER DAYTIME TEMPS WED
FOLLOWED BY JUST A DEGREE-OR-TWO OF WARMING FRI-SAT.

&&

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

&&

$$

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

MEYER/FRENCH/FRANCIS






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