Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 300351
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
851 PM MST MON SEP 29 2014

.SYNOPSIS...DRY CONDITIONS WILL PREVAIL INTO THIS WEEKEND. A GRADUAL
WARMING TREND WILL OCCUR ESPECIALLY DURING THE LATTER PART OF THE
WEEK AS HIGH PRESSURE ALOFT BUILDS OVER THE AREA.

&&

.DISCUSSION...THE UPPER WEATHER PATTERN IS DEFINED BY AN EJECTING
CLOSED LOW NOW OVER CO/WY/MT...A BROAD RIDGE EXTENDED OUT IN THE
EASTERN PACIFIC...AND A RAPIDLY WEAKENING TROPICAL STORM RACHEL
POSITIONED AT 23.3N 117.5W MOVING SLOWLY NORTH AT 2KTS.

DRY AIRMASS CONTINUES TO ADVECT INTO SOUTHEAST ARIZONA ON THE
WESTERLY FLOW BEHIND THE EJECTION UPPER LOW. THIS IS EVIDENT ON THE
00Z KTWC UPPER AIR SOUNDING...WITH A PRECIPITABLE WATER VALUE OF
0.61. THE CUMULUS CLOUDS THAT EXTENDED ACROSS THE EASTERN THIRD OF
THE FORECAST AREA HAS SINCE DISSIPATED...AND OTHER THAN A FEW HIGH
CIRRUS FROM DECAYING TROPICAL STORM RACHEL CLIPPING THE EXTREME
SOUTHEAST CORNER OF THE STATE...SKIES ARE CLEAR.

NO UPDATES TO DIGITAL GRIDS/FORECAST NECESSARY THIS EVENING.

&&

.PREV DISCUSSION...UPPER LOW CENTERED OVER ERN IDAHO WITH MID-LEVEL
TROUGH AXIS EXTENDING SWD INTO SRN AZ THIS AFTERNOON. THE BULK OF
MOSTLY CUMULOFORM CLOUDS FROM TUCSON EWD WILL DISSIPATE THIS EVENING
AS THE MID-LEVEL TROUGH AXIS MOVES WELL EAST OF THE AREA...AND WITH
THE LOSS OF DAYTIME HEATING. THUS...EXPECT DECREASING CLOUDS EARLY
THIS EVENING FOLLOWED BY CLEAR SKIES OR MOSTLY CLEAR SKIES THE REST
OF TONIGHT.

A BROAD UPPER TROUGH OVER THE WRN CONUS TUE WILL ADVANCE EWD INTO
THE ROCKIES AND CENTRAL CONUS PLAINS WED. A SHORTWAVE TROUGH MAY
BRING SOME SHOWERS ACROSS THE FOUR CORNERS REGION WED. THUS...ANY
RAINFALL ASSOCIATED WITH THIS SYSTEM IS EXPECTED TO REMAIN WELL NE
OF THIS FORECAST AREA. THEREAFTER...HIGH PRESSURE ALOFT IS PROGGED
TO AMPLIFY OVER THE SWRN CONUS THUR-MON. A SOMEWHAT TIGHT SURFACE
PRESSURE GRADIENT MAY PRODUCE LOCALLY GUSTY ELY WINDS THUR NIGHT-
FRI. OTHERWISE...CLEAR SKIES OR MOSTLY CLEAR SKIES WILL PREVAIL
THUR-MON.

HIGH TEMPS TUESDAY WILL BE NEARLY IDENTICAL TO TEMPS ACHIEVED THIS
AFTERNOON. A GRADUAL WARMING TREND WILL THEN OCCUR WED-FRI FOLLOWED
BY CONTINUED ABOVE NORMAL DAYTIME TEMPS THIS WEEKEND.

&&

.AVIATION...VALID THRU 01/06Z.
EXPECT CLEAR SKIES INTO TUESDAY. SURFACE WIND EAST OF KTUS TUESDAY
AFTERNOON WILL BE WLY/NWLY 12-18 KTS WITH GUSTS TO 25 KTS.
OTHERWISE...SURFACE WIND WILL BE MAINLY LESS THAN 10 KTS THRU
TUESDAY EVENINGN. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL INTO THIS WEEKEND.
DAYTIME MINIMUM RELATIVE HUMIDITIES WILL LOWER THIS WEEK AS DRIER
AIR MOVES INTO THE REGION...ALTHOUGH GOOD OVERNIGHT RECOVERIES ARE
STILL EXPECTED. 20-FOOT WINDS ACROSS GRAHAM...GREENLEE AND COCHISE
COUNTIES TUESDAY AFTERNOON WILL BE WEST TO NORTHWEST AT 8-18 MPH.
OTHERWISE...20-FOOT WINDS WILL BE LESS THAN 15 MPH THROUGH THURSDAY.
LOCALLY GUSTY EAST WINDS MAY OCCUR FRIDAY.

&&

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


&&

$$

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