Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 200936
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
230 AM MST MON OCT 20 2014

.SYNOPSIS...A SLOW MOVING WEATHER SYSTEM OVER NORTHERN MEXICO WILL
KEEP THE CHANCE OF RAIN IN THE FORECAST THROUGH TUESDAY...WITH THE
MOST FAVORABLE AREA FOR STORM DEVELOPMENT SHIFTING INTO EASTERN
AREAS. STRONG HIGH PRESSURE WILL BRING DRIER CONDITIONS THE SECOND
HALF OF THE WEEK ALONG WITH MUCH WARMER TEMPERATURES. NEAR RECORD
HIGH TEMPERATURES POSSIBLE IN SOME LOCATIONS THURSDAY INTO SATURDAY.

&&

.DISCUSSION...AT 2 AM THE MID LEVEL LOW CONTINUES TO TRACK ACROSS
FAR NORTHERN SONORA NEAR THE ARIZONA BORDER...JUST SOUTH OF SANTA
CRUZ COUNTY. THIS CUT-OFF HAS FILLED A LITTLE AS IT DRIFTS VERY
SLOWLY EASTWARD. A LITTLE BIT OF MID LEVEL DRYING IS STARTING TO EAT
AWAY AT SOME OF THE AVAILABLE MOISTURE...HOWEVER .75 TO .9
PRECIPITABLE WATER SHOULD BE ENOUGH TO SEE STORMS RETURN TO THE AREA
THIS AFTERNOON.

THE MOST FAVORABLE AREA OF UPPER LEVEL DIFFLUENCE ON THE ACTIVE
EASTERN TO NORTHERN PORTION OF THE LOW WILL FURTHER EMPHASIZE
EASTERN AREAS TODAY WITH BEST STORM CHANCES EAST OF TUCSON.
HOWEVER...IT SHOULD BE NOTED THAT INSTEAD OF YESTERDAY`S SOUTHERLY
FLOW...MUCH OF THE AREA WILL BE DEVELOPING AN EASTERLY STEERING
LEVEL FLOW ON THE NORTHERN FLANK OF THE LOW. THIS WILL STEER A FEW
STORMS ONCE AGAIN TOWARD CENTRAL AREAS INCLUDING THE GREATER TUCSON
AREA. THE BEST ORGANIZED AREAS SHOULD BE EAST OF TUCSON HOWEVER.

BY LATE TUESDAY THE LOW SHOULD START TO SHEAR AND LIFT INTO THE
FRONT OF KICKER SYSTEM PUSHING THROUGH THE REGION NORTH OF US...WITH
A WEAK TROUGH INFLECTION DEVELOPING THROUGH NEW MEXICO BY EARLY
WEDNESDAY.

OUR ATTENTION THEN SHIFTS TO A DEVELOPING RIDGE FOR THE SECOND HALF
OF THE WEEK. MEDIUM RANGE RESOLUTIONS CLEARLY AND REASONABLY DEVELOP
AN UNSEASONABLY STRONG RIDGE BUILDING THROUGH ARIZONA THURSDAY AND
FRIDAY WITH THE RIDGE AXIS DIRECTLY OVERHEAD OF SOUTHEAST ARIZONA.
SLIGHTLY DEEPER AND SLOWER TIMING OF ECMWF PREFERRED DUE TO
CONTINUED FAVORABLE ENSEMBLE MEAN TRENDS FOR THE INITIAL RIDGE
DEVELOPMENT THURSDAY AND NORMALIZED STANDARD DEVIATION TRENDS OVER
THE PAST 30 DAYS (HOWEVER IT SHOULD BE NOTED THAT ENSEMBLE TRENDS
ARE LESS FAVORABLE FOR THE POSITION OF THE DEVELOPING TROUGH THROUGH
THE PACIFIC NORTHWEST). WITH THIS IN MIND...HEIGHT AND THICKNESS
VALUES CONTINUE TO SUPPORT AFTERNOON SURFACE HIGHS NEAR RECORD
LEVELS AS EARLY AS THURSDAY WITH FRIDAY MAXING OUT 850-700MB
THICKNESS VALUES AROUND 165.6DAM. THIS WOULD SUPPORT A 93 TO 95 AT
TIA. IF WE WERE TO MANAGE A 95 FRIDAY (THE 24TH) IT WOULD BE THE
THIRD LATEST 95 DEGREE DATE EVER FOR TUCSON...WITH THE LATEST EVER
OCCURRING ON THE 26TH IN 2001 AND 1934.

A HIGHLY AMPLIFIED PATTERN DEVELOPING WHICH WILL TEND TO SLOW THINGS
DOWN...HOWEVER THE MID LEVEL REFLECTION OF THE RIDGE WILL STILL
PROBABLY SHIFT INTO NEW MEXICO BY LATE SATURDAY. THICKNESS VALUES
WILL STILL BE THERE FOR SE AZ FOR NEAR RECORD HIGHS SATURDAY...BUT
STARTING TO LOSE MID LEVEL HEIGHT SUPPORT WITH TRENDS STARTING
DOWN...SO PROBABLY DOWN A DEGREE OR TWO FROM FRIDAY.

MODEST CAA BEHIND A DRY TROUGH (FOR OUR LATITUDE) SUNDAY AND MONDAY
AS AFTERNOON HIGHS DROP BACK TOWARD CLIMO.

&&

.AVIATION...VALID THRU 21/09Z.
THE WEAK MID LEVEL LOW JUST SOUTH OF THE BORDER WILL STILL HAVE
ENOUGH MOISTURE TO WORK WITH FOR A CHANCE OF -TSRA TODAY...HOWEVER
THE BEST AREA OF COVERAGE SHOULD BE EAST OF KTUS. FEW-BKN CLOUDS
7-12KFT AGL WITH GENERALLY VFR CONDITIONS OUTSIDE OF TSRA. EASTERLY
SURFACE WINDS GENERALLY LESS THAN 10KTS OUTSIDE OF GUSTY OUTFLOWS
NEAR ANY TSRA. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A WEAK LOW NEAR THE AREA IN COMBINATION WITH MODEST
MOISTURE WILL RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS
THROUGH TUESDAY...MAINLY FROM TUCSON EASTWARD. DRY CONDITIONS WILL
THEN OCCUR AREA WIDE FOR THE END OF THE WORK WEEK WITH SIGNIFICANTLY
ABOVE NORMAL HIGH TEMPERATURES. 20-FOOT WINDS WILL GENERALLY BE
DIURNAL AND LESS THAN 15 MPH THIS WEEK.  SOME GUSTY WINDS ARE
POSSIBLE NEAR ANY THUNDERSTORMS.

&&

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

$$

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MEYER/MEADOWS




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