Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 250406
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 PM MST THU JUL 24 2014

.SYNOPSIS...THUNDERSTORMS ARE EXPECTED TO INCREASE FRIDAY INTO THE
WEEKEND...ESPECIALLY SATURDAY AFTERNOON AND SATURDAY NIGHT.
TEMPERATURES WILL ALSO FALL BACK CLOSER TO AVERAGE OVER THE NEXT FEW
DAYS.

&&

.DISCUSSION...LESS MOISTURE ACROSS MOST OF THE AREA AS PRECIPITABLE
WATER VALUES FELL BELOW 1 INCH FROM TUCSON EASTWARD AND SURFACE
DEWPTS FELL INTO THE 30S AND 40S. COMBINED WITH DOWNSLOPE
EFFECTS...THIS ALLOWED US TO REALIZE MORE OF THE POTENTIAL OF THE
STRONG HIGH PRESSURE PARKED OVER THE DESERT SOUTHWEST WITH SEVERAL
SPOTS APPROACHING RECORD LEVELS ACROSS SE AZ.

THIS MOISTURE TREND IS ALREADY REVERSING AS SURGE ACTIVITY INCREASES
THROUGH THE NORTHERN GULF AND NORTHWEST SONORA. A LONG AND DEEP
FETCH OF 20 TO 30 KT SOUTHERLY WINDS ARE STACKING THROUGH THE GULF
AS DEEP AS 6-7K FEET. LATEST 24 HOUR DEW POINT TRENDS SHOW CIUDAD
MEXICO UP 16 DEGREES...GUAYMAS UP 4-7 DEGREES AND HERMOSILLO UP 18
DEGREES. YUMA IS UP 10 DEGREES OVER THE PAST 24 HOURS WITH SOUTHERLY
VAD WIND PROFILE TRENDS STRENGTHENING OVER THE PAST 6 HOURS. LATEST
HRRR TRENDS ACTUALLY ARE PICKING THIS UP VERY WELL...WITH A VERY
STRONG SET OF SOUTHERLY STREAMLINES FORECAST INTO SOUTH CENTRAL AND
SOUTHWEST ARIZONA OVER THE NEXT 12 HOURS...INCLUDING WESTERN AND
CENTRAL PIMA COUNTY.

INITIALLY ON FRIDAY WE ARE GOING TO SEE A SHARP MOISTURE GRADIENT
WITH SOME AREAS EAST OF TUCSON CLOSER TO THE NEW MEXICO BORDER
REMAINING ON THE DRY SIDE AND MUCH DEEPER MOISTURE PUSHING IN FROM
TUCSON WESTWARD. WATCH FOR ORGANIZED DEEP BOUNDARY LAYER OUTFLOWS.
LATEST FORECAST HAS GREAT TRENDS INCLUDING A FOCUS ON LATE SATURDAY
INTO SATURDAY EVENING ENHANCEMENT FROM INVERTED TROUGH ACTIVITY...AS
WELL AS POTENTIAL BLOWING DUST ISSUES FRIDAY AND SATURDAY.

&&

.PREV DISCUSSION...INTERESTING ITEM MOVING UP THE GULF OF CALIFORNIA
TODAY. A VERY STRONG OUTFLOW...ORIGINATING FROM AN MCS THAT MOVED
ACROSS THE MOUTH OF THE GLFCA...IS MOVING NORTH. SEVERAL COAST SITES
IN SRN HALF OF GULF HAVE SEEN GUSTS UP TO 40 MPH EARLIER TODAY. THE
2 PM OB FROM HERMOSILLO HAD SUSTAINED 20 KTS AND 4 MILES BLOWING
DUST. THIS DUST WAS CLEARLY VISIBLE ON THE 2 PM VISIBLE IMAGERY.
WIND SPEEDS FROM ASCAT SATELLITE SHOWED WINDS SPEEDS OF 30 KTS SOUTH
OF GUYMAS. SO A GULF SURGE IN MOVING NORTH AND WILL PUSH HIGHER PW
VALUES INTO THE STATE ON FRIDAY.

WITH HIGHER PW VALUES PROGGED TO BE ACROSS THE AREA FRIDAY AND
SATURDAY...SHOULD SEE AN BIG INCREASE IN AREAL COVERAGE OF
THUNDERSTORMS WITH SATURDAY POSSIBLY BEING A BIG DAY THANKS TO
APPROACHING INVERTED TROF GIVING THE ATMOSPHERE THE NEEDED LIFT.
DUE TO THE RECENT DRY STREAK...I HAVE ADDED BLOWING DUST TO THE
FORECAST NEXT TWO DAYS FOR THOSE AREAS PRONE TO IT THIS TIME OF YEAR.

THE SUNDAY FORECAST HIGHLY DEPENDENT ON HOW WORKED OVER THE AREA
WILL BE AFTER SATURDAY EVENT. MAY ALSO BE MORE IN THE EVENING THAN
IN THE AFTERNOON.

NEXT WEEK...THE ECMWF SHOWING LESS ACTIVITY ACROSS THE AREA WITH
UPPER HIGH OVER THE AREA...WHILE GFS KEEPS IT EAST. IF ECMWF IS
RIGHT...IT COULD GET QUITE HOT AGAIN...LIKE TODAY. FOR NOW WILL HOLD
ON TO NEAR CLIMO POPS.

&&

.AVIATION...VALID THRU 26/03Z.
PARTIAL CLEARING TREND OVERNIGHT WITH ISOLD -SHRA POSSIBLE
OVERNIGHT. INCREASING MOISTURE FROM THE SOUTH WILL LEAD TO INCREASED
THUNDERSTORM COVERAGE FRIDAY AFTERNOON. STRONG OUTFLOWS FROM
THUNDERSTORMS DEVELOPING FRIDAY AFTERNOON...OTHERWISE NORMAL DIURNAL
WIND TRENDS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...MOISTURE WILL INCREASE TONIGHT INTO THE COMING
WEEKEND WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS FRIDAY
INTO SUNDAY. THE BEST PERIOD IS EXPECTED TO BE LATE SATURDAY INTO
SATURDAY NIGHT AS AN INVERTED TROUGH HELPS ENHANCE COVERAGE AND
BETTER ORGANIZE STORM OUTFLOW. THE NOT SO GOOD NEWS IS IT`S LOOKING
MORE LIKE ANOTHER HOT MID WEEK NEXT WEEK AS THE RIDGE SLIDES BACK
OVERHEAD. THOUGH TIME WILL TELL. THE MAIN WIND CONCERNS THRU THE
PERIOD WILL BE DUE TO THUNDERSTORM OUTFLOWS.

&&

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

&&

$$

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

MEYER/CERNIGLIA/GLUECK




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