Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 201602
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
902 AM MST SUN JUL 20 2014

.SYNOPSIS...EXPECT ISOLATED TO SCATTERED THUNDERSTORMS MOSTLY EAST
AND SOUTH OF TUCSON THROUGH THE MIDDLE OF THE UPCOMING WEEK. MUCH
HOTTER TEMPERATURES WILL OCCUR TUESDAY THROUGH THURSDAY...WITH NEAR
RECORD HIGHS POSSIBLE. A PRONOUNCED INCREASE IN THUNDERSTORM
ACTIVITY SHOULD THEN PREVAIL BY THE END OF THE UPCOMING WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 20/12Z UPPER-AIR PLOTS SHOW AN
UPPER LOW OVER SOUTH CENTRAL CALIFORNIA AND INTO SRN NEVADA AND
MOVING NORTH. MEANWHILE...A RIDGE IS PARKED OVER THE GENERAL
VICINITY OF WESTERN NEW MEXICO. THIS HAS RESULTED IN A STRONG
SOUTHERLY FLOW ALOFT IN THE MID TO UPPER LEVELS...WITH STEERING FLOW
AROUND 15 KNOTS.

THIS MORNINGS KTWC SOUNDING HAD THE LOWEST/DRIEST PRECIPITABLE WATER
VALUE THAT WE HAVE SEEN IN A WHILE...ESPECIALLY FOR A MORNING
SOUNDING WITH A VALUE OF 1.04 INCHES. CLIMATOLOGICALLY THIS PW VALUE
FALLS IN THE 25TH PERCENTILE FOR THIS TIME OF YEAR...WHICH IS PRETTY
DRY...RELATIVELY SPEAKING. THAT SAID...STILL EXPECT ISOLATED SHOWERS
AND THUNDERSTORMS TO DEVELOP OVER THE HIGHER TERRAIN OF NORTHEAST
SONORA AND NORTHWEST CHIHUAHUA THIS AFTERNOON...WITH A FEW CELLS
MOVING INTO SOUTHERN PORTIONS OF COCHISE COUNTY AND PERHAPS PARTS OF
SANTA CRUZ COUNTY AS WELL. U OF A 12Z WRF/NAM MODEL SHOWS A SIMILAR
SCENARIO. THAT SAID...THINK THE POP FORECAST FOR THIS AFTERNOON AND
EVENING SEEM TO BE ON TRACK...SO NO CHANGES PLANNED AT THIS TIME.

AS OF 15Z (8 AM MST)...TEMPERATURES ACROSS THE REGION RANGED FROM
THE UPPER 70S TO THE LOWER 80S...WITH THE TUCSON INTL AIRPORT
REPORTING A TEMP OF 81 DEGS...AFTER A MORNING LOW OF 78 DEGS. THINK
THE INHERITED AFTERNOON HIGH TEMPERATURES ARE ON TRACK...BUT WILL
CONTINUE TO MONITOR AND MAKE CHANGES IF NEEDED.

FOR DETAILS REGARDING THE FORECAST BEYOND THIS AFTERNOON...PLEASE
REFER TO THE PREVIOUS DISCUSSION BELOW.

&&

.CLIMATE...NEAR RECORD HEAT EXPECTED TUESDAY THROUGH THURSDAY. THE
FORECAST EXCEEDS RECORD LEVELS ON WEDNESDAY AND THURSDAY WITH
TEMPERATURES AROUND 110 AT TUCSON INTERNATIONAL. THIS WOULD BE THE
FIRST 110 TEMPS OF THE YEAR AND HOTTEST JULY TEMPS SINCE 2011 (110
OR GREATER OCCURRENCES ARE MOST COMMON IN JUNE BEFORE THE MONSOON
ARRIVES).

&&

.AVIATION...ISOLATED TO SCATTERED -TSRA/-SHRA WILL OCCUR MOSTLY EAST
AND SOUTH OF KTUS THIS AFTERNOON AND EVENING. THE BEST CHANCES WILL
OCCUR ACROSS THE WHITE MOUNTAINS NE OF KSAD...AND SOUTH OF KTUS
ESPECIALLY IN THE VICINITY OF THE KOLS/KDUG TERMINALS. BRIEF MVFR
VISIBILITIES AND WIND GUSTS TO NEAR 35 KTS MAY OCCUR WITH THIS
ACTIVITY. CLOUD DECKS THIS AFTERNOON GENERALLY AT 8-12K FT AGL.
BREEZY SURFACE WIND IN THE GILA RIVER VALLEY IN THE VICINITY OF
KSAD...WITH WLY/NWLY SURFACE WIND AT 14-18 KTS THIS AFTERNOON/EARLY
EVENING. OTHERWISE... SURFACE WIND OUTSIDE OF ANY TSRA OUTFLOW
INFLUENCES WILL GENERALLY BE 12 KTS OR LESS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...ISOLATED TO SCATTERED THUNDERSTORMS WILL OCCUR
MAINLY NEAR THE INTERNATIONAL BORDER AND IN THE EASTERN MOUNTAINS
ALONG THE NEW MEXICO BORDER THROUGH THE MIDDLE OF THE UPCOMING
WEEK. STRENGTHENING HIGH PRESSURE ALOFT WILL ALSO BRING HOTTER
TEMPERATURES TUESDAY THROUGH THURSDAY. THEREAFTER...INCREASED
THUNDERSTORM ACTIVITY SHOULD OCCUR DURING THE LATTER PART OF THE
UPCOMING WEEK AND INTO NEXT WEEKEND. BREEZY WINDS ARE EXPECTED IN
THE UPPER GILA RIVER VALLEY AROUND SAFFORD TODAY...AS WELL AS MONDAY
AFTERNOON AND EVENING.

&&

.PREVIOUS DISCUSSION...MOISTURE FOR THUNDERSTORMS WILL CONTINUE TO
BE RATHER LIMITED AGAIN TODAY AND FOR THE MOST PART THIS NEXT FEW
DAYS. THAT SAID...THUNDERSTORM CHANCES WILL TAKE A BACK SEAT TO NEAR
RECORD HEAT BY THE MIDDLE OF THE WEEK. MODELS WERE STILL SHOWING A
STRONG RIDGE OF HIGH PRESSURE ALOFT DEVELOPING OVER THE DESERT
SOUTHWEST THIS WEEK. THE TEMPERATURE FORECAST VALUES WILL BE KEYING
OFF OF THICKNESS VALUES WHICH CORRELATE WELL WITH HIGH TEMPERATURES
AND WERE PROGGED TO PEAK AROUND WEDNESDAY AND THURSDAY. THE GOING
FORECAST CALLS FOR HIGH TEMPERATURES TO BE ABOUT 5 DEGREES WARMER
THAN MOS WHICH STILL LOOKED REASONABLE. THE ONLY QUESTION WILL BE
THE AMOUNT OF MOISTURE WHICH WILL BE ON THE INCREASE LATER THIS WEEK
AS THE UPPER HIGH BUILDS AND BECOMES CENTERED AROUND EAST-CENTRAL
ARIZONA. AT ANY RATE...THE EXCESSIVE HEAT IN COMBINATION WITH A MORE
FAVORABLE FLOW PATTERN FOR THUNDERSTORMS SHOULD TRANSLATE TO
ELEVATED RAIN CHANCES BY THE END OF THE WEEK.

&&

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

&&

$$

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