Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 042058
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
158 PM MST SAT JUL 4 2015

.SYNOPSIS...SOUTHEAST ARIZONA WILL EXPERIENCE AN UPSWING IN SHOWERS
AND THUNDERSTORMS SUNDAY. SLOWER MOVING STORMS WILL ELEVATE HEAVY
RAINFALL CONCERNS. DAYTIME TEMPERATURES WILL REMAIN CLOSE TO
SEASONAL NORMALS.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 04/12Z UPPER-AIR PLOTS SHOW A
RIDGE IN THE GENERAL VICINITY OF THE GREAT BASIN...WITH A LOW
PRESSURE SYSTEM WELL OFFSHORE OF THE SOUTHERN CALIFORNIA COAST.

IR SATELLITE IMAGERY SHOWS EXTENSIVE CLOUDINESS COVERING MUCH OF THE
DESERT SOUTHWEST AND EXTENDING NW INTO THE GREAT BASIN. THE CLOUDS
ARE MOSTLY LEFT OVER DEBRIS CLOUDINESS FROM THE OVERNIGHT
THUNDERSTORM COMPLEX THAT DEVELOPED SOUTH OF THE BORDER AND PUSHED
INTO COCHISE COUNTY. IN ADDITION...THE LATEST VISIBLE SATELLITE
IMAGERY SHOWS AN MCV SEEMINGLY SOMEWHERE BETWEEN TUCSON AND NOGALES
AND CONTINUING TO MOVE TO THE NORTH NORTHWEST. NORMALLY WHEN THESE
FEATURES DEVELOP OVER THE REGION THE CONVECTION TENDS TO DEVELOP ON
THE PERIPHERY OF THE SYSTEM AND THAT IS THE CASE CURRENTLY WITH
RADAR MOSAIC SHOWING MOST OF THE SHOWERS AND STORMS SOUTHWEST OF
TUCSON THROUGH PARTS OF THE METRO AND INTO THE CATALINA`S. THESE
STORMS ALSO CONTINUE TO THE NORTHEAST OVER PARTS OF GRAHAM AND
GREENLEE COUNTIES AS WELL. ONLY ISOLATED ACTIVITY SEEN OVER COCHISE
AND SANTA CRUZ COUNTIES.

THE 17Z RUN OF THE HRRR WANTS TO SHOW ONLY ISOLATED ACTIVITY AS WE
HEAD INTO THIS EVENING...AND THIS WOULD GIVE CREDANCE TO THE NOTION
THAT THE MCV TENDS TO SUPPRESS ACTIVITY NEAR THE SYSTEM AS IT MOVES
NORTHWARD THROUGH THE STATE. HOWEVER...EARLIER RUNS OF THE HRRR
(EVEN THE 16Z RUN) WERE SHOWING MORE SCATTERED ACTIVITY INTO THE
EVENING HOURS. THAT SAID...GIVEN THAT TODAY IS THE FOURTH...WITH
PLENTY OF EVENING FESTIVITIES SCHEDULED...THINK THE BEST COURSE OF
ACTION WOULD BE TO KEEP THE SCATTERED ACTIVITY IN THE FORECAST FOR
TONIGHT. THEN...IF SATELLITE AND RADAR TRENDS SUGGEST THE 17Z RUN OF
THE HRRR WITH ONLY ISOLATED ACTIVITY IS CORRECT...THE EVENING SHIFT
CAN UPDATE THE FORECAST TO REFLECT A LOWER THREAT OF THUNDERSTORMS
IMPACTING EVENING HOLIDAY CELEBRATIONS.

MODELS SUGGEST SUNDAY WITH BE AN ACTIVE DAY WITH THE MCV HAVING
MOVED WELL TO THE NORTH BY THAT TIME. IF WE SEE MORE SUN
TOMORROW...THEN WE SHOULD DEFINITELY HAVE AN ACTIVE DAY.

BY MONDAY...AS THE LOW PRESSURE SYSTEM OVER THE PACIFIC IS PROGGED
TO MAKE ITS WAY TOWARD THE WEST COAST AND EVENTUALLY INTO THE GREAT
BASIN...WE SHOULD SEE MORE OF A SOUTHWESTERLY COMPONENT TO OUR
WINDS...WHICH WILL PUSH MOISTURE EASTWARD...THUS LIMITING
THUNDERSTORM ACTIVITY MOSTLY TO AREAS BETWEEN TUCSON AND THE NEW
MEXICO BORDER FOR MUCH OF THE WORK WEEK.

&&

.AVIATION...VALID THRU 06/00Z.
SCATTERED TO NUMEROUS -TSRA/-SHRA WILL OCCUR INTO SUNDAY AFTERNOON.
BRIEF WIND GUSTS OF 35-45 KTS MAY ACCOMPANY THE STRONGER TSRA.
OTHERWISE...CLOUD DECKS WILL MAINLY BE AT OR ABOVE 8K FT AGL AND
SURFACE WIND WILL GENERALLY BE LESS THAN 10 KTS. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL
OCCUR THIS WEEKEND. THE MAIN IMPACT WILL BE THE COMBINATION OF BRIEF
STRONG AND GUSTY WINDS AND HEAVY RAINFALL. SOMEWHAT REDUCED COVERAGE
OF SHOWERS AND THUNDERSTORMS WILL BEGIN MONDAY.
THEREAFTER...ADEQUATE MOISTURE WILL MAINTAIN ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS TUESDAY INTO NEXT SATURDAY. GENERALLY
LIGHT TERRAIN DRIVEN WINDS WILL PREVAIL OUTSIDE OF THUNDERSTORM
INFLUENCES.

&&

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

&&

$$

PUBLIC...MOLLERE
AVIATION/FIRE WEATHER...FRANCIS

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


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