Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 290400
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 PM MST THU AUG 28 2014

.SYNOPSIS...A DRY NORTHWEST TO WEST FLOW ALOFT WILL CONTINUE THROUGH
THE LABOR DAY HOLIDAY WEEKEND WITH AFTERNOON HIGH TEMPERATURES NEAR
OR ABOVE NORMAL THROUGH LABOR DAY. EARLY NEXT WEEK MOISTURE WILL
BEGIN TO SLOWLY INCREASE WITH A THREAT OF SHOWERS RETURNING TO
SOUTHERN PORTIONS OF THE AREA NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 29/00Z UPPER-AIR PLOTS
INDICATE HIGH PRESSURE IS CENTERED OVER THE GENERAL VICINITY OF THE
EASTERN PACIFIC WATERS OFF THE SOUTHERN CALIFORNIA COAST. A LARGE
AREA OF VERY DRY MID LEVEL AIR CAN BE SEEN FROM THE CALIFORNIA COAST
EASTWARD THROUGH ARIZONA INTO MUCH OF NEW MEXICO AND WEST TEXAS.
THIS EVENINGS KTWC SOUNDING SHOWED A PRECIPITABLE WATER VALUE OF
0.94 INCHES...WITH THE BULK OF THIS MOISTURE IN THE 700-625MB LAYER
WHERE EARLIER THIS AFTERNOON THERE WAS A DECENT AMOUNT OF CUMULUS
CLOUDS CORRESPONDING TO THIS MOIST LAYER.

IR SATELLITE IMAGERY INDICATES THAT THE CUMULUS CLOUDS HAVE BEEN
ERODING SINCE SUNSET FOR A CLEAR NIGHT EXPECTED ACROSS SOUTHEAST
ARIZONA.

AS OF 03Z (8 PM MST)...TEMPERATURES ACROSS THE REGION RANGED FROM
THE LOWER 70S TO 90 DEGS...WITH THE TUCSON INTL AIRPORT REPORTING 90
DEGS AFTER REACHING AN AFTERNOON HIGH OF 99 DEGS...WHICH WAS 1 DEG
ABOVE NORMAL FOR THIS DATE. THE CURRENT TEMPERATURE READINGS SEEM TO
BE ON TRACK WITH THE INHERITED OVERNIGHT LOW TEMPERATURE
FORECASTS...BUT WILL CONTINUE TO MONITOR SURFACE OBSERVATIONS AND
WILL MAKE ADJUSTMENTS IF NEEDED. OTHERWISE...THE FORECAST FOR THE
REMAINDER OF TONIGHT IS IN GOOD SHAPE.

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

&&

.AVIATION...VALID THRU 30/00Z. CLEAR SKIES EXPECTED THROUGH FRIDAY.
NW SFC WINDS LIGHT AND VARIABLE THROUGH 29/20Z.  AFTER 29/20Z SFC
WIND BECOMING NW TO 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS. CERNIGLIA

&&

.FIRE WEATHER...DRY AIR OVER THE REGION THROUGH THE WEEKEND WILL
RESULT IN MOSTLY CLEAR SKIES...WARMER AFTERNOON TEMPERATURES AND
BELOW NORMAL RH LEVELS FOR THIS TIME OF YEAR.  EXPECT A LIGHT
WESTERLY BREEZE EACH AFTERNOON WITH LIGHT TERRAIN DRIVEN WINDS THE
REMAINDER OF THE DAY.  NEXT WEEK WILL SEE A MODERATION IN RH LEVELS
EARLY IN THE WEEK AS MOISTURE TRIES EASING BACK INTO THE AREA WITH A
SMALL THREAT OF CONVECTION RETURNING AROUND MID WEEK.  LONGER RANGE
MODELS INDICATE A POTENTIAL FOR A SIGNIFICANT INCREASE IN MOISTURE
LATE NEXT WEEK INTO NEXT WEEKEND.  STAY TUNED.  CERNIGLIA

&&

.PREVIOUS DISCUSSION...IT IS EXPECTED TO BE A BIT DRIER TOMORROW
WITH FEWER CLOUDS AND LOWER RH VALUES.  PRECIPITABLE WATER VALUES
BELOW AN INCH WILL REMAIN LOW THROUGH SUNDAY AND THAT COMBINED WITH
HIGHER HEIGHTS AND THICKNESS VALUES WILL TRANSLATE INTO HIGHER
AFTERNOON TEMPERATURES.  I BOOSTED HIGH TEMPS A BIT THIS WEEKEND
WITH THE FORECAST ENDING UP 1 TO 4 DEGREES WARMER THAN NORMAL.  THIS
IS STILL NOT AS WARM AS LOCAL GUIDANCE BASED ON THICKNESS VALUES
WOULD SUGGEST BUT TEMPERED IT A BIT DUE TO THE MOISTURE WE HAVE HAD
LATELY.

MONDAY THROUGH WEDNESDAY THE UPPER LEVEL FLOW TRIES TO BECOME A BIT
SOUTHEASTERLY WITH PW VALUES INCREASING A BIT...MAINLY ACROSS THE
INTERNATIONAL BORDER AREA.  BESIDES A BIT OF AN INCREASE IN HUMIDITY
FROM BELOW NORMAL LEVELS...THE ADDED MOISTURE WILL ALSO BRING A
SLIGHT THREAT OF SHOWERS AND/OR THUNDERSTORMS TO THE SOUTHEAST PART
OF THE FORECAST AREA.  I INCREASED HIGH TEMPS A DEGREE OR TWO THIS
PERIOD AS WELL AS THE AIR MASS OVER THE REGION REMAINS WARM...MOSTLY
DRY AND MOSTLY SUNNY AND DIDN`T FEEL WE SHOULD UNDERCUT GUIDANCE.

BEYOND THAT GUIDANCE SUGGESTS MONSOON MOISTURE RETURNS LATE NEXT
WEEK THROUGH NEXT WEEKEND WITH SOUTHEAST FLOW STRENGTHENING OVER THE
REGION.  AT THIS EARLY STAGE IT LOOKS LIKE A GOOD FETCH OF MOISTURE
WITH A POTENTIAL FOR A FEW IMPULSES TO ACT AS TRIGGERS.  CAN`T COUNT
THE 2014 MONSOON SEASON DEAD YET.  CERNIGLIA

&&

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

&&

$$

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