Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 230336
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
836 PM MST WED JUL 22 2015

.SYNOPSIS...MOISTURE WILL CONTINUE TO INCREASE ACROSS SOUTHEAST
ARIZONA INTO FRIDAY. THIS WILL LEAD TO SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS FOR MUCH OF SOUTHEAST ARIZONA THURSDAY
INTO FRIDAY BEFORE A DRYING TREND RETURNS OVER THE WEEKEND. ANOTHER
UPSWING IN THUNDERSTORM ACTIVITY IS THEN EXPECTED NEXT WEEK.

&&

.DISCUSSION...JUST A FEW LINGERING SHOWERS OVER SOUTHEAST ARIZONA
THIS EVENING...MAINLY IN NOGALES AND DOUGLAS AREAS WHERE LIGHT RAIN
IS FALLING AT ABOUT 0.01 OR 0.02 INCH PER HOUR. PLENTY OF
THUNDERSTORM ACTIVITY UPWIND OVER SONORA BUT CLOUD TOP TRENDS ARE
WARMING...INDICATING WEAKENING.  STILL ENOUGH LOW LEVEL MOISTURE IN
PLACE THAT A STRAY STORM OR TWO CANNOT BE RULE OUT OVERNIGHT IN SE
AZ THOUGH...ESPECIALLY IN SRN AND ERN SECTIONS WHERE BEST OVERALL
MOISTURE RESIDES.  WILL KEEP IN A 10 PERCENT CHANCE FOR TUCSON.

UPWIND CONVECTION COULD THROW A WRENCH INTO THURSDAY`S FORECAST BUT
AT THIS POINT IT LOOKS LIKE CONVECTIVE DEBRIS WILL ROTATE
NORTHEASTWARD...LIKELY EXITING OR THINNING ACROSS SE AZ OVER THE
NEXT 6 TO 12 HOURS.  THEREFORE...THERE SHOULD BE ENOUGH HEATING OVER
MUCH OF THE AREA TO BRING MODEL INDICATED INSTABILITY TO FRUITION BY
AFTERNOON. THE RESULTANT UPTICK IN THUNDERSTORM COVERAGE IS ALREADY
FORECAST FOR THU AFTN SO NO ADJUSTMENTS WILL BE MADE AT THIS TIME.
SEE PREV DISCUSSION FOR DETAILS.

&&

.AVIATION...VALID THRU 24/06Z.
SCT-BKN CLOUDS AT 8 TO 12 KFT WITH ISOLD -SHRA AND POSSIBLY A -TSRA
SE OF A LINE FROM KSAD-KOLS OVERNIGHT.  A MORE ACTIVE DAY THURSDAY
WITH SCT TSRA POSSIBLE AFTER 23/19Z. OUTSIDE OF TSRA INFLUENCE
SURFACE WINDS WILL GENERALLY BE UNDER 12 KT...AND TERRAIN DRIVEN.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A MORE ACTIVE COUPLE DAYS ARE IN STORE THURSDAY AND
FRIDAY...WITH SOUTHERLY FLOW USHERING IN INCREASED MOISTURE. SHOWERS
AND THUNDERSTORMS SHOULD START EARLIER IN THE AFTERNOON AS WELL AS
SEEING A BIT WIDER COVERAGE COMPARED TO WEDNESDAY. DRIER AIR
SHOULD SUBDUE STORM CHANCES...OUTSIDE OF THE EASTERN ZONES...OVER
THE WEEKEND...BUT ANOTHER ROUND OF INCREASED MOISTURE IS EXPECTED
NEXT WEEK. 20-FT WINDS WILL GENERALLY BE TERRAIN DRIVEN AND UNDER 15
MPH...EXCEPT NEAR THUNDERSTORMS.

&&

.PREV DISCUSSION...WITH THE UPPER HIGH IN A FAVORABLE POSITION TO
PULL DEEPER MOISTURE SITUATED TO OUR SOUTH/SOUTHEAST INTO THE REGION
OVER THE NEXT 24-48 HOURS...EXPECT INCREASING AFTERNOON AND EVENING
PRECIPITATION CHANCES ACROSS MUCH OF SOUTHEAST ARIZONA THROUGH
FRIDAY. HAVE INCREASED POPS ON BOTH THURSDAY AND FRIDAY...BUT MORE
SUBSTANTIALLY THURSDAY AFTERNOON AND EVENING...WITH 50 POPS FOR THE
GREATER TUCSON METRO AREA LATE THURSDAY AFTERNOON/EVENING AND HIGHER
PRECIPITATION CHANCES TO THE SOUTH/SOUTHEAST ALONG THE INTERNATIONAL
BORDER. THERE WILL THEN BE A 40 PERCENT CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE TUCSON AREA FRIDAY AFTERNOON/EVENING.

AS THE UPPER HIGH SHIFTS CLOSER TO THE STATE OVER THE WEEKEND...
EXPECT LESS FAVORABLE FLOW...AS WELL AS WARMER TEMPERATURES ALOFT.
THIS WILL LEAD TO A DECREASE IN SHOWER AND THUNDERSTORM ACTIVITY...
WITH MOST OF THE CONVECTION CONFINED TO THE EASTERN ZONES. A GRADUAL
INCREASE IN SHOWERS AND THUNDERSTORMS IS THEN EXPECTED NEXT WEEK.

HIGH TEMPERATURES WILL BE BELOW NORMAL THROUGH FRIDAY (TOPPING OUT
IN THE MID 90S IN THE TUCSON METRO AREA THURSDAY AND FRIDAY)...THEN
WARMING BACK ABOVE NORMAL OVER THE WEEKEND...WITH A GRADUAL LOWERING
TREND NEXT WEEK.

&&

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

&&

$$

KD

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