Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 030450
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
950 PM MST WED SEP 2 2015

.SYNOPSIS...THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
THURSDAY AFTERNOON AND EVENING. ISOLATED TO SCATTERED THUNDERSTORMS
WILL THEN PREVAIL FRIDAY INTO EARLY NEXT WEEK. THE BULK OF THIS
ACTIVITY WILL OCCUR FROM TUCSON EAST AND SOUTH WITH LESSER CHANCES
WEST OF TUCSON. EXPECT REDUCED THUNDERSTORM CHANCES BY THE MIDDLE OF
NEXT WEEK.

&&

.DISCUSSION...IR SATELLITE IMAGERY AND SURFACE OBSERVATIONS DEPICTED
PARTLY CLOUDY TO CLOUDY SKIES FROM TUCSON EWD TO THE NEW MEXICO
BORDER AT THIS TIME. MEANWHILE...CLEAR SKIES PREVAILED ACROSS WRN
PIMA COUNTY. THIS FORECAST AREA WAS VOID OF PRECIP ECHOES VALID
0445Z AS PER KEMX WSR-88D. HOWEVER...A THUNDERSTORM COMPLEX
WAS MOVING NEWD ACROSS NERN SONORA MEXICO...AND CLOUD TOPS WERE
COOLING ACROSS FAR SERN SECTIONS AHEAD OF THIS RELATIVELY SMALL MCS.

BASED ON SATELLITE/RADAR TRENS AS WELL AS THE 03/00Z NAM12 AND
SEVERAL HRRR SOLUTIONS...HAVE MAINTAINED A SLIGHT CHANCE OF SHOWERS/
TSTMS ACROSS MUCH OF SE ARIZONA THE REST OF TONIGHT. PRECIP-FREE
CONDITIONS WILL CONTINUE ACROSS WRN PIMA COUNTY.

HOWEVER...HAVE NOTED SOME DIFFERENCES BETWEEN THE HRRR SOLUTIONS AND
THE NAM12 REGARDING PRECIP POTENTIAL INTO EARLY THUR MORNING. THE
HRRR HAS BEEN CONSISTENT WITH DEVELOPING MOSTLY LIGHT RAIN AMOUNTS
ACROSS COCHISE COUNTY LATER TONIGHT...ESSENTIALLY AROUND 10Z...THEN
EXPANDING THE COVERAGE OF SHOWERS/TSTMS NWWD INTO ERN PIMA/SE PINAL
COUNTIES AROUND DAYBREAK THUR.

MEANWHILE...THE NAM12 DEPICTED MEASURABLE RAINFALL TO OCCUR LATER
TONIGHT MAINLY CONFINED TO PORTIONS OF GRAHAM COUNTY AND NERN PIMA
COUNTY. THEREAFTER...THE NAM12 DEPICTED FAIRLY EXTENSIVE COVERAGE OF
LIGHT TO MODERATE RAIN AMOUNTS TO OCCUR ACROSS MUCH OF THE AREA BY
LATE THUR MORNING...THEN HEAVIER AMOUNTS TO OCCUR ESPECIALLY SE OF
TUCSON THUR AFTERNOON.

AT ANY RATE...THE OFFICIAL FORECAST CONTINUES WITH AT LEAST A SLIGHT
CHANCE OF SHOWERS/TSTMS ACROSS MUCH OF THE AREA THUR MORNING...THEN
AT LEAST CHANCE-CATEGORY POPS ACROSS MUCH OF THIS FORECAST AREA THUR
AFTERNOON/EVENING. HIGH TEMPS THUR ARE FORECAST TO AVERAGE ABOUT
5 DEGS F COOLER VERSUS TEMPS ACHIEVED THIS AFTERNOON.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.AVIATION...VALID THRU 04/06Z.
ISOLATED -TSRA/-SHRA WILL OCCUR INTO THURSDAY MORNING...WITH THE
BULK OF THIS ACTIVITY SE OF KTUS AND ESPECIALLY IN THE VICINITY OF
THE KDUG TERMINAL. SCATTERED TO NUMEROUS -TSRA/-SHRA WILL THEN OCCUR
ACROSS MUCH OF THE AREA THURSDAY AFTERNOON AND EVENING. MVFR
CONDITIONS AND WIND GUSTS OF 35-45 KTS WILL OCCUR WITH THE STRONGER
TSRA. OTHERWISE...EXPECT LAYERED CLOUDS MOSTLY BETWEEN 8-15K FT AGL
AND SURFACE WIND GENERALLY LESS THAN 10 KTS INTO THURSDAY EVENING.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A GOOD CHANCE OF THUNDERSTORMS WILL PREVAIL
THURSDAY AND THURSDAY EVENING...PARTICULARLY FROM TUCSON EAST AND
SOUTH TO THE NEW MEXICO/INTERNATIONAL BORDERS. ISOLATED TO
SCATTERED THUNDERSTORMS WILL THEN OCCUR FRIDAY INTO EARLY NEXT
WEEK. THE LEAST ACTIVITY WILL OCCUR ACROSS FIRE ZONE 150 WEST
TO NORTHWEST OF TUCSON. BRIEF STRONG...GUSTY AND ERRATIC WINDS WILL
ACCOMPANY THE STRONGER THUNDERSTORMS. A GRADUAL DRYING TREND WILL
LEAD TO LESS THUNDERSTORM ACTIVITY BY NEXT WEDNESDAY. OTHERWISE...
EXPECT TERRAIN DRIVEN WINDS MOSTLY LESS THAN 15 MPH INTO NEXT WEEK.

&&

.PREV DISCUSSION /135 PM MST/...THURSDAY THERE IS ANOTHER IMPULSE ON
ITS WAY TO AFFECT THE AREA ALTHOUGH MODELS INDICATE THAT IT MAY BE A
FEW HOURS LATER THAN TODAYS PUTTING THE FOCUS LATER IN THE DAY AND
OVERNIGHT THURSDAY. AGAIN THE POTENTIAL FOR LOCAL FLOODING AND WET
MICROBURST ACTIVITY. SHOULD BE ENOUGH FLOW ALOFT TO RESET THE
ATMOSPHERE SO WILL MAINTAIN THE RELATIVELY HIGH POPS.

BEYOND THAT WE STILL MAINTAIN A SOUTH TO SW FLOW ACROSS THE AREA
WITH MOISTURE STREAMING NORTH SATURDAY AND SUNDAY ALTHOUGH THE
MOISTURE ISN/T QUITE AS HIGH. COULD/SHOULD ALSO HAVE SOME
DISTURBANCES IN THAT FLOW TO HELP CONVECTION AT TIMES ALTHOUGH TOO
EARLY TO TRY TO CAPTURE AND TIME THOSE. THROUGH OUT THE THURSDAY
THROUGH SUNDAY TIME FRAME...DUE TO CLOUDS...PRECIPITATION AND LOWER
THICKNESS VALUES HIGH TEMPERATURES WILL BE SEVERAL DEGREES BELOW
NORMAL.

THEN BOTH THE GFS (WHICH PICKED THIS WHOLE SCENARIO UP WELL THUS
FAR) AND THE ECMWF INDICATED A MORE SIGNIFICANT DISTURBANCE WILL
ROTATE UP THROUGH HERE WITH A FAIR AMOUNT OF MOISTURE. THE DETAILS
DIFFER...HOWEVER WITH BOTH SHOWING A SIMILAR IDEA THIS FAR OUT IT
NEEDS TO BE NOTED. IF IT WERE TO COME TO PASS IT SHOULD PROVIDE FOR
ANOTHER VERY ACTIVE DAY OF CONVECTION. THEN BEYOND THAT THE TREND
IS TO A MORE WESTERLY FLOW WHICH WOULD SLOWLY DRY OUT THE AIR MASS
WITH TEMPERATURES CLIMBING BACK UP TO NORMAL LEVELS.

&&

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

&&

$$

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