Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 271055
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
355 AM MST SUN JUL 27 2014

.SYNOPSIS...EXPECT SCATTERED MAINLY AFTERNOON AND EVENING
THUNDERSTORMS THIS WEEK. SOME STORMS WILL GENERATE LOCALLY HEAVY
RAIN AND STRONG GUSTY WINDS.

&&

.DISCUSSION...KEMX WSR-88D DETECTED NUMEROUS 35-55 DBZ ECHOES ACROSS
WRN/CENTRAL PIMA COUNTY VALID 1050Z. ISOLATED MOSTLY LESS THAN 45
DBZ ECHOES WERE OCCURRING FROM TUCSON EWD/SWD TO THE NEW MEXICO/
INTERNATIONAL BORDERS. IR SATELLITE IMAGERY INDICATED MCS EXTENDING
FROM SOUTH CENTRAL AZ SEWD INTO NRN SONORA. VARIOUS RUC HRRR
SOLUTIONS HAVE BEEN VERY CONSISTENT WITH DEPICTING PRECIP TO
CONTINUE UNTIL AROUND MID-MORNING WEST OF TUCSON AS A MCV MOVES NWWD
ACROSS NWRN SONORA. MEANWHILE...THE ISOLATED SHOWERS/TSTMS ONGOING
FROM TUCSON EWD/SWD HAVE NOT BEEN WELL HANDLED BY THE RUC HRRR...
THAT HAD BEEN VERY CONSISTENT WITH DEPICTING PRECIP-FREE CONDITIONS
TO OCCUR THRU LATE THIS MORNING.

SUN-MON...
UPPER RIDGE IS PROGGED TO AMPLIFY OVER THE WRN CONUS. AMPLE MOISTURE
WILL BE AVAILABLE TO SUPPORT SCATTERED SHOWERS/TSTMS...WITH THE BULK
OF THE ACTIVITY TO OCCUR DURING THE AFTERNOON/EVENING HOURS.
ALTHOUGH NO TWO DAYS ARE EXACTLY IDENTICAL DURING THE MONSOON...FROM
A NWP MODEL PERSPECTIVE...THERE APPEAR TO BE SIMILARITIES WITH
HAPPENED SAT AND SAT NIGHT AND WHAT IS PROGGED TO OCCUR THIS PERIOD.
FOR INSTANCE...IF CLEARING IS SUFFICIENT ACROSS ERN SECTIONS DURING
THE MORNING HOURS...THEN SHOWER/TSTM INITIATION SHOULD OCCUR EAST-
TO-SOUTH OF TUCSON BY EARLY AFTERNOON. THIS ACTIVITY SHOULD THEN
MOVE GENERALLY NWWD AND BECOME DOMINANT WEST OF TUCSON AFTER
MIDNIGHT INTO THE EARLY MORNING HOURS. AT ANY RATE...THE MAIN
THREATS WILL BE STRONG WIND GUSTS AND HEAVY RAINFALL.

TUE-WED...
27/00Z GFS/ECMWF WERE SIMILAR WITH DEPICTING DECREASED COVERAGE OF
SHOWERS/TSTMS AS THE MID-LEVEL STEERING FLOW BECOMES INCREASINGLY
WLY. THERE WILL BE ENOUGH MOISTURE TO MAINTAIN SCATTERED MOSTLY
AFTERNOON AND EVENING SHOWERS/TSTMS EAST-TO-SOUTH OF TUCSON WITH
LESSER PRECIP CHANCES NORTHWEST OF TUCSON.

THUR-SAT...
GFS/ECWMF WERE SIMILAR WITH DEPICTING INCREASING MOISTURE ACROSS SE
AZ AS THE UPPER HIGH BECOMES CENTERED NEAR THE FOUR CORNERS REGION.
THESE SOLUTIONS DIVERGED FROM PREVIOUS SOLUTIONS THAT DEPICTED A
POTENTIAL DRYING TREND ESPECIALLY ACROSS WRN SECTIONS BY EARLY NEXT
WEEKEND. HAVE ALSO NOTED THAT THE ECMWF WAS MARKEDLY MORE ROBUST
WITH QPF/S AND THE POTENTIAL FOR HEAVY RAINFALL VERSUS THE GFS.
STILL MUCH TOO SOON TO HAVE HIGH CONFIDENCE IN JUST ONE SOLUTION OF
MEDIUM RANGE FORECAST MODELS. AT ANY RATE...HAVE OPTED TO INCREASE
INHERITED POPS SOMEWHAT...ESPECIALLY BY NEXT SAT SCATTERED COVERAGE
OF SHOWERS/TSTMS IS EXPECTED TO OCCUR ACROSS MUCH OF THE AREA.

HIGH TEMPS THRU SAT WILL GENERALLY BE QUITE CLOSE TO SEASONAL
NORMALS. THE EXCEPTION WILL BE WED-THUR WHEN HIGH TEMPS ARE FORECAST
TO AVERAGE ABOUT 2-5 DEGS F OR SO ABOVE NORMAL.

&&

.AVIATION...VALID THRU 28/12Z.
EXPECT SCATTERED TSRA/SHRA THRU EARLY MONDAY MORNING. MVFR VSBYS
SHOULD OCCUR WITH THE STRONGER TSRA ALONG WITH WIND GUSTS TO NEAR
40-45 KTS. CLOUD DECKS WILL GENERALLY BE AT 7-12K FT AGL THRU THE
PERIOD. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED MOSTLY AFTERNOON AND EVENING THUNDERSTORMS
WILL PREVAIL THIS WEEK. EXPECT STRONG...GUSTY AND ERRATIC WINDS NEAR
THE STRONGER STORMS. OTHERWISE...NORMAL DIURNAL WIND TRENDS WILL
OCCUR WITH OCCASIONAL GUSTS DURING THE AFTERNOON HOURS DUE TO
DAYTIME HEATING.

&&

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

&&

$$

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FRANCIS





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