Special Weather Statement, NWS Tucson, AZ

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE TUCSON AZ
1004 AM MST MON OCT 5 2015

.SYNOPSIS...A CHANCE OF SHOWERS AND THUNDERSTORMS TODAY AHEAD OF A
LOW PRESSURE SYSTEM APPROACHING FROM SOUTHERN CALIFORNIA. AFTER A
FEW SHOWERS THIS MORNING...THE BEST CHANCES WILL BE EAST OF TUCSON
TODAY. AS THE LOW PUSHES DIRECTLY INTO THE AREA...MUCH OF SOUTHEAST
ARIZONA WILL SEE A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS
TUESDAY. CONDITIONS ARE FAVORABLE FOR STRONGER STORMS TODAY AND
TUESDAY. IN ADDITION...EXPECT COOLER TEMPERATURES COMPARED TO RECENT
DAYS...AND GUSTY WINDS AT TIMES. A FEW SHOWERS STILL POSSIBLE NEAR
THE MOUNTAINS WITH A SLOW WARMING TREND LATE IN THE WEEK.

&&

.DISCUSSION...A FEW SHOWERS AND THUNDERSTORMS WERE DEVELOPING EARLY
THIS MORNING IN THE TUCSON MOUNTAINS AND NORTH OF TUCSON IN PINAL
COUNTY WHERE MOST OF THE ACTIVITY HAS BEEN SO FAR. THE CLOSED UPPER
LOW WAS CENTERED OVER SOUTHERN CALIFORNIA THIS MORNING...AND WAS
PROGGED TO EJECT EASTWARD TO A POSITION CENTERED OVER WEST-CENTRAL
AZ BY LATE TUESDAY MORNING. MOISTURE WAS STILL SOMEWHAT LIMITED
ACROSS SOUTHEAST ARIZONA AND SOME MID-LEVEL DRYING WILL TAKE PLACE
TODAY. NONETHELESS...THE SHEAR PROFILE AND CAPE VALUES WERE
FAVORABLE FOR SUPPORTING STRONG THUNDERSTORMS SOME WITH HAIL AND
STRONG WINDS TODAY. THIS DISCUSSION WAS UPDATED EARLIER THIS
MORNING...SO PLEASE REFERENCE THE PREVIOUS DISCUSSION SECTION IN
THIS PRODUCT FOR MORE DETIALS. OTHERWISE...NO UPDATES NECESSARY AT
THIS TIME.

&&

.AVIATION...VALID THRU 06/18Z.
SCT TO LOCALLY BKN CLOUDS 6-10 KFT WITH ISOLD -SHRA/TSRA FROM KTUS
AND KOLS EAST THRU 05/16Z. EAST WINDS 5-15 KTS ACROSS
COCHISE...GRAHAM AND GREENLEE COUNTIES WITH SOUTH WIND TO 10 KTS
ELSEWHERE. AFT 05/16Z SCT-BKN 6-10 KFT AND ISOLD-SCT -SHRA/-TSRA
WITH GREATEST CHANCES FROM EAST OF KTUS.  GUSTY SOUTHERLY WINDS WILL
AGAIN DEVELOP AFT 05/16Z AT 12-18 KTS AND GUSTS TO 30 KTS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...AN AREA OF LOW PRESSURE WILL BE IMPACTING SOUTHEAST
ARIZONA THROUGH MUCH OF THE COMING WEEK. THIS SYSTEM WILL BRING
INCREASED MOISTURE WITH A CHANCE OF SHOWERS AND THUNDERSTORMS
THROUGH WEDNESDAY. A FEW STORMS COULD BE STRONG MONDAY AND TUESDAY
AFTERNOON. OTHERWISE...EXPECT BREEZY SOUTHERLY WINDS AGAIN MONDAY
THEN LIGHT WINDS THE REMAINDER OF THE WEEK. TEMPERATURES WILL
CONTINUE TO COOL DOWN WITH HIGHS BELOW NORMAL THROUGH MIDWEEK...THEN
MODERATING LATER THIS WEEK.

&&

.PREV DISCUSSION...MORNING UPDATE...THE 12Z KTWC SOUNDING HAS PLENTY
OF MOISTURE WITH PRECIPITABLE WATER STILL AROUND 1 INCH. DECENT
CONVECTIVE POTENTIAL AND IMPRESSIVE SHEAR FOR OUR AREA WITH BRN AT
52 M^2/S^2. THE CURRENT CONVECTION IS ALONG A GOOD SHEAR AXIS
THROUGH SANTA CRUZ AND EASTERN PIMA COUNTIES...NORTHWARD THROUGH
PINAL AND GILA COUNTIES. THESE FACTORS WOULD ARGUE FOR A BUSIER DAY
THROUGH EASTERN PIMA COUNTY AND THE GREATER TUCSON AREA THAN
CURRENTLY ADVERTISED. HOWEVER...THE HRRR ROTATES (WE BELIEVE
CORRECTLY) THIS MOST FAVORABLE SHEAR AREA INTO GRAHAM COUNTY THIS
AFTERNOON. IN ADDITION...THE LATEST CIRA LAYERED PRECIPITABLE WATER
IMAGERY FOR 700-500 HPA IS PUSHING DRIER AIR ABOVE H7 IN FROM THE
SOUTHWEST THIS MORNING. THIS IS HINTED AT BY THE MORNING SOUNDING
WHERE THERE ARE SPIKES REPRESENTING THE ONSET OF THIS DRYING SHOWING
UP NEAR H7 AND H6. SO WE ARE STANDING PAT FOR NOW WITH THE CURRENT
FORECAST IN THE 20 PERCENT RANGE FOR CONVECTION IN THE TUCSON METRO
AREA THIS AFTERNOON. WE AGREE WITH THE POTENTIAL HIGHLIGHTED IN THE
SWODY1 BY SPC...HOWEVER WE WOULD EMPHASIZE AREAS EAST AND NORTH OF
TUCSON FOR SEVERE THUNDERSTORMS. ESPECIALLY GRAHAM...GREENLEE AND
PORTIONS OF EASTERN PINAL COUNTY THIS AFTERNOON.

FROM THE PREVIOUS DISCUSSION...ALL THE PIECES ARE IN PLACE...NOW
IT'S JUST A TIMING ISSUE. THE STRONG LOW HAS MADE IT'S WAY INTO
SOUTHERN CALIFORNIA THIS MORNING AND HAS LOST MOST OF IT'S HIGHER
LATITUDE SUPPORT AS EXPECTED. WE WILL SEE A SLOW WOBBLE EASTWARD
TODAY WITH A STRONG SOUTHWESTERLY FLOW ABOVE H7 AND LOWER LEVELS
CONTINUING TO IMPORT MOISTURE FROM THE SOUTH. OVERALL THE
CONDITIONAL RISK IS ELEVATED FOR HAIL AND DAMAGING WINDS THIS
AFTERNOON...WITH DECENT SHEAR AND INSTABILITY ACROSS MOST OF THE
AREA. SOME MID LEVEL DRYING MAY INHIBIT OVERALL COVERAGE FOR PART OF
THE AREA TODAY. PRECIPITABLE WATER VALUES BETWEEN 3/4 AND 1 INCH IN
EASTERN AREAS...HOWEVER SOME TEMPORARY MID LEVEL DRYING WRAPPING
INTO THE AREA FROM THE SOUTHWEST MAY TEND TO LIMIT COVERAGE IN
CENTRAL AREAS THIS AFTERNOON...INCLUDING EASTERN PIMA COUNTY AND THE
GREATER TUCSON AREA. THE BEST COVERAGE COMES TOGETHER WITH THE
INCREASED THREAT FOR SEVERE ACROSS EASTERN AREAS...INCLUDING
GRAHAM...GREENLEE AND COCHISE COUNTIES.

AS THE LOW SLOWLY PUSHES TOWARD SOUTHEAST ARIZONA TUESDAY AND
TUESDAY NIGHT...WE WILL SEE EVEN BETTER CONDITIONS FOR INCREASED
STORM COVERAGE. A POSSIBLE SWEET SPOT IN TIMING IS TUESDAY AFTERNOON
WHERE JET DYNAMICS JUST AHEAD OF THE LOW...A LITTLE DAYTIME
HEATING...AND A LOW LEVEL MOISTURE CONVERGENT FIELD COME TOGETHER
FOR POTENTIALLY STRONG THUNDERSTORM COVERAGE FOR OUR PART OF THE
STATE.

THIS CUTOFF ACTUALLY BEGINS TO REACT TO THE STRONG RIDGE WEST OF THE
AREA LATER THIS WEEK. A SLOW DROP INTO NORTH CENTRAL TO NORTHWEST
MEXICO KEEPS IT AROUND FOR DAYS AND DAYS AS IT SLOWLY FILLS.
INTERESTING THAT BOTH ECMWF AND GFS ARE KEEPING IT IN PROXIMITY
THROUGH 240 HOURS. SO SLOW WARMING TREND AS HEIGHTS REBOUND AND SOME
DRYING...BUT A FEW SHOWERS HANGING AROUND MAINLY MOUNTAIN AND
INTERNATIONAL BORDER AREAS INTO THE COMING WEEKEND.

&&

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

&&

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

PREV DISCUSSION...MEYER/RASMUSSEN

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TUCSON AZ
1221 PM MST MON OCT 5 2015

AZZ509-510-052000-
UPPER GILA RIVER AND ARAVAIPA VALLEYS INCLUDING CLIFTON/SAFFORD AZ-
WHITE MOUNTAINS OF GRAHAM AND GREENLEE COUNTIES INCLUDING HANNAGAN
MEADOW AZ-
1221 PM MST MON OCT 5 2015

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN GRAHAM AND SOUTHERN
GREENLEE COUNTIES UNTIL 100 PM MST...

AT 1220 PM MST...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM
NEAR GUTHRIE...MOVING NORTHEAST AT 25 MPH.

HALF INCH HAIL AND WINDS IN EXCESS OF 40 MPH WILL BE POSSIBLE WITH
THIS STORM.

LOCATIONS IMPACTED INCLUDE...
CLIFTON...MORENCI...DUNCAN...FRANKLIN AND GUTHRIE.

LAT...LON 3246 10957 3295 10954 3320 10905 3262 10905
TIME...MOT...LOC 1920Z 231DEG 22KT 3286 10926

GL