Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 291018
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 AM MST WED JUL 29 2015

.SYNOPSIS...AN ELEVATED CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
SOUTHEAST ARIZONA WILL CONTINUE THIS WEEK WITH SOME STORMS PRODUCING
LOCALLY HEAVY RAIN AND STRONG WINDS. CHANCES WILL CONTINUE OVER THE
WEEKEND...BUT COVERAGE WILL DECREASE WITH A WEAKER FLOW AS HIGH
PRESSURE INCREASES ALOFT.

&&

.DISCUSSION...LOTS OF DEBRIS SHOWERS WITH ISOLATED LIGHTNING STRIKES
IN REMAINS OF LAST NIGHT`S ACTIVITY...AND AHEAD OF REMNANT
CONVECTION MOVING IN FROM THE SOUTH AND EAST EARLY THIS MORNING.
THERE IS A REMNANT MESOSCALE CONVECTIVE VORTEX FROM JUST WEST AND
NORTHWEST OF TUCSON FROM OUR COMPLEX LAST NIGHT...MOVING NORTHWEST
INTO PINAL COUNTY AT 245 AM. A NICE LINE OF CONVECTION HAS FORMED ON
THE PERIPHERY JUST AHEAD OF THIS FEATURE THROUGH PORTIONS OF WESTERN
PINAL AND SOUTH TO SOUTHEAST MARICOPA COUNTIES. MEANWHILE...A SLOWLY
WEAKENING SMALLER AREA OF ORGANIZED CONVECTION REMAINS IN TACT
IMMEDIATELY SOUTHEAST OF DOUGLAS...MOVING INTO COCHISE COUNTY OVER
THE NEXT SEVERAL HOURS. ELSEWHERE SCATTERED EMBEDDED LIGHT SHOWERS
REMAIN.

A DIFFICULT CALL TODAY AS WE ARE NOT SEEING MUCH OF A CHANCE TO
CLEAR OVERNIGHT. WE WILL INITIALLY START THE DAY WITH MORE SHOWER
ACTIVITY THAN EXPECTED...LINGERING THROUGH AT LEAST THE MID MORNING
HOURS. WITH LATER HEATING WE WILL BE SLOW TO REDEVELOP THUNDERSTORMS
THIS AFTERNOON. INITIAL DEVELOPMENT SHOULD FAVOR AREAS THAT WERE NOT
AS HEAVILY IMPACTED WITH MID AFTERNOON DEVELOPMENT OF STORMS
EXPECTED ACROSS ESPECIALLY COCHISE COUNTY. AFTER THAT WE SHOULD FILL
IN ACROSS OTHER AREAS. THE STEERING LEVEL FLOW IS INCREASING BETWEEN
THE LOW NOW UP TO CENTRAL BAJA AND THE HIGH PRESSURE TO OUR
EAST...SO STORM MOVEMENT WILL INCREASE A BIT COMPARED TO YESTERDAY
AND WE SHOULD BE ABLE TO RESET THE ATMOSPHERE BY LATE AFTERNOON IN
AREAS THAT WERE HIT YESTERDAY. WITHOUT AS MUCH SUNSHINE IN THOSE
AREAS WILL WE HAVE SOMETHING TO TRIGGER THE RESET CONVECTIVE
POTENTIAL? OUTFLOWS FROM CONVECTION IN EASTERN AREAS MAY PLAY A ROLL
IN THAT. ALSO...LATER DEVELOPMENT NEAR THE INTERNATIONAL BORDER FROM
ANOTHER IMPULSE APPROACHING FROM THE SOUTH (AROUND 00Z OR SO) COULD
HELP IN THE EARLY EVENING HOURS. HEAVY RAIN AND ISOLATED FLASH FLOOD
CONCERNS ONCE AGAIN. ISOLATED SEVERE POSSIBLE. THIS IMPULSE LIFTING
THROUGH SOUTHEAST ARIZONA IN THE EVENING HOURS WILL ONCE AGAIN TEND
TO KEEP SOME ACTIVITY GOING OVERNIGHT.

BY THURSDAY THE LOW TO OUR SOUTHWEST WILL HAVE LIFTED OUT OF THE
PICTURE...BUT THE SOUTHERLY TO SOUTHEASTERLY FLOW WILL REMAIN...IF
PERHAPS A BIT WEAKER. WE SHOULD CONTINUE TO SEE A CHANCE OF STORMS
WITH MORE TYPICAL DIURNAL TRENDS. WE`LL HAVE TO SEE HOW BUSY TONIGHT
AND THURSDAY MORNING ARE. A WEAKER FLOW GENERALLY MEANS THE
ATMOSPHERE WILL TAKE LONGER TO RESET.

AFTER THAT WE WILL KEEP SOME FLAVOR OF MONSOONAL FLOW BUT NOT AT AN
INTENSITY THAT WILL FAVOR ORGANIZED CONVECTION. WE`LL KEEP THE
FORECAST AT CLIMATOLOGY OVER THE WEEKEND INTO EARLY NEXT WEEK AND
KEEP AN EYE OUT FOR UP/DOWN DETAILS AS MINOR FEATURES IN THE FLOW
PRESENT THEMSELVES.

NOTE THAT THE AIRPORT HAD 1.49 INCH OF RAIN YESTERDAY AND .02 TODAY
AS OF 3 AM. THE TUCSON ASOS STOPPED COUNTING PRECIP DUE TO AN ERROR
AFTER ABOUT 630 PM YESTERDAY BUT WE ARE MANUALLY ABLE TO SEE THE 1
MINUTE DATA HERE...HENCE THE 1.49 INCH VALUE WHICH IS HIGHER THAN
THE HOURLY METARS WHICH DIDN`T INCLUDE SOME OF THE PRECIP.

&&

.AVIATION...VALID THRU 30/12Z.
SCT-BKN CLOUDS AT 8-14K FT AGL AND BKN-OVC CLOUDS AT 15-20K FT AGL
WITH RESIDUAL -SHRA/-TSRA THIS MORNING. SCT-NUMEROUS SHRA/TSRA
DEVELOPING AGAIN AFT 29/21Z THROUGH ABOUT 30/04Z MVFR CONDITIONS AND
VRB WIND GUSTS TO 40 KTS POSSIBLE IN AND AROUND THE STRONGER TSRA.
OUTSIDE OF STORM INFLUENCES...SFC WINDS WILL GENERALLY BE LESS THAN
12 KTS WITH A FEW HIGHER GUSTS IN THE AFTERNOON/EARLY EVENING HOURS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...PLENTY OF MOISTURE FOR A CONTINUED CHANCE OF SHOWERS
AND THUNDERSTORMS. STRONG OUTFLOW WINDS WILL BE POSSIBLE NEAR
THUNDERSTORMS...WITH WIND GUSTS BETWEEN 40 AND 45 MPH. OTHERWISE...
20-FT WINDS WILL GENERALLY BE TERRAIN DRIVEN AND LESS THAN 15
MPH...WITH SOME AFTERNOON AND EARLY EVENING BREEZINESS DUE TO THE
STRONG DAYTIME HEATING.

&&

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

&&

$$


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