Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 040431
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
930 PM MST SUN MAY 3 2015

.SYNOPSIS...A PACIFIC LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
SHOWERS AND THUNDERSTORMS ALONG WITH A COOLING TREND THROUGH
TUESDAY. THE BEST CHANCE FOR WIDESPREAD RAINFALL WILL OCCUR MONDAY.
DRY CONDITIONS...AFTERNOON BREEZINESS AND HIGH TEMPERATURES A FEW
DEGREES BELOW NORMAL WILL THEN PREVAIL DURING THE LATTER PART OF
THIS WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY...04/00Z UPPER-AIR PLOTS AND THE
MOST RECENT MODEL DATA SHOW AN UPPER LOW SPINNING OVER THE EASTERN
PACIFIC WATERS JUST WEST OF SOUTHERN CALIFORNIA AND NORTHERN BAJA.
PLENTY OF DRY MID LEVEL AIR COVERING MUCH OF THE EASTERN PACIFIC AND
ACROSS NORTHERN BAJA...SRN CALIFORNIA AND INTO THE SOUTHERN HALF OF
ARIZONA. IR SATELLITE IMAGERY SHOWS MID LEVEL CLOUDINESS CONTINUING
TO DRIFT NORTHWARD ACROSS MOSTLY CENTRAL AND EASTERN PORTIONS OF MY
FORECAST AREA. RADAR MOSAIC SHOWS ISOLATED SHOWERS AND A FEW
THUNDERSTORMS CONTINUING TO MOVE NORTHWARD ACROSS THE STATE.
CURRENTLY SOME WEAK RETURNS OVER THE NORTHERN PORTIONS OF THE TUCSON
METRO...WITH ADDITIONAL ACTIVITY SOUTH OF THE BORDER TO THE SOUTH
SOUTHEAST OF NOGALES. FARTHER NORTH SHOWERS AND STORMS CAN BE SEEN
MOVING THROUGH NORTHERN PORTIONS OF THE PHOENIX METRO AND NORTH OF
THE MOGOLLON RIM AS WELL.

THIS EVENINGS KTWC SOUNDING SHOWED A SLIGHT INCREASE IN THE
PRECIPITABLE WATER VALUE...WITH A READING OF 0.59 INCHES COMPARED TO
0.55 INCHES FROM THIS MORNING...BUT DRIER THAN 24 HOURS AGO WHEN THE
PW WAS 0.70 INCHES. MODELS INDICATE THAT PW`S WILL CONTINUE TO
INCREASE OVERNIGHT AND INTO MONDAY AS THE UPPER LOW MAKES ITS WAY
INTO WESTERN ARIZONA AND SOUTH TO SOUTHWESTERLY FLOW AHEAD OF THE
LOW WILL ALLOW ADDITIONAL MOISTURE TO BE TRANSPORTED INTO ARIZONA.
MODELS SHOW PW`S INCREASING TO AROUND 0.65-0.80 INCHES BY MONDAY
AFTERNOON. INHERITED POP FORECAST REFLECTS SLIGHT CHANCE
SHOWERS/THUNDERSTORMS LINGERING OVERNIGHT...BUT THEN INCREASING
CONSIDERABLY MONDAY AFTERNOON...WITH THE BEST THREAT OVER
PINAL...GRAHAM AND GREENLEE COUNTIES WHERE SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS WILL DEVELOP. THAT SAID...THE FORECAST
SEEMS TO BE ON TRACK FOR THE OVERNIGHT PERIOD...SO NO CHANGES ARE
PLANNED BUT WILL CONTINUE TO MONITOR.

AS OF 04Z (9 PM MST)...TEMPERATURES ACROSS THE REGION RANGED FROM
THE UPPER 60S TO 80 DEGREES AT THE TUCSON INTL AIRPORT. THE HIGH
TEMP THIS AFTERNOON IN TUCSON WAS 90 DEGS...WHICH WAS 3 DEGS ABOVE
NORMAL FOR THIS DATE. THE CURRENT READINGS SEEM TO BE ON TRACK WITH
THE INHERITED OVERNIGHT LOW TEMPERATURE FORECASTS...SO NO CHANGES
ARE PLANNED TO THE TEMPS EITHER.

FOR DETAILS REGARDING THE FORECAST BEYOND TONIGHT...PLEASE REFER TO
THE PREVIOUS DISCUSSION BELOW.

&&

.AVIATION...VALID THRU 05/06Z. EXPECT ISOLATED -SHRA/-TSRA TO
CONTINUE TO LINGER THROUGH THE OVERNIGHT HOURS. MOST OF THE ACTIVITY
WILL OCCUR N AND E OF A INTERSTATE 10 WITH CLOUD BASES 9-12K FT AGL.
EXPECT LOWERING CLOUD BASES TO 4-7K FT AGL AND INCREASED COVERAGE OF
-SHRA/-TSRA THROUGH MONDAY. BRIEF ERRATIC WIND GUSTS TO 45 KTS WILL
BE POSSIBLE NEAR ANY CONVECTION ALONG WITH POCKETS OF BLOWING DUST
SUNDAY AFTERNOON AND EVENING. SURFACE WINDS WILL BE LIGHT AND
VARIABLE TONIGHT...THEN SWLY/WLY AT 10-18 KTS WITH GUSTS OF 20-25
KTS SUNDAY AFTERNOON...THEN DIMINISHING AFTER SUNSET. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...AN APPROACHING STORM SYSTEM WILL BRING AT LEAST A
SLIGHT CHANCE OF PRECIPITATION TO THE REGION THROUGH TUESDAY. A FEW
SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS EVENING...MAINLY NORTH
AND EAST OF TUCSON. PRECIPITATION COVERAGE IS EXPECTED TO INCREASE
SOMEWHAT LATE TONIGHT AND TOMORROW WITH THE BULK OF THE ACTIVITY
AGAIN PRIMARILY REMAINING NORTH AND EAST OF TUCSON. BRIEF AND
ERRATIC WIND GUSTS UP TO 40-50 MPH WILL BE POSSIBLE NEAR SHOWERS AND
STORMS...PARTICULARLY DURING THE AFTERNOON HOURS.

SUBSTANTIALLY DRIER CONDITIONS ARE ANTICIPATED FROM WEDNESDAY
THROUGH THE WEEKEND ALONG WITH BREEZY TO LOCALLY WINDY CONDITIONS.
THE COMBINATION OF LOW RELATIVE HUMIDITY VALUES AND STRONG WINDS MAY
PRODUCE AREAS OF CRITICAL FIRE WEATHER CONDITIONS ON THURSDAY AND
FRIDAY.

&&

.PREV DISCUSSION...AS LOW PRESSURE CURRENTLY WEST OF SRN CAL DRAWS
NEARER...LIFT WILL INCREASE AS FLOW BECOMES INCREASINGLY DIFFLUENT
OVERNIGHT INTO MONDAY AND AS COLDER AIR ALOFT INCREASES INSTABILITY
MONDAY. SOME MOISTURE WILL ALSO RETURN BUT BEST DYNAMICS WILL
GENERALLY REMAIN NORTH OF OUR AREA. SO WHILE CHANCES FOR SHOWERS AND
THUNDERSTORMS WILL INCREASE FROM LATER TONIGHT THROUGH MONDAY
NIGHT...BEST PRECIP CHANCES REMAIN TO THE NORTH. THUS HAVE LOWERED
CHANCES ALONG INTERNATIONAL BORDER.

AS THE LOW PASSES...SHOWERS AND COOLER DAYTIME TEMPERATURES MAY
LINGER INTO TUESDAY. TEMPERATURES WILL WARM SLIGHTLY WED AND
THU...BACK TO NEAR NORMAL. HOWEVER...THE NEXT AREA OF LOW PRESSURE
APPROACHING FROM THE NW WILL COOL TEMPERATURES FRI AND SAT. THIS
NEXT SYSTEM WILL PASS FARTHER TO OUR NORTH THAN THE ONE AFFECTING
OUR WEATHER THE NEXT COUPLE OF DAYS. THUS...WINDS WILL BE THE MAIN
CONCERN THURSDAY THROUGH SATURDAY WHILE RAIN CHANCES WILL SHOULD
REMAIN WELL TO OUR NORTH.

&&

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

&&

$$

CURRENT DISCUSSION...MOLLERE
PREVIOUS DISCUSSION...DROZD/CARLAW

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



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