Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 211634
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
934 AM MST THU MAY 21 2015

.SYNOPSIS...A SERIES OF LOW PRESSURE SYSTEMS MOVING NORTH OF THE
AREA WILL BRING GUSTY WINDS AND COOLER TEMPERATURES INTO SATURDAY.
WE SHOULD THEN SEE A WARMING TREND WITH TEMPERATURES RECOVERING TO
NORMAL VALUES ALONG WITH LESS WIND MOST OF NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 21/12Z UPPER-AIR PLOTS SHOW A
LOW PRESSURE SYSTEM JUST OFF THE NORTH CENTRAL CALIFORNIA COAST...
WITH RIDGING ACROSS TEXAS...NEW MEXICO AND INTO THE CENTRAL ROCKIES.

IR AND VISIBLE SATELLITE IMAGERY SHOWS EXTENSIVE CLOUDINESS OVER
MUCH OF THE SOUTHWEST U.S. WITH THE MOST OPAQUE CLOUDINESS COVERING
ARIZONA AND SOUTHERN UTAH.

THIS MORNINGS KTWC SOUNDING REVEALED A PRECIPITABLE WATER VALUE OF
0.37 WHICH IS FAIRLY SIMILAR FROM THE PAST SEVERAL SOUNDINGS. THE
WINDS IN THE PROFILE REFLECT THE EXPECTED INCREASE IN WINDS WITH
FAIRLY LIGHT WINDS RIGHT OFF THE DECK...WITH 13 KNOTS AT 850MB...
NEARLY 30 KN0TS AT 700MB AND 50+ KNOTS JUST ABOVE 500MB. WITH THE
EXTENSIVE MID AND HIGH LEVEL CLOUDS WE WILL NOT BE ABLE TO MIX AS
WELL...SO THE WINDS AT THE SURFACE SHOULD REMAIN MOSTLY BELOW RED
FLAG CONDITIONS TODAY...BUT WE WILL CONTINUE TO MONITOR THROUGHOUT
THE DAY IN CASE CONDITIONS BECOME MORE WIDESPREAD THAN CURRENT
THINKING...SINCE SOUTHERN ARIZONA IS ON THE SOUTHERN MOST FRINGE OF
THE CLOUDINESS AT THIS TIME.

AS OF 16Z (9 AM MST)...TEMPERATURES RANGED FROM THE UPPER 60S TO THE
MID 70S...WITH THE TUCSON INTL AIRPORT REPORTING A TEMP OF 72 DEGS
AFTER A MORNING LOW OF 60 DEGS...WHICH WAS 2 DEGS BELOW NORMAL.
THESE READINGS SEEM TO BE ON TRACK WITH RESPECT TO EXPECTED
AFTERNOON HIGH TEMPERATURES. HOWEVER...CURRENT TEMPS ALONG THE
INTERNATIONAL BORDER ARE SIGNIFICANTLY WARMER THAN WHAT IS CURRENTLY
IN THE HOURLY TEMP GRIDS. WILL MAKE ADJUSTMENTS TO REFLECT THESE
RECENT TRENDS. OTHERWISE...THE FORECAST FOR THE REMAINDER OF THIS
AFTERNOON IS ON TRACK.

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

&&

.AVIATION...VALID THRU 22/12Z.
EXPECT SCT CLOUDS AT 10-15K FT AGL AND BROKEN CLOUDS ABOVE 20K FT.
SURFACE WIND INCREASING THROUGH THE MORNING...BETWEEN 16Z-20Z...AND
CONTINUING INTO EARLY EVENING SLY/SWLY AT 12-25 KTS WITH GUSTS OF 25-
35 KTS. THE STRONGEST WIND WILL BE IN THE VICINITY OF KDUG. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A COOLING TREND IS EXPECTED THROUGH SATURDAY BEFORE
TEMPERATURES WARM TO NEAR-NORMAL LEVELS NEXT WEEK ALONG WITH DRY
CONDITIONS.

THE MAIN HIGHLIGHT OF THIS PERIOD CONTINUES TO BE THE DEVELOPMENT OF
STRONG SOUTHWESTERLY WINDS THROUGH THE END OF THE WEEK. CRITICAL
FIRE WEATHER CONDITIONS MAY BE MET IN A FEW LOCATIONS THIS AFTERNOON
BEFORE POSSIBLY BEING A LITTLE MORE WIDESPREAD FRIDAY
AFTERNOON...PRIMARILY ACROSS SOUTHERN PORTIONS OF FIRE WEATHER ZONES
151 AND 152. HOWEVER...CRITICAL THRESHOLDS ARE EXPECTED TO BE MET
ONLY FOR BRIEF PERIODS AND OVER RELATIVELY LOCALIZED AREAS. WE WILL
NEED TO KEEP A CLOSE EYE OUT FOR ANY POTENTIAL STRENGTHENING OF THIS
SYSTEM THAT MAY REQUIRE THE ISSUANCE OF WATCHES AND/OR WARNINGS
DURING THE NEXT 12 TO 24 HOURS.

&&

.PREV DISCUSSION...INCREASING CIRRUS LEVEL MOISTURE ALONG WITH SOME
MID LEVEL MOISTURE IN THE INCREASING SOUTHWESTERLY FLOW AHEAD OF THE
NEXT WEATHER SYSTEM. LOWER LEVELS STILL VERY MUCH ON THE DRY SIDE.
GUSTY SOUTHWEST WINDS WILL MIX DOWN TO THE SURFACE THIS AFTERNOON
BUT BELOW WIND ADVISORY LEVELS.

THE INITIAL IMPULSE WILL LIFT QUICKLY NORTHEAST TONIGHT AS A
STRONGER ONE SHIFTS IN FROM SOUTHERN CALIFORNIA FRIDAY. STRONGER
WINDS FRIDAY BUT STILL NOT STRONG ENOUGH FOR HEADLINES. PLEASE SEE
THE FIRE WEATHER DISCUSSION BELOW FOR ANY CRITICAL FIRE WEATHER
CONCERNS.

NEXT WEEK IS MORE PROBLEMATIC AS A RIDGE TRIES TO SET UP OVER
CENTRAL MEXICO AND NOSE NORTHWARD IN OUR DIRECTION. INITIALLY A
SIMPLE HEIGHT RECOVERY TO MORE SEASONAL LEVELS IN THE NEUTRAL FLOW
NORTH OF THIS FEATURE WILL BOUNCE SURFACE TEMPS BACK UP TO CLIMO.
WHAT THEN? THERE IS STILL A LOT OF ENERGY IN A CHAOTIC AND SOMEWHAT
AMPLIFIED PACIFIC PATTERN MORE COMMON TO APRIL THAN MAY. WE MAY BE
ABLE TO KNOCK THIS FIRST SERIOUS ATTEMPT AT A PATTERN CHANGE BACK
TOWARD ANOTHER WEEK OF SOME FLAVOR OF SOUTHERN ENERGY SPLIT. MOST
LIKELY HOWEVER...WE WILL SEE SOMETHING IN BETWEEN THAT WOULD TEND TO
BRING US EVEN SHARPER BUT LESS FREQUENT PERIODS OF WINDS AS WE
CONTINUE THE OVERALL SHIFT TO WARMER TEMPERATURES NEAR AND ABOVE
SEASONAL AVERAGES.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE

&&

$$

CURRENT DISCUSSION...MOLLERE
PREVIOUS DISCUSSION...MEYER/RASMUSSEN

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