Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 290954
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
254 AM MST FRI APR 29 2016

.SYNOPSIS...
ISOLATED SHOWERS ARE POSSIBLE ACROSS THE WHITE MOUNTAINS THROUGH
MONDAY AS A SERIES OF WEAK LOW PRESSURE SYSTEMS MOVE THROUGH THE
REGION. RIDGING WILL BUILD ACROSS THE SOUTHWESTERN UNITED STATES BY
THE MIDDLE OF NEXT WEEK...RESULTING IN INCREASING TEMPERATURES AND
DRY WEATHER.

&&

.DISCUSSION...
EARLY MORNING WATER VAPOR IMAGERY CONTINUES TO REVEAL SLOW MOVING
LOW PRESSURE OVER THE FOUR CORNERS. THIS IS THE SYSTEM THAT BROUGHT
STRONG WINDS TO PARTS OF THE AREA YESTERDAY ALONG WITH A FEW LATE-
AFTERNOON/EVENING SHOWERS NORTH/EAST OF TUCSON. SINCE THEN IT HAS
MOVED EAST AND TRIGGERED EARLY MORNING CONVECTION ACROSS THE TEXAS
PANHANDLE. IN ITS WAKE...NORTHWESTERLY FLOW PERSISTS ACROSS THE AREA
BUT A WEAK SHORTWAVE TROUGH IS NOTED IN THE FLOW NEAR LAS VEGAS.
CLOUDS ARE ON THE INCREASE ACROSS CENTRAL ARIZONA BUT MUCH OF
SOUTHEASTERN ARIZONA REMAINS CLEAR AS OF 09Z. TEMPS REMAIN SOMEWHAT
MILD THIS MORNING...GENERALLY IN THE MID/UPPER 50S GIVEN 5-10KTS OF
WIND AT NEARLY ALL SITES.

THE AFOREMENTIONED SHORTWAVE TROUGH WILL SWEEP THROUGH THE AREA
TODAY BUT WILL REMAIN TO THE NORTH OF TUCSON. MODEST INCREASES IN
MOISTURE IMMEDIATELY AHEAD OF THE TROUGH COULD BE JUST ENOUGH TO
PRODUCE SOME LIGHT SHOWERS/SPRINKLES BUT THIS WOULD LIKELY BE
CONFINED TO THE HIGHER TERRAIN LOCATIONS NORTH/EAST OF TUCSON.
FORECAST SOUNDINGS ARE LARGELY UNIMPRESSIVE ACROSS THE LOWER
ELEVATIONS AND POPS WILL REMAIN BELOW 10 PERCENT. SHORTWAVE RIDGING
IS FORECAST ACROSS THE AREA LATE FRIDAY NIGHT INTO SATURDAY...THUS
THE WINDOW OF OPPORTUNITY FOR PRECIP IS NARROW.

ANOTHER...DEEPER LOW IS FORECAST TO DROP THROUGH THE GREAT BASIN
THROUGH ARIZONA ON SUNDAY AND AT FIRST GLANCE IT MIGHT SEEM THAT
PRECIP CHANCES WOULD BE SIGNIFICANT...ESPECIALLY GIVEN H5 HEIGHT
PERCENTILES SOMEWHERE ON THE LOWER END OF THE SPECTRUM /BETWEEN 2-5
PERCENT/. HOWEVER...MOISTURE /PWATS AND IVT/ IS FORECAST TO REMAIN
WELL WITHIN CLIMATOLOGICAL NORMALS FOR EARLY MAY. FORECAST SOUNDINGS
ARE ONCE AGAIN LARGELY UNSUPPORTIVE OF PRECIPITATION ACROSS THE
LOWER ELEVATIONS AND ASIDE FROM A CHANCE OF SHOWERS IN THE
WHITES...THE MAIN IMPACT WILL BE IN THE FORM OF WINDS AND COOLER
TEMPS. GEFS PLUMES ARE DRY ACROSS THE LOWER ELEVATIONS AND NAEFS
INDICATES 20-30 POPS WOULD BE WARRANTED ONLY TO THE NORTH.

LOOKING TOWARD NEXT WEEK...HIGH AMPLITUDE RIDGING WILL TAKE SHAPE
FROM TUESDAY THROUGH AT LEAST THURSDAY...RESULTING IN A RETURN OF
THE ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS. THERE IS SOME
SUGGESTION FROM BOTH THE DETERMINISTIC AND PROBABILISTIC ECMWF AND GFS
THAT A LOW WILL DROP THROUGH SOUTHERN CALIFORNIA...POSSIBLY DRAWING
MOISTURE NORTHWARD INTO NEW MEXICO AND EASTERN ARIZONA. THE
AMPLITUDE OF THE TROUGH AND MAGNITUDE OF ANY MOISTURE ADVECTION IS
STILL UNCERTAIN AT THIS TIME BUT I FELT THAT HIGHER THAN CLIMO POPS
ARE WARRANTED IN THIS CASE ALONG WITH COOLER TEMPERATURES.

&&

.AVIATION...VALID THRU 30/12Z.
SKC TO FEW CLOUDS AT 8-12K FT AGL THIS MORNING WITH SCT COVERAGE
THIS AFTERNOON. THERE IS A CHANCE OF -SHRA/-TSRA MAINLY ACROSS THE
WHITE MOUNTAINS NE OF KSAD. TERRAIN DRIVEN SFC WIND THIS MORNING
WILL INCREASE AND BECOME WLY/NWLY AT 12-16 KTS WITH GUSTS TO 25 KTS
THIS AFTERNOON. STRONGEST WINDS WILL BE N AND E OF KTUS INCLUDING
KSAD. WIND SPEEDS LESSEN TO GENERALLY LESS THAN 10 KTS LATE THIS
EVENING INTO SATURDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS NORTH
TO NORTHEAST OF TUCSON AND ESPECIALLY ACROSS THE WHITE MOUNTAINS
THROUGH MONDAY. DRY CONDITIONS RETURN THEREAFTER ALONG WITH A
WARMING TREND. EXPECT AFTERNOON BREEZINESS FROM THE NORTHWEST TO
SOUTHWEST TO CONTINUE THROUGH THE WEEKEND WITH LESS WIND INTO THE
MIDDLE OF NEXT WEEK.

&&

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

&&

$$

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