Funnel Cloud in Arizona, December 11, 2007

AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1045 AM MST TUE DEC 11 2007

SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA
FORECAST DISCUSSION

.SYNOPSIS...
THE LAST IN A SERIES OF LOW PRESSURE SYSTEMS WILL MOVE THROUGH THE
SOUTHWEST UNITED STATES TODAY. SHOWERS WITH EMBEDDED THUNDERSTORMS
WILL DEVELOP MAINLY ACROSS ARIZONA THIS AFTERNOON AS THE LOW PUSHES
EASTWARD ACROSS THE REGION. SMALL HAIL WILL BE POSSIBLE WITH THE
THUNDERSTORMS. SNOW LEVELS WILL REMAIN AROUND 4500 FEET...WITH A FEW
INCHES OF SNOW LIKELY THROUGH THE DAY. LESSER CHANCES FOR
PRECIPITATION ARE EXPECTED ACROSS SOUTHEAST CALIFORNIA. MOSTLY SUNNY
SKIES AND DRIER CONDITIONS ARE EXPECTED TO RETURN BY WEDNESDAY
AFTERNOON...WITH A GRADUAL WARMING TREND FOR THE LATTER HALF OF THE
WEEK.

&&

.SHORT TERM...
DECEMBER 11 1650 GMT (DECEMBER 11 0950 MST)

TODAY THROUGH THURSDAY...
SHORT WAVE MOVING INTO THE FORECAST AREA HAD RESULTED IN THE
FORMATION OF TWO SURFACE LOWS...ONE NEAR YUMA AND THE OTHER OFF THE
SAN DIEGO COASTLINE. SOUTHERLY FLOW/ISENTROPIC LIFT AHEAD OF THE
YUMA LOW IS RESULTING IN AN INCREASE OF MOISTURE AHEAD OF THE
SYSTEM. SATELLITE AND RADAR TRENDS...COMBINED WITH RAOB DATA
SUGGESTS THE POTENTIAL FOR CONVECTION/THUNDERSTORMS THIS AFTERNOON.
HAVE UPDATED FORECAST/GRIDDED FIELDS TO REFLECT THIS.

MODELS INITIALIZED WELL THIS MORNING AND ARE IN AGREEMENT THAT THE
AREA MOST LIKELY TO SEE PRECIPITATION THROUGH THE DAY WILL BE
CENTERED AROUND PINAL COUNTY. LIKE YESTERDAY...THERE WILL BE A SHARP
GRADIENT TO THE PRECIPITATION...LIKELY ACROSS MARICOPA COUNTY. HAVE
ADJUSTED GRIDS TO REFLECT THIS LINE OF THINKING. WILL MAINTAIN SNOW
ADVISORY THROUGH THE AFTERNOON...AS SNOW LEVELS REMAIN AROUND
4500-5000 FEET AND PRECIP EXPECTED TO CONTINUE THROUGH THE DAY.
UPDATED PRODUCTS TO BE SENT SHORTLY.

MODELS PORTRAY THE LOW QUICKLY MOVING EAST INTO NM...AND INTO THE
GREAT PLAINS WEDNESDAY AFTERNOON. STRONG SUBSIDENCE SETS IN BEHIND
THE DEPARTING LOW...SO WITH CLEARING SKIES AND A DRIER FLOW EXPECT
OVERNIGHT TEMPERATURES TO DROP INTO THE 30S THROUGHOUT OUR DESERTS
WEDNESDAY NIGHT...FLIRTING WITH THE FREEZING MARK BY THURSDAY
MORNING AT MANY LOCALES. MOS GUIDANCE IS NOT SUGGESTING A BIG DIP
IN TEMPERATURES...CURRENTLY STAYING AROUND 40 DEGREES FOR THE
PHOENIX METRO AREA. STILL...TEMPERATURES WILL HAVE TO BE CLOSELY
MONITORED BY FUTURE SHIFTS.

A WEAKER SHORT WAVE THEN FORMS OFF THE WEST COAST OF CA/OR...SLIDING
SE ALONG THE CA COAST THURSDAY. THIS TROF DEEPENS...WITH THE AXIS
EXTENDING FROM YUMA NORTHWARD THROUGH SALT LAKE CITY...SWEEPING
ACROSS THE STATE LATE THURSDAY...AND INTO THE NM/TX FRIDAY. COULD
SEE SOME LOCALLY BREEZY CONDITIONS...GUSTY NORTHERLY WINDS ALONG THE
LOWER COLORADO RIVER FRIDAY AFTERNOON.

&&

.LONG TERM...
DECEMBER 10 2125 GMT (DECEMBER 10 1425 MST)

THURSDAY NIGHT THROUGH MONDAY...
RELATIVELY QUIET WEATHER EXPECTED IN THE EXTENDED. 12Z GFS RUN
INDICATED THAT A RELATIVELY SMALL CUT-OFF LOW WILL MOVE ACROSS THE
FORECAST AREA SATURDAY. SYSTEM NOT OVERLY IMPRESSIVE AT THIS
TIME...SO WILL CONTINUE WITH DRY FORECAST. TEMPERATURES WILL BE
WARMING THROUGH THE PERIOD AS WELL AS HEIGHTS/TEMPS INCREASE AT ALL
LEVELS. OVERALL FEW CHANGES MADE AS BULK OF FOCUS IS ON SHORT TERM
EVENT.

&&

.AVIATION...
DECEMBER 11 1745 GMT (DECEMBER 11 1045 MST)
UPPER LEVEL LOW PRESSURE SYSTEM CURRENTLY LOCATED OVER SOUTHEAST CA
WILL EVENTUALLY SHIFT EASTWARD ACROSS AZ TODAY. EXPECT CLOUDS
TO PERSIST OVER SITES KPHX/KIWA THROUGHOUT THE DAY...WITH LOWEST
CLOUD DECKS NEAR 5K FT. CHANCE OF SCATTERED SHOWERS WILL DEVELOP
BETWEEN 20-00Z OVER CENTRAL AZ AS LOW PRESSURE CENTER
APPROACHES...WITH CIGS LOWERING TO NEAR 3K FT IN SHOWERS. AN
ISOLATED THUNDERSTORM OR TWO MAY ALSO BE POSSIBLE ACROSS CENTRAL
AZ. EXPECT SHOWERS TO DIMINISH THIS EVENING AND CLOUDS TO
DECREASE OVERNIGHT.

FOR TAF SITES KYUM/KIPL/KBLH...CLOUDS WILL GRADUALLY CLEAR
THROUGHOUT THE DAY AS LIGHT NORTHERLY WINDS TAKE HOLD. A STRAY
SHOWER OR TWO MAY AFFECT KIPL DURING THE AFTERNOON.

AVIATION DISCUSSION IS NOT UPDATED FOR AMENDED TAFS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...SNOW ADVISORY IN EFFECT THROUGH 3 PM MST TODAY FOR
     AZZ024.

CA...NONE.

&&

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

SHORT TERM...INIGUEZ/MEYERS
LONG TERM...INIGUEZ
AVIATION...J ROGERS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
1000 AM MST TUE DEC 11 2007

AZZ023-027-028-121300-
GREATER PHOENIX AREA-SOUTHWEST MARICOPA COUNTY-
NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
1000 AM MST TUE DEC 11 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED TO NUMEROUS SHOWERS WITH EMBEDDED THUNDERSTORMS WILL BE
THE RULE ACROSS THE AREA THIS AFTERNOON AND EVENING. SMALL HAIL BE
POSSIBLE WITH THE STRONGER THUNDERSTORMS. SOME OF THE SHOWERS AND
THUNDERSTORMS COULD PRODUCE MODERATE TO HEAVY RAINFALL...WITH SOME
MINOR STREET FLOODING POSSIBLE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

A COLD AIRMASS WILL SETTLE OVER THE REGION THURSDAY. WITH CLEAR
SKIES...OVERNIGHT TEMPERATURES COULD DIP DOWN INTO THE 30S AT MANY
RURAL...OUTLYING LOCATIONS OF THE METRO AREA THURSDAY MORNING. WARMER
CONDITIONS ARE EXPECTED FOR THE REST OF THE WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ024-121300-
SOUTHERN GILA COUNTY/TONTO NATIONAL FOREST FOOTHILLS-
1000 AM MST TUE DEC 11 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

...SNOW ADVISORY REMAINS IN EFFECT THROUGH 3 PM ABOVE 5000 FEET...

WIDESPREAD RAIN SHOWERS WILL PREVAIL ACROSS THE AREA...ALONG WITH
ISOLATED AFTERNOON THUNDERSTORMS...THROUGH THE DAY AND INTO THIS
EVENING. THE SNOW LEVEL WILL BE AROUND 4500 FEET THIS MORNING...WITH
ACCUMULATIONS OF 3 TO 6 INCHES EXPECTED AT 5000 TO 7000 FEET BY THIS
AFTERNOON. ABOVE 7000 FEET...SNOW AMOUNTS WILL BE FROM 8 TO 12
INCHES. PRECIPITATION COVERAGE AND INTENSITY WILL BEGIN TO DECREASE
BY THIS EVENING...THOUGH PRECIPITATION CHANCES WILL CONTINUE INTO
WEDNESDAY MORNING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

NO WEATHER HAZARDS EXPECTED.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ020>022-025-026-CAZ030>033-121300-
LOWER COLORADO RIVER VALLEY AZ-WEST CENTRAL DESERTS-
NORTHWEST MARICOPA COUNTY-YUMA/MARTINEZ LAKE AND VICINITY-
SOUTHWEST DESERTS-JOSHUA TREE NATIONAL PARK-
LOWER COLORADO RIVER VALLEY CA-RIVERSIDE COUNTY/EASTERN DESERTS-
IMPERIAL COUNTY-
1000 AM MST TUE DEC 11 2007 /900 AM PST TUE DEC 11 2007/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME
SOUTHWEST ARIZONA...EXTREME WEST-CENTRAL ARIZONA...SOUTH-CENTRAL
ARIZONA...SOUTHWEST ARIZONA...WEST-CENTRAL ARIZONA...EXTREME
SOUTHEAST CALIFORNIA AND SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT

NO WEATHER HAZARDS EXPECTED.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

A COLD AIRMASS WILL BE SETTLING ACROSS THE REGION WEDNESDAY AND
THURSDAY. THERE IS THE POTENTIAL FOR FREEZING TEMPERATURES THURSDAY
MORNING ACROSS THE LOWER DESERT FLOOR...THOUGH AT THIS TIME IT APPEARS
THAT LOW TEMPERATURES WILL REMAIN A FEW DEGREES ABOVE FREEZING.
WARMER TEMPERATURES WILL RETURN FRIDAY.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

INIGUEZ