FXUS65 KTWC 120408
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
900 PM MST SUN MAY 11 2008

.SYNOPSIS...A COLD STORM SYSTEM OVER THE PACIFIC NORTHWEST WILL DROP
UNUSUALLY FAR SOUTH FOR THIS TIME OF YEAR AS IT PASSES ACROSS EAST
CENTRAL ARIZONA TUESDAY NIGHT. THIS WILL BRING GUSTY WINDS ON
MONDAY...FOLLOWED BY COOLER TEMPERATURES AND A FEW THUNDERSTORMS
TUESDAY. A WARMING TREND IS EXPECTED FOR THE SECOND HALF OF THE WEEK
AS A STRONGER UPPER LEVEL RIDGE DEVELOPS ALONG THE WEST COAST.

&&

.DISCUSSION...RIDGE AXIS NOW WELL EAST OF US WITH LOW DEVELOPING
THROUGH NORTHERN BASIN. WITH AMPLIFIED RIDGE FEATURES BOTH UPSTREAM
AND DOWNSTREAM THE LOW WILL HAVE PLENTY OF ROOM TO DIG IN TOWARD
ARIZONA OVER THE NEXT 36 HOURS. NEW GFS NOW BRINGS THE MAIN LOW A
BIT FURTHER WEST WHICH IS MORE IN LINE WITH PREVIOUS GFS AND
EUROPEAN RESOLUTIONS. INITIAL ONSET OF WINDS DEVELOPING MONDAY THE
MAIN CONCERN FOR NOW. CURRENT WIND ADVISORY AND FIRE WEATHER WATCH
LOOK FINE. CURRENT FORECAST ON THE RIGHT TRACK AS OUTLINED IN THE
PREVIOUS DISCUSSION BELOW.

&&

.FIRE WEATHER...A DEEP LOW PRESSURE SYSTEM OVER THE NORTHERN BASIN
WILL DROP SOUTH INTO ARIZONA ON TUESDAY. THIS WILL RESULT IN STRONG
AND GUSTY WINDS MONDAY. WITH DRY AIR IN PLACE AND A VERY HIGH TO
EXTREME FIRE DANGER ACROSS SOUTHEAST ARIZONA...A FIRE WEATHER WATCH
HAS BEEN ISSUED FOR MONDAY FOR FIRE WEATHER ZONE 146 (NORTHERN
GREENLEE AND GRAHAM COUNTIES) FIRE WEATHER ZONE 148 (COCHISE...SANTA
CRUZ...EASTERN PIMA...AND SOUTHERN GREENLEE AND GRAHAM COUNTIES) AND
EASTERN FIRE WEATHER ZONE 147 (EASTERN PORTIONS OF SOUTHEAST PINAL
COUNTY AND THE TOHONO OODHAM NATION). THE FIRE WEATHER WATCH IS IN
EFFECT ON MONDAY FROM 10 AM MST UNTIL 8 PM MST. OTHERWISE...THIS
STORM SYSTEM WILL BRING INCREASED CLOUD COVER AND MUCH COOLER
TEMPERATURES. THERE WILL ALSO BE A CHANCE OF SHOWERS AND
THUNDERSTORMS TUESDAY AND TUESDAY NIGHT...ESPECIALLY IN THE WHITE
MOUNTAINS AND THE HIGHER TERRAIN OF GRAHAM AND COCHISE COUNTIES.

&&

.AVIATION...SOME HIGH CIRRUS FILTERING IN FROM THE SOUTHWEST.
GENERALLY NORMAL DIURNAL WIND TRENDS OVERNIGHT WILL GIVE WAY TO
STRONGER WINDS DEVELOPING MONDAY. WINDS WILL INCREASE INTO THE
BREEZY TO WINDY CATEGORY AT MOST LOCATIONS BY LATE MORNING MONDAY AS
A STORM SYSTEM APPROACHES THE REGION. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.PREV DISCUSSION...MAIN FORECAST ISSUE THRU TUE NIGHT WILL INVOLVE
THE DEEP LOW OVER THE PAC NW AS IT SPLITS TOWARD AZ FOR TUE EVENING.
HAVE GONE WITH THE ECMWF BECAUSE OF ITS EXCELLENT RECENT TRACK
RECORD...ALTHOUGH THE GFS AND NAM...WHILE NOT AS AMPLIFIED...ARE
TELLING A SIMILAR STORY. AS MENTIONED THIS MORNING...THE LAST 2 RUNS
HAVE COME IN ABOUT 5KTS STRONGER ON 700MB WINDS...ABOUT 2F WARMER...
AND 1-2KFT DEEPER ON MIXING DEPTH. THAT HAS TAKEN US FROM WHAT
LOOKED LIKE JUST A BREEZY MON AFTERNOON TO A NOTABLE WIND EVENT. IN
CONCERT WITH OUR EASTERN NEIGHBORS...WILL HOIST A WIND ADVISORY FOR
THE 3 EASTERN ZONES MON AFTERNOON. AS FOR THE LOW PASSAGE ON
TUE...EVERYTHING REMAINS ON TRACK. MOISTURE WILL REMAIN
MEAGER...WHICH MAY MEAN A FEW DRY LIGHTNING STRIKES/GUSTY WINDS.
HOWEVER WITH THE EXCELLENT DYNAMICS AND THERMODYNAMICS...OUR
CONFIDENCE CONTINUES TO INCREASE FOR RECEIVING SOMETHING MEASURABLE
IN THE N GRAHAM/GREENLEE MOUNTAINS. WETBULB ZEROES AND 700MB TEMPS
ALSO SUGGEST A SMALL HAIL THREAT IN THE UPPER GILA VALLEY MON
AFTERNOON...AND MAYBE A MINOR SNOW ACCUMULATION TUE EVENING AROUND
HANNAGAN MEADOW. JUST LIKE THE CLOSED LOW LAST WEEK...THOUGH...ANY
RAIN OUTSIDE OF THE SOUTHERN WHITES IS GOING TO BE VERY SPOTTY AND
LIGHT...WHICH THE DIME POPS REFLECT.

THE LATEST RUNS ARE RATHER CONSISTENT WITH A SLEEPER SYSTEM DROPPING
DOWN THE FRONT RANGE ON THU AS THE REX BLOCK AMPLIFIES ALONG 122W.
WHILE THIS RIPPLE SHOULD DROP TOO FAR E TO DO MUCH FOR SE AZ...IT
WILL HAVE TO BE WATCHED. SAME STORY GOES FOR A POSSIBLE CLOSED LOW
DEVELOPING NEARBY NEXT WEEKEND. WHILE THE 00Z GFS MAY HAVE BEEN AN
OUTLIER...I AM CAUTIOUS ABOUT GOING COMPLETELY BACK TO A RIDGED
SOLUTION. THE TRACK OF ANY ENERGY DROPPING DOWN THE E SIDE OF THE
BLOCK WILL BE VERY SENSITIVE TO EXACTLY WHERE THE RIDGE AXIS
ANCHORS. JUST A COUPLE OF DEGREES EAST OR WEST WILL HAVE A BIG
IMPACT ON POSSIBLY OF SEEING OUR 1ST 100F NEXT WEEKEND...REMAINING A
BIT COOL AND UNSETTLED...OR GETTING SOMETHING IN BETWEEN. HAVE SPLIT
THE DIFFERENCE BETWEEN THE 00Z ECMWF AND 12Z GFS 850-700MB
THICKNESSES...WHICH CONVENIENTLY SUPPORTS WHAT WE HAD OUT ALREADY.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    FIRE WEATHER WATCH FIRE ZONES 146/EASTERN 147/148 10AM-8PM MON.
    WIND ADVISORY AZ ZONES 019/030/035 NOON-8PM MON.

$$

WEATHER.GOV/TUCSON