000
FXUS65 KTWC 150313
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
812 PM MST TUE MAY 14 2013

.SYNOPSIS...A WEAK UPPER LOW IN NORTHERN MEXICO WILL MOVE NORTHEAST
TONIGHT ENDING THE PRECIPITATION CHANCES ACROSS SOUTHEAST ARIZONA. A
RIDGE WILL THEN MOVE ACROSS THE AREA WEDNESDAY INTO THURSDAY NIGHT
FOR DRY AND WARMER TEMPERATURES. A TROUGH OF LOW PRESSURE WILL MOVE
ACROSS THE REGION THIS WEEKEND FOR SLIGHTLY COOLER AND BREEZIER
CONDITIONS THROUGH SUNDAY FOLLOWED BY A BIT OF A WARMING TREND EARLY
NEXT WEEK.

&&

.DISCUSSION...KEMX AND AREA RADARS STILL SHOW A FEW WEAK RETURNS
OVER PORTIONS OF GRAHAM...COCHISE AND SANTA CRUZ COUNTIES.
HOWEVER...RETURNS WEAKENING RAPIDLY AND DISSIPATING OVER THE LAST
HOUR OR SO AND EXPECT THIS TREND TO CONTINUE...WITH PRECIPITATION
CHANCES COMING TO AN END BY THE LATE EVENING HOURS. LIGHTNING DATA
INDICATED A COUPLE OF STRIKES OVER EASTERN PORTIONS OF THE FORECAST
AREA THIS AFTERNOON/EARLY EVENING AS WELL. WITH THE EXTREMELY DRY
LOWER LEVELS...SURFACE DEWPOINTS IN THE 20S AND THE 12Z/00Z KTUS
SOUNDINGS BOTH INDICATING A VERY DRY AIRMASS BELOW 550MB...WOULD
EXPECT THAT MOST PLACES ONLY RECEIVED TRACE AMOUNTS...IF ANYTHING AT
ALL.

OTHERWISE...SCATTERED TO BROKEN CLOUDS FROM TUCSON EASTWARD TO THE
NEW MEXICO BORDER. EXPECT CLOUDS TO ERODE FROM THE WEST TO EAST
TONIGHT...ALTHOUGH SOME CLOUDS WILL PERSIST OVER FAR EASTERN AREAS
INTO THE MORNING HOURS WEDNESDAY. THE MODELS INDICATE SOME LINGERING
MOISTURE ALONG THE NEW MEXICO BORDER THROUGH LATE WEDNESDAY
MORNING...BEFORE DRYING TAKES PLACE ACROSS ALL OF THE FORECAST AREA
AS A RIDGE WORKS IN FROM THE WEST AND THE FLOW TURNS WESTERLY.

OVERALL...CURRENT FORECAST PACKAGE ON TRACK. FOR MORE INFORMATION ON
THE LATTER PERIODS OF THE FORECAST...PLEASE REFER TO THE PREV
DISCUSSION SECTION BELOW. NO UPDATES.

&&

.AVIATION...FEW-SCT 10-12K FT AGL FROM KTUS WESTWARD. EAST OF
KTUS...SCT-BKN 9-12KFT WITH ISOLD -SHRA/TS MAINLY ACROSS WHITE MTNS
AND HIGHER TERRAIN EAST AND SOUTH OF KTUS. AFT 15/04Z THRU 16/00Z...
SKC-SCT LCLY BKN 10KFT AGL. SFC WND WLY-SWLY 8-15 KTS WITH OCNL
GUSTS 18-24 KTS...HIGHER GUSTS NR SHRA/TS E OF KTUS...AFT 15/04Z
WIND TERRAIN DRIVEN LESS THAN 10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...A WEAK UPPER LOW OVER NORTHERN MEXICO WILL MOVE
NORTHEAST THIS EVENING. DRIER WESTERLY FLOW ALOFT WILL THEN MOVE IN
WEDNESDAY AS A WEAK DISTURBANCE PASSES WELL TO THE NORTH OF THE
REGION. EXPECT BREEZY AFTERNOON WINDS WEDNESDAY BUT REMAINING BELOW
RED FLAG THRESHOLDS. A WEAK RIDGE OF HIGH PRESSURE WILL BE OVER THE
AREA THURSDAY BEFORE AN UPPER LEVEL TROUGH MOVES THROUGH THE
INTERMOUNTAIN WEST FRIDAY AND SATURDAY BRINGING BREEZY TO LOCALLY
WINDY CONDITIONS TO THE REGION.

&&

.PREV DISCUSSION...AN UPPER LOW MOVING NORTHEAST ACROSS NORTHERN
MEXICO WILL CONTINUE TO OPEN UP AND MOVE OFF TO THE NORTHEAST
THROUGH TONIGHT AS ANOTHER WEAK LOW MOVES ACROSS NORTHERN AZ LATE
TONIGHT INTO WEDNESDAY.  DECENT CONVECTION IS MOVING SOUTHWEST INTO
THE WHITE MOUNTAINS WITH ADDITIONAL STORMS DEVELOPING EAST AND
SOUTHEAST OF AZ.  SO IT LOOKS GOOD FOR THE ISOLATED THUNDERSTORMS
THROUGH THE EVENING HOURS MAINLY ACROSS THE EASTERN HALF OR SO OF
THE FORECAST AREA.  STILL SEE IT PRIMARILY AFFECTING THE MOUNTAINS
WITH THE STORMS DECAYING AS THEY DRIFT SOUTHWEST AWAY FROM THE
MOUNTAINS.  FLOW FROM AROUND 700 MB DOWN IS WESTERLY BUT STORMS ARE
BASED HIGH ENOUGH TO BE STEERED BY THE 650 MB AND UP FLOW AND THAT
WON`T COME AROUND TIL AROUND OR SHORTLY AFTER 00Z.  THE CURRENT AND
EXPECTED CONVECTION WILL DIMINISH INTO THE EVENING HOURS FROM WEST
TO EAST AS DRIER WESTERLY FLOW INCREASES AND DEEPENS IN THE WAKE OF
THE LOW PULLING OUT OF THE AREA.

THE WESTERLY FLOW WILL THEN BE OVER THE AREA WEDNESDAY WITH A SHORT
WAVE RIDGE PASSING BY ON THURSDAY.  THIS WILL ALLOW FOR A DRY PERIOD
WITH TEMPERATURES 4 TO 7 DEGREES WARMER THAN NORMAL WHICH MEANS A
FEW READINGS AROUND OR JUST ABOVE 100 ACROSS THE LOWER WESTERN
DESERTS.  AT THIS POINT I WOULD SAY WE PROBABLY WON`T REACH 100 AT
TIA THIS WEEK...ALTHOUGH WE WILL BE CLOSE AND HAVE LEARNED TO NEVER
SAY NEVER.

THEN THE NEXT SYSTEM POISED TO AFFECT THE REGION IS A FAIRLY
SIGNIFICANT TROUGH THAT WILL BE PUSHING ONTO THE WEST COAST
THURSDAY.  THE AXIS OF THIS TROUGH WILL PASS OVERHEAD LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING...THEN MOVE EAST OF THE REGION THROUGH
THE REMAINDER OF THE WEEKEND.  AT THIS POINT THIS SYSTEM SHOULD BE
DRY BUT IT WILL BRING SOME COOLING AND BREEZY TO LOCALLY WINDY
CONDITIONS TO THE AREA FRIDAY INTO THE WEEKEND.  AT THIS TIME AM
LEANING ON THE LESS DEEP ECMWF MODEL THUS HAVE NOT PULLED
TEMPERATURES BACK TO WHAT GFS MOS INDICATES.

THEN BEYOND THAT...A RIDGE IS MODELED TO BUILD WEST OF THE AREA BUT
THE LONGER RANGE MODELS ARE HAVING A HARD TIME WITH THE LOCATION OF
THE AXIS OF THE RIDGE AND THE DOWNSTREAM TROUGH AND THE PROGRESSION
OF THE VARIOUS FEATURES THROUGH NEXT WEEK SO CONFIDENCE IS LOW IN
THE DETAILS.  OVERALL IT LOOKS DRY AND WARM FOR US BUT THE MODEL
DIFFERENCES WILL INFLUENCE THE WINDS AND TEMPERATURES.
INTERESTINGLY...BOTH THE ECMWF AND GFS SHOW A DEEP TROUGH DEVELOPING
LATE NEXT WEEK ALONG THE WEST COAST WITH A CHANCE OF SHOWERS OVER
THE AREA.  A BIT DIFFERENT THAN ONE WOULD EXPECT THIS TIME OF YEAR
BUT THAT IS A LONG WAY OUT THERE IN THE MODEL WORLD AND I WOULDN`T
PLACE A BET ON THAT HAPPENING JUST YET.

&&

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

&&

$$

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