AREA FORECAST DISCUSSION

 
 FXUS65 KTWC 132148
 AFDTWC
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE TUCSON AZ
 245 PM MST FRI MAR 13 2009
 
 .SYNOPSIS...A WEATHER SYSTEM WILL MOVE ACROSS SOUTHEAST ARIZONA 
 TONIGHT AND SATURDAY. THIS FEATURE WILL BRING A FEW SHOWERS AND 
 THUNDERSTORMS THIS EVENING AND THEN AGAIN SATURDAY AFTERNOON FOR 
 AREAS FROM TUCSON EAST. DAYTIME TEMPERATURES WILL BE SLIGHTLY BELOW 
 NORMAL SATURDAY. HIGH PRESSURE WILL BUILD OVER THE AREA STARTING 
 SUNDAY AND CONTINUING THROUGH NEXT WEEK RESULTING IN A STRONG 
 WARMING TREND.
 
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 .DISCUSSION...ISOLATED SHOWERS MAINLY OVER/NEAR THE HIGHER TERRAIN 
 EAST OF TUCSON WITH A FEW GAGES IN GREENLEE COUNTY RECORDING BETWEEN 
 A TENTH AND TWO-TENTHS OF AN INCH OF RAIN THIS AFTERNOON. THESE 
 SHOWERS WILL CONTINUE INTO THE EVENING HOURS BEFORE FALLING APART. 
 UPPER TROF OVER THE AREA WITH TWO DISTINCT AREAS OF CIRCULATION 
 EMBEDDED IN THE TROF. THE FIRST ONE IS OVER WEST CENTRAL NEAR GRANT 
 NEW MEXICO AND IS WRAPPING MOISTURE AROUND IT ACROSS EASTERN 
 ARIZONA. AS THIS SYSTEM LIFTS EAST TONIGHT AND SECONDARY CIRCULATION 
 WILL DROP IN OVER WESTERN ARIZONA. AS OF 2 PM THIS CIRCULATION WAS 
 NEAR LAS VEGAS. ENTIRE TROF/CIRCULATION WILL MOVE OVER SOUTHEAST 
 ARIZONA SATURDAY AFTERNOON AND COMBINED WITH RESIDUAL MOISTURE...MID 
 LEVEL COLD POOL (-22C TO -24C) AND DAYTIME HEATING WILL BRING A 
 BETTER CHANCE OF SHOWER/THUNDERSTORMS FOR THE VALLEY LOCATIONS FROM 
 TUCSON EAST THAN TODAY. SNOW LEVEL AROUND 7000 FEET WITH 1-3 INCHES 
 POSSIBLE WHICH COULD BE HIGHER IS LOCALIZED SPOTS DUE TO CONVECTIVE 
 NATURE OF STORMS. 
 
 DRY NORTHWEST FLOW OVER THE AREA SUNDAY WITH SLIGHTLY WARMER 
 TEMPERATURES. UPPER RIDGE BUILDS OVER THE AREA NEXT WEEK PROVIDING A 
 NICE WARM-UP. HOWEVER THE LATEST MODELS ARE SHOWING THAT THIS RIDGE 
 MAY NOT BE AS AMPLIFIED/STRONG AS EARLIER THOUGHT. WITH THAT IN 
 MIND SHAVED OFF A DEGREE OR TWO ON DAILY FORECAST HIGHS. 
 
 THE END OF NEXT WEEK COULD SEE SOME MOISTURE BACK DOORING IN FROM 
 THE EAST FOR A SMALL CHANCE OF STORMS. PLENTY OF TIME TO SEE HOW THE 
 MODELS HAVE THIS SITUATION OVER THE WEEKEND BEFORE HITTING POPS A 
 BIT HARDER. I PUT SOME LOW END CLIMO POPS TO ACCOUNT FOR THIS 
 UNCERTAINTY. 
 
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 .AVIATION...UPPER LEVEL TROF REMAINS OVER THE AREA WITH LIMITED 
 MOISTURE IN PLACE. FOR THE THREE TERMINAL SITES FEW-SCT CLOUD BASES 
 AT 8-10KFT AGL. THERE IS A SLIGHT CHANCE OF STORMS AT THE TERMINAL 
 SITES SATURDAY AFTERNOON. SUSTAINED SURFACE WINDS GENERALLY LESS 
 THAN 12 KTS THRU 18Z SATURDAY. AVIATION DISCUSSION NOT UPDATED FOR 
 TAF AMENDMENTS.
 
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 .TWC WATCHES/WARNINGS/ADVISORIES...NONE.
 
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 WEATHER.GOV/TUCSON