HAMweather.com Area Forecast Discussion for County Warning Area TWC

Thu, 16 Feb 2012 06:31:08 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
925 PM MST WED FEB 15 2012

.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM OVER SOUTHERN CALIFORNIA 
TONIGHT WILL MOVE SOUTH OF THE AREA BY FRIDAY MORNING. THIS SYSTEM 
WILL BRING A CHANCE OF SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS 
THURSDAY AFTERNOON INTO FRIDAY MORNING. DRY AND WARMER TO START THE 
WEEKEND. HOWEVER...THERE MAY BE A FEW MAINLY MOUNTAIN SHOWERS SUNDAY 
ALONG WITH BREEZY TO WINDY CONDITIONS.

.DISCUSSION...UPPER LOW MOVING SWD FROM SRN NEVADA INTO SRN 
CALIFORNIA AT THIS TIME. FAIRLY DECENT RAINFALL AMOUNTS ACROSS 
PORTIONS OF SRN CALIFORNIA THIS EVENING ASSOCIATED WITH THIS SYSTEM. 
MEANWHILE...MAINLY HIGH-LEVEL CLOUDINESS SPREADING NEWD ACROSS SE AZ 
IN ADVANCE OF THIS LOW PRESSURE SYSTEM. PRECIP-FREE CONDITIONS TO 
OCCUR ACROSS SE AZ TONIGHT.

PRECIP CHANCES TO INCREASE ESPECIALLY WEST OF TUCSON THURSDAY 
MORNING. BASED ON RECEIPT OF THE 16/00Z NAM AS WELL AS RADAR TRENDS 
ACROSS SRN CALIFORNIA...OPTED TO INCREASE THE INHERITED POPS THRU 
THURSDAY AFTERNOON. BELIEVE THAT THESE VALUES ESPECIALLY THUR 
AFTERNOON MAY YET BE TOO LOW. HOWEVER...WILL DEFER TO THE MIDNIGHT 
SHIFT FOR ANY ADDITIONAL ADJUSTMENTS TO THE POPS...ESPECIALLY FOR 
THE PERIOD FROM THUR AFTERNOON THRU FRIDAY MORNING WHEN THE BEST 
CHANCE OF PRECIP ASSOCIATED WITH THIS SYSTEM SHOULD OCCUR. SLIGHT 
CHANCE OF THUNDERSTORMS THUR AFTERNOON FROM TUCSON WWD/SWD IS ALSO 
MERITED.

PLEASE REFER TO THE PREVIOUS DISCUSSION SECTION BELOW FOR ADDITIONAL 
DETAIL.

.AVIATION...CLOUD DECKS GENERALLY 10-15K FT AGL THRU THURSDAY 
MORNING LOWERING TO 3-7K FT AGL 00Z-12Z FRIDAY. ISOLD -SHRA MAINLY 
WEST OF KTUS THRU THURSDAY MORNING. SCT-NUMEROUS -SHRA AND ISOLD 
-TSRA SPREADING WEST-EAST ACROSS SE AZ THUR NIGHT. PRECIP DECREASING 
FROM WEST-EAST FRIDAY MORNING. SURFACE WIND THRU THURSDAY NIGHT 
MOSTLY LESS THAN 10 KTS EXCEPT SLY/SWLY 12-18 KTS WITH GUSTS TO 25 
KTS THURSDAY AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR TAF 
AMENDMENTS. 

.FIRE WEATHER...NO FIRE WEATHER CONCERNS AT THIS TIME.

.PREV DISCUSSION...MODELS PROG THE LOW TO BE IN THE GENERAL VICINITY 
OF YUMA BY AROUND MIDDAY ON THURSDAY. IT WILL THEN BEGIN TO TURN TO 
THE EAST ACROSS THE NORTHERN GULF OF CALIFORNIA AND SONORA THURSDAY 
NIGHT. THIS TRACK WILL KEEP MOST OF THE MOISTURE ASSOCIATED WITH THE 
SYSTEM TO OUR SOUTH...BUT ENOUGH MOISTURE WILL BE IN PLACE ON THE 
ARIZONA SIDE OF THE BORDER TO JUSTIFY LOW END CHANCE CATEGORY POPS 
FOR MOST AREAS.
 
THE LOW WILL PUSH QUICKLY TO THE EAST ON FRIDAY WITH PRECIPITATION 
CHANCES TAPERING OFF FROM WEST TO EAST DURING THE DAY. THE THREAT 
FOR PRECIP SHOULD BE OVER BY FRIDAY EVENING...WITH THE EXCEPTION OF 
A FEW LINGERING SHOWERS OVER SOME OF THE MOUNTAIN TOPS. 

SHORTWAVE RIDGING WILL BUILD OVER THE REGION ON SATURDAY...BUT IT 
WILL BE SHORT LIVED AS YET ANOTHER TROUGH BEGINS TO AFFECT THE 
REGION ON SUNDAY AS THE LOW MOVES ACROSS THE GREAT BASIN. THIS 
SYSTEM SHOULD BE MORE OF A WIND MAKER THAN A PRECIPITATION PRODUCER. 
FOR NOW I HAVE JUST SLIGHT CHANCE POPS FOR CENTRAL AND EASTERN 
ZONES...BUT THIS MAY CHANGE AS NEW MODEL RUNS HELP TO SHED MORE 
LIGHT ON THIS SYSTEM. SO...AT A MINIMUM EXPECT BREEZY TO WINDY 
CONDITIONS ON SUNDAY WITH INCREASING CLOUDINESS. 

FOR MONDAY AND TUESDAY I HAVE A SLIGHT CHANCE OF SHOWERS MAINLY IN 
THE WHITE MOUNTAINS AS THE SYSTEM MOVES FROM THE GREAT BASIN AND 
THROUGH ARIZONA. THIS COULD ALSO CHANGE WITH SUBSEQUENT MODEL 
RUNS...SO STAY TUNED.  

HIGHS WILL BE BELOW NORMAL THROUGH THE ENTIRE FORECAST PERIOD BY AT 
LEAST 1 TO 3 DEGS...BUT THE COOLEST DAYS WILL BE THURSDAY AND FRIDAY 
AND AGAIN MONDAY AND TUESDAY WHEN HIGHS WILL BE AROUND 6 TO 8 DEGS 
BELOW NORMAL. LOWS WILL ALSO BE BELOW NORMAL EACH DAY BY AROUND 1 TO 
2 DEGS...BUT THE COOLEST MORNINGS WILL BE TONIGHT AND TUESDAY MORNING
WHEN LOWS WILL BE ABOUT 3 TO 5 DEGS BELOW NORMAL. 

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