FXUS65 KPSR 261717
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1015 AM MST SAT DEC 26 2009
.SYNOPSIS...
DRY CONDITIONS AND BELOW NORMAL TEMPERATURES WILL CONTINUE THROUGH
THE WEEKEND...BEFORE ANOTHER PACIFIC LOW PRESSURE SYSTEM APPROACHES
THE AREA MONDAY. THIS NEXT SYSTEM WILL BRING A SLIGHT CHANCE OF
SHOWERS TO MAINLY SOUTH-CENTRAL ARIZONA EARLY NEXT WEEK. A DRIER
PATTERN WILL RETURN TO THE REGION LATE NEXT WEEK.
&&
.DISCUSSION...
HIGH CLOUDS BEGINNING TO OVERSPREAD THE REGION AHEAD AN UPPER LEVEL
DISTURBANCE. CLOUDINESS EXPECTED TO PERSIST UNTIL SUNDAY MORNING...
HELPING TO KEEP OVERNIGHT TEMPS SEVERAL DEGREES WARMER TONIGHT.
CURRENT SURFACE CONDITIONS STILL QUITE DRY WITH DEW POINT TEMPS IN
THE TEENS AND 20S...AND TEMPERATURES HAVE WARMED UP NICELY FROM THE
FREEZING MARK...INTO THE 40S AT MANY LOCATIONS. OTHER THAN SOME
MINOR TWEAKS TO THE INHERITED DIGITAL GRIDS/SHORT TERM FORECAST...NO
CHANGES MADE AT THIS TIME. PREVIOUS DISCUSSION STILL APPLIES.
PREVIOUS DISCUSSION...
TODAY AND SUNDAY...CLEAR AND COLD NORTHWESTERLY FLOW ALOFT OF RECENT
DAYS WILL TRANSITION INTO A MORE WESTERLY FLOW ALOFT LATER TODAY AND
SUNDAY. INCREASING WESTERLY FLOW MARKS AN APPROACHING STORM TRACK.
AS A RESULT...A SMALL UPPER LEVEL DISTURBANCE WILL RACE ACROSS THE
AREA LATE TONIGHT/EARLY SUNDAY FOR INCREASING MID AND HIGH CLOUDS.
THIS SLIGHTLY MORE HUMID AIRMASS ALOFT SHOULD LIFT SUNDAY MORNING
MINIMUM TEMPERATURES A FEW DEGREES...AND OUT OF FREEZE WARNING
CRITERIA FOR SOUTH CENTRAL DESERTS...INCLUDING PHOENIX AND VICINITY.
MONDAY AND TUESDAY...THE STORM TRACK WILL SETTLE OVER THE REGION.
ALL MEDIUM RANGE MODELS ARE IN AGREEMENT IN MOVING A PACIFIC
DISTURBANCE INTO THE AREA MONDAY AND TUESDAY. ALTHOUGH MOST UPPER
LEVEL DYNAMICS WILL REMAIN OVER NORTHWEST MEXICO...A VERY SATURATED
MID/UPPER LEVEL AIRMASS WILL SPREAD WEST TO EAST ACROSS THE FORECAST
AREA MONDAY AND TUESDAY. FORECAST SOUNDINGS INDICATE ENOUGH MOISTURE
FOR POSSIBLE AREAS OF LIGHT SHOWERS. THEREFORE WE WILL CONTINUE
WITH A SLIGHT CHANCE OF SHOWERS AREA-WIDE MONDAY AND TUESDAY.
WEDNESDAY...MODELS ARE IN DISAGREEMENT WITH A SECONDARY FOLLOW
SHORTWAVE ACROSS CENTRAL AND EASTERN ARIZONA WEDNESDAY. NO SUCH
FEATURE IS SEEN IN THE EUROPEAN MODEL. SINCE THE STORM TRACK IS OVER
THE AREA...WE WILL OPT TO CONTINUE WITH A THREAT FOR SHOWERS OVER
MOUNTAINOUS ZONE 24 SOUTHERN GILA COUNTY ON WEDNESDAY.
THURSDAY THROUGH SATURDAY...HIGH PRESSURE BUILDING OVER THE AREA
WILL RESULT IN DRY WEATHER THIS PERIOD.
&&
.AVIATION...
WEAK RIDGING ALOFT WILL MEAN QUIET WEATHER AND LIGHT WINDS FOR THE
REGION TODAY. AT KPHX/KIWA...WINDS WILL BE LIGHT WITH NO DOMINANT
WIND DIRECTION. GRADIENT SHOULD FAVOR NORTHERLY COMPONENT TO WINDS
THROUGH LATE MORNING/EARLY AFTERNOON. EASTERLIES WILL SET UP BY LATE
EVENING. BAND OF HIGH CLOUDS WILL STREAM IN FROM THE PACIFIC
TODAY...LEADING TO BKN LYR AOA 20 THSD FT.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
THERE IS A SLIGHT CHANCE OF SHOWERS IN SOUTHEAST CALIFORNIA ON
MONDAY...FOLLOWED BY MOSTLY SUNNY DAYS.
THERE IS A SLIGHT CHANCE OF SHOWERS IN SOUTHWEST AND SOUTH-CENTRAL
ARIZONA MONDAY AND TUESDAY...FOLLOWED BY MOSTLY SUNNY DAYS.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...MEYERS/VASQUEZ
AVIATION...ROGERS
FIRE WEATHER...SIPPLE
