HAMweather.com Area Forecast Discussion for County Warning Area PSR

Thu, 16 Feb 2012 13:16:40 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
523 AM MST THU FEB 16 2012

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

.SYNOPSIS...
LOW PRESSURE WILL MOVE THROUGH THE REGION TODAY...BRINGING A CHANCE 
OF RAIN MAINLY TO SOUTHEAST CALIFORNIA...SOUTHWEST ARIZONA...AND THE 
HIGHER TERRAIN EAST OF PHOENIX. ANOTHER WEATHER DISTURBANCE IS 
EXPECTED TO MOVE THROUGH THE REGION SUNDAY INTO MONDAY...FOLLOWED BY 
DRY WEATHER NEXT WEEK. 

.DISCUSSION...
09Z WATER VAPOR AND IR SATELLITE IMAGERY CONTINUE TO SHOW LOW 
PRESSURE LOCATED OVER IMPERIAL COUNTY CA...WITH AN AREA OF SHOWERS 
ACROSS SOUTHEAST CALIFORNIA AND A BAROCLINIC LEAF ACROSS 
SOUTHEAST/EASTERN ARIZONA. RADAR TRENDS HAVE BEEN FAIRLY CONSISTENT 
THROUGH THE MORNING HOURS...SHOWERS HAVE MOVED LITTLE SINCE LATE 
WEDNESDAY EVENING AND THE HEAVIEST RAINFALL REMAINS OVER EASTERN 
IMPERIAL COUNTY. MEANWHILE ACROSS SOUTHERN AND CENTRAL 
ARIZONA...SKIES WERE CLEAR.  

IN THE VERY SHORT TERM...SOME SUGGESTION IN THE RADAR DATA THAT THE 
NORTHERN EDGE OF THE PRECIP IS NOW RETREATING THROUGH JOSHUA TREE 
NATIONAL PARK. TWENTYNINE PALMS IS STILL REPORTING LIGHT RAIN WITH A 
NORTH WIND BUT THEIR DEWPOINT IS SLOWLY DECREASING...SIGNALING AN 
INTRUSION OF DRY AIR WELL ADVERTISED BY THE MODELS. I HELD ONTO THE 
WINTER WEATHER ADVISORY FOR J.T.N.P. UNTIL 10AM PST BUT I COULD SEE 
CONDITIONS IMPROVING WELL BEFORE THAT TIME IF CURRENT TRENDS 
CONTINUE. AT THIS POINT IT WOULD APPEAR THE MAJORITY OF THE 
ACCUMULATING SNOW IS OVER BUT I\LL KEEP THE ADVISORY IN PLACE UNTIL 
I HAVE SOME GROUND TRUTH TO VERIFY THIS THINKING.

FOR THE REST OF THE AREA TODAY...THE LOW WILL CONTINUE IT\S 
SOUTHEASTWARD TRACK INTO THE GULF OF CALIFORNIA AND INTO MEXICO. THE 
MOST ACTIVE AREA WILL BE CLOSE TO THE UPPER LOW ITSELF...THUS I 
RE-ORIENTED POPS A BIT TO HIGHLIGHT AREAS ACROSS SOUTHEAST 
CALIFORNIA AND FAR SOUTHWEST ARIZONA WHERE MOISTURE CONVERGENCE IS 
GREATEST AND ISENTROPIC FORCING IS STRONGEST. IT WILL BE SEVERAL 
HOURS BEFORE ANY PRECIP TRIES TO MAKE ITS WAY INTO THE PHOENIX AREA 
AND EVEN THEN...THERE WILL BE A FAIRLY DEEP LAYER OF DRY AIR BELOW 
700MB THAT WILL NEED TO BE OVERCOME. I RETAINED SLIGHT CHANCE POPS 
AROUND 10-20 PERCENT ACROSS THE METRO...BUT MY CONFIDENCE IN 
MEASURABLE RAIN ACROSS THE PHOENIX AREA IS DWINDLING QUICKLY GIVEN 
THE SOUTHERN TRACK OF THIS LOW. TO THE EAST OF PHOENIX...A BIT OF AN 
UPSLOPE FLOW WILL DEVELOP LATE THIS AFTERNOON AND SOME SHOWERS COULD 
BLOSSOM CLOSER TO 00Z. STILL NOT LOOKING AT AN ABUNDANT AMOUNT OF 
PRECIP BUT WORTHY OF A CHANCE MENTION. NOT CONCERNED ABOUT SNOWFALL 
IN THE HIGHER TERRAIN OF SOUTHERN GILA COUNTY AS THE LOW WILL BE 
WRAPPING SOME PRETTY WARM AIR INTO EASTERN ARIZONA. SNOW LEVELS WILL 
RISE A BIT THIS EVENING...ENOUGH TO PRECLUDE ANY ISSUANCE OF A 
WINTER WEATHER ADVISORY.

WEAK SHORTWAVE RIDGING IS EXPECTED ON FRIDAY AND SATURDAY IN THE 
WAKE OF THIS LOW. THIS WILL YIELD DRY CONDITIONS AND A RETURN TO 
NEAR NORMAL TEMPERATURES. 

THE LATTER HALF OF THE WEEKEND WILL SEE THE ARRIVAL OF AN UPPER 
TROUGH THAT IS EXPECTED TO MOVE MAINLY THROUGH NORTHERN ARIZONA INTO 
NEW MEXICO. DECENT AGREEMENT BETWEEN THE 00Z EUROPEAN AND GFS MODELS 
BUT STILL SOME SPREAD AMONG THE ENSEMBLE MEMBERS. MAINLY LOOKING AT 
TIMING ISSUES...WHEN EXACTLY WILL THE TROUGH ARRIVE AND WILL THERE 
BE ANY SORT OF SECONDARY TROUGH ON MONDAY. NO OPERATIONAL MODEL 
SOLUTION LOOKS OVERLY MOIST AT THIS POINT...ALL SOLUTIONS INDICATE 
WHAT LITTLE MOISTURE THERE IS WILL MOVE THROUGH EASTERN ARIZONA 
OUTSIDE THE FORECAST AREA...JUST CLIPPING SOUTHERN GILA COUNTY. 
PREVIOUS FORECASTS HIGHLIGHTED THIS AREA AND THIS STILL LOOKS 
REASONABLE. PREVIOUS FORECASTS ALSO HELD ONTO CLIMO-LIKE POPS ACROSS 
SOUTHERN GILA COUNTY ON MONDAY AND GIVEN TODAY\S 00Z UNCERTAINTY I 
AM INCLINED TO STICK WITH THIS THINKING. 

RIDGING RETURNS ON TUESDAY AND SHOULD REMAIN IN PLACE THROUGH THE 
LATTER PORTION OF NEXT WEEK. LOOKS LIKE DRY WEATHER AND ANOTHER 
RETURN TO ABOVE NORMAL TEMPERATURES IS IN STORE BY NEXT WEDNESDAY 
AND/OR THURSDAY. 

.AVIATION...
SOUTH CENTRAL AZ...INCLUDING KPHX AND KIWA...
FEW TO SCATTERED HIGH CLOUDS WILL INCREASE TO OCCASIONALLY BROKEN TO 
OVERCAST CONDITIONS WITH A SLIGHT CHANCE OF SHOWERS BY MID TO LATE 
AFTERNOON AND INTO THE EARLY EVENING. LIGHT EAST WINDS WILL BECOME 
WESTERLY BY LATE AFTERNOON FOR SEVERAL HOURS. MID AND HIGH CLOUDS 
ARE EXPECTED TO CLEAR AT NIGHT.
 
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KIPL AND KBLH...

AS THE LOW TRACKS INTO NORTHWESTERN MEXICO EXPECT BREEZY NORTHERLY 
WINDS AND LINGERING SHOWERS WITH LOW...MID...AND HIGH CLOUDS. BY 
EARLY EVENING EXPECT LIGHT WINDS OUT OF THE NORTH AND WEST WITH GOOD 
VISIBILITIES AND MOSTLY SCATTERED CLOUDS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

.FIRE WEATHER... 
SATURDAY THROUGH WEDNESDAY... 
EXPECT BELOW NORMAL HIGH TEMPERATURES OVER SOUTH-CENTRAL ARIZONA 
WITH HUMIDITIES IN THE MID TEENS IN SOUTHEAST CALIFORNIA TO THE 
LOWER 30S IN GILA COUNTY...WITH GOOD TO EXCELLENT OVERNIGHT 
RECOVERIES. EXPECT BREEZY CONDITIONS TO DEVELOP OVER SOUTHEAST 
CALIFORNIA AND SOUTH-CENTRAL ARIZONA ON SUNDAY THROUGH EARLY MONDAY 
AND AGAIN ON LATE TUESDAY INTO WEDNESDAY...PARTICULARLY AROUND THE 
COLORADO RIVER VALLEY. HIGH TEMPERATURES SHOULD RETURN TO NEAR 
NORMAL BY WEDNESDAY.

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...WINTER WEATHER ADVISORY UNTIL 10 AM PST THURSDAY ABOVE 4000     
     FEET FOR CAZ030.