000
FXUS65 KPSR 201045
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
345 AM MST SAT MAR 20 2010
.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS...
&&
.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE REGION AND BRING WARM TEMPERATURES
AND DRY CONDITIONS THROUGH THE WEEKEND INTO EARLY NEXT WEEK.
TEMPERATURES WILL WARM ONCE AGAIN TO ABOVE NORMAL STARTING SUNDAY
AND MONDAY BEFORE COOLING AS ANOTHER LOW PRESSURE SYSTEM MOVES
ACROSS MAINLY SOUTH-CENTRAL ARIZONA TUESDAY INTO WEDNESDAY. HIGH
PRESSURE WILL RETURN THURSDAY FOR DRY CONDITIONS AND ANOTHER WARMING
TREND.
&&
.DISCUSSION...
FAST MOVING SHORT WAVE HAS NOW MOVED EAST OF THE AREA AND INTO NEW
MEXICO...WITH CLEAR SKIES SEEN IN IR IMAGERY IN THE WAKE OF THE
DEPARTING SHORT WAVE. N-S SURFACE GRADIENT HAS TIGHTENED BEHIND THE
DEPARTED COLD FRONT...AND THE NORTHERLY LOW LEVEL BREEZES HAVE
USHERED VERY DRY AIR INTO THE SRN DESERTS. AT 2 AM SURFACE DEWPOINTS
OVER THE LOWER DESERTS RANGED FROM SINGLE DIGITS TO MID 20S...VALUES
THAT ARE 20-30 DEGREES LOWER THAN 24 HOURS AGO. HIGH AMPLITUDE UPPER
RIDGE WILL REMAIN SITUATED TO OUR WEST TODAY...KEEPING DRY SUBSIDENT
NLY/NWLY FLOW IN PLACE OVER THE CWA FOR SUNNY SKIES. THICKNESS
VALUES ARE NOT PROGGED TO RISE TODAY HOWEVER...SO NO WARMING IS
EXPECTED. IN FACT...FORECAST SOUNDINGS AND MOS NUMBERS INDICATE
SOUTH-CENTRAL AZ WILL FALL ANOTHER 2-3 DEGREES...TO VALUES SLIGHTLY
BELOW SEASONAL NORMALS.
FOR SUNDAY INTO MONDAY...MODELS AGREE THAT THE UPPER RIDGE WILL
SHIFT EAST AND MOVE OVER ARIZONA...FOR GENLY CLEAR SKIES AND A
WARMING TREND. MONDAY SHOULD SEE HIGHS IN THE LOW TO MID 80S OVER
MOST OF THE LOWER DESERTS...WELL ABOVE CLIMO.
MEDIUM RANGE MODELS CONTINUE TO AGREE THAT SOMEWHAT UNSETTLED AND
COOLER WEATHER WILL RETURN TUESDAY INTO WEDNESDAY AS ANOTHER SHORT
WAVE AFFECTS THE DESERT SOUTHWEST. BOTH THE GFS AND ECMWF INDICATE
THAT THERE WILL BE TWO BRANCHES OF SHORT WAVE ENERGY TO IMPACT
ARIZONA...A WEAK UPPER LOW EMBEDDED IN THE SRN BRANCH FORECAST TO
MOVE INTO NRN BAJA/FAR SRN AZ...AND THE NORTHERN STREAM WHERE MOST
OF THE ENERGY WILL RESIDE. AS OF TUESDAY AFTERNOON BOTH MODELS HAVE
THE STRONGER UPPER LOW SITUATED TO OUR NORTH...CENTERED OVER SRN
UTAH...WITH THE WEAKER SOUTHERN BRANCH LOW MOVING INTO NRN BAJA/NWRN
MEXICO/FAR SRN AZ.
ECMWF FORECASTS SHORTWAVE ENERGY FROM BOTH BRANCHES TO PHASE
TOGETHER INTO ONE LOW...WHICH BECOMES CENTERED OVER SOUTH-CENTRAL AZ
WEDNESDAY MORNING...THEN SLOWLY MOVES EAST ACROSS THE STATE
WEDNESDAY. GFS KEEPS MOST OF THE ENERGY ASSOCIATED WITH THE NORTHERN
STREAM LOW...WHICH IT SHIFTS INTO NEW MEXICO DURING THE DAY WED. GFS
IS A DRIER SOLUTION...AND A BIT MORE PROGRESSIVE...AND ALL MEX MOS
NUMBERS ARE VERY LOW ATTM...IN THE SINGLE DIGITS. HAVE OPTED TO KEEP
FORECAST CLOSER TO THE ECMWF AND AS SUCH HAVE SLIGHT CHANCE POPS
OVER SOUTH-CENTRAL AZ TUESDAY INTO WEDNESDAY. OF COURSE...WE WILL
SEE COOLER TEMPS TUESDAY INTO WEDNESDAY WITH HIGHS TO FALL INTO THE
LOW TO MID 70S BY WED AFTERNOON OVER THE CENTRAL DESERTS...AND INTO
THE UPPER 70S TO AROUND 80 OVER SERN CA.
BOTH PROGS BRING HIGH PRESSURE BACK INTO THE STATE ON THURSDAY FOR
SUNNY SKIES AND ANOTHER WARMING TREND.
&&
.AVIATION...
KIPL...KBLH...AND SURROUNDING AIRFIELDS...
EXPECT NORTHEASTERLY WINDS...GENERALLY LESS THAN 10 KTS...LATER THIS
MORNING INTO THE EVENING HOURS. WINDS WILL BECOME LIGHT
OVERNIGHT...WITH TYPICAL WEST TO NORTHWEST DRAINAGE WINDS THROUGH
12Z SUNDAY. OTHERWISE...ANTICIPATE MOSTLY CLEAR SKIES.
KPHX...KIWA...AND SURROUNDING AIRFIELDS...
NORTHEASTERLY WINDS THIS MORNING WILL CONTINUE UNTIL ABOUT 21Z
TODAY...WITH GUSTY WINDS UP TO 20 KTS POSSIBLE STARTING AFTER 15Z.
HAVE LEFT A TEMPO GROUP IN THE TAFS FOR THESE GUSTY WINDS AS THE
LOW-LEVEL PRESSURE GRADIENT REMAINS ENHANCED. WINDS ARE EXPECTED TO
WEAKEN AFTER 21Z...BECOMING LIGHT NORTHWESTERLY FOR A SHORT PERIOD
OF TIME. TYPICAL EASTERLY DRAINAGE WINDS WILL COMMENCE AROUND 05Z
SUNDAY AND CONTINUE THROUGH 12Z. OTHERWISE...ANTICIPATE MOSTLY CLEAR
SKIES.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
ABOVE NORMAL MAXIMUM TEMPERATURES AND DRY CONDITIONS ARE EXPECTED
MONDAY...BEFORE ANOTHER LOW PRESSURE SYSTEM TRACKS ACROSS THE REGION
TUESDAY INTO WEDNESDAY PROVIDING THE FORECAST AREA WITH COOLER
MAXIMUM TEMPERATURES...BREEZY CONDITIONS...AND A SLIGHT CHANCE OF
PRECIPITATION FOR SOUTH-CENTRAL ARIZONA. HIGH PRESSURE RETURNS
THURSDAY...ALONG WITH WARMER AND DRIER CONDITIONS THROUGH FRIDAY.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...CB
AVIATION...PADDOCK
FIRE WEATHER...PADDOCK
