Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 301549
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
848 AM MST THU OCT 30 2014

.SYNOPSIS...
HIGH TEMPERATURES WILL CONTINUE TO BE WELL ABOVE NORMAL THROUGH
FRIDAY...THOUGH THERE WILL BE SOME HIGH CLOUDS AROUND TODAY. OVER
THE WEEKEND...A LOW PRESSURE SYSTEM MOVES INTO THE WESTERN STATES.
IT WILL BRING MUCH COOLER TEMPERATURES AND BREEZY CONDITIONS TO OUR
REGION...WITH HIGHS DROPPING INTO THE 70S ON THE LOWER DESERTS. RAIN
CHANCES WILL BE SLIGHT AND CONFINED TO THE HIGHER TERRAIN.
ANTICIPATE LITTLE CHANGE IN TEMPERATURES MONDAY... FOLLOWED BY A
WARMING TREND TUESDAY AND WEDNESDAY.

&&

.DISCUSSION...
SATELLITE THIS MORNING SHOWS PATCHES OF HIGH CLOUDINESS BEGINNING TO
MOVE INTO SE CA AND SW AZ JUST EAST OF A LOW PRESSURE SYSTEM
SPINNING OFF THE CALIFORNIA COAST. TRENDS AND MODEL GUIDANCE
INDICATE THE CLOUDINESS WILL CONTINUE PUSHING ACROSS THE FORECAST
AREA THROUGH THIS EVENING. NOT EXPECTING THIS TO BE OPAQUE ENOUGH
THOUGH TO CAUSE MUCH EFFECT ON SURFACE HEATING. SO EXPECT TODAYS
HIGH TEMPERATURE READINGS TO ONCE AGAIN TO BE SEVERAL DEGREES ABOVE
NORMAL. IN FACT...AT 8 AM READINGS ACROSS THE REGION WERE AT OR
SLIGHTLY WARMER THAN 24 HOURS AGO.

EARLIER FORECAST PACKAGE WAS PRETTY MUCH ON TRACK. MINOR ADJUSTMENTS
WERE MADE TO SKY...WIND...TEMPERATURE...AND DEWPOINT GRIDS TO BETTER
ALIGN WITH OBSERVED CONDITIONS AND TRENDS.

&&

.PREV DISCUSSION...
ISSUED 340 AM MST THU OCT 30 2014

TODAY AND FRIDAY...
CLEAR SKIES ACROSS THE FORECAST AREA EARLY THIS MORNING.
HOWEVER...THAT WILL CHANGE VERY QUICKLY AS A BATCH OF HIGH CLOUDS
MOVES IN FROM THE SOUTHWEST. HIGH CLOUDS SHOULD BE JUST THIN ENOUGH
TO ENABLE HIGH TEMPS TODAY TO BE AS WARM AS YESTERDAY. THE FEATURE
PRODUCING THE HIGH CLOUDS IS A WEAK UPPER LOW EMANATING FROM
SUBTROPICAL LATITUDES. IT IS BEING ADVECTED NORTHEASTWARD BY A MUCH
LARGER LOW PRESSURE SYSTEM CURRENTLY CENTERED JUST WEST OF BRITISH
COLUMBIA. FRIDAY WILL SEE LESS CLOUDINESS AS THE LARGE SYSTEM DIGS
SOUTHWARD. THUS THERE WILL BE LITTLE CHANGE IN TEMPERATURES FRIDAY
WITH READINGS IN THE LOW 90S BEING COMMON ON THE LOWER DESERTS. OF
NOTE...THE SREF CONTINUES TO GENERATE SOME MODEST QPF OVER EASTERN
AND CENTRAL ARIZONA FRIDAY. THIS IS DUE LARGELY TO ADVECTING MORE
MOISTURE WESTWARD...FROM A BACKDOOR FRONT...COMPARED TO OTHER
MODELS. SOME OF THE HIGH RES NCEP MODELS PRODUCE SOME VERY SPOTTY
QPF IN CENTRAL ARIZONA...OUTSIDE OF OUR FORECAST AREA. GFS AND ECMWF
KEEP FRIDAY PRECIP NEAR NEW MEXICO BORDER. WILL KEEP FORECAST DRY.

SATURDAY AND SUNDAY...
THE SYSTEM TRACKS INLAND FRIDAY NIGHT THROUGH SUNDAY. A DRY COLD
FRONT MOVES ACROSS OUR FORECAST AREA FRIDAY NIGHT AND SATURDAY.
THERE MAY BE SOME SEMBLANCE OF A FRONTAL CLOUD BAND WITH IT BUT
LIKELY THIS WILL BE SHALLOW. KEPT SLIGHT CHANCE FOR HIGHER TERRAIN
SATURDAY DUE TO OROGRAPHIC LIFT AIDING THE FRONTAL LIFT.
ALOFT...THERE LOOKS TO BE TWO MAIN SHORT WAVE/VORT MAXES WITH THE
TROUGH THAT WILL AFFECT SOUTHERN CALIFORNIA AND ARIZONA THIS
WEEKEND. THE FIRST ONE PASSES JUST NORTHWEST OF OUR AREA EARLY
SATURDAY. THE SECOND ONE BRUSHES US LATER SATURDAY INTO SUNDAY. THE
SECOND ONE LOOKS TO HAVE THE BEST POTENTIAL TO PRODUCE PRECIP AS QG
FORCING WILL BE BETTER FOR OUR AREA AND THERE WILL BE COOLER AIR
MAKING PRECIP PROCESSES MORE EFFICIENT. HOWEVER...PRECIP CHANCES
WILL BE SLIGHT AND STILL CONFINED TO HIGHER TERRAIN AREAS. MAIN
IMPACT WILL BE THE NICE COOL DOWN AND BREEZY CONDITIONS. OUR WESTERN
AREAS WILL GET MOST OF THEIR COOLING ALL ON SATURDAY. OUR EASTERN
AREAS INCLUDING PHOENIX METRO WILL DROP ABOUT 10 DEGREES SATURDAY
THEN ANOTHER NOTABLE DROP FOR SUNDAY LEADING TO HIGHS IN THE LOW TO
MID 70S ACROSS THE LOWER DESERTS.

MONDAY THROUGH WEDNESDAY...
A COUPLE OF TRAILING VORT MAXES ARE ADVERTISED TO CARVE OUT A
PROMINENT SHORT WAVE TROUGH OVER THE AREA EARLY MONDAY INTO TUESDAY.
THE ECMWF HAS RETURNED TO THE IDEA OF DEVELOPING A CLOSED LOW WITHIN
THE BOTTOM OF THE TROUGH...CENTERED OVER PHOENIX BY 00Z
TUESDAY...WHICH IS A DEEPER SOLUTION THAN THE GFS. THE GEM HAS A
SIMILAR IDEA BUT IS FASTER WITH THE ARRIVAL AND DEPARTURE.
HOWEVER...THE ECMWF LOOKS TO BE AN OUTLIER WITH RESPECT TO ITS
ENSEMBLE...THE ECENS. ALSO...IT IS INDICATIVE OF LESS RUN TO RUN
CONSISTENCY. THE GFS IS WELL SUPPORTED BY THE GEFS AND FORECASTS
WERE WEIGHTED MORE HEAVILY TOWARD THAT SOLUTION. THUS MENTION OF
PRECIP CHANCES ENDS SUNDAY NIGHT AND A WARMING TREND STARTS TUESDAY
AS A RIDGE BEGINS BUILDING IN.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...SOUTHEAST
CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

THROUGH 20Z THURSDAY...SLOWLY INCREASING HIGH CLOUDS AOA 25 THSD
FEET. LIGHT WIND UNDER 8 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
A SEASONABLY STRONG COLD FRONT WILL MOVE THROUGH THE REGION SATURDAY
ALLOWING SLIGHTLY COOLER THAN NORMAL TEMPERATURES TO FILTER INTO THE
DISTRICT THE FIRST HALF OF NEXT WEEK. BEHIND THIS FRONTAL
PASSAGE...WIND SPEEDS WILL INCREASE AND BECOME OCCASIONALLY GUSTY
DURING THE AFTERNOON HOURS...ESPECIALLY SATURDAY THROUGH MONDAY.
GUSTS TO AROUND 30 MPH WILL BE POSSIBLE ALONG RIDGE TOPS AND THROUGH
FAVORED RIVER VALLEY LOCATIONS. MINIMUM RELATIVE HUMIDITY VALUES
WILL INITIALLY ONLY FALL INTO A 25-40 PERCENT RANGE OVER THE
WEEKEND...BUT AS MUCH DRIER AIR MOVES INTO THE DISTRICT...HUMIDITIES
WILL FALL INTO THE TEENS MONDAY AND TUESDAY POSSIBLY LEADING TO A
SOMEWHAT LOCALIZED ELEVATED FIRE DANGER. OTHERWISE...OVERNIGHT
RECOVERY WILL BE GOOD...AND CONDITIONS BECOMING MORE TRANQUIL
TOWARDS THE MIDDLE OF NEXT WEEK.

&&


.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...MCLANE/AJ
AVIATION...VASQUEZ
FIRE WEATHER...MO










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