Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 261316
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
615 AM MST MON JAN 26 2015

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

&&

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL AFFECT THE REGION TODAY AND TONIGHT
BRINGING AN INCREASE IN MOISTURE AND A PERIOD OF LIGHT RAIN.
THIS DISTURBANCE WILL MOVE NORTH OF THE REGION ON TUESDAY...AND IN
ITS WAKE ABOVE NORMAL TEMPERATURES AND HIGHER THAN NORMAL HUMIDITIES
WILL PREVAIL. ANOTHER LOW PRESSURE SYSTEM WILL BRING ADDITIONAL
MOISTURE AND ANOTHER CHANCE FOR PRECIPITATION LATE IN THE WEEK AND
INTO THE WEEKEND.

&&

.DISCUSSION...
AN UPPER LEVEL LOW CENTERED WELL WEST OF BAJA CONTINUES TO WOBBLE TO
THE WEST-NORTHWEST WHILE STRONG SOUTHEASTERLY MID LEVEL FLOW OVER
NORTHERN MEXICO STREAMS MOISTURE NORTHWARD INTO ARIZONA. CURRENT IR
IMAGERY SHOWS AN EXTENSIVE BAND OF CLOUDS OVER SOUTHERN ARIZONA AND
NORTHERN MEXICO. AS THE UPPER LOW CENTER AND A JET STREAK POSITIONED
OVER NORTHERN BAJA AND SOUTHERN CALIFORNIA LIFT NORTHWESTWARD OVER
THE NEXT 12 HOURS...THE BAND OF CLOUDS AND MOISTURE WILL GET
STRETCHED AND EVENTUALLY LIFT NORTHWARD INTO CENTRAL ARIZONA BY THIS
AFTERNOON. ANTICIPATING A BAND OF RAIN SHOWERS TO DEVELOP BY MID
MORNING IN AN AREA OF FAVORED VERTICAL ASCENT OVER SOUTHWEST ARIZONA
AND SOUTHEAST CALIFORNIA. MODEL QPF ALONG WITH HIGH-RES MODEL
FORECAST REFLECTIVITY PAINT A LARGE AREA OF RAIN AFFECTING THE
AFOREMENTIONED AREAS THROUGH AROUND NOON. THE STRONGEST MID LEVEL
OMEGA OVER SOUTHEAST CALIFORNIA BETWEEN 12-18Z AND PRECIPITABLE
WATER VALUES QUICKLY INCREASING TO JUST OVER ONE INCH BOTH SUPPORT
THIS AREA OF EXPECTED RAIN.

AS THE BULK OF THE MOISTURE GRADUALLY SHIFTS NORTHWARD INTO CENTRAL
ARIZONA BY LATE IN THE AFTERNOON AHEAD OF A NORTHWARD MOVING
SHORTWAVE TROUGH...AM EXPECTING ANOTHER RAIN BAND TO FORM FURTHER TO
THE EAST AND EVENTUALLY SWING THROUGH THE PHOENIX AREA SOMETIME THIS
EVENING. THE LATEST MODEL RUNS HAVE BACKED OFF SLIGHTLY ON QPF
AMOUNTS OVER SOUTH-CENTRAL ARIZONA AS THE BEST AREA OF VERTICAL
ASCENT HAS SHIFTED TO THE WEST A BIT. STILL THINKING NEARLY ALL THE
CWA WILL COME AWAY WITH AT LEAST SOME LIGHT RAIN. BY THE TIME THE
RAIN ENDS SOMETIME TUESDAY MORNING...STORM TOTAL RAINFALL AMOUNTS
SHOULD VARY BETWEEN 0.10-0.25 INCHES IN MOST AREAS WITH POSSIBLY
SOME LOCALIZED HALF INCH AMOUNTS OVER FAR SOUTHWEST ARIZONA AND
SOUTHEAST CALIFORNIA. THE TEMPERATURE FORECAST FOR TODAY IS A BIT
TRICKY WITH RAIN AFFECTING THE AREA. WENT 60-65 IN LOWER DESERT
SPOTS ACROSS SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA AND CLOSER
TO 70 IN PHOENIX SINCE THE RAIN WILL LIKELY HOLD OFF UNTIL THE EARLY
EVENING.

MUCH DRIER AIR ALOFT WILL SURGE IN LATE TONIGHT AND EARLY
TUESDAY...BUT AMPLE LOW LEVEL MOISTURE SHOULD INITIALLY KEEP SOME
LINGERING STRATO-CU CLOUDS OVER PARTS OF THE AREA THROUGH AROUND
NOON TUESDAY. FEEL WE SHOULD HAVE ENOUGH SUN ON TUESDAY TO WARM
THINGS BACK UP TO ABOVE NORMAL WITH MOST LOWER DESERT AREAS BREAKING
70 DEGREES. THE UPPER LEVEL LOW WILL QUICKLY SHIFT INTO THE GREAT
BASIN ON TUESDAY LEAVING A BRIEF PERIOD OF RIDGING OVER THE DESERT
SOUTHWEST. THIS SHOULD LAST THROUGH WEDNESDAY PROVIDING ANOTHER WARM
DAY WITH MOSTLY CLEAR SKIES. HOWEVER...ANOTHER UPPER LOW TRAILING
BEHIND THIS FIRST ONE WILL MOVE INTO OUR REGION STARTING WEDNESDAY
NIGHT. INITIALLY THIS SYSTEM WILL JUST BE A WEAK OPEN WAVE AS IT
NEARS THE SOUTHWESTERN COAST...BUT WE WILL START TO SEE A GOOD DEAL
OF MID AND UPPER LEVEL MOISTURE STREAMING IN FROM THE SOUTHWEST BY
THURSDAY MORNING.

THE SYSTEM FOR LATE THIS WEEK WILL FORM IN AN UPPER LEVEL SPLIT FLOW
SYNOPTIC REGIME AND BY LATE FRIDAY A SUPPORTING JET STREAK WILL DIVE
SOUTHWARD INTO THE BACK SIDE OF THE DEVELOPING TROUGH ALLOWING THE
TROUGH DO DEEPEN. AT THIS POINT...MOISTURE SEEMS TO BE A BIT MORE
LIMITED THIS TIME AROUND AS THE LOW AND MID LEVEL FLOW REMAIN OUT OF
THE SOUTHWEST. HOWEVER...INITIALLY THERE SHOULD BE ENOUGH MOISTURE
AND DYNAMICS TO BRING SOME RAINFALL TO PORTIONS OF OUR AREA SOMETIME
FRIDAY. FOR NOW IT SEEMS BEST CHANCES WILL BE ACROSS SOUTH-CENTRAL
AND EASTERN ARIZONA. EXACT TIMING OF THE RAIN IS HARD TO NAIL DOWN
AT THIS POINT...BUT FEEL BEST CHANCES WILL BE DURING THE DAYTIME
HOURS FRIDAY. WOULD NOT BE SURPRISED IF WE HAVE LINGERING SHOWERS
THROUGH MUCH OF SATURDAY AS THE UPPER LOW COULD BE STATIONARY OVER
THE REGION FOR A DAY OR SO. HAVE DECREASED HIGHS BY A FEW DEGREES ON
FRIDAY OVER SOUTH-CENTRAL ARIZONA GIVEN THE HIGHER CONFIDENCE OF
RAIN AND KEPT FAIRLY SIMILAR VALUES FOR SATURDAY.

CONFIDENCE FOR THIS COMING WEEKEND IS STILL FAIRLY LOW AS MODELS
HAVE HAD SOME DIFFICULTY OVER THE PAST FEW MODEL RUNS...BUT IN
GENERAL IT WOULD SEEM THINGS MAY DRY OUT BY SATURDAY NIGHT OR EARLY
SUNDAY. SLIGHT CHANCE POPS REMAIN IN THE FORECAST INTO SATURDAY
NIGHT...BUT HAVE TRIMMED POPS ON SUNDAY WITH THE ONLY SLIGHT CHANCE
POPS NOW OVER THE HIGHER TERRAIN EAST OF PHOENIX.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA AND KSDL...
A LOW PRESSURE SYSTEM WILL BRING INCREASING MOISTURE AND LIGHT RAIN
TO THE PHOENIX TERMINALS TODAY. BEST CHANCE FOR RAIN APPEARS TO BE
BETWEEN 22Z AND 08Z WITH THE STEADIEST RAIN BETWEEN 01Z AND 04Z THIS
EVENING. CLOUDS WILL CONTINUE TO LOWER AND THICKEN THROUGH THE DAY
WITH 6K FT CIGS LIKELY BY 01Z. CIGS WILL PERSIST INTO TUESDAY
MORNING...PERHAPS LOWERING TO AROUND 5K FT AT KPHX/KIWA BETWEEN 09Z
AND 15Z AND AS LOW AS 4K FT AT KSDL. HOWEVER...LATEST GUIDANCE
INDICATES THAT MVFR CIGS ARE UNLIKELY. IMPROVING CONDITIONS EXPECTED
AFTER 18Z TUESDAY AS THE CLOUDS DISSIPATE.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT SHOWERS HAVE ALREADY BEEN OBSERVED THIS MORNING AT KIPL BUT
HAVE LIFTED NORTH OF THE IMPERIAL VALLEY. ANOTHER BATCH OF SHOWERS
IS EXPECTED TO REDEVELOP ACROSS THE AREA...BEFORE LIFTING NORTHWARD
TOWARDS KBLH LATER THIS MORNING. CIGS MAY ALSO DROP TO AROUND 5-6K
FT THROUGHOUT THE LATE MORNING AND AFTERNOON. IMPROVING CONDITIONS
EXPECTED AFTER 04-6Z TUESDAY AS THE RAIN TAPERS OFF AND CLOUDS
BECOME MORE SCATTERED.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
ABOVE NORMAL TEMPERATURES AND RELATIVELY MOIST CONDITIONS WILL
PREVAIL WEDNESDAY-THURSDAY AS A RIDGE PREDOMINATES ACROSS MEXICO.
ANOTHER LOW PRESSURE SYSTEM WILL RESULT IN INCREASING RAIN CHANCES
AND COOLER TEMPERATURES FRIDAY AND SATURDAY. A WARMING AND DRYING
TREND IS EXPECTED SUNDAY AS A RIDGE BUILDS ACROSS CALIFORNIA.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
AVIATION...HIRSCH
FIRE WEATHER...HIRSCH




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