Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 192140
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 PM MST WED NOV 19 2014

.SYNOPSIS...DRY CONDITIONS WILL CONTINUE THURSDAY. A LOW PRESSURE
SYSTEM MOVING ACROSS THE AREA WILL BRING A CHANCE OF VALLEY RAIN AND
MOUNTAIN SNOW SHOWERS FRIDAY AFTERNOON AND EVENING. ONLY LIGHT
PRECIPITATION AMOUNTS ARE EXPECTED. DRY CONDITIONS WITH A SLOW
WARMING TREND WILL THEN PREVAIL SATURDAY THROUGH WEDNESDAY.

&&

.DISCUSSION...THE BACK EDGE OF MAINLY HIGH-LEVEL CLOUDS REPRESENTING
A SHORTWAVE TROUGH AXIS EXTENDED FROM SRN NEVADA SEWD INTO WRN PIMA
COUNTY THIS AFTERNOON. THE BULK OF THESE CLOUDS WILL MOVE EWD INTO
NEW MEXICO THIS EVENING. MOSTLY CLEAR SKIES WILL THEN PREVAIL LATE
TONIGHT AND THUR. A STRONGER SHORTWAVE TROUGH IS PROGGED VIA THE
19/12Z GFS/ECWMF TO BE OVER THE GREAT BASIN/SRN CALIFORNIA REGION
THUR NIGHT. THIS SYSTEM WILL MOVE SEWD ACROSS THE AREA FRI AFTERNOON
AND EVENING.

HAVE NOTED THAT THE GFS/ECMWF HAVE TRENDED SLIGHTLY FURTHER SOUTH
WITH THE PATH OF THE MID-LEVEL CYCLONIC CIRCULATION VERSUS PREVIOUS
SOLUTIONS. THE GFS/ECMWF FAVOR LOCALES SOUTH OF TUCSON FOR THE
HIGHEST QPF/S. HOWEVER...THESE AMOUNTS STILL REMAIN MOSTLY LESS THAN
ONE TENTH OF AN INCH. HAVE MADE SOME MINOR MODIFICATIONS TO THE
GRIDDED DATA POP FIELDS FOR FRI AFTERNOON/EVENING TO ACCOUNT FOR
SLIGHTLY BETTER PRECIP CHANCES SOUTH-TO-SOUTHEAST OF TUCSON.

FOR CONTINUITY AND PER COORD WITH NEIGHBORING WFO/S...HAVE
MAINTAINED CHANCE-CATEGORY POPS ACROSS THE WHITE MOUNTAINS. HAVE
OPTED TO DEPICT THE ENTIRE FORECAST AREA FRI AFTERNOON WITH A SLIGHT
CHANCE OF SHOWERS. THERE IS A SLIGHT CHANCE OF SHOWERS FRI EVENING
FROM TUCSON EWD/SWD. GIVEN THE RAPID PROGRESSION OF THIS SYSTEM AND
THE LACK OF SIGNIFICANT LOWER LEVEL MOISTURE...LIQUID AMOUNTS SHOULD
BE QUITE LIGHT. SNOW LEVELS BY FRI EVENING SHOULD GENERALLY BE NEAR
7000 FEET...AND SNOW ACCUMULATIONS SHOULD BE LIMITED TO ONLY AN INCH
OR SO ACROSS THE HIGHEST PEAKS. DRY CONDITIONS UNDER NWLY FLOW ALOFT
WILL OCCUR LATE FRI NIGHT-SAT NIGHT.

THE NEXT SHORTWAVE TROUGH WILL THEN MOVE RAPIDLY SEWD ACROSS THE
CENTRAL ROCKIES SUN. HAVE REMOVED THE PREVIOUS DEPICTION OF A SLIGHT
CHANCE OF SNOW SHOWERS SUN ACROSS THE WHITE MOUNTAINS. A TIGHT MID-
LEVEL GRADIENT WILL PRODUCE GUSTY WLY/NWLY WINDS SUN. THE
ORIENTATION OF THE MID-LEVEL GRADIENT FAVORS THE UPPER GILA VALLEY
WITH THE STRONGER WINDS. DRY CONDITIONS WILL THEN OCCUR MON-WED AS
HIGH PRESSURE ALOFT REMAINS CENTERED WEST OF THE SRN CALIFORNIA
COAST NEAR 30N/130W.

HIGH TEMPS THUR WILL BE A FEW DEGS COOLER VERSUS TEMPS ACHIEVED THIS
AFTERNOON. EXPECT AN ADDITIONAL 5 DEGS OR SO OF COOLING FRI FOLLOWED
BY A VERY GRADUAL WARMING TREND SATURDAY THROUGH WEDNESDAY.

&&

.AVIATION...VALID THRU 21/00Z.
A FEW TO SCATTERED MAINLY HIGH CLOUDS THIS EVENING WILL GIVE WAY TO
CLEAR SKIES LATER TONIGHT AS A WEAK UPPER LEVEL DISTURBANCE EXITS
THE REGION. MOSTLY CLEAR CONDITIONS WITH PERHAPS A FEW CIRRUS WILL
THEN PREVAIL THROUGH THE DAY THURSDAY. SURFACE WIND GENERALLY LESS
THAN 10 KTS WITH NORMAL DIURNAL PATTERNS WILL CONTINUE THROUGH
THURSDAY AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WITH LIGHT TERRAIN DRIVEN WINDS WILL
PREVAIL THROUGH THURSDAY. A LOW PRESSURE SYSTEM WILL BRING ISOLATED
TO SCATTERED RAIN SHOWERS WITH PERHAPS A FEW MOUNTAIN SNOW SHOWERS
FRIDAY AFTERNOON AND FRIDAY EVENING. DRY CONDITIONS WILL THEN
CONTINUE THROUGH EARLY NEXT WEEK. ANOTHER LOW PRESSURE SYSTEM
PASSING TO THE NORTH OF THE REGION SUNDAY WILL BRING GUSTY WEST TO
NORTHWEST WINDS TO THE AREA. THE UPPER GILA VALLEY MAY SEE WINDS OF
10-15 MPH WITH GUSTS OF 25-30 MPH. SLIGHTLY ELEVATED EASTERLY WINDS
ARE EXPECTED OVERNIGHT MONDAY AND INTO TUESDAY MORNING.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

DISCUSSION...FRANCIS
AVIATION/FIRE WEATHER...FRENCH





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