Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 202206
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
305 PM MST THU NOV 20 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL MOVE NEAR THE INTERNATIONAL
BORDER FRIDAY AFTERNOON INTO FRIDAY NIGHT. THIS SYSTEM WILL BRING
ISOLATED TO SCATTERED VALLEY RAIN AND MOUNTAIN SNOW SHOWERS. LIGHT
PRECIPITATION AMOUNTS WILL BE THE RULE. DRY CONDITIONS WILL THEN
PREVAIL THIS WEEKEND INTO THANKSGIVING DAY. EXPECT COOLER DAYTIME
TEMPERATURES THIS WEEKEND FOLLOWED BY A WARMING TREND BY
THANKSGIVING DAY.

&&

.DISCUSSION...UPPER LEVEL LOW PRESSURE SYSTEM OVER NRN CALIFORNIA
THIS AFTERNOON WILL MOVE SEWD INTO FAR SWRN AZ MIDDAY FRI. THIS
SYSTEM WILL CONTINUE TO MOVE SEWD INTO NERN SONORA FRI NIGHT. 20/12Z
NAM TRENDED POPS HIGHER FOR FRI AFTERNOON/EVENING VERSUS PREVIOUS
NAM SOLUTIONS. MEANWHILE...THE 20/12Z GFS WAS SIMILAR TO PREVIOUS
GFS SOLUTIONS...WHILE THE 20/12Z ECMWF WAS SOMEWHAT FURTHER SOUTH
WITH THE PATH OF THE UPPER LOW VERSUS EARLIER SOLUTIONS.

FOR THE OFFICIAL FORECAST...HAVE MAINTAINED DRY CONDITIONS TONIGHT
AND FOR MOST LOCALES FRI MORNING. STILL APPEARS THAT ISOLATED TO
SCATTERED SHOWERS WILL OCCUR MAINLY WEST OF TUCSON FRIDAY AFTERNOON.
HAVE MADE SOME ADDITIONAL MINOR ADJUSTMENTS TO THE GRIDDED DATA POPS
TO DEPICT THE BEST TIME PERIOD FOR PRECIP TO OCCUR FRI EVENING. MOST
NWP MODELS FAVOR SANTA CRUZ/SRN COCHISE COUNTIES FOR THE BEST CHANCE
OF PRECIP.

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. ISOLATED SHOWERS SHOULD CONTINUE LATE
FRI NIGHT ACROSS FAR SERN SECTIONS. DRY CONDITIONS WILL PREVAIL SAT
BEHIND THIS SYSTEM.

THE NEXT SHORTWAVE TROUGH WILL THEN MOVE RAPIDLY SEWD ACROSS THE
CENTRAL ROCKIES SUN. 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. HAVE OPTED FOR DRY
CONDITIONS MON-THUR AS A RIDGE OF HIGH PRESSURE REMAINS EITHER NEAR
THE WEST COAST OR OVER THE WRN CONUS.

HIGH TEMPS FRI WILL BE ABOUT 5 DEGS OR SO COOLER VERSUS TEMPS
ACHIEVED THIS AFTERNOON. EXPECT NO SIGNIFICANT CHANGE IN DAYTIME
TEMPS SAT-MON FOLLOWED BY A GRADUAL WARMING TREND TUE-THUR.

&&

.AVIATION...VALID THRU 22/12Z.
AN APPROACHING WEATHER SYSTEM WILL SPREAD INCREASING HIGH LEVEL
CLOUDINESS OVER THE REGION THROUGH FRIDAY. LOW LEVEL MOISTURE WILL
SLOWLY BE ON THE INCREASE WITH LOWER CLOUDS INCREASING MID DAY
FRIDAY INTO FRIDAY EVENING. SHOWERS MAY IMPACT TERMINAL AREAS
ESPECIALLY BETWEEN 21/21Z TO 22/06Z. THE WEATHER SYSTEM IS EXPECTED
TO BE EAST OF THE AREA BY EARLY SATURDAY. VFR CONDITIONS ARE
ANTICIPATED FOR MOST LOCALES THROUGHOUT THE EVENT. WINDS WILL
GENERALLY REMAIN BELOW 10 KNOTS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...A LOW PRESSURE SYSTEM WILL BRING ISOLATED TO
SCATTERED RAIN SHOWERS WITH PERHAPS A FEW MOUNTAIN SNOW SHOWERS
FRIDAY AFTERNOON AND FRIDAY NIGHT. DRY CONDITIONS WILL THEN PREVAIL
THIS WEEKEND THROUGH THANKSGIVING DAY. 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 TUESDAY NIGHT INTO WEDNESDAY.

&&

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

&&

$$

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

DISCUSSION...FRANCIS
AVIATION/FIRE WEATHER...CANTIN




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