Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 270439
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
940 PM MST FRI DEC 26 2014

.SYNOPSIS...WIDESPREAD FREEZING TEMPERATURES WILL OCCUR TONIGHT WITH
A HARD FREEZE FOR MANY AREAS. COLD AGAIN SATURDAY NIGHT FOLLOWED BY
A WARMING TREND SUNDAY THROUGH TUESDAY. A STRONG STORM SYSTEM WILL
THEN BRING A FEW SHOWERS WITH GUSTY WINDS WEDNESDAY. VALLEY RAIN AND
MOUNTAIN SNOW SHOULD BECOME MORE WIDESPREAD WEDNESDAY NIGHT AND NEW
YEARS DAY AS THIS SYSTEM MOVES ACROSS THE AREA.

&&

.DISCUSSION...A FEW CLOUDS WERE HANGING AROUND FAR SE COCHISE COUNTY
THIS EVENING OTHERWISE IT WAS CLEAR ACROSS SE AZ. COLD NIGHT IN
STORE FOR THE AREA WITH WIDESPREAD FREEZING TEMPERATURES. FORECAST
LOW TEMPERATURES ON TRACK WITH A FEW SPOTS NEAR RECORD LOWS FOR
DECEMBER 27TH. CHECK CLIMATE SECTION BELOW FOR LISTING OF LOCATIONS.

A HARD FREEZE WARNING REMAINS IN EFFECT SATURDAY FROM MIDNIGHT TO 9
AM MST FOR THE TUCSON METRO AREA AND SOUTHEAST PINAL COUNTY. A
FREEZE WARNING CONTINUES IN EFFECT SATURDAY FROM MIDNIGHT TO 9 AM
MST FOR WRN PIMA COUNTY...THE TOHONO O`ODHAM NATION...AND SOUTH
CENTRAL PINAL COUNTY. WIDESPREAD FREEZING TEMPS WILL OCCUR AGAIN SAT
NIGHT INTO SUN MORNING.

MADE SOME SLIGHT TWEAKS TO VERY SHORT TERM TEMPERATURE/DEWPOINT
TRENDS INTO SATURDAY MORNING.

CHECK PREVIOUS DISCUSSION BELOW FOR DETAILS ABOUT TURN OF THE YEAR
STORM.

&&

.AVIATION...VALID THRU 28/06Z.
FEW CLOUDS AT 7-11KFT AGL VCNTY KDUG...OTRW SKC ACROSS SE AZ. SFC
WIND LESS THAN 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.

&&

.FIRE WEATHER...DRY CONDITIONS WITH GENERALLY LIGHT TERRAIN DRIVEN
WINDS WILL PREVAIL THROUGH TUESDAY NIGHT. A DEEP LOW PRESSURE SYSTEM
WILL THEN BRING A SLIGHT CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW
WEDNESDAY. BREEZY TO WINDY CONDITIONS ARE FORECAST TO OCCUR AHEAD OF
THIS SYSTEM WEDNESDAY. PRECIPITATION CHANCES WILL INCREASE WEDNESDAY
NIGHT AND NEW YEARS DAY AS THIS SYSTEM MOVES ACROSS THE AREA. A
SLIGHT CHANCE OF SHOWERS WILL OCCUR MAINLY NEAR THE NEW MEXICO
BORDER FRIDAY WITH DRY CONDITIONS ELSEWHERE.

&&

.CLIMATE...NEAR RECORD LOW TEMPERATURES FOR DECEMBER 27TH.

                          FCST RCD/YR
BISBEE-DOUGLAS AIRPORT     16   13/1987
AJO                        32   30/1920
TOMBSTONE                  19   18/1987


&&


.PREV DISCUSSION...OTHERWISE DRY CONDITIONS WILL PREVAIL INTO TUE
NIGHT AS NWLY FLOW ALOFT INITIALLY BECOMES INCREASINGLY WLY TUE
AHEAD OF A DEEPENING LOW PRESSURE SYSTEM OVER THE GREAT BASIN
REGION. THIS LOW PRESSURE SYSTEM IS PROGGED VIA THE 26/12Z GFS/ECMWF
TO BE CENTERED NEAR LAS VEGAS NEVADA MIDDAY WED. MEANWHILE...THE
26/12Z CMC DEPICTED A 542 DM LOW TO BE CENTERED FURTHER WEST...OR
NEAR LOS ANGELES. THE GFS/ECMWF WERE FAIRLY SIMILAR WITH THE EWD
PROGRESSION OF THIS SYSTEM ACROSS NRN/CENTRAL AZ LATE NEXT WEEK.
HOWEVER...THE CMC DEPICTED A CONSIDERABLY SLOWER EWD PROGRESSION OF
THIS SYSTEM. THE GFS/ECMWF WERE FAVORED FOR THIS FORECAST ISSUANCE
IN ORDER TO HAVE MAINTAINED CONTINUITY AND PER COORD WITH
NEIGHBORING WFO/S.

AT ANY RATE...THERE IS A SLIGHT CHANCE OF VALLEY RAIN/MOUNTAIN SNOW
WED. A TIGHT MID-LEVEL GRADIENT SHOULD PRODUCE GUSTY SWLY WINDS WED
SIMILAR TO SPEEDS ACHIEVED CHRISTMAS DAY. POPS WERE INCREASED WED
NIGHT ESPECIALLY FROM TUCSON EWD TO DEPICT A CHANCE OF VALLEY RAIN/
MOUNTAIN SNOW ACROSS MUCH OF THE AREA. A SIMILAR SCENARIO EXISTS NEW
YEARS DAY...WITH CHANCE-CATEGORY POPS FROM TUCSON EWD...BUT ONLY A
SLIGHT CHANCE OF SHOWERS ACROSS WRN SECTIONS.

HAVE NOTED SOMEWHAT LOWER QPF/S PRODUCED VIA THE 26/12Z GFS/ECMWF
VERSUS THE 26/00Z SOLUTIONS. WOULD NOT BE SURPRISED TO SEE CONTINUED
QPF VARIATIONS WITH SUBSEQUENT SOLUTIONS. GIVEN THAT THIS SYSTEM IS
DEEPER/COLDER VERSUS THE MOST RECENT SYSTEM...EVENTUAL SNOW LEVELS
SHOULD BE LOWER...AND LIQUID AMOUNTS AND SNOW ACCUMULATIONS SHOULD
BE HIGHER. PRECIPITATION SHOULD GRADUALLY DECREASE FROM WEST-TO-EAST
THUR NIGHT...AND A SLIGHT CHANCE OF SHOWERS SHOULD CONTINUE ACROSS
ERN SECTIONS FRI WITH DRY CONDITIONS ELSEWHERE.

HIGH TEMPS SAT WILL BE SIMILAR TO TEMPS ACHIEVED THIS AFTERNOON...
AND WILL AVERAGE ABOUT 10-15 DEGS F BELOW NORMAL. A WARMING TREND
WILL THEN OCCUR SUN-TUE FOLLOWED BY MUCH COOLER TEMPS TO RETURN
THUR-FRI.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
  HARD FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM MST SATURDAY
   FOR AZZ504-506.

  FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM MST SATURDAY
   FOR AZZ501-502-505.

&&

$$

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