Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 150408
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
908 PM MST SUN DEC 14 2014

.SYNOPSIS...COLD MORNINGS WITH DRY CONDITIONS TO START THE WEEK. A
SERIES OF LOW PRESSURE SYSTEMS WILL THEN BRING A GOOD CHANCE OF
VALLEY RAIN AND MOUNTAIN SNOW WEDNESDAY INTO THURSDAY AND THEN AGAIN
NEXT WEEKEND.

&&

.DISCUSSION...WATER VAPOR IMAGERY AND 15/00Z UPPER-AIR PLOTS SHOW
SHORTWAVE RIDGE OVER CALIFORNIA...WITH SOME HIGH LEVEL CIRRUS CLOUDS
SPILLING ACROSS THE DESERT SOUTHWEST. THESE CLOUDS SHOULD BE ENOUGH
TO KEEP LOW TEMPS FROM FALLING TOO LOW ACROSS NORTHEAST PIMA
COUNTY...INCLUDING THE TUCSON METRO...BUT STILL EXPECTING LOWS
GENERALLY IN THE MID TO UPPER 30S ACROSS THE CITY...WITH A FEW LOW
SPOTS FALLING TO RIGHT AROUND THE FREEZING MARK. FOR AREAS TO THE
SOUTH AND EAST OF TUCSON...MORE SPECIFICALLY FOR AREAS TOWARD BOTH
THE INTERNATIONAL AND NEW MEXICO BORDERS...LOWS WILL FALL WELL BELOW
THE FREEZING MARK.

AS OF 04Z (9 PM MST)...TEMPERATURES RANGED FROM THE MID 30S TO THE
MID 40S...WITH THE TUCSON INTL AIRPORT REPORTING A TEMP OF 46 DEGS
AFTER REACHING AN AFTERNOON HIGH OF 59 DEGS...WHICH WAS 6 DEGS BELOW
NORMAL FOR THIS DATE. THESE CURRENT READINGS ARE RIGHT ON TRACK WITH
THE INHERITED OVERNIGHT LOW TEMPERATURE FORECASTS...SO NO CHANGES
ARE PLANNED AT THIS TIME. HOWEVER...WILL CONTINUE TO MONITOR TEMPS
AND WILL MAKE ADJUSTMENTS IF NEEDED.

FOR DETAILS REGARDING THE FORECAST BEYOND TONIGHT...REFER TO THE
PREVIOUS DISCUSSION BELOW.

&&

.AVIATION...VALID THRU 16/06Z.
VFR WITH PATCHES OF CIRRUS FILTERING IN FROM THE WEST AS A SHORTWAVE
RIDGE MOVES IN FROM THE PACIFIC. EXPECT NORMAL DIURNAL WIND TRENDS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...COOL AND DRIER TO START THE WEEK. ANOTHER STORM
SYSTEM WILL THEN BRING A GOOD CHANCE OF VALLEY RAIN AND MOUNTAIN
SNOW WEDNESDAY INTO THURSDAY.

&&

.PREVIOUS DISCUSSION...THE NEXT TROUGH LINING UP IN OUR CURRENT BUSY
PATTERN FROM THE EASTERN PACIFIC IS EXPECTED TO AGAIN SPLIT SOME
ENERGY DOWN THE COAST OVER THE NEXT 72 HOURS. THIS INITIAL SHOT OF
ENERGY LATE TUESDAY NIGHT INTO EARLY WEDNESDAY WILL SET THE TABLE
FOR A STRONGER IMPULSE CARVING DOWN THE BACK SIDE OF THE NEW
REGIONAL MEAN TROUGH POSITION LATER WEDNESDAY INTO THURSDAY. IT WILL
ALSO ALLOW SNOW LEVELS TO FALL FARTHER BEFORE THE MAIN
MOISTURE/DYNAMICS COUPLET PUSHES IN FROM THE WEST WITH THE POTENTIAL
FOR MORE SIGNIFICANT SNOWFALL ABOVE 6K FEET WEDNESDAY NIGHT INTO
THURSDAY.

THE OVERALL LARGER SCALE MEAN TROUGH POSITION PHASING OVERHEAD
WEDNESDAY INTO THURSDAY LOOKS VERY SOLID WITH DECENT ENSEMBLE MEAN
AGREEMENT...HOWEVER THE DETAILS OF UP TO 3 INDIVIDUAL IMPULSES
EMBEDDED IN THIS PATTERN IS SHAKY. WE WILL CONTINUE TO BLEND 2
PREVIOUS ECMWF RUNS WITH SOME 12Z NAM INPUT FOR SHARPENING MEDIUM TO
SHORTER RANGE TIMING...HOWEVER WE AREN`T LOOKING AT A CLASSIC
FRONTAL PASSAGE WITH THIS MORE COMPLICATED AND POTENTIALLY WETTER
AND COOLER SYSTEM.

THIS BUSY PATTERN COULD SPLIT YET ANOTHER SIGNIFICANT PIECE OF
ENERGY INTO OUR GENERAL AREA NEXT WEEKEND FOR ANOTHER SOLID CHANCE
OF VALLEY RAIN AND MOUNTAIN SNOW SATURDAY NIGHT INTO SUNDAY NIGHT.

&&

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

&&

$$

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

CURRENT DISCUSSION...MOLLERE
PREVIOUS DISCUSSION...MEYER/RASMUSSEN






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