National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KTWC 050438
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
935 PM MST WED DEC 4 2013

.SYNOPSIS...A STRONG STORM SYSTEM MOVING THROUGH THE WESTERN UNITED
STATES WILL BRING A CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW TO
SOUTHEAST ARIZONA THROUGH THURSDAY. THIS SYSTEM WILL ALSO BRING MUCH
COOLER TEMPERATURES...WITH WIDESPREAD FREEZING TEMPERATURES ACROSS
ALL OF SOUTHEAST ARIZONA FRIDAY MORNING. ANOTHER STORM SYSTEM WILL
BRING GUSTY WINDS...A CHANCE OF THE PRECIPITATION AND A
REINFORCEMENT OF COLDER AIR LATE THIS WEEKEND.

&&

.DISCUSSION...SCATTERED SHOWERS PRODUCING GENERALLY A FEW HUNDREDTHS
OF AN INCH DURING THE PAST 1-3 HOURS ONGOING FROM THE NWRN PORTION
OF THE TUCSON METRO AREA WESTWARD AND NORTHWESTWARD INTO CENTRAL
PIMA COUNTY AND SE PINAL COUNTY. ALTHOUGH CELL MOVEMENT HAS BEEN
NEWD...AREAL COVERAGE CONTINUES TO GRADUALLY EXPAND EWD. RUC HRRR
CONTINUES TO EXPAND THE COVERAGE OF PRECIP ACROSS MUCH OF SE AZ
DURING THE NEXT SEVERAL HOURS.

THUS...EXPECT SCATTERED TO NUMEROUS SHOWERS THE REST OF TONIGHT
MAINLY FROM THE TUCSON METRO AREA EWD/SWD. FOR NOW HAVE MAINTAINED
ISOLATED SHOWERS ACROSS WRN PIMA COUNTY...ALTHOUGH SATELLITE/RADAR
TRENDS SUGGEST THIS ACTIVITY MAY BE OVERDONE. PRECIP TO CONTINUE
ACROSS MUCH OF THE AREA THURSDAY MORNING...THEN PRECIP TO DECREASE
FROM NORTHWEST-TO-SOUTHEAST THUR AFTERNOON. SNOW LEVELS BY MIDDAY
THUR ARE EXPECTED TO RANGE FROM ABOUT 4000 FEET ACROSS THE WHITE
MOUNTAINS TO ABOUT 6500 FEET IN FAR SERN SECTIONS.

THE OFFICIAL FORECAST WAS UPDATED TO DECREASE MIN TEMPS ABOUT 2-4
DEGS FROM TUCSON WWD THE REST OF TONIGHT. OCCASIONALLY GUSTY SLY
WINDS SHOULD CONTINUE TONIGHT EAST AND SOUTH OF TUCSON. HOWEVER...
WIND SPEEDS WILL BE WELL BELOW WIND ADVISORY CRITERIA. GUSTY
SOUTHWEST TO WEST WINDS ARE ON TAP EAST AND SOUTH OF TUCSON THUR.
MARKEDLY LIGHTER WINDS WILL OCCUR FROM TUCSON WWD THUR. EXPECT MUCH
COOLER TEMPS THUR...WITH HIGH TEMPS PARTICULARLY FROM TUCSON WWD
NEARLY 15 DEGS F COOLER VERSUS TODAY.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.PREV DISCUSSION...THE UPPER PATTERN IS DEFINED BY A HIGH AMPLITUDE
UPPER RIDGE IN THE EASTERN PACIFIC...AND A LONGWAVE TROUGH ACROSS
THE WESTERN STATES. SHORTWAVE ENERGY MOVING SOUTH ALONG THE
CALIFORNIA COAST WILL ROTATE INTO THE SOUTHERN EDGE OF THIS TROUGH
BEFORE IT TRACKS ACROSS THE AREA TONIGHT AND THURSDAY. THE TIGHT
GRADIENT OUT AHEAD OF THIS TROUGH HAS RESULTED IN BREEZY TO WINDY
CONDITIONS...ESPECIALLY TO THE EAST AND SOUTH OF TUCSON. SURFACE
OBSERVATIONS IN KDUG INDICATE SUSTAINED WINDS IN THE 25 TO 30 MPH
RANGE WITH GUSTS TO 45 MPH. A WIND ADVISORY IS IN EFFECT TO THE EAST
UNTIL 8 PM MST THIS EVENING. THE LATEST MODEL GUIDANCE STILL
INDICATES 45 KT FLOW ACROSS COCHISE AT 06Z TONIGHT. THIS USUALLY
MEANS THAT LOCALIZED AREAS NEAR THE HUACHUCA MOUNTAINS WILL CONTINUE
TO EXPERIENCE STRONG AND GUSTY WINDS WELL INTO THE OVERNIGHT HOURS.

ACCORDING TO THE LATEST SURFACE OBSERVATIONS...THE SOUTHERN TIP OF
THE SURFACE COLD FRONT ASSOCIATED WITH THIS SYSTEM IS CURRENTLY
POSITIONED ACROSS CENTRAL PIMA COUNTY EXTENDING INTO NW PINAL
COUNTY. AT 230 PM MST...KEMX RADAR JUST BEGINNING TO INDICATE SHOWERS
DEVELOPING ACROSS THE TOHONO OODHAM NATION. THE HRRR AND UNIVERSITY
OF ARIZONA WRF MODELS INDICATE THAT THE COLD FRONT WILL PUSH WEST
INTO TUCSON BY 5 PM THIS AFTERNOON WITH PCPN BEGINNING TO EXPAND AND
ENHANCE AS IT MOVES FARTHER EAST. EXPECT SHOWERS TO BECOME MORE
NUMEROUS THIS EVENING WITH THE MAJORITY OF THE PCPN AFFECTING THE
CWA OVERNIGHT INTO THURSDAY MORNING. MOISTURE SOMEWHAT LIMITED WITH
THIS SYSTEM AND STILL EXPECT ONLY A TENTH TO A THIRD INCH WITH MAYBE
A HALF INCH IN THE MOUNTAINS. THIS TRANSLATES INTO SNOWFALL AMOUNTS
JUST BELOW ADVISORY CRITERIA. IT IS POSSIBLE THAT SOME OF THE
HIGHEST PEAKS MAY BARELY HIT LOW END SNOW ADVISORY CRITERIA...BUT IT
WILL NOT BE WIDESPREAD ENOUGH TO WARRANT AN ADVISORY.

THE MAIN ISSUE WITH THIS SYSTEM IS NOT THE WIND OR THE PCPN...BUT
THE TEMPERATURES. COLD AIRMASS MAKING ITS WAY SOUTH WILL BRING THE
FIRST WIDESPREAD FREEZING TEMPERATURES TO THE LOWER DESERTS FROM
TUCSON WEST. HAVE DECIDED TO ISSUE A FREEZE WARNING FOR FRIDAY
MORNING TO GET THE WORD OUT TO PROTECT PEOPLE...PETS...PIPES AND
PLANTS.

ANOTHER STRONG WEATHER SYSTEM WILL MAKE ITS WAY SOUTH INTO ARIZONA
THIS WEEKEND. THE ECMWF IS MUCH COLDER AND THUS MORE AGGRESSIVE THAN
THE GFS BRINGING PCPN AND ANOMALOUSLY COLDER TEMPS. INCREASED POPS AND
LOWERED TEMPS SAT NIGHT INTO MONDAY TO REFLECT THIS TREND.

&&

.AVIATION...VALID THRU 06/00Z.
SCATTERED SHOWERS AND HIGHER TERRAIN SNOW SHOWERS GENERALLY FROM
KTUS VICINITY EWD/SWD THRU THURSDAY MORNING...THEN PRECIPITATION
ENDING FROM NORTHWEST-TO-SOUTHEAST BY THURSDAY EVENING. CLOUD DECKS
THRU THURSDAY AFTERNOON GENERALLY 3-6K FT AGL. AREAS MVFR CIGS/VSBYS
THRU THURSDAY AFTERNOON ESPECIALLY NEAR HIGHER TERRAIN NORTH TO
NORTHEAST OF KTUS. CLEAR SKIES FROM WEST-TO-EAST WILL OCCUR THURSDAY
EVENING. SURFACE WIND EAST AND SOUTH OF KTUS THRU THURSDAY EVENING
WLY 12-18 KTS WITH GUSTS TO 30 KTS. SURFACE WIND KTUS VICINITY WWD/
NWWD GENERALLY LESS THAN 10 KTS. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...LOW PRESSURE TROUGH OVER THE WEST IS EXPECTED TO
REMAIN THROUGH THE FIRST PART OF NEXT WEEK. THE STRONG WINDS
ASSOCIATED WITH THIS TROUGH WILL SUBSIDE AROUND MIDNIGHT AND MUCH
COLDER AIR WILL ADVECT INTO THE AREA THURSDAY. TEMPERATURES WILL
DROP ABOUT 15 DEGREES BELOW AVERAGE LATE THURSDAY AND CONTINUE
THROUGH THE WEEKEND. MOISTURE WITH THIS TROUGH IS LIMITED...ALTHOUGH
MANY AREAS WILL SEE LIGHT PRECIPITATION AMOUNTS. A SECOND STORM
SYSTEM WILL DROP INTO THIS TROUGH LATE SATURDAY FOR A CHANCE OF
VALLEY RAIN AND MOUNTAIN SHOWERS...ALONG WITH REINFORCING THE COLDER
TEMPERATURES INTO EARLY NEXT WEEK.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
    FREEZE WARNING FROM 10 PM THURSDAY TO 10 AM MST FRIDAY FOR
    AZZ501>506.

&&

$$

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