Winter Storm in Arizona, January 9, 2001

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
240 AM MST TUE JAN 9 2001

SYNOPSIS...A COLD AND STORMY PATTERN WILL CONTINUE FOR THE NEXT 7
DAYS. THE FIRST IN A SERIES OF PACIFIC STORM SYSTEMS WILL MOVE
SLOWLY ACROSS NORTHERN BAJA TODAY. WEAK HIGH PRESSURE WILL THEN
FOLLOW FOR WEDNESDAY INTO THURSDAY BEFORE A POTENTIALLY MAJOR WINTER
STORM DROPS FROM THE GULF OF ALASKA AND INTO ARIZONA BY FRIDAY
MORNING. A THIRD STORM ORIGINATING OVER THE GULF OF ALASKA WILL
THREATEN THE AREA LATE SUNDAY INTO MONDAY.

DISCUSSION...A LITTLE BIT BEHIND THE 8-BALL THIS MORNING AS
SITUATION CONTINUES TO EVOLVE A LITTER FASTER THAN EXPECTED AND
WRING OUT A LITTLE MORE QPF. WARM CONVEYOR BELT AND ASSOCIATED
ISENTROPIC LIFT IS SHIFTING SLOWLY E, WHICH HAS LED TO A TEMPORARY
SHUTDOWN TO THE PRECIP W OF KTUS. THERE ARE PLENTY OF SHOWERS
FURTHER W CLOSER TO THE COLD POOL, THOUGH, SO THIS DRY SLOTTING WILL
BE BRIEF. QUICK CALLS AROUND THIS MORNING INDICATE SNOW LEVELS ARE
ABOVE 6KFT, BUT NEW MODEL GUIDANCE SUGGESTS THEY WILL FALL SOMEWHAT
DURING THE DAY THE CLOSER YOU GO TO THE BORDER. BASED ON THE AMOUNT
OF PRECIP WE'VE RECEIVED SO FAR IN THE VALLEYS (UP TO 0.5") WE'RE
PROBABLY GOING TO TOUCH WARNING CRITERIA ON THE UPSLOPE SIDES OF
SOME OF THE MOUNTAINS. SINCE THIS IS BECOMING A 2-PERIOD EVENT,
THOUGH, AND WINDS ARE DIMINISHING AS WE GET INTO THE COLD CORE,
ADVISORIES SHOULD STILL WORK ALTHOUGH WE'LL UP TOTAL STORM
ACCUMULATIONS TO JUST BELOW WARNING LEVELS. WE'VE HAD A TSTM OR TWO
ROLL NNW WITHIN THE WARM CONVEYOR BELT, AND NEW MODELS STEEPEN LAPSE
RATES EVEN FURTHER TODAY AS THE CORE APPROACHES. WE'LL GO AHEAD AND
MENTION IT IN THE ZONES.

OTHER THAN FINE-TUNING, FORECAST IN THE OUT PERIODS LOOKS PRETTY
GOOD. FOR THE 5TH RUN IN A ROW IT LOOKS LIKE WE'RE GOING TO GET
BLASTED ON FRI. I'VE NEVER SEEN THE AVN GO FOR OMEGA OF +20
MICROBARS/SEC. AVN TENDS TO RUN A BIT COLD, BUT WITH SUCH STRONG
DYNAMICS ON FRI, THE AVN 1000-500MB THICKNESSES DROP TO 5400M COULD
VERY WELL PAN OUT, DROPPING SNOW LEVELS TO 3KFT IN THE PROCESS,
INCLUDING THE E VALLEYS AND THE FOOTHILLS AROUND TUCSON ITSELF.
TSTMS ARE A DECENT BET, TOO. WE'LL HAVE LITTLE TIME TO DRY OUT
BETWEEN SYSTEMS, TOO, AND THIS ONE ALSO CURRENTLY HAS A SUBTROPICAL
TAP, SO 1"+ QPF IS LOOKING GOOD WITH AT LEAST A FOOT OF SNOW IN THE
MOUNTAINS. WE'LL TWEAK WORDING TO REFLECT ALL THIS AND FRESHEN THE
SPS. WE'RE STILL TALKING ABOUT DAY 4 HERE, SO IT'S TOO EARLY TO PUT
IN A GHOST PERIOD THU NIGHT. HOWEVER, MUCH OF THE CWA SHOULD BE
RAINING/SNOWING BY 12Z FRI. THE NEXT ONE IN THE CHAIN FOR LATE SUN/
MON DOESN'T LOOK AS WET AS FRI, BUT IT LOOKS JUST AS COLD, IF NOT
COLDER, AND IT MAY GET STUCK OVER THE STATE AS OVERALL LONGWAVE
TRIES TO BECOME MORE BLOCKY. WINTER IS HERE WITH A VENGEANCE. PYTLAK

.TWC...SNOW ADVISORY ABOVE 6500FT TODAY ZONES 19/29/30/33
       SNOW ADVISORY ABOVE 6000FT TODAY ZONES 32/34/35.