Flash Flooding in Arizona, July 10, 2001

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
300 PM MST TUE JUL 10 2001

.SYNOPSIS...SOUTHERLY FLOW WILL CONTINUE TO BRING TROPICAL MOISTURE
NORTHWARD AND INTO NORTHERN ARIZONA. THE PATTERN OF DAILY SHOWERS
AND THUNDERSTORMS WILL CONTINUE OVER MUCH OF THE AREA THROUGH THE
END OF THE WEEK. BY THE WEEKEND...A DRIER SOUTHWESTERLY FLOW WILL
DEVELOP WITH THUNDERSTORM ACTIVITY CONFINED MAINLY TO THE EASTERN
PORTIONS OF THE STATE.

.DISCUSSION...WEAK SHEAR ZONE HAS SET UP OVER THE CENTRAL PORTION OF
ARIZONA FROM MEXICO TO UTAH. TO THE EAST SHOWERS ARE MOVING
NORTHWARD WHILE TO THE WEST THE SHOWERS ARE MOVING SLOWLY TO THE
SOUTH. SOME OF THESE HAVE PRODUCED COPIOUS AMOUNTS OF RAINFALL THIS
AFTERNOON AND EXPECT THAT THERE WILL BE A FEW HEAVY DOWNPOURS THIS
EVENING AS WELL. WILL WORD THE FIRST PERIOD APPROPRIATELY.

MODELS DIVERGE SIGNIFICANTLY AFTER THE FIRST PERIOD WITH THE AVN
SUGGESTING SOME MID LEVEL DRYING AND THE ETA MAINTAINING THE
MOISTURE. BY THE 4TH PERIOD THE ETA HAS DRIED SIGNIFICANTLY THROUGH
A DEEP LAYER WHILE THE AVN HAS MOISTENED SIGNIFICANTLY. BECAUSE IT
IS VERY DIFFICULT TO SCOUR OUT THE MONSOON MOISTURE SO QUICKLY
BELIEVE THE ETA SOLUTION IS UNREALISTIC. ON THE OTHER HAND...THERE
IS DRYING ASSOCIATED WITH THE UPSTREAM TROF SO BELIEVE THAT SOME
DRYING IS POSSIBLE. WILL WAIT UNTIL SOME CONSENSUS DEVELOPS IN THE
MODELS BEFORE INTRODUCING A DRYING TREND IN THE LATTER PERIODS.

EXTENDED...AVN/MRF SUGGEST A MONSOON BREAK AS THE WEST COAST TROF
DIGS AND MOVES EASTWARD. CLIMATOLOGY SUGGESTS THAT THE TROF WILL BE
WEAKER AND SLOWER TO MOVE INLAND AND HAVE TEMPERED THE MODEL
SOLUTION IN THAT DIRECTION. HAVE KEPT A MENTION OF SHOWERS IN MOST
ZONES EXCEPT FOR THE MOST WESTERN ZONES WHERE PARTLY CLOUDY
SUFFICES.  DB

.FGZ...NONE.