Severe Thunderstorm Warning 42, NWS Flagstaff, AZ

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST TUE AUG 15 2000

SYNOPSIS...HIGH PRESSURE WILL REMAIN OVER THE DESERT SOUTHWEST
THROUGH MUCH OF THE WEEK. MOISTURE WILL INCREASE ACROSS THE REGION
BY THURSDAY. EXPECT SHOWERS AND THUNDERSTORMS TO CONTINUE THE NEXT
DAY OR TWO...AND THEN INCREASE IN COVERAGE BY THE MIDDLE TO LATTER
PARTS OF THE WEEK. TEMPERATURES WILL REMAIN AROUND SEASONAL NORMALS.

DISCUSSION...A STRONG MID-LEVEL RIDGE WILL REMAIN OVER THE SOUTHWEST
UNITED STATES THE NEXT TWO DAYS WITH THE CIRCULATION CENTER
REMAINING NEAR THE FOUR CORNERS. THERE ARE SOME DIFFERENCES BETWEEN
THE NGM/ETA AND THE AVN MODLES. THE AVN KEEPS THE 500 MB RIDGE OVER THE
FOUR CORNERS WHILE THE ETA/NGM MOVE IT INTO SOUTHERN NEVADA. WITH A
TROUGH APPROACHING IN THE PACIFIC THINK THE AVN IS HANDLING THE
LARGE SCALE PATTERN THE BEST AND THAT IS HOW THE FORECAST WILL BE
WEIGHTED. FLOW AT 500 MB WILL CONTINUE OUT OF THE SOUTHEAST ON
WEDENSDAY FOR A NEAR REPEAT OF THE WEATHER ON TODAY. FOR THURSDAY
THE FLOW WILL BECOME MORE SOUTHERLY. ON WEDNESDAY DRIER AIR WILL
CONTINUE TO MOVE INTO NORTHERN ARIZONA FROM THE SOUTHEAST.
HOWEVER...500 MB TEMPERATURES WILL BE IN THE -7 TO -8 DEGREE C RANGE
WITH NEAR ADIABATIC MID-LEVEL LAPSE RATES. LOOKS LIKE A HIGH
BASED...DRY LIGHTNING TYPE OF DAY AGAIN ON WEDNESDAY WITH THE
WETTEST THUNDERSTORMS OVER THE FAR WEST. ON THURSDAY MID TO UPPER
INVERTED TROUGH NOW OVER NORTHEAST MEXICO (ASSOCIATED WITH ONCE
TROPICAL STORM BERYL) WILL MOVE INTO NORTHWEST MEXICO. EXPECT MCS
ACTIVITY TO PICK UP BY WEDNESDAY NIGHT OVER NORTHWEST MEXICO AND
WITH MORE SOUTHERLY FLOW THE AIR MASS SHOULD GRADUALLY BECOME MORE MOIST
OVER THE WESTERN TWO-THIRDS OF NORTHERN ARIZONA. THE POSITION OF THE
HIGH OVER THE FOUR CORNERS WILL LIKELY LIMIT MOISTURE VALUES OVER
THE NORTHEAST AND EAST WITH ISOLATED HIGH BASED THUNDERSTORMS CONTINUING
OVER THOSE LOCATIONS.

IN THE EXTENDED...BROAD RIDGE REMAINS OVER THE SOUTHWEST UNITED
STATES WITH THE CIRCULATION CENTER NEAR THE FOUR CORNERS REGION.
EXPECT A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY...ESPECIALLY
OVER THE MOGOLLON RIM AND AND LOCATIONS SOUTH AND WEST.

MCCOLLUM

.FGZ...NONE.

AZZ004>018-037>040-142030-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 AM MST TUE AUG 15 2000

...SCATTERED THUNDERSTORMS OVER NORTHERN ARIZONA TODAY...

SPOTTER REPORTS OF HAIL...RAINFALL AMOUNTS...GUSTY WINDS AND SMOKE
ARE REQUESTED.

MOISTURE AND INSTABILITY REMAINS ACROSS ARIZONA. THIS WILL RESULT
IN SCATTERED SHOWER AND THUNDERSTORM ACTIVITY PRIMARILY OVER THE RIM
COUNTRY INTO GRAND CANYON COUNTRY BY LATE MORNING. A FEW STORMS
WILL MOVE INTO YAVAPAI COUNTY...THE LITTLE COLORADO RIVER VALLEY AND
THE NAVAJO NATION BY MID TO LATE AFTERNOON. STORMS WILL BE HIGH BASED
TODAY WITH THE MAIN THREAT BEING STRONG WINDS AND DRY LIGHTNING.
MOST STORMS TODAY WILL BE CAPABLE OF PRODUCING GUSTY WINDS OF 25
TO 35 MPH. HEAVY RAIN PRODUCING STORMS WILL REMAIN VERY ISOLATED.

THE HAZARDOUS WEATHER OUTLOOK GIVES PRELIMINARY INFORMATION FOR THE
POSSIBILITY OF WEATHER THAT COULD BECOME SEVERE...DAMAGING WINDS IN
EXCESS OF 57 MPH...HAIL 3/4 INCH IN DIAMETER OR LARGER...AND HEAVY
RAINFALL THAT COULD CAUSE FLOODING OR RUNNING WASHES. WHEN
HAZARDOUS WEATHER BEGINS...IMPORTANT LIFE SAVING INFORMATION WILL BE
PROVIDED IN SHORT TERM FORECASTS...SEVERE WEATHER AND FLOOD WARNINGS
...AND FOLLOW-UP STATEMENTS.

MCCOLLUM