Severe Thunderstorm Warning 14, NWS Flagstaff, AZ

NORTHERN ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
230 PM MST WED JUL 04 2001

SYNOPSIS...HIGH PRESSURE ALOFT WILL SHIFT EASTWARD OVER THE NEXT FEW
DAYS WITH SOME INCREASE IN MOISTURE OVER NORTHERN ARIZONA AS SOUTHERLY
FLOW DEVELOPS. AS A RESULT...LOOK FOR THE CHANCE OF MAINLY AFTERNOON
AND EVENING THUNDERSTORMS TO CONTINUE INTO EARLY NEXT WEEK.

DISCUSSION...STRONG UPPER RIDGE CENTERED OVER THE UTAH/COLORADO
BORDER THIS AFTERNOON. MODELS IN GENERAL AGREEMENT IN MOVING THE
RIDGE EASTWARD OVER THE NEXT TWO DAYS. DEEP SOUTHEASTERLY FLOW WILL
CONTINUE ON THURSDAY BUT BECOME MORE SOUTHERLY ON FRIDAY AS A TROUGH
ON THE WESTERN EDGE OF THE RIDGE MOVES NORTHWARD ACROSS ARIZONA.
EXPECT A GENERAL UPTICK IN MOISTURE AND THUNDERSTORM COVERAGE
THURSDAY AND FRIDAY AS FLOW TURNS TO A MORE MOIST SOUTHERLY
TRAJECTORY. TEMPERATURES WILL REMAIN ABOVE NORMAL WITH LIGHT AND
VARIABLE WINDS ON THURSDAY. WITH UPPER TROUGH APPROACHING ON FRIDAY
WILL GO WITH A GENERAL PARTLY TO MOSTLY CLOUDY FORECAST WITH NO
SIGNIFICANT DIURNAL TRENDS IN CLOUDINESS OR THUNDERSTORM ACTIVITY.
DAYTIME HIGHS WILL LOWER SOME ON FRIDAY WITH INCREASED MOISTURE AND
CLOUDINESS. FRIDAY COULD GET INTERESTING NEAR THE MOGOLLON RIM WITH
DEEP MOISTURE POISED TO MOVE INTO CENTRAL ARIZONA..STRONG SOUTHERLY
FLOW AND VERTICAL SHEAR. A GOOD SETUP FOR HEAVY RAIN PRODUCING
STORMS WITH A TRAINING BEHAVIOR. HOWEVER...IF A MIDLEVEL CLOUD DECK
FORMS IN ADVANCE OF THE TROUGH AXIS ON FRIDAY WONT SEE MUCH MORE
THAN SCATTERED STORMS.

IN THE EXTENDED...INVERTED TROUGH OVER BAJA CALIFORNIA WILL PHASE
WITH WEAK SHORT-WAVE TROUGH IN THE WESTERLY FLOW OFF THE CALIFORNIA
COAST. THIS WILL CAUSE A RELATIVELY STRONG TROUGH TO MOVE ACROSS
ARIZONA ON FRIDAY. THE LATEST AVN MODEL DATA IS SUGGESTING THIS
SYSTEM WILL DEVELOP STRONG SOUTHWEST TRAJECTORIES WITH A DRIER AIR
MASS PUNCHING INTO ARIZONA OVER THE WEEKEND. HOWEVER...WOULD LIKE TO
SEE A COUPLE MODEL RUNS BEFORE CHANGING THE CURRENT TRENDS IN THE
EXTENDED. WILL CONTINUE WITH THE GENERAL PARTLY CLOUDY WITH A CHANCE
OF THUNDERSTORMS IN THE EXTENDED.

MCCOLLUM

.FGZ...NONE.

AZZ004>018-037>040-041930-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
930 PM MST WED JUL 04 2001

...ISOLATED SEVERE THUNDERSTORMS OVER YAVAPAI AND NORTHERN GILA
COUNTIES LATER THIS AFTERNOON AND INTO THE EVENING...

DISCUSSION...SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM THIS
AFTERNOON...MAINLY OVER THE KAIBAB PLATEAU...MOGOLLON RIM AND
WHITE MOUNTAIN AREAS. EASTERLY FLOW ALOFT WILL PUSH THESE STORMS
INTO THE LOWER VALLEYS OF YAVAPAI AND GILA COUNTIES BY MID AFTERNOON.
AS THE STORMS MOVE INTO DEEPER MOISTURE A FEW WILL BECOME SEVERE WITH
THE MAIN THREAT BEING WIND GUSTS OF 50 TO 60 MPH. STORMS WILL ALSO
BE CAPABLE OF PRODUCING ISOLATED DOWNPOURS OF 1 TO 2 INCHES BUT
WIDESPREAD HEAVY RAINFALL IS NOT ANTICIPATED. STORMS SHOULD
CONTINUE INTO THE EARLY EVENING HOURS BEFORE DIMINISHING.