FXUS65 KFGZ 261624
AFDFGZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
924 AM MST SAT DEC 26 2009
.SYNOPSIS...A COLD AIRMASS BEHIND THE LARGE LOW PRESSURE SYSTEM OVER
THE CENTRAL PART OF THE COUNTRY WILL CONTINUE TO BRING BELOW NORMAL
TEMPERATURES TO NORTHERN ARIZONA THROUGH THE WEEKEND. A TROUGH OF
LOW PRESSURE IS FORECAST TO MOVE ACROSS THE SOUTHWEST STATES LATE
MONDAY THROUGH WEDNESDAY...BRINGING UNSETTLED WEATHER TO NORTHERN
ARIZONA.
&&
.DISCUSSION...A WEAK SHORTWAVE RIDGE WILL DEVELOP ACROSS THE
NORTHLAND THROUGH TONIGHT WITH RATHER COLD AND DRY CONDITIONS
CONTINUING. PERIODS OF MID-TO-UPPER LEVEL CLOUDINESS CAN BE EXPECTED
OVER THE NEXT 24HRS. CURRENT FORECAST PACKAGE APPEARS TO REFLECT
THESE ANTICIPATED CONDITIONS WELL.
&&
.PREV DISCUSSION /325 AM MST/...A LARGE LOW PRESSURE SYSTEM OVER THE
CENTRAL PART OF THE COUNTRY HAS PUSHED A COLD AIRMASS INTO THE
SOUTHWEST STATES. BELOW NORMAL TEMPERATURES CAN BE EXPECTED THROUGH
THE WEEKEND INTO THE FIRST HALF OF NEXT WEEK.
A FIRST IN A SERIES OF LOW PRESSURE TROUGHS WILL MOVE INTO THE
INTERMOUNTAIN WEST ON SUNDAY AND WEAKEN AS IT MOVES ACROSS
ARIZONA...PRODUCING A LOW CHC FOR SNOW FLURRIES ON SUNDAY...FROM
FLAGSTAFF NORTHWEST TO THE KAIBAB PLATEAU. A STRONGER TROUGH OF LOW
PRESSURE IS FORECAST TO MOVE INTO THE WEST COAST STATES ON
MONDAY...AND THEN ACROSS ARIZONA TUESDAY WITH A THIRD DISTURBANCE
AND LAST IN THE SERIES OF LOW PRESSURE TROUGHS MOVING ACROSS
NORTHERN ARIZONA ON WEDNESDAY. LOOK FOR AN INCREASING CHC FOR RAIN
SHOWERS AND SNOW SHOWERS STARTING EARLY TUESDAY AND LASTING THROUGH
THE DAY...AND AGAIN ON WEDNESDAY. THE GFS AND ECMWF ARE BECOMING
MORE CONSISTENT WITH THIS FEATURE AND THE POSSIBILITY OF
ACCUMULATING SNOW ABOVE 5500 TUESDAY AND AGAIN WEDNESDAY. TIMING OF
THESE SYSTEMS STILL REMAINS SOMEWHAT IN QUESTION AT THIS POINT IN
TIME...AND HENCE THE REASON FOR THE 20 AND 30 PERCENT CHANCE OF
PRECIPITATION TUESDAY AND WEDNESDAY.
THURSDAY THROUGH SATURDAY...NORTHERN ARIZONA IS FORECAST TO BE EAST
OF A LARGE SCALE HIGH PRESSURE RIDGE WITH THE RIDGE AXIS ALONG THE
WEST COAST. THIS POSITION OF THE HIGH PRESSURE RIDGE WILL ALLOW FOR
WEAK DISTURBANCES TO MOVE OVER THE TOP OF THE RIDGE AND THEN INTO
NORTHERN ARIZONA. DURING THIS TIME PERIOD HIGH TEMPERATURES ARE
FORECAST TO MODERATE BACK CLOSER TO SEASONAL AVERAGES.
&&
.AVIATION...FOR THE 18Z PACKAGE...EXPECT VFR CONDITIONS WITH LIGHT
EAST WINDS TODAY. HIGH CLOUDS WILL INCREASE FROM THE WEST BY 20Z-22Z
THIS AFTERNOON. AVIATION DISCUSSION NOT UPDATED FOR AMENDMENTS.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC.........KD
AVIATION.......PETERSON
VISIT WEATHER.GOV/FLAGSTAFF FOR NORTHERN ARIZONA WEATHER
INFORMATION.
