NORTHERN ARIZONA FORECAST DISCUSSION
NWS FLAGSTAFF AZ
AFDFLG 300 AM MST FRI FEB 23 2001
SYNOPSIS...A COLD PACIFIC STORM SYSTEM WILL MOVE INTO ARIZONA THIS
MORNING AND LINGER THROUGH FRIDAY NIGHT. THIS SYSTEM WILL BRING MUCH
COLDER TEMPERATURES...ALONG WITH MOUNTAIN SNOW AND VALLEY RAIN
SHOWERS. SNOW LEVELS WILL BE NEAR 5000 FEET THIS MORNING AND LOWER
TO 3500 DURING THE DAY. EXPECT A BREAK IN THE WEATHER ON SATURDAY
AND SUNDAY...WITH MORE VALLEY RAIN AND MOUNTAIN SNOW BY MONDAY AS
ANOTHER STORM SYSTEM AFFECTS THE DESERT SOUTHWEST.
DISCUSSION...CLOSED LOW LOCATED OVER NRN CALIF THIS MORNING AND
MOVING TO THE SE. WAVELENGTH IS BEGINNING TO SHORTEN AS NEXT RIDGE
PROGRESSES TO THE EAST. ACARS DATA SHOWS 140+ KT JET ON THE BACKSIDE
OF THE TROUGH AND THIS IS ANALYZED WELL BY AVN GRIDDED DATA. THIS
JET CONFIG SUGGESTS THAT THE UPPER LOW WILL BE SLOWER TO ARRIVE THAN
ORIGINALLY FCST...EVEN THOUGH THE SURFACE FRONT IS ALREADY HERE.
SURFACE COLD FRONT IS MARCHING ACROSS WESTERN ARIZONA THIS MORNING
AND PCPN HAS BROKEN OUT IN A WIDE BAND EXTENDING FROM THE UTAH
BORDER ALL THE WAY TO SRN AZ. RADAR SHOWS SOME STRONG RETURNS
DEVELOPING IN WESTERN YAVAPAI AND COCONINO COUNTIES AND EXPECT THESE
TO EXPAND IN COVERAGE THROUGHOUT THE MORNING. SNOW LEVELS SOMEWHERE
AROUND 6000 ATTM AND LOWERING QUICKLY. EXPECT TO SEE LEVELS DROP TO
NEAR 3500 FEET AS THE COLD CORE BEGINS TO MOVE ACROSS THE REGION
LATER TODAY.
AVN AND ETA QPF VALUES ARE VERY DIFFERENT AGAIN TODAY WITH THE ETA A
FACTOR OF FIVE GREATER THAN THE AVN. AGAIN BELIEVE THE AVN IS A BIT
DRY AND THE ETA MUCH TOO WET AND WILL GO WITH SOMETHING IN BETWEEN.
EXPECT SNOW ACCUMULATIONS TO REMAIN BELOW ADVISORY LEVELS.
DYNAMICS RAPIDLY CHANGE SIGN OVERNIGHT TONIGHT AND INTO SATURDAY
MORNING AND EXPECT A QUICK CLEARING BEHIND THE SYSTEM.
EXTENDED...NEXT STORM WILL APPROACH THE AREA LATE ON SUNDAY OR
MONDAY AND CONTINUE INTO TUESDAY. THIS HAS THE POTENTIAL TO BE A
WETTER SYSTEM THAN THE CURRENT ONE. WILL MENTION SHOWERS FOR MONDAY
AND TUESDAY. OTHERWISE IT SHOULD BE NEAR CLIMO FOR THE REMAINDER OF
THE EXTENDED. DB
.FGZ...NONE.
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
AFDSDF 420 AM EST FRI FEB 23 2001
MAIN FORECAST PROBLEM..IN THE SHORT TERM...IS THE LOW CLOUDS ACROSS
THE FORECAST AREA AND WHEN THEY WILL DECREASE. THIS WILL IMPACT HIGH
TEMPERATURES TODAY. IN THE LONGER TERM...SHOWERS AND THUNDERSTORMS
MOVING IN AHEAD OF NEXT COLD FRONT ON SATURDAY AND SATURDAY NIGHT.
MODELS ARE GENERALLY CONSISTENT BRINGING STRONG SYSTEM INTO FORECAST
AREA SATURDAY AND SATURDAY NIGHT. NCEP DISCUSSIONS LIKE FASTER ETA
BETTER AND WILL GO A CLOSER TO ETA FOR TIMING.
AIRCRAFT SOUNDING AT 07Z INDICATES STRONG SUBSIDENCE INVERSION OVER
FORECAST AREA KENTUCKY. CLOUD AREA EXTENDING BACK INTO CENTRAL
ILLINOIS WILL BE SLOW TO DECREASE. CLOUDS MAY NOT BEGIN TO DECREASE
UNTIL CLOSE TO NOONTIME ACROSS NORTHWEST PART OF FORECAST AREA AND
AFTERNOON IN THE EASTERN AND SOUTHERN SECTIONS AS HIGH MOVES INTO
CENTRAL KENTUCKY AND SOUTH CENTRAL INDIANA. WILL ADJUST WORDING TO
INDICATE LATER CLEARING AND WILL ALSO LOWER HIGHS SOME TODAY.
HIGHER CLOUDS AHEAD OF NEXT SYSTEM WILL SPREAD EAST INTO FA
OVERNIGHT AND AS HIGH MOVES TO THE EAST WINDS WILL INCREASE SOME
FROM THE SOUTHEAST. SINCE TEMPERATURES WILL BE COOLER IN THE
AFTERNOON AND CLOUDS WILL BE MID LEVEL WILL ADJUST LOWS MORE TOWARD
LOWER COOLER NGM MOS TEMPERATURES.
TIME SECTIONS SHOW DEEP LAYERED MOISTURE MOVING INTO FORECAST AREA
ALONG WITH UPWARD MOTION SATURDAY AFTERNOON. WILL STAY WITH HIGH
CHANCE OF SHOWERS/THUNDERSTORMS. MOS GUIDANCE GOING CATEGORICAL FOR
SATURDAY NIGHT BUT WILL STAY WITH LIKELY FOR NOW. WITH STRONG
SOUTHWEST GRADIENT WINDS...TEMPERATURES SATURDAY SHOULD REACH 60 MOST
LOCATIONS EVEN WITH CLOUD COVER.
.SDF...NONE
SCHOLZ