Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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000
FXUS65 KFGZ 282204
AFDFGZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1020 AM MST WED JAN 28 2015

.SYNOPSIS...
FAIR WEATHER WILL RETURN TODAY...BEFORE SHOWERS BEGIN TO ARRIVE LATE
THURSDAY WITH WIDESPREAD SHOWERS FRIDAY THROUGH SATURDAY...THEN
DECREASING THROUGH SUNDAY MORNING. IMPROVING CONDITIONS ARE EXPECTED
BY MID-DAY SUNDAY.

&&

.DISCUSSION...HAVE UPDATED FORECAST FOR FOG AND LOW CLOUDS IN
COCONINO PLATEAU...GLEN/GRAND CANYON...AND THE LITTLE COLORADO RIVER
VALLEY IN NAVAJO COUNTY ZONES FOR TODAY. HAVE ALSO CHANGED WORDING
IN SEVERAL ZONES CONCERNING SNOW ACCUMULATIONS AND SNOW LEVELS FOR
THIS NEXT STORM SYSTEM. SNOW LEVELS WITH THIS NEXT STORM SYSTEM WILL
BE RELATIVELY HIGH FOR THIS TIME OF YEAR.

&&

.PREV DISCUSSION /400 AM MST/...

TODAY LOOK FORWARD TO A HIGH PRESSURE RIDGE WHICH WILL BRING WARMER
HIGH TEMPERATURES AND DRY CONDITIONS.

A WEATHER SYSTEM IS BEGINNING TO TAKE SHAPE WELL TO THE WEST OF THE
BAJA/CALIFORNIA COAST LINE TODAY. THIS SYSTEM IS GENERATING DEEP
CONVECTION ON ITS EAST FLANKS...THIS WILL TEND TO HELP DEEPEN THE
MOISTURE PLUME THAT WILL EVENTUALLY BE PULLED NORTH INTO SOUTHERN
CAL/SOUTHERN NV/AND AZ FRIDAY AND SATURDAY.

THE SYSTEM WILL BEGIN TO MOVE EAST LATE THURSDAY/EARLY FRIDAY
MORNING...AS IT DOES THIS SYSTEM WILL BEGIN TO ADVECT MOISTURE
NORTHWARD WITH OVER AN INCH PW VALUES BEING PULLED INTO WESTERN
ARIZONA. WEAK LARGE SCALE LIFT...STEEPENING LAPSE RATES AND WEAK
OROGRAPHIC LIFT IS FORECAST TO MOVE INTO THE AREA THURSDAY NIGHT
INTO FRIDAY/SATURDAY. THE COMBINATION OF THESE WEATHER PARAMETERS
ALONG WITH A WARM AND MOIST ATMOSPHERE WILL BRING LIGHT TO MODERATE
RAIN SHOWERS TO MOST AREAS ON FRIDAY INTO EARLY SATURDAY MORNING.

THE SNOW LEVELS FOR THIS SYSTEM STILL HAVE THE GREATEST FORECAST
UNCERTAINTY. CURRENT FORECAST GUIDANCE IS KEEPING SNOW LEVELS FROM
8000 TO 8500 FEET THROUGH EARLY SATURDAY MORNING...THEN SNOW LEVELS
LOWERING THROUGH THE DAY SATURDAY TO AROUND THE 7000 FOOT LEVEL.
THERE COULD BE A CHANCE EARLY FRIDAY MORNING BEFORE THE DEEPER...AND
WARMER SUBTROPICAL PLUME OF MOISTURE ARRIVES THAT SNOW COULD MIX
WITH RAIN OR BRIEFLY CHANGE OVER TO ALL SNOW FROM AROUND 7000 FEET
AND ABOVE. HOWEVER ONCE THE SUBTROPICAL PLUME ARRIVES THE SNOW
LEVELS WILL RISE BACK UP. IT IS STILL UNDETERMINED HOW MUCH COLD AIR
THIS SYSTEM WILL PULL FROM THE NORTHERN STREAM AND HOW LOW THE SNOW
LEVELS COULD POTENTIALLY FALL ON SATURDAY. IF THIS SYSTEM CAN
DEVELOP SOME COLDER AIR ALOFT...THEN THE POTENTIAL FOR ACCUMULATING
SNOW ON SATURDAY COULD BE COME A WEATHER HAZARD...BUT FOR NOW WE
WILL CONTINUE TO MONITOR THIS SYSTEM.

STORM TOTAL RAINFALL OR LIQUID WATER EQUIVALENT COULD RANGE FROM 0.5
INCHES IN THE LOWER VALLEYS TO OVER 2.0 INCHES OVER FAVORED UPSLOPE
AREAS AND HIGHER TERRAIN AREAS OF NORTHERN ARIZONA.

HIGH PRESSURE IS EXPECTED TO BUILD OVER ARIZONA FROM THE NORTHWEST
ON SUNDAY AS THE LOW DROPS SOUTH AND THEN SOUTHEAST...WITH DRYING
CONDITIONS AND WARMER HIGH TEMPERATURES

&&

.AVIATION...FOR THE 18Z PACKAGE...FOG AND LOW CLOUDS WITH IFR TO
LIFR CONDITIONS IN GLEN CANYON AND INSIDE THE GRAND CANYON WELL INTO
THE AFTERNOON. OTHERWISE....EXPECT VFR CONDITIONS FOR THE NEXT 24
HOURS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC.........MAS/TC
AVIATION.......BOLHIN

FOR NORTHERN ARIZONA WEATHER INFORMATION VISIT
WEATHER.GOV/FLAGSTAFF















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