FXUS63 KOAX 250920
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
320 AM CST FRI FEB 25 2011
.DISCUSSION...
SNOW CHANCES THROUGH SATURDAY...THEN PRECIPITATION CHANCES/TYPES
SATURDAY NIGHT THROUGH SUNDAY NIGHT...ARE THE PRIMARY FORECAST
CONCERNS.
UPPER SYSTEM THAT BROUGHT 1 TO 5 INCHES OF SNOW TO SOUTHEAST
NEBRASKA AND SOUTHWEST IOWA THURSDAY WAS PUSHING EAST OF IOWA THIS
MORNING. FLAT ZONAL MID LEVEL FLOW WAS NOTED IN THE WAKE OF THIS
SYSTEM...EXTENDING FROM THE CENTRAL PLAINS TO THE WEST COAST WHERE
AN UPPER LOW WAS DRIFTING SOUTH ALONG THE WA/OR COASTS. THIS LOW
WILL AFFECT OUR AREA SUNDAY OR SUNDAY NIGHT. RUC MODEL SHOWED A 100
TO 130KT 300MB JET WITHIN THIS ZONAL FLOW REGIME...EXTENDING FROM
THE WEST COAST INTO CENTRAL NEBRASKA. WEAK ASCENT IN LEFT EXIT
REGION OF THIS JET WAS HELPING TO SPARK LIGHT SNOW ACROSS MUCH OF
WESTERN AND CENTRAL NEBRASKA...AND THAT SNOW WAS PUSHING INTO
EASTERN NEBRASKA THIS MORNING. VISIBILITIES WERE GENERALLY 2 TO 5
MILES AT REPORTING STATIONS IN CENTRAL AND WESTERN
NEBRASKA...INDICATING ONLY LIGHT SNOW WAS FALLING. MODELS WERE
HANDLING THIS SCENARIO FAIRLY WELL THIS MORNING...AND SHOW LIGHT
SNOW SPREADING TOWARD THE MISSOURI RIVER BEFORE TAPERING TO FLURRIES
THIS AFTERNOON. BASED ON RADAR TRENDS...WILL HAVE FAIRLY HIGH SNOW
CHANCES FOR MOST OF THE CWA TODAY...BUT AMOUNTS WILL BE FAIRLY LIGHT
WITH ABOUT A HALF INCH EXPECTED OVER MUCH OF OUR AREA.
AS WEST COAST UPPER LOW SETTLES SOUTH TONIGHT...A PIECE OF ENERGY IN
MEAN TROUGH AXIS FROM THE LOW INTO THE SOUTHERN CANADIAN PLAINS WILL
BREAK LOOSE AND SWING THROUGH THE NORTHERN PLAINS. ISENTROPIC
UPGLIDE WILL COMMENCE THIS EVENING ACROSS MUCH OF THE CENTRAL PLAINS
IN RESPONSE TO APPROACH OF THIS UPPER WAVE. WHILE UPGLIDE WILL
INITIALLY BE WEAK...CONVERGING MID AND UPPER LEVEL Q VECTORS IN GFS
FORECASTS SUGGEST LIFT WILL INCREASE LATER TONIGHT AND SATURDAY
MORNING AS FRONTOGENETICAL FORCING IS ENHANCED...ESPECIALLY OVER OUR
SOUTHERN CWA IN THE 850-500MB LAYER. GARCIA METHOD SUGGESTS SOME
AREAS COULD SEE 4 OR SO INCHES OF SNOW BETWEEN MIDNIGHT AND NOON
SATURDAY. BUT WITH VARIED MODEL SOLUTIONS ON LOCATION OF BEST
FRONTOGENESIS...WILL BROAD BRUSH MUCH OF THE CWA WITH A 1 TO 3 INCH
TOTALS FOR THAT TIME PERIOD. AND THOSE TOTALS ARE A BIT HIGHER THAN
MY NEIGHBORING OFFICES.
DEEP ISENTROPIC UPGLIDE SUBSIDES SATURDAY AFTERNOON/NIGHT...BUT LOW
LEVEL WARM/MOIST ADVECTION CONTINUES. FORECAST SOUNDINGS SHOW DRYING
MID LEVELS OVER MOIST BOUNDARY LAYER...WITH WEAK LOW LEVEL LIFT
SATURDAY NIGHT. THIS LOOKS LIKE FREEZING DRIZZLE SITUATION SO WILL
INCLUDE THAT IN THE FORECAST SATURDAY NIGHT AND SUNDAY MORNING.
FORECAST THEN HINGES ON WEST COAST UPPER LOW EJECTING INTO THE
PLAINS. GFS AND ECMWF OFFER VERY SIMILAR SOLUTIONS IN TAKING UPPER
LOW THROUGH SOUTHERN KANSAS...WITH SURFACE LOW MOVING JUST SOUTH OF
THE KANSAS CITY METRO BY 06Z MONDAY. STRONG WARM ADVECTION AHEAD OF
THIS SYSTEM WILL DRIVE TEMPERATURES WELL ABOVE FREEZING FOR MUCH OF
THE CWA WITH FORECAST SOUNDINGS INDICATING RAIN THE LIKELY
PRECIPITATION TYPE SUNDAY AFTERNOON FOR ALL BUT NORTHEAST NEBRASKA
WHERE RAIN OR SNOW IS POSSIBLE. ELEVATED INSTABILITY ALSO INCREASES
SUNDAY AFTERNOON WITH 850 LIFTED INDICES WELL BELOW ZERO IN
SOUTHEAST NEBRASKA. WILL HAVE HIGHEST PRECIP CHANCES IN OUR SOUTHERN
CWA AND MENTION THUNDER SUNDAY AFTERNOON THERE. A CHANGE FROM RAIN
TO SNOW WILL FOLLOW SUNDAY NIGHT FROM NORTHWEST TO SOUTHEAST...BUT
MOISTURE/LIFT SHOULD EXIT RATHER QUICKLY TO THE EAST...LIMITING
ADDITIONAL SNOWFALL.
DID NOT CHANGE FORECAST FOR THE REST OF THE WEEK. SHOULD HAVE A
MODEST WARMING TREND AS BOTH GFS AND ECMWF INDICATE WEAK UPPER
RIDGING SETTING UP IN THE MIDDLE OF THE COUNTRY BY MID WEEK.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
COLD HIGH PRESSURE AT THE SURFACE WILL BE IN PLACE OVER THE REGION
DURING THE PERIOD WITH WEAK WAVES MOVING THROUGH WESTERLY FLOW
ALOFT. FAIRLY DEEP MOISTURE PROFILE INDICATED DURING THIS TIME WITH
MAINLY MVFR CIGS WITH PERIODS OF LIGHT SNOW PRODUCING MVFR VSBYS.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$