000
FXUS63 KOAX 061737
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1137 AM CST FRI DEC 6 2013

.DISCUSSION...
TEMPERATURE AND WIND FORECAST THIS MORNING IS ON TRACK...AND
SHOULD BE ABLE TO ALLOW THE WIND CHILL ADVISORY TO EXPIRE ON
SCHEDULE AT NOON...THOUGH NEAR-ADVISORY CONDITIONS WILL LINGER UP
THERE THROUGH THE REST OF THE DAY. OTHERWISE...HAVE UPDATED SKY
COVER FOR THE DAY...WITH CLEAR SKIES NORTH AND CLOUDY SKIES IN THE
SOUTHERN CWA.

MAYES

&&

.AVIATION...
18Z TAFS FOR KOMA...KLNK...AND KOFK.

VFR CONDITIONS ARE EXPECTED THROUGH THE TAF CYCLE. NORTHWEST WINDS
AT AROUND 13-16KT TODAY WILL DIMINISH AROUND SUNSET...THEN BECOME
LIGHT AND VARIABLE LATER TONIGHT.

MAYES

&&

.PREV DISCUSSION... /ISSUED 324 AM CST FRI DEC 6 2013/

DISCUSSION...
COLD TEMPERATURES THROUGH THE WEEKEND AND SNOW CHANCES SATURDAY
NIGHT AND SUNDAY REMAIN THE PRIMARY FORECAST CONCERNS.

DEEP AND BROAD MID LEVEL TROUGH REMAINED OVER THE WESTERN HALF OF
THE COUNTRY THIS MORNING. AT THE SURFACE...ARCTIC HIGH PRESSURE
EXTENDED FROM ALBERTA THROUGH THE CENTRAL PLAINS AND INTO THE RED
RIVER AND MID MISSISSIPPI RIVER VALLEYS. STRONG JET STREAM ON THE
FRONT SIDE OF UPPER TROUGH...EXTENDING FROM THE TEXAS BIG BEND AREA
INTO THE GREAT LAKES...RIDING OVER ARCTIC AIR WAS CAUSING HAVOC
ACROSS MUCH OF THE SOUTHERN PLAINS INTO THE OHIO VALLEY WHERE
VARIOUS WINTER STORM WARNINGS ARE IN EFFECT. ONLY AFFECT IN OUR AREA
WITH THIS SETUP WAS MID AND HIGH LEVEL CLOUDS ON THE NORTHWEST SIDE
STREAMING THROUGH SOUTHEAST NEBRASKA AND SOUTHWEST IOWA.

THOSE CLOUDS WERE HOLDING TEMPERATURES IN THE 5 TO 10 DEGREE RANGE
THIS MORNING...WHILE CLEAR SKIES IN NORTHEAST NEBRASKA HAVE ALLOWED
TEMPERATURES TO DIP BELOW ZERO. THESE COLD TEMPS ALONG WITH
NORTHWEST WINDS NEAR 10 MPH WERE DRIVING WIND CHILLS CLOSE TO 20
BELOW. EXPECT WINDS TO CONTINUE THIS MORNING...SO WILL MAINTAIN OUR
WIND CHILL ADVISORY THROUGH NOON TODAY FOR PARTS OF NORTHEAST
NEBRASKA.

COLD ADVECTION WILL CONTINUE TODAY INTO SATURDAY AS CORE OF ARCTIC
HIGH CONTINUES TO SPILL INTO THE PLAINS. DESPITE SUNSHINE
TODAY...HIGHS LOOK TO ONLY GAIN A FEW DEGREES FROM MORNING LOWS.
EXPECT HIGHS FROM 5 ABOVE IN THE NORTH TO NEAR 15 IN THE SOUTH.
CLEARING SKIES AND DECREASING WINDS TONIGHT SHOULD PROVIDE FOR A
DECENT RADIATIONAL COOLING REGIME. WITH TEMPS THIS MORNING DROPPING
BELOW ZERO IN THE NORTH WITH SOME WIND...EXPECT EVEN COLDER LOWS
TONIGHT. HAVE ALL AREAS BELOW ZERO FOR SATURDAY MORNING.

CLOUDS WILL BEGIN TO INCREASE DURING THE DAY SATURDAY AS MID LEVEL
WARM ADVECTION STARTS TO KICK IN AHEAD OF STRONG SHORT WAVE ROUNDING
BASE OF MAIN TROUGH AXIS. RESULTING ISENTROPIC UPGLIDE WILL BEGIN TO
SLOWLY SATURATE MID LEVELS BEFORE LIFT INCREASES LATER SATURDAY
AFTERNOON. FORECAST SOUNDINGS AND CROSS SECTIONS SHOW DEEP DRY
SURFACE LAYER THAT WILL HAVE TO BE OVERCOME BEFORE SNOW BEGINS.
SOUNDINGS SUGGEST THIS WILL OCCUR SATURDAY EVENING IN OUR WEST AND
NORTHWEST...SPREADING EAST AFTER MIDNIGHT. ALL OF THE CWA SHOULD SEE
SNOW BY SUNDAY MORNING.

FORCING WITH THIS SYSTEM APPEARS TO BE BROAD AND RELATIVELY
WEAK...BUT WILL BE AROUND FOR A GOOD 18 HOURS OR SO BEFORE LIFTING
OUT SUNDAY AFTERNOON AND EVENING. MOISTURE WILL ALSO BE SOMEWHAT
LIMITED. HOWEVER WHEN THE SNOW DOES BEGIN TO FALL...A DEEP SATURATED
DENDRITIC LAYER FROM ABOUT 600MB TO THE SURFACE WILL EXIST...MAKING
FOR AN EFFICIENT SNOW-MAKING REGIME. AND LIQUID/SNOW RATIOS WILL BE
QUITE HIGH...15 OR 20 TO 1...ALLOWING FOR MORE MORE ACCUMULATION IN
COLD ENVIRONMENT. VARIOUS SNOWFALL PREDICTORS FROM MODEL OUTPUT
INCLUDING COBB CALCULATIONS...STRAIGHT QPF TO SNOWFALL USING AVERAGE
17 TO 1 RATIO...AND GARCIA METHOD USING 280K TO 285K LAYER OVER 18
HOURS...ALL SUGGEST A BROAD AREA OF 2 INCH SNOWS WITH POCKETS OF 3
TO 4 INCHES LOOK LIKELY.

SNOW SHOULD BE MOVING OUT OF THE AREA SUNDAY EVENING AS SHORTWAVE
LIFTS TOWARD THE GREAT LAKES. TEMPERATURES SUNDAY NIGHT AND MONDAY
WILL CONTINUE VERY COLD GIVEN FRESH SNOW COVER. BEYOND
MONDAY...UPPER TROUGH BEGINS TO BREAK DOWN FOR A TIME. STRONG
SHORTWAVE WILL RACE THROUGH MINNESOTA INTO THE GREAT LAKES ON
TUESDAY...BRINGING SOUTHWEST TO NORTHWEST LOW LEVEL FLOW TO OUR AREA
WHICH WILL MIX UP ATMOSPHERE AND COULD PUSH HIGHS INTO THE 20S. A
GRADUAL EVOLUTION TO NEARLY ZONAL MID LEVEL FLOW LOOKS ON TRACK FOR
MID TO LATE WEEK ALLOWING SOME WARMTH TO RETURN. WE MAY EVEN SEE
NEAR FREEZING TEMPERATURES BY LATE IN THE WEEK.

DERGAN

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WIND CHILL ADVISORY UNTIL NOON CST TODAY FOR NEZ011-012-015>018-
     030>032.

IA...NONE.
&&

$$