FXUS63 KOAX 070946
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
346 AM CST MON MAR 7 2011
.DISCUSSION...
PRECIP TYPES AND AMOUNTS ARE THE MAIN FORECAST CONCERNS THROUGH
MID WEEK.
THE SHRTWV TROF ASSOCIATED WITH THE FIRST OF THE TWO STORM SYSTEMS
IS NOW MOVG THRU THE CNTRL ROCKIES...AND WILL MOV ACROSS THE
CNTRL PLAINS TODAY. THIS SYSTEM IS EXPECTED TO DAMPEN AS IT MOVS
ACRS THE FA TODAY. NEVERTHELESS...PERSISTENT UPGLIDE HAS ALLOWED
FOR WIDESPREAD PRECIP TO DVLP ACRS CNTRL AND WRN NEB AS EXPECTED.
THIS HAS MOVED INTO NE NEB EARLY THIS MRNG PER WEB CAMS AND
SURFACE OBSERVATIONS. THE BEST COMBINATION OF MID-LVL SATURATION
AND PERSISTENT LIFT IS EXPECTED OVER NE NEB TODAY. FARTHER EAST
THE PRECIP WILL BE FIGHTING CONTD DRY AIR ADVECTION FM THE E...AS
WELL AS A WEAKENING SYNOPTIC SYSTEM. AMOUNTS NEAR THE MO RIVER
WILL LIKELY BE LESS THAN INCH AND MAINLY ON GRASSY SURFACES WITH
PAVEMENT TEMPS RUNNING ABOVE FREEZING EARLY THIS MORNING. LITTLE
IF ANY ACCUMULATION IS EXPECTED OVER SOUTHWEST IOWA OR FAR SE NEB.
EARLIER THIS MORNING WE ISSUED AN ADVRY FOR NE NEB FOR THIS
EVENT. THIS WAS DONE FOR A COUPLE OF REASONS:
1. THE SNOW STARTED DURING THE OVERNIGHT HOURS...AND WITH SURFACE
TEMPERATURES IN THE MID 20S...SNOW HAS A GOOD CHANCE OF
ACCUMULATING ON ROADWAYS. THIS WAS ALSO INDICATED IN THE 21Z SREF
SNOW ON ROADWAYS PRODUCT AS WELL.
2. WITH THE SNOW ACCUMULATING DURING THE OVERNIGHT HOURS...FURTHER
ACCUMULATIONS WILL BE EASIER DURING THE DAY LIGHT HOURS TO OFF-SET
THE TIME OF YEAR THE SNOW IS FALLING.
3. THE MOST INTENSE SNOWFALL OF THE EVENT WILL BE FALLING DURING
THE MORNING RUSH HOUR.
THE LIFT WITH THIS SYSTEM IS EXPECTED TO DECREASE THROUGH THE AFTN
WITH MUCH OF THE PRECIP ENDING BY LATE AFTN. SOME LIFT CONTS TO BE
INDICATED THROUGH BEHIND THE INVERTED SFC TROF ACRS NE NEB THROUGH
THE NIGHT. HERE...POINT FORECAST SOUNDING INDC SOME SATURATION
NEAR THE DENDRITIC ZONE...BUT RH VALUES ARE NOT ALL THAT HIGH.
THUS A LITTLE MIX OF -SN OR FZDZ CLD FALL BUT WE ARE NOT EXPECTING
MUCH IN THE WAY OF PROBLEMS OVERNIGHT.
THE NEXT SYSTEM TO AFFECT THE FA WILL THEN START TO MOV INTO THE
CNTRL PLAINS ON TUES. MODELS CONT TO BE FAIRLY CONSISTENT IN THE
FORECAST OF THIS STORM SYSTEM. WE DID NOT USE THE 00Z GFS THOUGH
AS IT WAS A SRN OUTLIER...AND THE 00Z EC WAS ON THE NORTHERN EDGE
OF THE GUIDANCE ENVELOPE BUT NOT BY MUCH. THE NAM/GEM/SREF WERE A
DECENT COMPROMISE ON TIMING AND PLACEMENT OF FEATURES FOR THE
TUE/WED PERIOD AND WERE USED. STG LIFT IS EXPECTED TO GET GOING IN
THE MRNG OVER THE SRN FA...AND LIFT NWD THRU THE DAY. THERE
REMAINS LITTLE CHANGE FROM THE FORECAST REASONING FM LAST NIGHT
REALLY. THE BEST COMBINATION OF WEAK STABILITY...TEMPERATURE
PROFILE AND STRONG LIFT SEEM TO LINE UP WELL WITH THE H6
FRONTOGENESIS AXIS...AND THIS AGAIN WILL BE USED TO DETERMINE
WHERE THE HEAVIEST SNOW WILL FALL. DID INCREASE HIGHS DURING THE
DAY ON TUES DUE TO THE EXPECTED DELAY OF THE ONSET OF PRECIP...BUT
ONCE PRECIP BEGINS THE WEB BULB PROCESS SHLD COOL TEMPERATURES
THRU THE AFTN. LIFT WILL CONT INTO THE EVENING HOURS ACRS THE
ENTIRE FORECAST AREA...BUT SHLD START TO DECREASE AFTER MIDNIGHT
AS THE FRONTOLYSIS TAKES OVER AND Q-G FORCING SHIFTS EWD.
SNOW AMOUNTS STILL REMAIN PROBLEMATIC. THE THERMAL PROFILE DIDN'T
REALLY CHANGE OVER THE LAST 24 HOURS...SO THAT LENDS SOME
CONFIDENCE TO THE FORECAST. PRECIP MAY START AS SNOW IN SE NEB
TUES MRNG BUT SHLD QUICKLY BECOME A RA/SN MIX BECOMING ALL RAIN BY
AFTN. IN NE NEB WE ARE STILL EXPECTING ALL SNOW. ALNG THE I-80
CORRIDOR...AND EAST OF HIGHWAY 77 IN NEB...A MIX OF RA/SN WILL
DEVELOP BY AFTN AND WILL LIKELY CONT INTO THE EVNG HOURS BEFORE
BECOMING ALL SN AGAIN. ALL THIS SAID...WE DID TAPER SNOW TOTALS A
TOUCH IN THE WATCH AREA WHERE WE HAVE AMOUNTS NOW RUNNING RIGHT AT
6 INCHES. THEN AMOUNTS SIGNIFICANTLY DROP OFF TO THE S OF THE
WATCH...AND DECREASE N AS WELL. GIVEN THE EVENT IS STILL 3 RD
PERIOD...THERE REMAINS UNCERTAINTY AS TO THE RA/SN LINE...AND WE
HAVE THE ADVRY EVENT TO DEAL WITH TODAY...WE WILL LEAVE THE WATCH
IN PLACE. THE SYSTEM STILL LOOKS TO EXIT THE AREA BY WED AFTN.
ONLY CHANGE PAST THE WED PERIOD WAS TO WARM TEMPERATURES TOWARD
THE END OF THE WEEK. THERE IS NO REAL ARCTIC AIR BEHIND THIS
SYSTEM...AND DESPITE THE EXPECTED SNOW COVER IN SOME AREAS...A
QUICK WARM UP AND MELT DOWN IS EXPECTED.
BOUSTEAD
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
DETERIORATING CONDITIONS ARE EXPECTED AT ALL TAF SITES TODAY AS SNOW
MOVES INTO THE AREA...WITH IFR CONDITIONS AT KOFK AND MVFR TO
INTERMITTENT IFR AT KLNK/KOMA. MOST PERSISTENT SNOW DURING THE DAY
TODAY...AND LOWEST VIS...SHOULD AFFECT KOFK DURING THE MORNING
HOURS. SITES WILL SEE A REPRIEVE FROM PRECIPITATION THIS EVENING
AND TONIGHT...BEFORE PRECIP BEGINS AGAIN BETWEEN AROUND 06-12Z
TUESDAY.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR NEZ015-018-032>034-044-045-051.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT
FOR NEZ016-017-030-031-042-043-050-065.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR NEZ011-
012-016>018-030>032-042.
IA...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR IAZ043.
&&
$$