FXUS63 KOAX 070956
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
356 AM CST MON DEC 7 2009

.DISCUSSION...

SYNOPSIS...00Z UPPR AIR ANLYS INDCD DEEP TROF CONTD OVR THE CNTRL
AND WRN US. LEAD SHRTWV TROF ASSOCIATED WITH 60-70 M H5 HEIGHT
FALLS WAS OVR NEB/KS AT 00Z. UPSTREM NEXT MORE SIG SYSTEM WAS
DIVING SWD ALNG THE CA/OR COAST. BEST HEIGHT FALLS APPEARED TO BE
JUST OFF THE COAST...BUT A 130 KT H3 WAS SAMPLED DIVING SWD THRU BC.
LO LVL MOISTURE WAS STARTING TO INCREASE ALNG SRN MS RVR VALLEY
WITH 0 C DEW POINTS IN SW MO. 09Z SFC ANLYS INDCD LO PRES EXITING
THE AREA OVR NE MO WITH HI PRES FM THE WRN DAKOTAS INTO WRN NEB.
REGIONAL RADAR MOSAIC INDCD ONLY VERY LIGHT PRECIP OVR THE ERN
CWA. 

FORECAST...MAIN FORECAST CONCERN NOW TURNS TO INCOMING POTENTIAL
SIG WNTR STORM OVR THE WRN US. MODELS ARE IN FAIR AGREEMENT WITH
THIS SYSTEM...BUT THERE WERE SOME SIG DIFFERENCES NOTED. FOR TODAY
WE SHLD SEE A MOSTLY CLDY DAY FOR THE FA. GIVEN THE NEW SN COVER
FOR MOST OF THE AREA...LIGHT WINDS...CLDS AND LITTLE TEMPERATURE
ADVECTION WE HAVE DROPPED HIGHS BELOW COOLEST MET GUIDANCE. H3
120 KT JET OVR THE GREAT BASIN AT 00Z IS EXPECTED TO MOV INTO THE
NRN PLAINS BY THIS AFTN AND AMPLIFY SOME AT CA STORM SYSTEM
DEEPENS INTO THE GREAT BASIN. THIS WL ALLOW FOR LARGE-SCALE
SUPPORT FOR ASCENT TO BEGIN AS EARLY AS THIS AFTN. THERMAL
GRADIENT ALREADY IN PLACE FM GENERALLY ZONAL FLOW ACRS THE AREA WL
LEAD TO WEAK FRONTOGENESIS BY LATE AFTN OVR THE SRN CWA. HAVE
ADDED SOME AFTN FLURRIES FOR THIS REGION. LIFT CONTS TO DEEPEN AND
EXPAND THRU THE EVNG AS JET OVR THE NRN PLAINS REMAINS IN PLACE
AND A WEAK SHRTWV TROF /SEEN ON WV APPROACHING THE CA COAST THIS
MRNG/ MOVS INTO THE WRN HI PLAINS. SHLD SEE PRECIP EXPAND IN
COVERAGE QUICKLY OVR THE SRN CWA...BUT MAINLY LIGHT. HAVE
INCREASED EVNG POPS OVR THE S TO CAT AND HAVE BASICALLY 100 POPS
OVR THE ENTIRE CWA AFTER 06Z. NOT EXPECTING HEAVY SN TNGHT...BUT
SHLD SEE A GOOD COVERAGE OF -SN. THINKING IS 2 TO 3 INCHES IN THE
S AND MAYBE AN INCH ELSEWHERE. LIFT CONTS TO INCREASE DURING THE
MRNG ON TUES /ESPECIALLY OVR THE SRN CWA/ AS Q-G FORCING
INCREASES. MAY ACTUALLY SEE A DECREASE IN PRECIP OVR THE CNTRL AND
NWRN AREAS FOR A TIME TUES MRNG AS LARGE-SCALE WAA DECREASES AND
BEFORE DYNAMICS REACH THAT AREA. NEVERTHELESS SHLD SEE AT LEAST
SOME LIGHT STUFF THERE AND CONTD WITH THE HIGH POPS. BEST FORCING
FOR ASCENT MOVS THRU THE FA TUES AFTN TILL 03Z WED AND THIS IS
WHEN THE BEST SN ACCUM SHLD HAPPEN.

THERE ARE STILL SOME CONCERNS THOUGH WITH THIS SYSTEM THAT MAY
LIMIT SNOWFALL POTENTIAL. FIRST...WITH THE UPPR LVL PV ANOMALY
GOING DIRECTLY OVR THE CWA THE ATMOSPHERE IS PRETTY STABLE. THIS
WILL NOT ELIMINATE THE JET-FRONT CIRCULATION FM DVLPNG...BUT IT
WILL NOT BE AS EFFECTIVE IF WE WERE MUCH LESS STABLE. IN
ADDITION...THE DEPTH OF THE DENDRITIC ZONE IS PRETTY SHALLOW WHICH
CLD ONCE AGAIN LEAD TO LESS EFFECTIVE SNOW ACCUMULATING FLAKES
DESPITE THE HIGH QPF /LIKE WE SAW ON SUN WITH THE FINE SNOW/.
LASTLY...THERE REMAINS SOME MODEL DIFFERENCES AS TO THE STRENGTH
AND DEPTH TO THE MID LVL SHRTWV WHERE THE CANADIAN AND EC ARE MUCH
STRONGER CLOSING OFF A CIRCULATION AT LEAST FOR A TIME...AND THE
NAM/GFS A LITTLE WEAKER. IN ADDITION THE NAM IS ALSO FARTHER
NORTH.

GIVEN THE ABOVE CONCERNS THOUGHT IT WAS BEST TO LEAVE THE WATCH
GOING FOR ANOTHER SHIFT. THERE IS A GOOD DEAL OF CONFIDENCE THAT
WE WILL MEET WARNING CRITERIA FOR A GOOD PART OF THE AREA...BUT
WITH THE BEST HEIGHT FALLS STILL OFF THE COAST AT 00Z...NEXT
SYNOPTIC SUITE OF MODELS WILL HOPEFULLY ALLOW FOR A GOOD HANDLE ON
THE DETAILS. WILL BREAK THE WATCH INTO TWO GROUPS AS THE NW CWA
LOOKS LESS LIKELY TO MEET ACTUAL WARNING CRITERIA /N OF A LINE FM
WAYNE TO NELIGH/. ALSO DID UPGRADE THE SW CWA TO A WARNING DUE TO
THE EARLY EVNG EXPECTED DVLPMNT OF SNOW THERE. WE STILL FEEL THERE
WILL BE CONSIDERABLE BLOWING AND DRIFTING OF SNOW BEHIND THE
SYSTEM AS 925 MB WINDS INCREASE TO 40 KT...BUT CURRENT FEELING IS
BLIZZARD CONDS WILL NOT BE MET IN OUR CWA AS THE SYSTEM REALLY
DOES MOST OF THE SIG DEEPENING AS IT MOVS E OF OUR AREA.

REST OF THE FORECAST WAS VIRTUALLY UNCHANGED. DID LOWERED HIGHS AND
LOWS THRU THURS...BUT LIKELY NOT ENOUGH GIVEN LATEST GUIDANCE. 

BOUSTEAD

&&

.AVIATION...

TAF SITES KOFK/KOMA/KLNK 

06Z TAFS

VIS/CIG CONDITIONS WILL CONTINUE TO IMPROVE FROM MVFR TO VFR AS -SN 
MOVES TO THE EAST.  WITH SURFACE RIDGE PASSING THROUGH TODAY...WINDS 
WILL DIMINISH AND VEER TO EASTERLY.  CIGS/VIS WILL AGAIN DETERIORATE 
AFTER 00Z...AFFECTING KLNK CLOSER TO 00Z AND KOMA/KOFK CLOSER TO 
06Z...AS SNOW OVERSPREADS THE AREA.

MAYES

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT 
     FOR NEZ011-012-015>018-030>034-042>045-050>053-066>068-091-
     093.

     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST 
     WEDNESDAY FOR NEZ065-078-088>090-092.

IA...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT 
     FOR IAZ043-055-056-069-079-080-090-091.

&&

$$