000
FXUS63 KOAX 070520
AFDOAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1120 PM CST FRI DEC 6 2013

.AVIATION...06Z TAFS FOR KOMA...KLNK AND KOFK. VFR CONDITIONS
THROUGH MOST OF THE PERIOD WITH THICKENING CLOUDS. LIGHT NORTHWEST
WINDS BECOME LIGHT AND VARIABLE AND EVENTUALLY SOUTHEAST. SHOULD
SEE LIGHT SNOW DEVELOP AT KOFK/KLNK BY 05-06Z ABOUT 24 HOURS FROM
NOW...BUT SNOW WILL HOLD OFF UNTIL JUST AFTER THE END OF THE TAF
PERIOD AT KOMA.

DEWALD

&&

.PREV DISCUSSION... /ISSUED 923 PM CST FRI DEC 6 2013/

DISCUSSION...

FORECAST REMAINS IN GOOD SHAPE. I DID BACK OFF ON CLOUD COVER A
BIT OVERNIGHT AND TWEAKED TEMPS FOR CURRENT TRENDS. REGARDING THE
SNOW...LATEST 00Z NAM IS IN LINE WITH PREVIOUS MODELS. IT STILL
PRODUCES SNOWFALL ON THE 2 TO 4 INCH RANGE...BEGINNING FROM WEST
TO EAST LAST SATURDAY EVENING...CONTINUING THROUGH THE NIGHT
SUNDAY AND TAPERING OFF SUNDAY AFTERNOON OR EARLY EVENING. GIVEN
SNOW WATER RATIOS ON THE HIGHER SIDE FROM 15 TO 20 TO 1...AND A
HIGH PROBABILITY FOR A DEEP DENDRITIC SNOW GROWTH ZONE...MAY HAVE
TO CONSIDER OPENING THE HIGH END JUST A BIT WITH SOME SPOTS HAVING
A SHOT AT 5 INCHES OF SNOW. FORTUNATELY...IT SHOULD NOT BE A HEAVY
WEIGHT SNOW SO IT WILL PROBABLY PUSH EASIER. WINDS WILL ALSO BE ON
THE LIGHTER SIDE AROUND 10 TO 15 MPH.

DEWALD

PREV DISCUSSION... /ISSUED 520 PM CST FRI DEC 6 2013/

AVIATION...00Z TAFS FOR KOMA...KLNK AND KOFK. VFR CONDITIONS
THROUGH THE PERIOD.

DEWALD

PREV DISCUSSION... /ISSUED 335 PM CST FRI DEC 6 2013/

SHORT TERM...TONIGHT THROUGH MONDAY.

BITTER COLD TEMPERATURES THEN ACCUMULATING SNOW THIS WEEKEND...

THE MAIN FORECAST CONCERNS THROUGH THE PERIOD WILL BE THE COLD
TEMPERATURES AND ACCUMULATING SNOW SATURDAY NIGHT INTO SUNDAY.

BITTER COLD TEMPERATURES OCCURRED THIS MORNING WITH AROUND 0 LOCALLY
IN THE SINGLE DIGITS FOR SOUTHEAST NEBRASKA AND SOUTHWEST IOWA
AND AS COLD AS 15 BELOW ZERO AT VERDEL. COMBINED WITH THE
WIND...WIND CHILLS WERE 10 TO 25 BELOW ZERO. AT H5...A
DEEP...BROAD TROF OF LOW PRESSURE ENCOMPASSED MUCH OF THE U.S. THE
CENTER OF THE TROF EXTENDED FROM JAMES BAY BACK TOWARD MONTANA.
WHILE A MAJOR WINTER/ICE STORM IMPACTS MUCH OF THE SOUTHERN PLAINS
INTO THE TENNESSEE/OHIO VALLEYS...WE ARE UNDER THE INFLUENCE OF
ARCTIC HIGH PRESSURE. THIS ARCTIC HIGH PRESSURE WILL MEAN
DIMINISHING WINDS TONIGHT AND LOWS FROM AROUND ZERO TO 8 BELOW
ZERO FOR MUCH OF THE FORECAST AREA. AREAS CLOSER TO THE SOUTH
DAKOTA AND IN PARTS OF NORTHWEST IOWA COULD SEE LOWS FROM 10 TO
18 BELOW ZERO. DUE TO THE COLD TEMPERATURES...WILL ISSUE A WIND
CHILL ADVISORY FOR PARTS OF NORTHEAST NEBRASKA AND WEST CENTRAL
IOWA UNTIL 9AM SATURDAY

FOR US...ATTENTION TURNS TO THE PORTION OF THE MID LEVEL TROF THAT
IS OVER THE NORTHWEST U.S.  60M HEIGHT FALLS WERE NOTED WITH THE
TROF WITH 100+KT WINDS AT H3 STILL OFF TO THE WEST OF THE TROF.
THROUGH 18Z SATURDAY...THE H3 JET STRENGTHENS TO 140KTS AND MOVES INTO
CENTRAL CALIFORNIA. HT FALLS INCREASE TO 100M OVER NEVADA AND THE
MID LEVEL AREA OF LOW PRESSURE WILL BE CLOSED OFF OVER NEVADA.

IT IS STILL VERY DRY OVER THE LOCAL AREA AND FORECAST SOUNDINGS AND
CROSS-SECTIONS SHOW TOP-DOWN SATURATION.  BY SATURDAY
AFTERNOON...THERE IS GOOD SATURATION IN THE NORTHWEST PART OF THE
FORECAST AREA.  SATURDAY NIGHT...SATURATION OCCURS...ESPECIALLY
BETWEEN 03Z-09Z. THE NAM IS A LITTLE FASTER...ABOUT 3-6HRS WITH
SATURATION COMPARED TO THE GFS. THE 00Z AND THE 12Z EC ARE ALSO
MORE IN LINE WITH THE GFS. BY 12Z...THE H5 TROF EXTENDS FROM
SASKATCHEWAN AND MANITOBA BACK TOWARD UTAH...WITH SOME LEAD ENERGY
IN NORTHEAST COLORADO. WARM ADVECTION/ISENTROPIC LIFT/OMEGA/MID
LEVEL LAPSE RATES AND UPPER LEVEL DIVERGENCE ALL INCREASE SATURDAY
NIGHT AND CONTINUE INTO SUNDAY...SHIFTING OUT OF THE AREA SUNDAY
NIGHT. A DEEP 12000FT LAYER OF LIFT WHERE DENDRITIC TEMPERATURES
FROM -12 TO -18 DEG C EXIST WILL RESULT IN INCREASED SNOW
EFFICIENCY AND HIGHER LIQUID TO SNOW RATIOS. MOST SNOW RATIOS
SHOULD BE IN THE 15 TO 18:1 RANGE...FLUFFY. DURING THE EVENING
HAVE ACCUMULATING SNOW DEVELOPING AND SPREAD ACROSS THE ENTIRE
FORECAST AREA CONTINUING DURING THE DAY SUNDAY. AT THIS TIME DO
HAVE ADVISORY TYPE AMOUNTS MENTIONED WITH WIDESPREAD 2 TO 4 INCH
AMOUNTS. SHOULD THE INTENSITY BE STRONGER...LONGER IN SOME AREAS
COULD SEE SOME LOCALLY HIGHER AMOUNTS. THE SYSTEM SHOULD BE
WINDING DOWN SUNDAY EVENING AS WE LOSE OUR LIFT AND SATURATION
WITH LITTLE OR NO ADDITIONAL ACCUMULATION AFTER 06Z.

COLD AIR FOLLOWS IN BEHIND FOR MONDAY WITH NORTHWEST
WINDS...HOWEVER SOUTHWEST WINDS DEVELOP BY AFTERNOON AHEAD OF THE
NEXT SHORTWAVE TROF. HIGHS SATURDAY THROUGH MONDAY WILL TOP OUT
IN THE SINGLE DIGITS AND TEENS WITH A FEW 20S SUNDAY.

LONG TERM...MONDAY NIGHT THROUGH FRIDAY.

THE LONGER RANGE MODELS ARE IN FAIR AGREEMENT THIS PERIOD WITH THE
LARGE-SCALE PATTERN THAT WILL SEE THE DEEP CENTRAL US TROUGH FILL
AND SHIFT EAST A BIT...AND PUT THE CNTRL PLAINS MORE IN A NORTHWEST
FLOW PATTERN. THERE WILL BE A COUPLE OF SHORTWAVE TROUGHS THAT WILL
AFFECT THE REGION DURING THE PERIOD...BUT MOISTURE AND LIFT WILL BE
LIMITED AND WE WILL MAINTAIN A DRY FORECAST ATTM FOR THE EXTENDED.

THE FIRST SHORTWAVE TROUGH WILL MOVE THROUGH THE REGION ON MONDAY
NIGHT AND ALLOW FOR A GOOD INCREASE IN WINDS FOR A GOOD PART OF THE
FA. THE EC/GFS INDICATE 925 MB WINDS INCREASE TO AROUND 45 KT...BUT
THERE REMAINS SOME UNCERTAINTY AS TO HOW MUCH OF THIS WILL MAKE IT
DOWN TO THE SURFACE. WE HAVE INCREASED WINDS FOR MON NIGHT AND THIS
MAY LEAD TO SOME BLOWING SNOW...ESPECIALLY IN THE NORTHERN FA. THIS
SYSTEM WILL ACT TO SCOUR SOME OF THE ARCTIC AIR OUT OF THE REGION
AND ALLOW FOR SOME WARMER PACIFIC AIR TO SPILL IN FOR TUESDAY WITH
HIGHS GETTING BACK INTO THE 20S FOR MOST AREAS. ANOTHER WEAK
SHORTWAVE TROUGH WILL MOVE THROUGH THE AREA ON TUE NIGHT AND THERE
MAY BE ENOUGH LIFT AND MOISTURE WITH THIS SYSTEM TO SQUEEZE OUT
SOME FLURRIES PER THE EC...BUT OTHER GUIDANCE IS DRY ATTM. THIS
SYSTEM WILL ALLOW FOR A BACK DOOR COLD FRONT TO SLIP INTO THE AREA
FOR WED AND CREATE A BRIEF COOL DOWN FOR WED/WED NIGHT BEFORE THE
UPPER LEVEL FLOW BECOMES MORE ZONAL AND TEMPERATURES WARM TO END
THE WORK WEEK.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WIND CHILL ADVISORY UNTIL 9 AM CST SATURDAY FOR NEZ011-012-015-
     018-034.

IA...WIND CHILL ADVISORY UNTIL 9 AM CST SATURDAY FOR IAZ043-055-056.

&&

$$