FXUS63 KOAX 120308
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
908 PM CST SAT DEC 11 2010
.UPDATE...
HAVE DONE SEVERAL UPDATES THIS EVENING FOR HEADLINES.
&&
.DISCUSSION...
INTENSE AND FAIRLY WIDESPREAD BLIZZARD CONTS ACRS PARTS OF THE FA
THIS EVNG. EXPANDED AND EXTENDED BLIZZARD WARNINGS EARLIER THIS
EVNG AS CONDS WERE MEETING CRITERIA...AND LATE AFTN SFC ANLYS
INDCD THAT BEST PRES RISES /AND THUS BEST WIND POTENTIAL/ WAS JUST
GETTING TO OUR FA. THIS SEEMS TO BE PASSING NOW TO OUR EAST AND
WLD EXPECT THE TREND TO BE DOWN ON WINDS THROUGH MIDNIGHT.
NEVERTHELESS...STILL VERY DANGEROUS TRAVEL CONDS OUT
THERE...ESPECIALLY ALNG AND EAST OF THE MO RIVER AND OUTSIDE OF
THE METRO AREAS. THUS WL CONT WITH THE BLIZZARD WARNING TILL 4 AM.
ONE LAST STG BAND OF SN WAS MOVG SLOWLY SEWD THRU WRN IA ATTM AND
LINED UP WELL WITH 600 MB FRONTOGENESIS. 00Z KOAX SOUNDING ALSO
SHOWED WEAKER STABILITY IN THE SOUNDING NEAR THIS LEVEL. WLD
EXPECT THIS TO WEAKEN AS IT MOVES SEWD BUT SHLD CONT TO PRODUCE
MEASURABLE SNOW AND THUS CONTD CAT POPS TILL ABOUT 06Z IN WRN IA.
WLD EXPECT /BASED ON VISBY AND WEB CAMERAS/ THAT THIS BAND IS
GIVING AN ADDITIONAL INCH OR TWO. OTHERWISE WLD JUST EXPECT
BLOWING SNOW TO CONT IN ERN NEB WITH THE STG WINDS.
WE HAVE ALSO JUST UPDATED TO EXTEND THE WIND ADVISORY FOR SE NEB
TILL MIDNIGHT WITH ALL SITES CURRENTLY MEETING CRITERIA AND
PROFILERS STILL SHOWING 50 KT AT 925 MB. AS FAR AS TMPS...THESE
HAVE BEEN SLOW TO FALL THIS EVNG DUE TO THE MIXING AND CLDS. WIND
CHILL VALUES ARE RUNNING BELOW ZERO ALREADY BUT NO ONE IS MEETING
CRITERIA YET...BUT WLD EXPECT THIS TO CHANGE AFTER MIDNIGHT AND
THUS NO CHANGES TO THESE HEADLINES ATTM.
NEW ZFP/NPW AND GRIDS HAVE BEEN SENT. WILL UPDATE AGAIN AT
MIDNIGHT TO ALLOW FOR WIND ADVISORY TO EXPIRE AND THE COUPLE OF
COUNTIES IN THE WINTER WEATHER ADVRY.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 326 PM CST SAT DEC 11 2010/
SHORT TERM...TONIGHT THROUGH TUESDAY
DEEPENING UPPER LOW IS CREATING HAZARDOUS WINTER WEATHER CONDITIONS
ACROSS MOST OF THE CWA. 20Z WATER VAPOR IMAGERY INDICATES DEEPENING
UPPER LOW CENTERED OVER WRN IA...WITH WRAPAROUND SNOW BAND PUSHING
SOUTHWARD ALONG THE MO RIVER VALLEY. COMBINED WITH WINDS SUSTAINED
AROUND AT LEAST 35-40MPH AND GUSTS 45-50MPH...BLOWING SNOW HAS
BEEN A HAZARD TODAY EVEN WHEN SNOWFALL RATES ARE RELATIVELY
LIGHT...WITH WHITEOUT CONDITIONS IN HEAVIER BANDS. LONGER DURATION
OF EVENT IN THE NRN AND NERN CWA HAS PROMPTED BLIZZARD WARNINGS
THERE...THOUGH SHORTER DURATION WHITEOUT/NEAR-BLIZZARD CONDITIONS
ARE OCCURRING IN SOME OF THE ADVISORY AREA AS WELL. TEMPERATURES
FELL ABRUPTLY IN THE LATE NIGHT/EARLY MORNING HOURS TODAY AND HAVE
BECOME MAINLY STEADY DURING THE DAYTIME HOURS...THOUGH MUCH COLDER
TEMPERATURES HAVE BEEN ADVECTED AT 850MB...WITH -12C JUST
UPSTREAM.
MAIN FORECAST CONCERN IS TIED TO THIS SYSTEM AS IT EXITS THE AREA
TODAY...FOLLOWED BY VERY COLD TEMPERATURES IN ITS WAKE TONIGHT
THROUGH SUNDAY NIGHT. HEADLINES ARE GOING TO BE NEEDED...BUT THEY
ARE COMPLEX AS BLOWING SNOW TAPERS DOWN AND WIND CHILLS BECOME THE
PRIMARY THREAT. SYSTEM HAS REALLY BOGGED DOWN IN ITS EASTWARD
PROGRESS THIS AFTERNOON AS IT DEEPENS...WITH STRONG UPPER-LEVEL JET
STILL CUTTING IN BEHIND THE SYSTEM. THINK THE SLOWER MOTION WILL
HOLD FOR A WHILE...AND HAVE SLOWED EXIT OF SNOW AS A RESULT. DID
PUSH UP THE END TIME OF THE BLIZZARD/WINTER WEATHER HEADLINES IN
NERN NEB TO 00Z AND ALLOW THE WIND CHILL ADVISORY TO TAKE OVER...BUT
WILL HOLD THE MO RIVER VALLEY AND WRN IA IN WINTER WEATHER/BLIZZARD
HEADLINES UNTIL 06Z BEFORE ALLOWING WIND CHILL TO TAKE OVER. SRN
CWA WILL BE ONLY MARGINALLY NEAR WIND CHILL CRITERIA...BUT HAVE
INCLUDED BOTH FOR COORDINATION WITH SRN NEIGHBORS AT LESSER WIND
CHILL CRITERIA AND ALSO BECAUSE IT IS AN ABRUPTLY COLDER SYSTEM AND
FIRST TRUE COLD SPELL OF THE SEASON.
HIGH PRESSURE WILL BRING CLEARING SKIES AND QUIETING WINDS ON SUNDAY
NIGHT...ALLOWING TEMPS TO FALL TO COLDER READINGS THAN TONIGHT.
WITH LOWER WIND SPEEDS...DOES NOT APPEAR THAT WIND CHILLS WILL BE
HEADLINE-WORTHY...THOUGH THEY WILL FLIRT WITH THE TEENS BELOW ZERO
IN THE NRN CWA WHEN WINDS ARE NOT CALM. NWRLY FLOW WILL CONTINUE AT
UPPER LEVELS THROUGH TUESDAY...BUT SFC WINDS WILL RETURN TO
SOUTHERLY ON MONDAY BEHIND THE SFC RIDGE...ALLOWING TEMPERATURES TO
MODERATE. A SHORTWAVE IS PROGGED TO SWEEP THROUGH SD INTO NERN
NEB/NWRN IA ON MONDAY...POSSIBLY PROVIDING JUST ENOUGH FORCING FOR
ASCENT TO CREATE A SHORT-LIVED PERIOD OF LIGHT SNOW. HAVE KEPT SCHC
POPS IN THE NRN CWA ON MONDAY. AFTER THIS...WEATHER WILL REMAIN
QUIET THROUGH TUESDAY.
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
LOOKS LIKE A RELATIVELY DRY FORECAST FOR MID TO LATE WEEK. MAIN
UPPER AIR PATTERN IN THE PLAINS WILL BE DOMINATED BY QUASI-ZONAL
FLOW WITH UPPER LOWS IN THE GULF OF ALASKA AND OFF THE NORTHERN NEW
ENGLAND COAST. EXPECTED DEEPENING OF THESE LOWS POINTS TO RIDGING IN
THE CENTRAL CONUS FOR NEXT WEEK...SIGNALING WARMING CONDITIONS
THEN. HOWEVER FOR THE DAYS 4 THROUGH 7 PERIOD...A SOMEWHAT COOL
FORECAST REMAINS WITH NO BIG SWINGS IN TEMPERATURES AS FAST-MOVING
MINOR WAVES BUMP TEMPS UP AND DOWN AS THEY PASS BY. AND TIMING OF
THESE WAVES IS DIFFICULT ENOUGH IN THE SHORTER TERM...AND NEARLY
IMPOSSIBLE IN THE LONGER RANGE. ECMWF AND GFS CONCUR WITH LARGE
SCALE PATTERN...BUT DIFFER IN THE SUB-SYNOPTIC SCALE IN REGARDS TO
THESE MINOR WAVES AND SUBSEQUENT SURFACE REFLECTIONS. A BLENDED
APPROACH SHOULD CAPTURE TEMPERATURES TRENDS...BUT WILL LIKELY SEE
FLUCTUATIONS IN FORECAST TEMPS AS WE HEAD INTO THE EARLY PART OF THE
WEEK.
WE SHOULD START THE LONG TERM PERIOD WITH LOW PRESSURE TROUGH ALONG
THE LEE OF THE ROCKIES...WITH SOUTHEAST FLOW ACROSS MID AMERICA.
THIS SHOULD KEEP TEMPS IN THE 20S FOR LOWS AND 30S TO NEAR 40 FOR
HIGHS ON WEDNESDAY. THAT LOW PRESSURE TROUGH WILL CONGEAL INTO A
SURFACE LOW THAT TRACKS WELL SOUTH OF OUR AREA THURSDAY...THUS NO
PRECIPITATION EXPECTED. HOWEVER TEMPERATURES WILL RESPOND DOWNWARD
ON THE BACK SIDE OF THIS SYSTEM AS HIGH PRESSURE SETTLES SOUTH. WILL
HAVE HIGHS/LOWS TREND DOWN INTO THE TEENS AND SINGLE DIGITS FOR LOWS
AND 20S/30S FOR HIGHS BY FRIDAY AND SATURDAY.
AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
IFR TO MVFR CONDITIONS WILL CONTINUE THROUGH 12/06Z AS DEEP SURFACE
LOW OVER NORTH CENTRAL IOWA TRACKS SLOWLY EAST WITH STRONG NW WINDS
CONTINUING THROUGH THE PERIOD. VSBY EXPECTED TO IMPROVE AT SITES AS
FALLING SNOW ENDS BUT WINDS WILL KEEP BLOWING SNOW AROUND AND MVFR
VSBY THROUGH MOST OF THE PERIOD.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WIND CHILL ADVISORY FROM 4 AM TO NOON CST SUNDAY FOR NEZ015-018-
033-034-044-045-051>053-067.
BLIZZARD WARNING UNTIL 4 AM CST SUNDAY FOR NEZ015-018-033-034-
044-045-051>053-067.
WIND ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR NEZ030-042-043-050-
065-066-078-088>093.
WIND CHILL ADVISORY UNTIL 9 AM CST SUNDAY FOR NEZ030-042-043-050-
065-066-078-088>093.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR NEZ032-
068.
WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST SUNDAY FOR
NEZ032-068.
WIND CHILL ADVISORY UNTIL NOON CST SUNDAY FOR NEZ011-012-016-017-
031.
IA...WIND CHILL ADVISORY FROM 4 AM TO NOON CST SUNDAY FOR IAZ043-055-
056-069-079-080-090-091.
BLIZZARD WARNING UNTIL 4 AM CST SUNDAY FOR IAZ043-055-056-069-
079-080-090-091.
&&
$$