FXUS63 KOAX 251712
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1112 AM CST FRI DEC 25 2009
.DISCUSSION...
12Z UPPR AIR ANLYS INDCD TWO H5 LOWS THIS MRNG OVR THE CNTRL
PLAINS. THE SRN STREAM LO WAS NOW LOCATED OVR FAR NE MO. THE NRN
STREAM LO WAS LOCATED OVR SW NEB. HEIGHT FALLS OVR THE CNTRL
PLAINS WERE CENTERED OVR ERN MO AND IL WITH A 210 M H5 HEIGHT FALL
AT KILX. H7 LO WAS CENTERED JUST NE OF MCI WITH A SHARP NW TO SE
TMP GRADIENT WITH -22 C AT LBF TO -6 AT KDVN. H85 LO WAS LOCATED
OVR SRN IA WITH INVERTED TROF EXTNDD NWD INTO WRN MO AND ERN ND.
IMPRESSIVE MOISTURE ADVECTION CONTD WITH THE SYSTEM WITH A +4 H85
DEWPOINT NOTED AT KDVN. 16Z SFC ANLYS INDCD 986 MB LO NR KDMS WITH
THE BEST PRES FALLS OF 3 MB LOCATED OVR KSUX.
MAJOR WNTR STORM CONTS TODAY AND MAIN FORECAST CHALLENGE IS TO
DETERMINE HOW MUCH MORE SN WL FALL...WHERE AND WHEN...AS WELL AS
ASSOCIATED CONDS WITH THE WIND. STG H75 FRONTOGENESIS FM ERN SD
INTO ERN NEB WAS SHIFTING SWWD AS NRN STREAM UPPR LVL LO SHIFTS
TOWARD ERN KS AND SRN STREAM SYSTEM MOVS THRU ERN IA. BEST PRES
ADVECTION ON THE 1.5 PVU SFC AND ASSOCIATED LARGE-SCALE FORCING
FOR ASCENT HAS SHIFTED TO NRN IA INTO ERN SD AND THIS IS EXPECTED
TO CONT THRU THE AFTN. STG FRONTOGENESIS WL CONT OVR OUR WRN FA
THRU THE AFTN THOUGH WITH THE NRN END OF THE BAND BEING THE MOST
EFFECTIVE AT PRODUCING STG LIFT DUE TO THE CLOSER PROXIMITY TO THE
FORCING FOR ASCENT WEAKER STABILITY /OVR THE NRN CWA/. WITH MID
LVL DRY AIR MOVG INTO WRN IA SHLD SEE SNOW REALLY DECREASE THERE
THIS AFTN. DUE TO LOSS OF ICE WITHIN THE SOUNDINGS...MAY ACTUALLY
SEE SOME -FZDZ DVLP AND HAVE INCLUDED THAT IN WRN IA ZONES FOR
THIS AFTN. SO...BEST SNOWFALL THIS AFTN SHLD CENTER OVR NE NEB
WHERE 2-4 CLD FALL TAPERING TO AROUND AN INCH IN SE NEB AND LITTLE
IF ANYTHING IN WRN IA.
AS SFC LO WRAPS WWD INTO NW IA THIS AFTN...WNDS WL CONT TO
DECREASE OVR WRN IA AND INTO THE FIRST COUPLE OF ROWS OF COUNTIES
INTO ERN NEB. WE ARE NO LONGER MEETING BLIZZARD CRITERIA OVR WRN
IA AND RIGHT ALONG THE MO RIVER IN ERN NEB AND THIS TREND IS
EXPECTED TO CONT THRU THE AFNT AND OVERNIGHT. MAY SEE ANOTHER
QUICK PEAK IN THE WINDS THIS EVNG AS LO STARTS TO PULL AWAY AND
PRES RISES AGAIN INCREASE FOR A SHORT TIME. WL CONSIDER DROPPING
TO A WINTER WEATHER ADVISORY FOR THIS AREA LATER TODAY. OUT WEST
THOUGH THE RAGING BLIZZARD CONDS AND EXTREMELY DANGEROUS
CONDITIONS EXIST WITH WIDESPREAD QUARTER MILE VISBY OR LESS AND
THUS NO CHANGES ARE ANTICIPATED HERE. BLIZZARD CONDS EXPECTED TO
CONT TO INTO THE OVERNIGHT HOURS THERE.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 316 AM CST FRI DEC 25 2009/
DISCUSSION...
BLIZZARD/NEAR BLIZZARD CONDITIONS ACROSS ENTIRE CWA WILL CONTINUE
AT LEAST THIS MORNING WITH SOME IMPROVEMENT POSSIBLE ERN ZONES
THIS AFTN AS SFC LOW BEGINS RETROGRADING WWD. HOWEVER...NO CHANGES
WILL BE MADE TO HEADLINES AS VSBYS REMAIN POOR/ZERO AND REPORTS
FILTERING IN OF ROAD CLOSURES. THUS MAIN FORECAST CHALLENGE WILL
BE ADDITIONAL PCPN/SNOW AMOUNTS INTO SATURDAY AND SECONDLY WILL BE
HOW FAR WWD TO BRING SLIGHTLY MILDER TEMPERATURES TODAY AS LOW
APPROACHES ERN ZONES.
EARLY MORNING WATER VAPOR IMAGERY SHOWED DUAL UPPER LOWS MOVG
ACROSS THE CENTRAL PART OF THE COUNTRY WITH WESTERN ONE DROPPING
INTO WRN NEBRASKA WITH ERN ONE DUMB-BELLING AROUND IT INTO SERN
MO. WRN LOW WAS AIDING IN PULLING DOWN ARCTIC AIR INTO NEBRASKA
WHILE SERN LOW WAS PULLING MILDER/MORE MOIST AIR FM SFC THRU 700
MB UP MS VALLEY WITH NICE TROWAL WRAPPING ALL THE WAY BACK INTO
NEBRASKA OVR ARCTIC AIR. SFC LOW AT 08Z WAS NEAR IRK MO WITH
SUSTAINED SFC WINDS OVR CWA MOSTLY IN MID 20 TO LOWER 30 KT RANGE
ALTHOUGH GLAZED SENSORS WERE MAKING SOME SITES UNRELIABLY LIGHT.
SNOW RETURNS...WITH MODERATE EMBEDDED BANDS...ON RADAR IMAGES
WERE ALIGNED NW TO SE ACROSS CWA BUT IT WAS NOTED THAT HIGHER
RETURNS ON KTOP/KEAX RADARS WERE SHRINKING THRU 09Z. WITH SERN
UPPER LOW LIFTING NWD TOWARD IA TDA AND WITH SYSTEMS ATTEMPTING TO
PHASE/MERGE TNGT...DECENT FORCING/OMEGA WAS NOTED OVR MUCH OF THE
CWA THRU 12Z SAT. WITH CROSS SECTIONS SHOWING SOME OF THAT LIFT
OCCURRING IN FAVORED DENDRITIC RANGE...EXPECT ADDITIONAL MODERATE
SNOW AMOUNTS OVR CWA...SPCLY NERN 1/2. QPF FM 00Z NAM/GFS AND 12Z
ECMWF WERE SIMILAR TODAY WITH ANOTHER 1/4 TO 1/2 INCH LIQUID
TODAY...ALTHOUGH 00Z ECMWF SEEMED TO SHIFT A LITTLE MORE QPF INTO
THE TNGT PD. 00Z GFS/NAM WERE THEN HALF TO THREE-QUARTERS AS MUCH
WITH QPF TNGT WITH AMOUNTS TAPERING OFF EVEN MORE ON SAT. SO
GENERALLY WENT CLOSE TO PREV FCST WITH QPF TDA/TNGT A BIT UNDER
GUIDANCE. USED A 14-1 LSR FOR SNOW AMOUNTS. IN ANY EVENT STRONG WINDS
WILL MAKE MEASURING NEW SNOW DIFFICULT TO IMPOSSIBLE. STRONG WINDS
THIS MORNING WERE CREATING WIDESPREAD BLIZZARD/NEAR BLIZZARD
CONDITIONS WITH THE WORST IN OPEN AREAS WITH ROAD CLOSURES.
ALTHOUGH SOME IMPROVEMENT IN VSBYS MAY OCCUR BY AFTN ERN ZONES AS
SFC LOW BACKS TOWARD REGION...WL CONTINUE BLIZZARD WARNING THRU
12Z SAT. HOWEVER...WILL BEGIN DROPPING AREA OF 1/4 MILE VSBYS IN
BS A BIT IN SERN ZONES THIS AFTN WITH BS AND 1 MILE VSBYS TNGT
ALTHOUGH CONDITIONS STILL LOOK TO BE BAD.
SNOW SHOULD BEGIN WINDING DOWN SAT INTO SUNDAY WITH NO SIGNIFICANT
CHANGES MADE TO POPS/WX. LOOKING AT AIR MASS UPSTREAM...AS SFC LOW
AND MILDER AIR ASSOCD WITH IT PULL AWAY...TEMPS POSSIBLY MAY NEED
SOME DOWNWARD REVISIONS LATER. SFC RIDGE MOVES OVR CWA MON NGT
WHICH COULD BE THE COLDEST IN THIS FCST PD. LOWERED LOWS SOME THEN
BUT MADE NO OTHER CHANGES TO EXTENDED.
AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
LIFR CONDS ARE EXPECTED THRU THE PERIOD AS STRONG NW WINDS AND
SNOW PRODUCE BLIZZARD CONDITIONS ACROSS THE AREA.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...BLIZZARD WARNING UNTIL 6 AM CST SATURDAY FOR NEZ011-012-015>018-
030>034-042>045-050>053-065>068-078-088>093.
IA...BLIZZARD WARNING UNTIL 6 AM CST SATURDAY FOR IAZ043-055-056-069-
079-080-090-091.
&&
$$
