FXUS63 KOAX 300326
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
926 PM CST WED DEC 29 2010
.UPDATE...
UPDATED TO INCREASE TMPS OVERNIGHT AND TO INCREASE POPS IN THE FAR
NW ON THURSDAY.
&&
.DISCUSSION...
GOING FORECAST IN PRETTY GOOD SHAPE TONIGHT. AS EXPECTED
WIDESPREAD CLOUDS AND AREAS OF FOG HAVE SET IN OVER ERN NEB AND
WRN IA AS WARM MOIST AIR RUSHES NORTH. THIS SHLD CONT THRU THE
OVERNIGHT HOURS AND INTO THURS MRNG. WL KEEP DENSE FOG ADVRY
ISSUED EARLIER GOING WITH THE EXPECTATION OF LOCALLY DENSE FOG
OVR SN PACK OVR WRN IA. WITH CONTD SRLY FLOW...ACTUALLY INCREASING
THRU THE NIGHT...SHLD SEE TMPS CONT TO SLOWLY INCREASE OVERNIGHT
AND HAVE UPDATED THE GRIDS AND OVERNIGHT LO FOR THIS. OTHERWISE
JUST A SCHC OF ACTUAL MEASURABLE RAIN...MAINLY OVR WRN IA...EXISTS
OVERNIGHT WITH A GENERAL LACK OF LARGE-SCALE FORCING FOR ASCENT.
OTHERWISE IT APPEARS THE MODELS ARE UNDER-FORECASTING THE STRENGTH
OF A LEAD SHRTWV TROF CURRENTLY OVR AZ ATTM. THIS IS PROGGED TO
EJECT THRU THE DAY TMRW WITH A SFC REFLECTION MOVG NEWD ALNG A STG
BAROCLINIC ZONE OVER NE NEB...THEN ALLOWING THE STG ARCTIC FNT TO
SWING EWD. GIVEN THE EXPECTED STRENGTH OF THIS WAVE /DECENT SHRTW
AND MODERATE MID LVL FRONTOGENESIS/ AND A MOIST ATMOSPHERE...SEE
NO REASON WE WON'T SEE PRECIP DVLP THURS BY MID TO LATE MRNG IN
FAR NW CWA /I.E. KNOX AND ANTELOPE COUNTIES/ AND CONT INTO THE
AFTN HOURS. AT THE SAME TIME THE ARCTIC CDFNT WL BE MOVG THRU THE
AREA AND THUS PRECIP SHLD CHANGE FM RA-IP-SN THRU THE DAY. CLD SEE
A QUICK INCH OF SNOW IN THE WRN PARTS OF THOSE COUNTIES BY LATE
AFTN WHEN LIFT CUTS OFF. THUS HAVE UPDATED TO INCREASE POPS INTO
CAT RANGE AND INSERTED AN INCH OF SNOW THERE.
OTHERWISE NO CHANGES AT THIS TIME TO THE SYSTEM STILL PROGGED TO
MOV INTO THE AREA THURS NIGHT INTO FRI. GIVEN THE LATEST GUIDANCE
/INCLUDING THE 00Z NAM...18Z OPERATIONAL AND ENSEMBLES
PRODUCTS..AS WELL AS THE 21Z SREF/ STILL LOOKS LIKE THE TRACK OF
THE UPPR LVL LO WL GO TO OUR WEST. GIVEN THIS TRACK IS APPEARS
MORE OF A WARM ADVECTION SHOT OF PRECIP THAT WILL QUICKLY MOV THRU
THE AREA LATE THURS NIGHT AND THRU THE FIRST HALF OF FRI. ARCTIC
AIR APPEARS SUFFICIENT FOR SN IN THE NW AND IP IN THE CNTRL...BUT
GIVEN THE SPEED OF THE SYSTEM AND THE LACK OF A DEFORMATION
ZONE...THIS APPEARS TO BE MORE OF AN ADVISORY EVENT FOR OUR CWA.
MIDNIGHT SHIFT WL HAVE MORE TIME TO DIGEST ALL NEW GUIDANCE
THOUGH.
BOUSTEAD
&&
.PREV DISCUSSION... /ISSUED 329 PM CST WED DEC 29 2010/
SHORT TERM...TONIGHT THROUGH SATURDAY.
POTENTIAL WINTER STORM THURSDAY NIGHT AND FRIDAY REMAINS THE PRIMARY
FORECAST CONCERN.
WARM MOIST AIR HAS INUNDATED THE CWA TODAY...WITH SURFACE DEW POINTS
IN THE UPPER 30S AND LOWER 40S. LOW PRESSURE REMAINS IN THE LEE OF
THE ROCKIES AND WILL DO SO UNTIL UPPER SYSTEM ROLLS INTO THE PLAINS
THURSDAY NIGHT AND FRIDAY. THUS SOUTH WINDS WILL MAINTAIN LOW CLOUDS
AND POTENTIAL FOR DRIZZLE OR FOG ACROSS THE CWA INTO THURSDAY.
ARCTIC COLD FRONT BEGINS TO PUSH INTO THE NORTHWEST CWA THURSDAY
MORNING AS HEIGHTS LOWER WITH APPROACHING SYSTEM AND WITH PASSAGE OF
INITIAL SURFACE LOW EJECTING THROUGH THE PLAINS. TEMPERATURES WILL
DROP BELOW FREEZING IN OUR NORTHWEST SOMETIME BEFORE NOON AND
CONTINUE TO FALL THROUGH THE DAY. ANY LINGERING DRIZZLE THERE MAY
POSE A PROBLEM...BUT CONFIDENCE IS LOW ON DRIZZLE OCCURRING IN THE
AFTERNOON.
MAIN SYSTEM WILL BE ENTERING THE PLAINS BY MIDNIGHT FRIDAY. A REAL
TRICKY FORECAST ENSUES AS SHALLOW ARCTIC AIR RUSHES UNDER RELATIVELY
WARM AIR ALOFT. SURFACE LOW IN SOUTHWEST KANSAS AT MIDNIGHT WILL
PUSH INTO NORTHERN MISSOURI OR SOUTHERN IOWA BY NOON FRIDAY. GFS HAS
BEEN MOST CONSISTENT WITH THIS TRACK...AND ECMWF HAS TRENDED TOWARD
THE GFS THE LAST COUPLE OF DAYS. HOWEVER QPF FORECASTS ARE QUITE
DIFFERENT BETWEEN THOSE MODELS WITH GFS MOST BULLISH ON
PRECIPITATION. HOWEVER BOTH MODELS ARE POINTING TO A SIGNIFICANT
SNOW EVENT FOR OUR NORTHWEST CWA. SO HAVE HOISTED A WINTER STORM
WARNING THERE FOR SNOW AMOUNTS GREATER THAN 6 INCHES AND SOME
BLOWING SNOW WITH WIND GUSTS OVER 30 MPH.
THE REST OF THE CWA IS STILL A QUESTION MARK WITH WARM AIR ALOFT
HOLDING STEADY FROM NEAR OMAHA SOUTHEAST THROUGH FRIDAY NOON. THIS
PUTS A COMPLEX MIX OF PRECIPITATION OVER A GOOD SWATH OF THE CWA.
AND PIN-POINTING WHERE SNOW/SLEET/FREEZING RAIN DELINEATION IS STILL
IN QUESTION. SUFFICE IT TO SAY...THE COMBINATION OF WINTRY MIX IN
THE CENTRAL PART OF THE CWA...ALONG WITH AN ICING THREAT IN THE
SOUTHEAST WHERE WARM TEMPS ALOFT LINGER DURING THE HEIGHT OF
EXPECTED QPF. THUS HAVE POSTED A WINTER STORM WATCH FOR THE
REMAINDER OF THE CWA. LESS CONFIDENCE EXISTS IN OUR SOUTH WHERE QPF
LOOKS TO BE LESS THAN FARTHER NORTH.
TEMPERATURES WILL BE VERY COLD RIGHT ON THROUGH SATURDAY WITH HIGHS
ONLY IN THE TEENS IF WE ARE LUCKY.
DERGAN
LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY.
TEMPERATURES LOOK TO BE THE ONLY FORECAST CONCERN IN THE EXTENDED
PERIOD WITH NO MAJOR SYSTEMS TAKING AIM AT THE REGION. SLUG OF
ARCTIC AIR WL PUSH EAST OF THE REGION BY SATURDAY NIGHT HOWEVER
FRESH SNOW COVER AND CLEARING SKIES SHOULD KEEP TEMPERATURES COLD
THROUGH THE REMAINDER OF THE WEEKEND. NEARLY ZONAL FLOW ALOFT AND
NEUTRAL TEMPERATURES ADVECTION SHOULD KEEP TEMPERATURES NEAR NORMAL
FOR THIS TIME OF YEAR THRU THE REMAINDER OF THE EXTENDED.
KERN
AVIATION...
TAF SITES KOFK/KOMA/KLNK
18Z TAFS
IFR CIGS AND VSBYS EXPECTED TO CONTINUE AT ALL THREE SITES THROUGH
ABOUT 30/14Z AS MOIST SOUTHERLY FLOW REMAINS OVER THE REGION IN
ADVANCE OF DEVELOPING SYSTEM OVER THE WESTERN CONUS. SOME DRIER AIR
POSSIBLE FOR SOUTHEAST NEBRASKA AFTER 30/14Z WITH KLNK SEEING SOME
MVFR CONDITIONS AFTER THAT TIME AND POSSIBLY KOMA BEFORE LOW LEVEL
MOISTURE RETURNS WITH COLD SURFACE AIR JUST BEYOND END PERIOD OF
CURRENT TAFS.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...DENSE FOG ADVISORY UNTIL NOON CST THURSDAY FOR NEZ015-034.
WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
AFTERNOON FOR NEZ015-032>034-042>045-050>053-065>068-078-
088>093.
WINTER STORM WARNING FROM 6 PM THURSDAY TO 6 PM CST FRIDAY FOR
NEZ011-012-016>018-030-031.
IA...DENSE FOG ADVISORY UNTIL NOON CST THURSDAY FOR IAZ043-055-056-
069-079-080.
WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
AFTERNOON FOR IAZ043-055-056-069-079-080-090-091.
&&
$$