FXUS63 KOAX 130907
AFDOAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
307 AM CST SAT NOV 13 2010
.DISCUSSION...
HEAVIEST PRECIPITATION HAS WANED ACROSS MOST OF THE CWA THIS MORNING
WITH ONLY THE HARRISON...SHELBY AND MONONA COUNTIES SEEING MODERATE
SNOW AS OF 230 AM. SURFACE LOW WAS MOVING NORTH THROUGH CENTRAL IOWA
AS CORE OF MID LEVEL COOL AIR WAS BEGINNING TO EXIT OUR CWA TO THE
NORTHEAST. WATER VAPOR IMAGERY/LOOPS SUGGEST HEAVIEST PRECIPITATION
WILL MOVE QUICKLY NORTHEAST OF OUR AREA...BUT WILL LIKELY SEE
LINGERING LIGHT SNOW OR FLURRIES FOR A FEW HOURS AFTER SUNRISE AS
MID LEVEL DEFORMATION AXIS/TROWAL LAGS MAIN UPPER LOW. LITTLE
ADDITIONAL ACCUMULATION EXPECTED AS TEMPERATURES REMAIN ABOVE
FREEZING AND PRECIPITATION RATES DIMINISH DRAMATICALLY. WILL GET A
GOOD SAMPLING OF SNOWFALL REPORTS AROUND 7 AM THIS MORNING...BUT A
SMALLER SAMPLE OF CALLED-IN REPORTS SUGGESTS SNOW AMOUNTS BETWEEN 1
AND 5 INCHES WERE COMMON FROM SOUTHEAST NEBRASKA THROUGH THE
OMAHA/COUNCIL BLUFFS METRO AND NORTH THROUGH MISSOURI VALLEY AND
ONAWA WITH THE HIGHER TOTALS FROM OMAHA AND COUNCIL BLUFFS TO THE
NORTH AND NORTHEAST. WITH SNOW WINDING DOWN RAPIDLY...WILL LIKELY
END WINTER WEATHER ADVISORY FOR MOST OF THE CWA WITH GRID/ZONE
ISSUANCE AT 4 AM...BUT WILL HOLD ON TO OUR THREE NORTHEAST
COUNTIES UNTIL 6 AM. ROAD REPORTS IMPLY ONLY WET OR SLUSHY
CONDITIONS...AND WITH TEMPERATURES HANGING ABOVE FREEZING...EXPECT
MELTING TO CONTINUE.
ALREADY SEEING SOME CLEARING IN OUR WESTERN CWA AS SUBSIDENCE BEHIND
UPPER LOW SCOURS OUT LOW CLOUDS. HOWEVER A LARGE SWATH OF LOW CLOUDS
WAS NOTED FROM EASTERN NEBRASKA AND WESTERN IOWA SOUTH THROUGH
KANSAS AND MISSOURI. SO SHOULD SEE GRADUAL CLEARING FROM WEST TO
EAST THROUGH THE MORNING WITH PARTLY CLOUDY SKIES COMMON IN THE
AFTERNOON. COOL NORTHWEST WINDS BEHIND EXITING SYSTEM AND LINGERING
SNOW COVER WILL KEEP TEMPS FROM CLIMBING HIGHER THAN THE LOW TO MID
40S. AND AREAS IN OUR FAR NORTHEAST MAY LINGER IN THE 30S DUE TO
LATER CLEARING AND DEEPER SNOW.
THE REST OF THE FORECAST AT LEAST THROUGH MID WEEK WILL BE DOMINATED
BY SEVERAL MID LEVEL IMPULSES ROLLING THROUGH SYNOPTIC SCALE BROAD
TROUGH CENTERED IN THE MIDDLE OF THE COUNTRY. MODELS DIVERGE ON
TIMING AND PLACEMENT OF THESE MINOR WAVES...SO WILL NOT ADD PRECIP
THROUGH MONDAY ALTHOUGH A STRAY FLURRY OR SPRINKLE IS POSSIBLE BOTH
SUNDAY AND MONDAY. THERE IS BETTER AGREEMENT ON A STRONGER WAVE
ENTERING THE PLAINS TUESDAY THEN EXITING TO THE EAST WEDNESDAY. 00Z
ECMWF IS CLOSER TO GFS THAN PREVIOUS RUNS...AND THERMAL PROFILES ARE
BEGINNING TO ALIGN AS WELL. PREVIOUS FORECAST HAD LIQUID
PRECIPITATION ENTERING THE AREA TUESDAY...WITH COOLING TUESDAY NIGHT
SUGGESTING A CHANGE TO OR MIX WITH SNOW. GIVEN SIMILAR
GFS/ECMWF...IT LOOKS MORE LIKE SNOW TUESDAY NIGHT IN OUR NORTH WITH
A RAIN/SNOW MIX IN THE SOUTH. WILL KEEP OUR MENTION OF RAIN OR SNOW
TUESDAY NIGHT FOR NOW AS PER COLLABORATION WITH NEIGHBORING
OFFICES...BUT WILL MENTION ACCUMULATING SNOW POSSIBILITY IN THE
HAZARDOUS WEATHER OUTLOOK.
TEMPERATURES SHOULD HOLD IN THE 40S NORTH AND LOWER 50S SOUTH MONDAY
AND TUESDAY...WITH COOLER AIR SPILLING BACK IN ON WEDNESDAY BEHIND
AFOREMENTIONED SYSTEM. NO CHANGES TO FORECAST BEYOND WEDNESDAY.
DERGAN
&&
.AVIATION...
TAF SITES KOFK/KOMA/KLNK
06Z TAFS
PRECIP EXPECTED TO END AT KLNK BY 12 AND KOMA BY 15Z AS SFC LOW OVER
SOUTH CENTRAL IOWA LIFTS OFF TO THE NORTHEAST. IFR CIGS BECOMING
MVFR BETWEEN 12Z-18Z AND VFR AFTER 18Z AT KOMA. GUSTY NW SURFACE
WINDS SHOULD ALSO DIMINISH AFTER 18Z AS TIGHTER GRADIENT SHIFTS TO
THE NORTHEAST.
FOBERT
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...WINTER WEATHER ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR
IAZ043-055-056.
&&
$$