Flooding in Nebraska, March 17 to 26, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
315 PM CDT WED MAR 17 2010

.DISCUSSION...

FORECAST CHALLENGE REMAINS TIMING OF RAIN/SNOW CHANGEOVER ON FRIDAY AND
THEN HOW LONG WILL THE LIFT PERSIST AFTER PCPN CHANGES TO SNOW.
SECONDARY ISSUES DEAL WITH TEMPERATURES AS SEVERAL WEAK BOUNDARIES
POSSIBLY PUSH INTO THE FORECAST AREA BEFORE STALLING OUT/LIFTING
BACK N.

FIRST OFF AND FINALLY...19Z OB IN OMAHA HIT 50 DEGREES...FIRST TIME IN
THE 50S OR GREATER HERE SINCE DEC. 1...5TH LONGEST STRETCH ON
RECORD...105 DAYS. AND IT APPEARS WE WILL GO FROM FINALLY REACHING
50 TO MAKING IT INTO THE 60S TOMORROW AS SHORTWV ENERGY DRIVING
ACROSS CANADA PUSHES FLATTENING UPPER RIDGE EWD ACROSS MID MO
RIVER VALLEY. PESKY LOW CLOUDS CONTD TO ERODE AND WITH MODEST WSW
BLYR WINDS OVERNIGHT THIS TREND SHOULD CONT AND ONLY HIGH CLOUDS
EXPECTED ON THU THROUGH MAX HEATING. COULD BE PATCHY FOG FAR SE
TNGT BUT WL LEAVE OUT OF FORECAST ATTM. CI ABOUT THE ONLY THING
THAT WILL HOLD TEMPS BACK ON THU AND ALTHO WSHIFT COULD REACH AS
FAR SE AS OMAHA/LNK BY MID AFTN...COOLING WILL LAG A BIT BEHIND IT
AND A SHIFT TO NW WINDS COULD EVEN AID IN MIXING BOOSTING MAX
TEMPS. MAIN CHANGE WAS TO RAISE TEMPS A BIT IN CNTRL AND SRN
SECTIONS OF NRN ZONES TO ACCOUNT FOR THE BUMP UP IN TEMPS
W/INITIAL WSHIFT BEFORE COOLING TAKES OVER. IF IT WASN/T FOR
THICKER CI THREAT WOULD BOOST READINGS INTO UPPER 60S NEAR FRONT
SWRN ZONES.

STRONG FRONTOGENETICAL FORCING NOTED BHND FRONT ON FRIDAY WHICH
MODELS HAVE BEEN SUGGESTING NOW FOR SEVERAL DAYS AND CATEGORICAL
POPS STILL A GOOD BET. MAIN CHANGE WITH 12Z RUNS OF THE GFS/NAM WAS A
QUICKENING OF THE PCPN CHANGEOVER TO SNOW...WITH BUFKIT SOUNDINGS
INDICATING THIS CHANGEOVER AN HR OR TWO EARLIER PER NAM TO 6 HRS
QUICKER PER GFS. 850 MB MOISTURE WAS NOT VERY IMPRESSIVE W/SYS
WHEN MOST OF THE PCPN IS FORECAST TO FALL...THUS DESPITE STRONG
FORCING FEEL THAT NAM MAY BE OVERDOING QPF AMOUNTS...SPCLY WHEN
SOUNDINGS WERE COOL ENOUGH TO SUPPORT SNOW. IN ADDITION
...MARGINALLY WARM GROUND/TEMPS MAY LIMIT SNOW ACCUMULATIONS
SOMEWHAT AND ATTM PENCILED IN ROUGHLY 2-3 INCH AMOUNTS MOST AREAS.
12Z GFS/ECMWF CONTINUED TO BRING ENOUGH FOLLOWING ENERGY IN NRN
STREAM TO PUSH TROUGH FAR ENOUGH BEFORE IT CLOSES OFF...PER 12Z
ECMWF...OR TO KEEP IT PROGRESSIVE PER GFS. THUS THIS FORECAST WAS
SOMEWHAT AGGRESSIVE IN TRIMMING BACK POPS FRI NGT. CUT BACK HIGHS
DOWN THRU OMAHA AND LNK WITH EXPECTED PCPN FRI...BUT LEFT THEM
GENERALLY ALONE SE CORNER IN CASE THE SLOWER NAM WOULD VERIFY.

AFTER THAT WK COLD FRONTS WERE FORECAST TO SLIP INTO CWA...MAINLY
NRN SECTIONS...SUN AND AGAIN TUE WITH DECENT AGREEMENT BETWEEN
GFS/ECMWF. HOWEVER...CONFIDENCE IN TIMING AND HOW FAR S THEY PUSH
WAS LOW. DID RAISE TEMPS A LITTLE IN SUN-TUE PD...SPCLY S...SINCE
THERE SEEMED A DECENT CHANCE THESE NEW NUMBERS COULD BE REACHED...AND
THEY COULD EVEN PROVE CONSERVATIVE IF FRONT/FRONTS DO REMAIN OR
PUSH BACK N BASED ON FORECAST 850 MB TEMPS. INTRODUCED NEXT CHC OF
PCPN ON DAY 7 AS THERE WAS DECENT AGREEMENT BETWEEN GFS/ECMWF IN
BRINGING NEXT TROUGH CLOSER TO AREA BY THEN.

&&

.AVIATION...
TAF SITES KOFK/KOMA/KLNK

18Z TAFS

LOW CLOUDS FINALLY ERODING ACROSS THE AREA THIS AFTERNOON AND EXPECT
TREND TO CONTINUE INTO THE EVENING AS UPPER WAVE AND SURFACE HIGH
PRESSURE SHIFT SOUTH. VFR CONDITIONS EXPECTED THROUGH THE REMAINDER
OF THE PERIOD.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&

CHERMOK/FOBERT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
540 PM CDT WED MAR 17 2010

IAZ043-055-056-069-080-091-NEZ011-012-015>018-030>034-042>045-
050>053-065-066-078-088>090-092-181245-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MONTGOMERY-PAGE-KNOX-CEDAR-
THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-STANTON-CUMING-BURT-
PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-SAUNDERS-DOUGLAS-SARPY-
SEWARD-LANCASTER-SALINE-JEFFERSON-GAGE-JOHNSON-PAWNEE-
540 PM CDT WED MAR 17 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN NEBRASKA
AND SOUTHWEST IOWA.

.DAY ONE...TONIGHT AND THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY NIGHT TROUGH WEDNESDAY

ACCUMULATING SNOW IS EXPECTED TO DEVELOP OVER THE AREA FRIDAY BEHIND
A STRONG COLD FRONT THAT WILL PUSH ACROSS THE REGION. THE SNOW
COULD BEGIN AS EARLY AS FRIDAY MORNING OVER THE AREA NORTHWEST OF
OMAHA AND LINCOLN AND BY LATE MORNING OR EARLY AFTERNOON IN THE
LINCOLN AND OMAHA AREAS AND A BIT LATER SOUTH OF THERE.  THE SNOW
SHOULD DECREASE AND END FROM NORTHWEST TO SOUTHEAST ACROSS THE
REGION THROUGH FRIDAY EVENING. AT THIS TIME SEVERAL INCHES OF WET
SNOW SEEMS LIKELY. THE SNOW WILL BE DRIVEN BY NORTH WINDS OF 15 TO
25 MPH.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TONIGHT OR THURSDAY.

IAZ079-090-NEZ067-068-091-093-181245-
MILLS-FREMONT-CASS-OTOE-NEMAHA-RICHARDSON-
540 PM CDT WED MAR 17 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST IOWA
AND SOUTHEAST NEBRASKA.

.DAY ONE...TONIGHT AND THURSDAY

LOWLAND FLOODING CAN BE EXPECTED TO CONTINUE THROUGH THURSDAY AND
POSSIBLY INTO THE WEEKEND ALONG THE MISSOURI NEAR AND DOWNSTREAM
OF ITS CONFLUENCE WITH THE PLATTE RIVER.

.DAYS TWO THROUGH SEVEN...THURSDAY NIGHT THROUGH WEDNESDAY

ACCUMULATING SNOW IS EXPECTED TO DEVELOP OVER THE AREA FRIDAY
AFTERNOON OR BY EARLY EVENING BEHIND A STRONG COLD FRONT THAT
WILL PUSH ACROSS THE REGION. AT THIS TIME SEVERAL INCHES OF WET
SNOW SEEMS LIKELY. THE SNOW WILL BE DRIVEN BY NORTH WINDS OF 15 TO
25 MPH.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TONIGHT OR THURSDAY.

CHERMOK