Severe Thunderstorm Warning 79, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
615 AM CDT SUN MAY 10 2015

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 350 AM CDT SUN MAY 10 2015

...LOCATION OF SEVERE STORMS TODAY IS THE MAIN CHALLENGE...

EXCEPTIONALLY ACTIVE/DYNAMIC PATTERN CONTINUES OVER THE CENTRAL
UNITED STATES TODAY AS LARGE UPPER LOW SPINS OVER THE HIGH PLAINS.
WATER VAPOR IMAGERY SHOWED THE CLOSED AND WRAPPED UP CIRCULATION
DRIFTING NORTHEAST AROUND 30 KNOTS...OUT OF NORTHEAST COLORADO
AND HEADED FOR NORTHWEST NEBRASKA THIS MORNING.

A COMPLEX AND HIGHLY BAROCLINIC SURFACE PATTERN WAS ANALYZED AT
06Z WITH A CLOSED 1004MB LOW NEAR THE KANSAS-COLORADO BORDER AND A
TIGHT THERMAL AND PRESSURE GRADIENT NORTH OF THE LOW. WARM FRONT
EXTENDED FROM THE LOW EASTWARD WITH LOW TO MID 60S DEW POINTS OVER
KANSAS...AND AN INVERTED TROF EXTENDED NORTHEAST INTO THE SIOUX
CITY AREA. AIRMASS NORTH OF THE LOW WAS COLD ENOUGH FOR WIDESPREAD
SNOW IN THE WESTERN HIGH PLAINS THIS MORNING.

AS THIS PATTERN EVOLVES THROUGHOUT THE DAY...THE FEATURES BY MID-
LATE AFTERNOON APPEAR TO BE SETTING UP FOR A NEARLY CLASSIC
LOOKING COLD CORE SUPERCELL OUTBREAK. UNFORTUNATELY THERE ARE
SMALL BUT IMPORTANT DIFFERENCES IN THE SUITE OF MODEL SOLUTIONS
REGARDING WHERE THE UPPER AND SURFACE LOWS WILL TRACK...AND THESE
DIFFERENCES COULD RESULT IN THE LOCATION OF THE SUPERCELLS VARYING
BY SEVERAL COUNTIES DEPENDING ON THE SOLUTION.

THE CONSENSUS SOLUTION OF THE SREF MEAN FOR THE PLACEMENT/TRACK
OF THE UPPER AND SURFACE LOWS IS SIMILAR TO THE GOING FORECAST AS
WELL AS CURRENT TRAJECTORIES OF THE UPPER LOW. USING THE SREF MEAN
SOLUTION...THE FORECAST PATTERN IN THE 18-21Z TIME FRAME INCLUDES
THE FOLLOWING INGREDIENTS TO SUPPORT SUPERCELLS OVER NORTHEAST
NEBRASKA AND WEST CENTRAL IOWA: UPPER LOW OVER WESTERN NEBRASKA
WITH 500 MB TEMPERATURES AROUND -19C... TRIPLE POINT AND DEEP
SURFACE LOW NEAR O'NEILL...100+ KNOT UPPER LEVEL JET OVER EASTERN
NEBRASKA...WELL PRONOUNCED DRY SLOT OVER EASTERN NEBRASKA WHICH
WILL SUPPORT ML CAPE VALUES EXCEEDING 1200 J/KG AND A DIFFERENTIAL
THERMAL BOUNDARY ON THE EASTERN EDGE OF THE DRY SLOT... AND 0-1KM
SHEAR VALUES AT OR ABOVE 20 KNOTS.

HOWEVER...NUMEROUS FACTORS INCREASE THE UNCERTAINTY IN THESE
SCENARIOS INCLUDING THE ABOVE MENTIONED SPREAD IN MODEL SOLUTIONS.
IF THE MODELS DISPLAYING A NORTHERN TREND ARE CORRECT...MUCH OF
THE FORECAST AREA WOULD BE DRY AND SUNNY UNDER THE DRY SLOT WITH
THE STRONG STORM DEVELOPMENT NORTH OF THE AREA. IF THE SOUTHERN
SOLUTIONS ARE CORRECT...THE STORMS COULD DEVELOP AS FAR SOUTH AS
INTERSTATE 80 AND TRACK NORTH THROUGHOUT THE AFTERNOON. THE
FORECAST PROBABILITY OF STORMS WILL BE A FUNCTION OF THE
DISTRIBUTION OF THESE MODEL SOLUTIONS. THE MOST LIKELY AREA FOR
SEVERE STORMS WILL BE THE FAR NORTHEAST CORNER OF NEBRASKA AND
WEST CENTRAL IOWA...WITH A CHANCE FOR SEVERE STORMS EXTENDING
SOUTH TO INTERSTATE 80.

LATEST OPERATIONAL HRRR SOLUTIONS SUPPORT THUNDERSTORM
DEVELOPMENT BY EARLY AFTERNOON AND JUST EAST OF THE MISSOURI
RIVER.

THE STORMS AND SHOWERS SHOULD EXIT THE FORECAST AREA BY EVENING.
LOW AMPLITUDE UPPER RIDGING AND SURFACE HIGH PRESSURE BUILDS INTO
THE PLAINS MONDAY-TUESDAY WITH COOL BUT DRY WEATHER EXPECTED.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 350 AM CDT SUN MAY 10 2015

THE UPPER PATTERN RETURNS TO BROAD SCALE TROFFING OVER THE WESTERN
US AND PACIFIC COASTAL AREAS WITH SHORTWAVES ONCE AGAIN RETURNING
TO THE PLAINS. AFTER THE DRY BEGINNING OF THE WEEK...GOOD CHANCES
FOR RAIN AND THUNDERSTORMS RETURN FOR THE PERIOD BEGINNING
WEDNESDAY NIGHT AND PERSISTING INTO THE WEEKEND.

&&

.AVIATION...(12Z TAFS FOR KOFK...KLNK AND KOMA.)
ISSUED AT 613 AM CDT SUN MAY 10 2015

IFR/MVFR CEILINGS EARLY THIS MORNING...WHICH SHOULD SCATTER OUT BY
16 TO 18Z. SOUTHEAST WINDS AROUND 12 KNOTS...WITH GUSTS DEVELOPING
INTO THE LOWER TO MID 20 KNOT RANGE BY 18Z. THUNDERSTORMS WILL BE
POSSIBLE PRIMARILY AT THE KOMA TAF SITE 19-23Z. WINDS THEN SHIFT
TO THE SOUTH...SOUTHWEST AND EVENTUALLY WEST NORTHWEST AS A COLD
FRONT MOVES ACROSS THE AREA. COULD SEE MVFR CEILINGS AND SPOTTY
SHOWERS DEVELOP AT KOFK BY 11/03Z.

&&

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

SHORT TERM...NIETFELD
LONG TERM...NIETFELD
AVIATION...DEWALD

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1126 AM CDT SUN MAY 10 2015

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-110630-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT-
PAGE-KNOX-CEDAR-THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-
STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-
SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE-
JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE-RICHARDSON-
1126 AM CDT SUN MAY 10 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IOWA...WEST CENTRAL IOWA...EAST CENTRAL NEBRASKA...NORTHEAST
NEBRASKA AND SOUTHEAST NEBRASKA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SEVERE THUNDERSTORMS WITH THE POSSIBILITY OF A FEW TORNADOES...
LARGE HAIL...AND HIGH WINDS WILL BE POSSIBLE THIS AFTERNOON AND
INTO THE EARLY EVENING HOURS. THE GREATEST CHANCE FOR SEVERE
STORMS APPEARS TO BE IN THE NORTHEAST CORNER OF NEBRASKA AND WEST
CENTRAL IOWA...OR FROM THE HARTINGTON AND WAYNE AREAS TO HARLAN.
THERE IS ALSO A CHANCE FOR SEVERE STORMS FROM NORFOLK TO THE OMAHA
METRO AREA AND INTO SOUTHWEST IOWA WITH LARGE HAIL AND DAMAGING
WINDS THE MAIN THREATS IN THIS AREA.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

INTERMITTENT CHANCES FOR THUNDERSTORMS RETURN FROM WEDNESDAY
NIGHT THROUGH SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND POSSIBLY INTO
THE EARLY EVENING HOURS...MAINLY IN WEST CENTRAL IOWA AND
NORTHEAST NEBRASKA.

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