Severe Thunderstorm Warning 46, NWS Omaha, NE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1229 PM CDT SUN MAY 19 2013

.AVIATION...18Z TAFS FOR KOFK...KLNK AND KOMA.

SCATTERED THUNDERSTORMS COULD AFFECT ALL EASTERN NEBRASKA TAF
SITES THROUGH THE EVENING. KOFK WILL SEE SCATTERED THUNDERSTORMS
THROUGH ABOUT 21Z BEFORE A BREAK IN THE ACTION THERE. AT KLNK AND
KOMA...MOST STORMS WILL REMAIN WEST OF THE TAF SITE THROUGH 00Z
BEFORE A BAND OF STORMS SWEEPS THROUGH. WHILE STORMS COULD POP AT
JUST ABOUT ANY TIME DURING THE AFTERNOON AND EVENING...TAFS WERE
WRITTEN TO INCLUDE A 2 TO 4 HOUR WINDOW OF MOST LIKELY STORM
ACTIVITY. EACH ROUND OF STORMS WILL BRING AT LEAST MVFR
CONDITIONS...BUT IFR CIGS/VSBYS CAN BE EXPECTED WITHIN
THUNDERSTORM AREAS. MOST OF THE ACTIVITY SHOULD BE MOVING EAST OF
TAF SITES BY 04-06Z TIME FRAME...BUT MORE SHOWERS WILL LIKELY
FILTER INTO KOFK FROM THE NORTHWEST AFTER 06Z. VFR CONDITIONS ARE
EXPECTED OUTSIDE OF ANY PRECIPITATION.

DERGAN

&&

.PREV DISCUSSION... /ISSUED 1132 AM CDT SUN MAY 19 2013/

UPDATE...
A COUPLE OF VORTICITY MAXIMA WERE NOTED ON SATELLITE AND RADAR LATE
THIS MORNING...ONE LIFTING NORTH INTO NORTHWEST IOWA...AND ANOTHER
MOVING NORTHEAST INTO NORTH CENTRAL NEBRASKA. EASTERN VORT WAS
TAKING SHOWERS AND ISOLATED THUNDERSTORMS WITH IT...SO EXPECT A FEW
MORE HOURS OF PESKY SHOWERS IN WEST CENTRAL IOWA. TO THE
WEST...SHOWERS AND THUNDERSTORMS WERE BEGINNING TO FIRE ALONG A
SPOKE OF VORTICITY AROUND WESTERN CENTER...BUBBLING UP IN OUR FAR
WESTERN CWA. NOT EXPECTING ANYTHING MAJOR WITH THESE STORMS AS
INSTABILITY HAS REMAINED IN CHECK DUE TO LINGERING MORNING RAINS.

HOWEVER INSTABILITY IS EXPECTED TO INCREASE MARKEDLY ACROSS A GOOD
PART OF EASTERN NEBRASKA AND WESTERN IOWA THIS AFTERNOON AS
SOUTHERLY FLOW DRAWS MOISTENING LOW LEVEL AIR NORTH AND MID LEVEL
TEMPERATURES COOL WITH APPROACH OF UPPER TROUGH/LOW. MID LEVEL LAPSE
RATES GREATER THAN 8 C/KM ARE EXPECTED. RAP CAPE FORECASTS SUGGEST
SURFACE BASED VALUES WILL APPROACH 2500 J/KG OVER THE SOUTHERN HALF
OF OUR CWA WHERE SUNSHINE IS MOST LIKELY AND SOUTH OF WARM FRONTAL
BOUNDARY SLOWLY LIFTING TOWARD OR JUST NORTH OF INTERSTATE 80 BY MID
AFTERNOON. SHEAR PROFILES WILL BE WEAKENING WITH TIME WITH APPROACH
OF UPPER/SURFACE LOWS...BUT 40 TO 50KT OF 0-6KM BULK SHEAR IS STILL
EXPECTED ACROSS SOUTHEAST NEBRASKA THROUGH 00Z..COINCIDENT WITH
RELATIVE MAXIMUM IN CAPE FIELD. AND 0-1KM STORM-RELATIVE HELICITY
APPROACHES 120. SO AT LEAST MODERATE INSTABILITY WILL BRING A HAIL
THREAT TO MUCH OF THE SOUTHEAST HALF OF THE CWA...WHILE SHEAR
PROFILES ARE MORE FAVORABLE TO A VARIETY OF SEVERE MODES FARTHER TO
THE SOUTHEAST. WHILE TORNADO THREAT LOOKS TO BE LOWER THAN WHAT THE
MODELS SHOWED YESTERDAY...IT IS CERTAINLY NOT ZERO IN FAR SOUTHEAST
NEBRASKA.

AM EXPECTING CONTINUED DEVELOPMENT OF SCATTERED THUNDERSTORMS
THROUGH THE AFTERNOON AS BROAD ASCENT OVERSPREADS THE AREA AHEAD OF
UPPER LOW. A COUPLE OF CLUSTERS OR LINES COULD FORM FROM TIME TO
TIME IN OUR WEST OR SOUTHWEST CWA AND MOVE NORTHEAST. BUT THE BEST
SEVERE THREAT WILL COME LATER IN THE DAY...SAY AFTER 4 PM...IN
SOUTHEAST NEBRASKA AND SOUTHWEST IOWA WHERE WARMING/MOISTENING WILL
OCCUR OUTSIDE OF CONTAMINATED AIR TO THE WEST WHERE INTERMITTENT
STORMS/CLOUDS WILL TEND TO DAMPEN THREAT OF SURFACE-BASED STORMS.

DERGAN

PREV DISCUSSION... /ISSUED 641 AM CDT SUN MAY 19 2013/

DISCUSSION...
HAVE UPDATED FORECAST FOR TEMPERATURE TRENDS AS TEMPS DIP INTO THE
LOWER 60S...AS WELL AS FOR PRECIP TRENDS. CWA IS CURRENTLY
DRY...WITH SHOWERS JUST SOUTHEAST AND JUST NORTHWEST...AND BOTH OF
THOSE AREAS WEAKENING AS SHOWERS APPROACH. THINK CWA WILL LARGELY
BE DRY THROUGH THE MORNING...THOUGH DID HEDGE WITH SLIGHT CHANCE
POPS IN THE LATE MORNING IN CASE SOME SHOWERS/ISOLATED THUNDER
SNEAK INTO THE AREA. SHOULD SEE QUICK TEMPERATURE RECOVERY THIS
MORNING WITH RELATIVELY LOW CLOUD COVER...AND WINDS WILL RETURN
OUT OF THE SOUTHEAST AS OUTFLOW FROM OVERNIGHT CONVECTION MIXES
OUT. STILL POTENTIAL FOR THUNDERSTORMS - INCLUDING SEVERE - THIS
AFTERNOON AND EVENING...PARTICULARLY IN THE SOUTHEASTERN CWA WHERE
SHEAR PROFILES ARE BETTER.

MAYES

AVIATION...
12Z TAFS FOR KOMA...KLNK...AND KOFK.

COMPLEX FORECAST AGAIN FOR THE NEXT 24 HRS REGARDING TIMING AND
LOCATION OF THUNDERSTORMS AND RAIN. MORNING SHOULD BE CLEAR OF
ACTIVITY...WITH SHOWERS AND THUNDERSTORMS INCREASING IN THE
AFTERNOON. FOR NOW...HAVE KEPT A FAIRLY GENERIC MENTION OVER A
BROAD TIME SWATH...BUT THIS IS ONE OF THOSE CASES WHERE STORMS MAY
INDEED LINGER IN VICINITY OF AIRPORTS FOR SEVERAL HOURS. TIMING OF
STORMS MAY NEED TO BE ADJUSTED THOUGH...AS SITUATION BECOMES MORE
CLEAR. STORMS WOULD HAVE POTENTIAL TO REDUCE VIS AND MAYBE
CEILINGS TO MVFR BRIEFLY...WITH GUSTY WINDS ALSO POSSIBLE.
ACTIVITY SHOULD CLEAR THROUGH DURING THE EVENING...WITH LINGERING
SHOWERS THROUGH THE NIGHT THAT ARE LESS LIKELY TO CAUSE CATEGORY
RESTRICTIONS.

MAYES

PREV DISCUSSION... /ISSUED 408 AM CDT SUN MAY 19 2013/

DISCUSSION...(TODAY THROUGH NEXT SUNDAY)
ISSUED AT 408 AM CDT SUN MAY 19 2013

THE MAIN FORECAST CONCERN DURING THIS PERIOD IS SEVERE WEATHER
POTENTIAL THIS AFTERNOON AND TONIGHT.

TO START OUT THE DAY EXPECT GENERALLY DRIER WEATHER ONCE LAST
NIGHTS CONVECTION LEAVES THE AREA IN THE NEXT COUPLE HOURS. THIS
DRY WEATHER SHOULD BE SHORT LIVED ONCE THE MAIN UPPER LOW SHIFTS
EAST INTO NEBRASKA THIS EVENING ALLOWING A SURFACE FRONT TO SHIFT
ACROSS THE AREA. SEVERE WEATHER PARAMETERS INDICATE BEST POTENTIAL
FOR SEVERE WEATHER IS ACROSS FAR SOUTHEASTERN NEBRASKA WHERE A
MODERATE RISK FOR SEVERE WEATHER EXISTS. HERE...DEEP LAYER SHEAR
VALUES PUSH 50 KNOTS ALONG WITH PLENTY OF SURFACE BASED
INSTABILITY. THE MAIN SEVERE WEATHER THREAT IN THIS AREA IS LARGE
HAIL...DAMAGING WINDS AND POSSIBLY A FEW TORNADOES. ELSEWHERE THE
SEVERE WEATHER THREAT IS LOWER...BUT STILL REMAINS. AWAY FROM THE
MODERATE RISK AREA HAIL AND WIND ARE THE PRIMARY SEVERE WEATHER
THREATS.

FOR MONDAY AND TUESDAY THE UPPER LOW LINGERS ACROSS THE AREA. WITH
DEEPER MOISTURE PROGGED OVER THE NORTHERN HALF OF THE CWA...HAVE
FAVORED HIGHER PRECIPITATION CHANCES THERE. ALSO TEMPERATURES WILL
BE COOLER WITH HIGHS IN THE 70S ON MONDAY AND GENERALLY IN THE 60S
ON TUESDAY. THEREAFTER THE COOLER WEATHER LINGERS UNTIL THE UPPER
LOW FINALLY DEPARTS ON THURSDAY AND HIGH PRESSURE IS ESTABLISHED
BY THE END OF THE WEEK.

DJP

&&

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

99/99

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
311 PM CDT SUN MAY 19 2013

NEZ011-012-015>018-030>034-042>045-050>053-200300-
KNOX-CEDAR-THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-STANTON-
CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-SAUNDERS-
DOUGLAS-SARPY-
311 PM CDT SUN MAY 19 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
NEBRASKA AND NORTHEAST NEBRASKA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE MOVING ACROSS
THE OUTLOOK AREA THROUGH THIS EVENING. THUNDERSTORMS THOUGH SHOULD
BECOME ISOLATED IN NATURE AFTER MIDNIGHT

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

WITH THE UPPER LEVEL SYSTEM CLOSING OFF AND STALLING OVER THE
PLAINS...ISOLATED THUNDERSTORMS REMAIN POSSIBLE MONDAY THROUGH
WEDNESDAY...MAINLY WITH AFTERNOON HEATING.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

IAZ043-055-056-069-079-080-090-091-NEZ065>068-078-088>093-200300-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT-
PAGE-SEWARD-LANCASTER-CASS-OTOE-SALINE-JEFFERSON-GAGE-JOHNSON-
NEMAHA-PAWNEE-RICHARDSON-
311 PM CDT SUN MAY 19 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

TORNADO WATCH IS IN EFFECT THROUGH THIS EVENING.

SEVERE THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS ARE
POSSIBLE MAINLY ACROSS SOUTHEAST NEBRASKA AND SOUTHWEST IOWA
THROUGH THIS EVENING. SOME STORMS MAY PRODUCE ISOLATED TORNADOS
DURING THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

WITH THE UPPER LEVEL SYSTEM CLOSING OFF AND STALLING OVER THE
PLAINS...ISOLATED THUNDERSTORMS REMAIN POSSIBLE MONDAY THROUGH
WEDNESDAY...MAINLY WITH AFTERNOON HEATING.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION MAY BE REQUIRED LATE THIS AFTERNOON AND
EVENING.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
229 PM CDT SUN MAY 19 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0210 PM     HAIL             LIBERTY                 40.08N 96.48W
05/19/2013  M1.00 INCH       GAGE               NE   TRAINED SPOTTER

            MOSTLY NICKEL BUT A FEW QUARTER-SIZE.

&&

CHERMOK