Tornadoes and Damaging Winds in Iowa, June 6 to 7, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
638 AM CDT SAT JUN 6 2015

.SHORT TERM /TODAY/...
ISSUED AT 356 AM CDT SAT JUN 6 2015

FORECAST CHALLENGES TODAY WILL FOCUS ON EVENTUAL PLACEMENT OF
CONVECTION CURRENTLY ACRS NEBRASKA AND THEN REDEVELOPMENT OF
CONVECTION TOWARD THE END OF THE PERIOD.  MCS ACROSS SOUTHERN
NEBRASKA HAS BEEN PROPAGATING EASTWARD ON NORTHEAST FLANK OF THE LOW
LEVEL JET IN AN AREA OF GOOD THETA-E ADVECTION BETWEEN 900-750MB.
MODELS HAVE GENERALLY HAD A POOR HANDLING OF THIS CONVECTION BY
TRYING TO LIFT IT NORTHEAST WITH THE BETTER QG FORCING.  WOULD STILL
ANTICIPATE THE CONVECTION SPREADING INTO THE WEST THIS MORNING AS
LLJ AXIS VEERS INTO THE STATE TOWARD DAYBREAK.  HOWEVER...BEST
SUPPORT WILL LIE TO THE NORTHWEST DURING THE DAY AND ANTICIPATE ANY
LINGERING CONVECTION TO WEAKEN DURING THE MORNING AS IT MOVES EAST
INTO CENTRAL IOWA.  FOCUS WILL THEN SHIFT TO REDEVELOPMENT BY LATE
THIS AFTERNOON IN THE FAR NORTHWEST NEAR APPROACHING SURFACE
BOUNDARY.  AT THIS POINT...FEEL THE BULK OF CONVECTION WILL NOT GET
INTO THE AREA UNTIL LATER THIS EVENING ALTHOUGH A FEW STORMS MAY
CLIP THE NORTHWEST BEFORE THE END OF THE PERIOD.  INSTABILITY
SOMEWHAT LIMITED BY NEARLY MOIST ADIABATIC LAPSE RATES IN THE MID
LEVELS AND WHILE THE HODOGRAPHS ARE NICELY LOOPING BY 21Z THE SPEED
IN THE WIND FIELD DOESN'T GET MUCH ABOVE 30KTS UNTIL NEARLY
300MB. WOULD ANTICIPATE SOME SEVERE WEATHER ALTHOUGH AS PREVIOUSLY
MENTIONED...THE BETTER SHOT COMES THIS EVENING AFTER THIS PERIOD.
TEMPERATURES WILL BE SOMEWHAT PROBLEMATIC DEPENDING ON CLOUD COVER
BUT HAVE GENERALLY GONE AT OR ABOVE GUIDANCE GIVEN THE WARM SECTOR
ACROSS MUCH OF THE STATE AND INCREASING WARM ADVECTION THROUGH THE
DAY.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 356 AM CDT SAT JUN 6 2015

THE FORECAST WILL BE DIFFICULT AS THERE IS A LOT GOING ON AND THE
MODELS DO NOT SEEM TO BE HANDLING THINGS VERY WELL.  STORMS WILL
LIKELY BE ONGOING OR NEARING THE FORECAST AREA EARLY THIS EVENING
INT THE VICINITY OF A WARM FRONT EXPECTED TO LIE ACROSS WESTERN
IOWA. CO-INCIDENT WITH THIS WILL BE A SHORTWAVE SHIFTING ACROSS
IOWA AT THE START OF THE PERIOD. RESIDUAL QG
FORCING...PARTICULARLY IN THE 850-700MB LAYER WILL INCREASE
THROUGH THE EVENING AS A LOW LEVEL JET INCREASES. IT IS DIFFICULT
TO SAY WHERE THE HIGHEST POPS WILL BE TONIGHT AND HI-RES MODELS
ARE FAR FROM AGREEMENT. THE NMM LIFTS MOST OF THE ACTIVITY INTO MN
AND DRIBBLES SOME STORMS INTO IA ALONG THE COLD FRONT. THE NAM12
BLOWS UP CONVECTION ALONG THE WARM FRONT THEN TRACKS AN MCS ACROSS
IA IN THE EVENING AND OVERNIGHT WITH WIDESPREAD HEAVY RAINFALL
ACROSS MUCH OF THE CWA. THE ARW IS A COMPROMISE BETWEEN THESE BUT
DOESN'T DEVELOP CONVECTION UNTIL NEAR 06Z ACROSS NW IA TRACKING AN
MCS ACROSS NORTHERN IOWA.

IT WOULD APPEAR NORTHERN INTO CENTRAL IOWA WOULD BE THE FAVORED AREA
CLOSER TO THE SURFACE LOW AND FRONTAL BOUNDARY AND ALSO WHERE THE
QG FORCING IS BEST. IT WOULD APPEAR THAT STORMS SHOULD BE ONGOING
BY EARLY EVENING OR SHORTLY THEREAFTER AND MERGE INTO AN MCS
SOMEWHERE NEAR THE HIGHWAY 20 CORRIDOR BY LATE EVENING INTO THE
OVERNIGHT. I HAVE HIGHEST QPF IN NW IA EARLY TONIGHT BUT I HAVE
KEPT A MORE BROAD SWATH OF HIGH QPF BETWEEN HIGHWAY 20 AND I-80
OVERNIGHT DUE TO UNCERTAINTY OF WHERE THE STRONGER STORMS/HEAVIER
RAINFALL WILL OCCUR. THERE IS SUFFICIENT SHEAR FOR SEVERE STORMS
BUT WEST CENTRAL INTO NORTHWEST IOWA COULD BE INTERESTING
DEPENDING ON HOW CONVECTION OCCURS DURING THE DAY. A COUPLE
TORNADOES INITIALLY NEAR THE SURFACE LOW AND WARM FRONT CANNOT BE
RULED OUT. IN ADDITION...HEAVY RAINFALL IS LIKELY AND DEPENDING ON
WHERE EARLIER CONVECTION OCCURS...THIS COULD BE A CONCERN.

THE COLD FRONT WILL DRAG ACROSS IOWA FROM LATE SATURDAY NIGHT
THROUGH SUNDAY...LYING ACROSS EASTERN INTO SOUTHERN IOWA DURING PEAK
HEATING SUNDAY AFTERNOON. SO WHILE STORMS WILL LIKELY BE ONGOING
SUNDAY IN THE VICINITY OF THE COLD FRONT...THE FOCUS FOR
ADDITIONAL STRONG/SEVERE STORMS WILL BE ALONG/AHEAD OF THE FRONT
DURING PEAK HEATING. HOWEVER THE FRONT SHOULD NEARLY BE OUT OF
THE FORECAST AREA BEFORE THIS HAPPENS. ABOUT THE SOUTHEAST QUARTER
TO THIRD OF THE STATE WILL CONTINUE TO BE UNDER THE GUN ON SUNDAY.
BY SUNDAY NIGHT THE FRONT WILL BE IN THE VICINITY OF SOUTHERN IOWA
BUT MORE LIKELY INTO NORTHERN MISSOURI. I WASN'T CONFIDENT ENOUGH
TO PULL POPS FROM SOUTHERN IOWA SUNDAY NIGHT BUT CERTAINLY
COVERAGE AND INTENSITY WILL BE LESS.

FOR MONDAY INTO MID WEEK UPPER LEVEL RIDGING WILL BUILD TO THE
WEST...OVER THE ROCKIES BUT A FEW SHORTWAVES WILL TOP THE RIDGE.  I
AM NOT LOOKING FOR MUCH WITH THIS.  BLENDED MODELS KEPT PERIODIC
SLIGHT CHANCE POPS GOING INTO MID WEEK WHICH WAS REASONABLE.

FOR THURSDAY AND FRIDAY THUNDERSTORM CHANCES IMPROVE AS ANOTHER
SURFACE LOW IS FORECAST TO MOVE ACROSS THE AREA DRAGGING ANOTHER
FRONTAL BOUNDARY ACROSS THE AREA.

&&

.AVIATION...06/12Z
ISSUED AT 638 AM CDT SAT JUN 6 2015

SHOWERS AND A FEW THUNDERSTORMS WILL MOVE INTO WESTERN IOWA THIS
MORNING BUT GRADUALLY DISSIPATE AS LIFT WEAKENS AND LOW LEVEL FLOW
BEGINS TO FOCUS FARTHER WEST. VFR CEILINGS WILL BE WIDESPREAD
TODAY WITH INCREASING SOUTHEAST SURFACE WINDS. SHOWER AND
THUNDERSTORM ACTIVITY WILL BECOME WIDESPREAD TONIGHT WITH LOWERING
CEILINGS AND RESTRICTED VISIBILITIES IN AND AROUND THUNDERSTORMS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SHORT TERM...COGIL
LONG TERM...FAB
AVIATION...COGIL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
514 AM CDT SAT JUN 6 2015

IAZ006-007-016-017-026>028-038-039-050-062-075-086-097-071015-
WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-FRANKLIN-BUTLER-BREMER-GRUNDY-
BLACK HAWK-TAMA-POWESHIEK-MAHASKA-WAPELLO-DAVIS-
514 AM CDT SAT JUN 6 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON AND
ESPECIALLY TONIGHT. A FEW SEVERE STORMS ARE POSSIBLE TONIGHT.
DAMAGING WIND AND LARGE HAIL WOULD BE THE THREATS FROM THESE
STORMS ALONG WITH HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A CHANCE OF THUNDERSTORMS AGAIN ON SUNDAY. SOME STORMS IN
THE AFTERNOON AND EARLY EVENING COULD BE SEVERE ACROSS THE EAST
AND SOUTH. HEAVY RAIN IS AGAIN POSSIBLE WITH ANY THUNDERSTORM.

THERE WILL BE ADDITIONAL THUNDERSTORM CHANCES FROM TIME TO TIME
THROUGHOUT THE WEEK BUT THE THREAT OF SEVERE STORMS IS LOW THROUGH
WEDNESDAY. SOME STORMS THURSDAY AND FRIDAY MAY BE SEVERE BUT IT IS
TOO EARLY TO DETERMINE SPECIFIC THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TONIGHT AND AT TIMES ON SUNDAY.

IAZ004-005-015-023>025-033>037-044>049-057>061-070>074-081>085-
092>096-071015-
EMMET-KOSSUTH-PALO ALTO-POCAHONTAS-HUMBOLDT-WRIGHT-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-CRAWFORD-CARROLL-GREENE-BOONE-STORY-
MARSHALL-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-CASS-ADAIR-MADISON-
WARREN-MARION-ADAMS-UNION-CLARKE-LUCAS-MONROE-TAYLOR-RINGGOLD-
DECATUR-WAYNE-APPANOOSE-
514 AM CDT SAT JUN 6 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE THIS MORNING. THE RISK OF
SEVERE STORMS IS LOW. ADDITIONAL THUNDERSTORMS ARE LIKELY LATE
THIS AFTERNOON AND ESPECIALLY TONIGHT. LARGE HAIL AND DAMAGING
WIND ARE THE MAIN THREATS BUT AN ISOLATED TORNADO CANNOT BE RULED
OUT ACROSS THE FAR WESTERN OUTLOOK AREA LATE THIS AFTERNOON INTO
EARLY EVENING. HEAVY RAINFALL IS POSSIBLE WITH ANY THUNDERSTORM.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A CHANCE OF THUNDERSTORMS AGAIN ON SUNDAY. SOME STORMS IN
THE AFTERNOON AND EARLY EVENING COULD BE SEVERE ACROSS THE EAST
AND SOUTH. HEAVY RAIN IS AGAIN POSSIBLE WITH ANY THUNDERSTORM.

THERE WILL BE ADDITIONAL THUNDERSTORM CHANCES FROM TIME TO TIME
THROUGHOUT THE WEEK BUT THE THREAT OF SEVERE STORMS IS LOW THROUGH
WEDNESDAY. SOME STORMS THURSDAY AND FRIDAY MAY BE SEVERE BUT IT IS
TOO EARLY TO DETERMINE SPECIFIC THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED FROM LATE THIS AFTERNOON THROUGH
THIS EVENING AND AT TIMES ON SUNDAY.

FAB