Severe Thunderstorm Warning 76, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
642 PM CDT WED MAY 12 2010

...UPDATED FOR 18Z AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
VERY WET AND SOMEWHAT STORMY FORECAST ON THE WAY FOR TONIGHT. LOW
OVER THE SOUTHERN PLAINS AND STRONG DYNAMICS...COUPLED WITH RATHER
HIGH MOISTURE TRANSPORT FOR MAY WILL COMBINE FOR A HEAVY RAINFALL
EVENT OVER THE SOUTHEAST AS THE COOL FRONT TRACKS ACROSS THE STATE
OVERNIGHT. ACROSS THE NORTHEAST...THE H850 BOUNDARY WHICH WILL NOT
MOVE MUCH FROM THIS MORNINGS ANALYSIS WILL BE THE FOCUS FOR ANOTHER
AREA OF HEAVY RAINFALL...THOUGH THE NORTHERN SECTIONS CAN HANDLE THE
RAIN WHILE THE SOUTHEAST HAS ALREADY HAD A FEW DAYS OF MODERATE TO
HEAVY RAINFALL AND CANNOT HANDLE MUCH MORE.  PWATS OVER AN INCH FOR
MUCH OF THE CWA THIS AFTERNOON AND WILL INCREASE TO BETWEEN 1.5 AND
1.75 INCHES BETWEEN 00 AND 06Z THIS EVENING. THOUGH MODELS DIFFER ON
STRENGTH OF INSTABILITY AND EXTENT NORTH THIS EVENING...BOTH THE GFS
AND NAM INDICATE INCREASING INSTABILITY AS THE TX LOW DRIFTS
NORTHEAST. AN AREA OF TSRA ALREADY BREAKING OUT IN EASTERN KS IN
RESPONSE TO SFC MOISTURE CONVERGENCE AND INSTABILITY INCREASES
THERE. WILL EXPECT THAT LINE TO BECOME THE MAIN PLAYER SOUTHEAST
THIS EVENING WHILE CURRENT LINE OF STORMS ALONG I80 US30 CORRIDOR
ROTATES NW ALONG THE H850 BOUNDARY AND CONTINUES TO FIRE THIS
EVENING AND TOWARD MIDNIGHT BEFORE MOVING EAST. CORFIDI VECTORS FROM
03-08Z SUGGEST SLOW EASTWARD TRANSLATION OF STORMS OVER THE
SOUTHEAST WHICH WILL CERTAINLY LEAD TO HEAVIER RAINFALL THERE. HPC
MOD RISK OF EXCEEDING FFG OVER THE SOUTHEAST AND LIGHT RISK TO I80
LOOKS VERY GOOD. WILL EXPAND CURRENT FFA BACK TO WEST/NW BY ONE TIER
COUNTIES. AS THE H850 MOISTURE TRANSPORT SHIFTS EAST AFT 06Z...
THREAT FOR HEAVIER RAINFALL WILL ALSO MOVE EAST. SOUTHEAST SECTIONS
MAY SEE WARMER READINGS DURING THE OVERNIGHT AS WARM AIR MOVES
THROUGH. SPC JUST EXTENDED SLIGHT RISK INTO SOUTHERN IA THROUGH
OVERNIGHT HOURS...WHICH IS MORE CONSISTENT WITH MODEL TRENDS AND
ELEVATED SVR RISK ONGOING NOW.  WARM FRONT AND WARM SECTOR LOOKS TO
SNEAK INTO THE SOUTHEAST LATER THIS EVENING AND HAVE ADDED A DIURNAL
TEMP TREND TO GRIDS. EXPECTING THE BULK OF THE HEAVY RAINFALL TO BE
NEARLY OUT OF THE REGION BY 12Z THURSDAY.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
LINGERING SHOWERS IN THE MORNING WILL MOVE EAST OF THE CWA DURING
THE AFTN.  NON DIURNAL TEMPS OVR THE ERN ZONES WITH MAX T OCCURRING
MID TO LATE MRNG WITH LTL CHNG THEREAFTER.  DRY WEATHER IS ON TAP
FOR FRI INTO ERY SAT...BUT THE FLY IN THE OINTMENT FOR THE WEEKEND
IS STILL THERE IN ALL MDLS.  HAVE UPPED POPS SIG FOR SAT NGT INTO
MON TIMEFRAME.  FEEL THE GFS IS TOO AGRESSIVE WITH THE PCPN FCST AND
THE ECMWF TOO LIGHT WITH IT.  IN EITHER CASE...BOTH AGREE ON TREND
OF A WETTER WEEKEND AS S/WV BREAKS OUT OF STRONG TROF 43N 161W AND
CARVES OUT ALNG THE EAST SIDE OF THE PROGRESSIVE UPR RIDGE MOVG INTO
THE RCKYS.  AS A RESULT OF THE CLOUDS AND PCPN...ALSO LOWERED HIGH
TEMPS FOR SAT INTO EARLY NEXT WEEK AS WELL.  STILL...READINGS WILL
BE AOA NORMAL BY WED.

&&

.AVIATION...
13/00Z...CONDITIONS WILL BE RELATIVELY POOR THROUGH 12Z ON THURSDAY
AS A SFC LOW MOVES FROM KANSAS ACRS IA INTO WI.  NUMEROUS SHOWERS
AND THUNDERSTORMS WILL PASS THROUGH THE STATE DURING THIS TIME WITH
WIDESPREAD MVFR TO IFR CIGS AND VSBYS. SFC WINDS WILL GENERALLY BE
FROM THE EAST BUT SWITCH TO THE NORTH BEHIND THE SYSTEM BY THURSDAY
MORNING AS IT PULLS NORTHEAST.  A GRADUAL IMPROVEMENT IS EXPECTED ON
THE DAY THURSDAY WITH CIGS EVENTUALLY BECOMING VFR AND VSBYS RISING
TO VFR AS THE RAIN ENDS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM 7 PM CDT THIS EVENING THROUGH THURSDAY
MORNING FOR APPANOOSE-CLARKE-DAVIS-DECATUR-JASPER-LUCAS-MADISON-
MAHASKA-MARION-MARSHALL-MONROE-POLK-POWESHIEK-RINGGOLD-STORY-
TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE.

&&

SHORT TERM REV
AVIATION...COGIL
LONG TERM...MS MAY 10

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
351 PM CDT WED MAY 12 2010

IAZ048>050-060>062-072>075-082>086-092>097-132100-
STORY-MARSHALL-TAMA-POLK-JASPER-POWESHIEK-MADISON-WARREN-MARION-
MAHASKA-UNION-CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-
WAYNE-APPANOOSE-DAVIS-
351 PM CDT WED MAY 12 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A FLASH FLOOD WATCH IS IN EFFECT FOR THE AREA. PLEASE REFER TO
THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR
FURTHER DETAILS.

STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS EVENING
AND CONTINUE ACROSS THE AREA TONIGHT. LARGE HAIL AND DAMAGING
WINDS WILL BE THE MAIN THREAT WITH THE SEVERE WEATHER. IN ADDITION
TO THE SEVERE WEATHER POTENTIAL...AREAS OF FLASH FLOODING ARE
POSSIBLE AS THE GROUND IS STILL VERY SATURATED FROM THE RAIN
EARLIER IN THE WEEK AND THE RAINFALL AMOUNTS FORECAST FOR TONIGHT
RANGE FROM 2 TO 3 INCHES AND LOCALLY HIGHER AMOUNTS. RIVER FLOODING
MAY ALSO POSE A PROBLEM IN SOME AREAS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME...THOUGH RIVER
FLOODING MAY BE A PROBLEM IN SOME AREAS OVER THE NEXT SEVERAL
DAYS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAYBE NEEDED TONIGHT. RAINFALL REPORTS WOULD
ALSO BE APPRECIATED IN ADDITION TO HAIL AND WIND REPORTS.

IAZ004>007-015>017-023>028-033>039-044>047-057>059-070-071-081-
132100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-AUDUBON-GUTHRIE-DALLAS-CASS-ADAIR-ADAMS-
351 PM CDT WED MAY 12 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE LATE THROUGH TONIGHT. THE
SEVERE THREAT IS LOW...BUT AN ISOLATED SEVERE THUNDERSTORM COULD
PRODUCE LARGE HAIL ALONG AND SOUTH OF HIGHWAY 20. LOCALLY HEAVY
RAIN IS ALSO EXPECTED WERE UP TO 2 INCHES OF NEW RAINFALL MAY
ACCUMULATE BY LATE TONIGHT. AT THIS TIME THE SOIL MOISTURE
SITUATION WOULD ALLOW FOR LOCALLY HEAVY RAINFALL TO OCCUR WITH
MINIMAL WATER ISSUES. SOME MINOR STREET FLOODING OR PONDING OF
WATER WILL OCCUR IN THE HEAVIER STORMS THIS EVENING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED TONIGHT.

REV

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>