Flash Flood Watch 8, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
300 PM CDT TUE AUG 10 2010

.SHORT TERM...TONIGHT THROUGH FRIDAY

FORECAST FOCUS CONTINUES TO BE ON THE PCPN CHANCES INTO THE
WEEKEND...WITH AN EMPHASIS ON THE HEAVY RAIN THREAT. IN
ADDITION...HEAT/HUMIDITY WILL BE A CONCERN.

LINE OF CONVECTION CURRENTLY RUNNING FROM CENTRAL MN INTO WESTERN
IA...ASSOCIATED WITH AN UPPER LEVEL FRONT AND ASSOCIATED SFC
BOUNDARY. THE LOW LEVEL MOISTURE TRANSPORT WAS ALSO PUSHING INTO
THIS LINE OF THUNDERSTORMS...PER LATEST RUC13...WITH A 30 KT 850 MB
JET. THE STORMS SHOULD CONTINUE TO EXPAND AND MOVE EAST/NORTHEAST
LATE THIS AFTERNOON AND EVENING...FEEDING OFF OF A VERY UNSTABLE
AIRMASS AHEAD OF IT. WITH MUCAPES OVER 4000 J/KG IN IA AND EFFECTIVE
SHEAR AROUND 40 KTS...SEVERE WEATHER WILL BE A RISK. DAMAGING WINDS
LOOK TO BE THE MAIN THREAT AS THE STORMS APPROACH THE FORECAST
AREA...ALONG WITH THE HEAVY RAIN INDUCING FLASH/URBAN FLOODING
POTENTIAL. HAIL WILL BE A BIT HARDER TO COME BY AS THE FREEZING
LEVEL REMAINS RATHER HIGH //16 KFT//. TO FURTHER ACCENTUATE THE LIFT
ON THE SOUTHERN EXTENT OF THE FRONT...ANOTHER...WEAKER SHORTWAVE
TROUGH IS EVIDENT ON THE WATER VAPOR IMAGERY...MOVING FROM NEB
TOWARD WESTERN IA.

WITH DECREASING INSTABILITY OVERNIGHT...EXPECT A SIMILAR DECREASE IN
THE SEVERE STORM POTENTIAL. PERIODS OF HEAVY RAIN SHOULD CONTINUE
THOUGH...AS THE MAIN MASS OF PRECIPITATION SHIFTS INTO WESTERN WI.
THE POTENTIAL FOR FLOODING ISSUES WILL HAVE TO BE WATCHED CLOSELY.

THE UPPER LEVEL SHORTWAVE TROUGH WILL CONTINUE TO LIFT NORTHWEST
INTO EASTERN CANADA...WHILE THE SFC FRONT SLIDES OVER THE EASTERN
GREAT LAKES ON WED. THE BULK OF THE MOISTURE TRANSPORT LOOKS TO
SHIFT NORTH INTO THE HEART OF THE TROUGH...PER THE GFS/NAM...BUT
EXPECT SOME CONVECTION TO STILL BE GOING ON OVER WESTERN WI IN THE
MORNING...WITH A GRADUAL SHIFT EAST IN THE AFTERNOON.

ANOTHER UPPER LEVEL SHORTWAVE TROUGH WILL DRIVE ACROSS THE NORTHERN
PLAINS ON THU NIGHT/FRI MORNING FLATTENING OUT THE RIDGE AS IT MOVES
OVER THE UPPER MISSISSIPPI RIVER VALLEY FRI NIGHT. AN ASSOCIATED
NORTH-SOUTH RUNNING SFC COLD FRONT LOOKS TO TRACK ACROSS MN
FRI...MOVING ACROSS EASTERN WI BY SAT AFTERNOON. UPWARDS OF 3000
J/KG OF SBCAPE PROGGED TO BUILD OUT AHEAD OF THE FRONT...WITH NEARLY
40 KTS OF 0-6 KM SHEAR. NO CHANGE IN THE AIRMASS...SO AMPLE FUEL FOR
SHOWER/STORM PRODUCTION...BUT THE LOW LEVEL MOISTURE RETURN DOES RUN
SOUTH TO NORTH AHEAD OF THE FRONT...PROVIDING AN ADDITIONAL FORCING
MECHANISM. SO AT THE MOMENT...ALL SIGNS POINTING TO A REAL GOOD SHOT
FOR SHOWERS AND THUNDERSTORMS IN THE FRI-SAT TIME FRAME...ESPECIALLY
FRI NIGHT. DEPENDING ON TIMING AND POSITIONING OF THE
SYSTEM...SEVERE WEATHER COULD BE A WORRY. PERIODS OF HEAVY RAIN LOOK
LIKE A FOREGONE CONCLUSION CONSIDERING THE VERY MOIST ATMOSPHERE.

NOT TO BE FORGOTTEN IS THE HIGH HEAT/HUMIDITY THAT THE REGION HAS
BEEN UNDER...AND WILL CONTINUE TO BE UNDER THROUGH FRIDAY. THE
CLOUDS AND PERIODIC RAINFALL HAVE HELPED OUT A BIT...BUT AFTERNOON
HEAT INDICES ARE STILL CLIMBING INTO THE MID TO UPPER 90S...100 IN
SOME LOCATIONS. THU COULD BE THE WORST DAY HEAT-WISE FOR THE REST OF
THE WEEK...LOOKING RAIN FREE AT THE MOMENT...MORE SUNSHINE...AND
THUS MORE HEAT AND HUMIDITY. THINK AN ADVISORY MIGHT BE NEEDED FOR
THU...BUT WILL HAVE ANOTHER DAY TO EVALUATE. RESIDENCES SHOULD BE
PREPARED FOR HIGH...POTENTIALLY DANGEROUS HEAT REGARDLESS.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY

GFS AND ECMWF CONTINUE TO DRIVE AN UPPER LEVEL TROUGH/SFC COLD FRONT
ACROSS THE REGION FRI NIGHT/SAT...EXITING IT TO THE EAST SAT NIGHT.
SHOWERS AND THUNDERSTORMS LOOK LIKE A GOOD BET...AND THERE COULD BE
SOME SEVERE WEATHER EARLY FRIDAY NIGHT...DEPENDING ON OTHER WEATHER
FACTORS. THE VERY MOIST AIR MASS WILL CONTINUE TO SUPPORT HEAVY
RAIN. HOWEVER...WITH THE PASSAGE OF THIS SYSTEM SHOULD COME A BREAK
FROM THE SULTRY CONDITIONS AS NORTHWEST FLOW REPLACES THE WARM
RIDGING...AND COOLER/DRIER AIR SINKS SOUTH FROM CANADA. THIS DOESN/T
MEAN DRY WEATHER...AS CYCLONIC FLOW AND COOLER AIR A LOFT COULD LEAD
TO SCATTERED AFTERNOON SHOWERS/STORMS SUNDAY AFT. ALSO...THE MODELS
POINT TO VARIOUS BITS OF SHORTWAVE ENERGY MOVING ALONG THE UPPER
LEVEL FLOW FOR THE EARLY PART OF THE NEW WORK WEEK...BRINGING
ADDITIONAL RAIN CHANCES. WITH A LESS MOIST AIR
MASS...HOWEVER...HEAVY RAIN SHOULD NOT BE AS BIG OF A THREAT.

&&

.AVIATION...

CURRENTLY MONITORING A LINE OF STRONG TO SEVERE THUNDERSTORMS ACROSS
SOUTHWEST MINNESOTA AND NORTHWEST IOWA. THIS LINE IS EXPECTED TO
MOVE INTO SOUTHEAST MINNESOTA AND NORTHEAST IOWA BETWEEN 10.22Z AND
11.01Z. MUCH OF THE UNCERTAINTY WITH THIS TIMING IS HOW THE COLD
POOL DEVELOPS WITH THIS LINE. AT ITS CURRENT SPEED...KRST WOULD
BEGIN TO BE AFFECTED BY THIS LINE AROUND 10.23Z...AND KLSE AROUND
11.02Z.

DURING THE OVERNIGHT...THIS LINE IS EXPECTED TO EVOLVE INTO ONE OR
MORE THUNDERSTORM COMPLEXES. DUE TO UNCERTAINTY AND LOCATION OF
THESE COMPLEXES...THUNDERSTORMS WERE NOT ADDED TO THE TAFS. WITH A
VERY MOIST BOUNDARY LAYER...THERE WILL BE THE POTENTIAL THAT FOG MAY
REDUCE THE VISIBILITIES TO 3 MILES OR LESS.

ON WEDNESDAY MORNING...THE THUNDERSTORM COMPLEXES SHOULD BE MOVING
EAST OF THE REGION...AND THERE WILL BE RAPIDLY IMPROVING CONDITIONS.

&&

.HYDROLOGY...

NO CHANGE IN THE TROPICAL-LIKE AIRMASS FOR THE REGION UNTIL AN UPPER
LEVEL TROUGH/COLD FRONT SWEEPS THROUGH ON SATURDAY. PWS WILL
CONTINUE TO BE CLOSE TO 2 INCHES WITH WARM CLOUD DEPTHS OF 4000-4500
M...BOTH VERY CONDUCIVE FOR HEAVY RAIN PRODUCTION. AS A RESULT...ANY
SHOWERS/THUNDERSTORMS INTO SATURDAY MORNING WILL BE CAPABLE OF
PRODUCING INCH PER HOUR RAINFALL RATES. SATURATED GROUNDS FROM
RECENT RAINS COULD LEAD TO FLOODING CONCERNS DUE TO RUNOFF WITH ANY
ADDITIONAL HEAVY RAIN. TONIGHT/WED AND THEN AGAIN FRI/SAT WILL BE
THE MAIN RAIN THREAT PERIODS...AND THUS CARRY THE HEAVY
RAIN/FLOODING POTENTIAL. CURRENTLY...FRI/SAT LOOKS LIKE IT MAY HOLD
THE GREATEST THREAT FOR A WIDESPREAD...HEAVY RAIN. WILL CONTINUE TO
ISSUE AN HYDROLOGIC OUTLOOK...ALTHOUGH FLASH FLOOD WATCHES MAY
BECOME NECESSARY...ESPECIALLY IN THIS FRI/SAT TIME FRAME. ON THE
PLUS SIDE...THU LOOKS DRY AT THE MOMENT.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.

&&

SHORT/LONG TERM... RIECK
AVIATION.......... BOYNE

<!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>

<!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>