Severe Thunderstorm Warning 172, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
323 PM CDT MON OCT 25 2010

.SYNOPSIS...
12Z UA ANALYSIS HAS A STRONG EXTRATROPICAL CYCLONE DEVELOPING IN THE
PLAINS WITH A LLJ OF 30-40KTS FROM TEXAS INTO THE MISSOURI VALLEY. A
INTENSE UPPER LEVEL JET OF 150+ KNOTS RAN FROM THE ROCKIES BACK INTO
THE PACIFIC. THE H85 TEMPERATURE RIDGE RAN FROM SOUTH TEXAS INTO
SOUTH DAKOTA. H85 ANALYSIS INDICATED THE BETTER MOISTURE WAS
CONFINED TO THE GULF COAST WITH GENERALLY DRY AIR ACROSS THE PLAINS.
SATELLITE TRENDS THROUGH EARLY AFTERNOON SHOW THE CI/CS SHIELD
CONTINUING TO THICKEN WHICH IS HELPING TO SUPPRESS TEMPERATURES
SOMEWHAT.

18Z SFC ANALYSIS HAD A STRONG 983 LOW NEAR KABR WITH ADDITIONAL LOWS
NEAR KHLC AND KODX. THE MAIN COLD FRONT RAN FROM THE KABR LOW
THROUGH CENTRAL NEBRASKA AND INTO SOUTHEAST COLORADO. DEW POINTS
WERE IN THE 60S ACROSS THE DEEP SOUTH AND INTO THE LOWER MISSISSIPPI
VALLEY WITH 50S GENERALLY FROM THE PLAINS INTO THE GREAT LAKES.

&&

.SHORT TERM...TONIGHT AND TUESDAY...
LOW LEVEL MOISTURE INITIALIZATION IN THE MODELS WAS SUB PAR WITH
THE MODELS BEING EITHER TOO DRY/MOIST. THESE BIASES ARE RELATED TO
THE HEAT OF VAPORIZATION/SUBLIMATION IN REGARDS TO WATER/ICE.

FIRST HEADLINES...THE HIGH WIND WATCH WILL GO INTO A HIGH WIND
WARNING FOR THE NORTHERN 2/3RDS OF THE CWFA TUESDAY. THE SOUTH
THIRD WILL GO WITH A WIND ADVISORY. THE HIGH WIND WATCH WILL
CONTINUE FOR TUES NIGHT/WEDNESDAY BUT WILL LIKELY GO INTO A WIND
ADVISORY IN SUBSEQUENT FCSTS.

ALL MODELS ARE PLAYING CATCH UP GIVEN THE HIGHLY NONLINEAR
PROCESSES INVOLVED WITH THE STORM SYSTEM. THE INCOMING 18Z WRF HAS
TRENDED STRONGER THAN THE 12Z RUN.

THE EVENING HOURS WILL INITIALLY BE QUIET. AS INTENSE WAA
STRENGTHENS THE OVERALL SYSTEM...ISOLD/SCT SHRA OR EVEN A TSRA
WILL DEVELOP BY MID TO LATE EVENING AS THE WARM FRONT MOVES ACROSS
THE CWFA. AFTER MIDNIGHT IS WHERE THINGS GET REAL INTERESTING.

VARIOUS TOOLS/TECHNIQUES INDICATE A STRONG SQUALL LINE WILL
DEVELOP FROM IOWA SOUTHWARD THIS EVENING AND RACE EAST OVERNIGHT.
SAID SQUALL LINE SHOULD SWEEP THROUGH THE CWFA DURING THE 07Z-13Z
TIME FRAME PLUS/MINUS A FEW HOURS. FCST SOUNDINGS SHOW 40 KNOTS A
FEW THOUSAND FEET OFF THE SURFACE WITH THE LLJ INCREASING TO 60-70
KNOTS. THE THREAT OF SEVERE IS JUSTIFIED. HOWEVER...THE KEY WILL
BE THE THETA E AND MOISTURE ADVECTION FROM THE BOUNDARY LAYER UP
TO ABOUT 850 MB. MOISTURE WILL BE SHALLOW AS EVIDENT BY THE 12Z UA
WHICH WILL MAKE THE ENVIRONMENT PRIME FOR MINI SUPERCELLS.

ANY STORM WILL HAVE THE POTENTIAL TO PULL DOWN THE HIGHER MOMENTUM
AIR AND CAUSE DAMAGING WINDS. THE LOW LEVEL SHEAR IS QUITE
IMPRESSIVE SO IF BOWING SEGMENTS TO THE LINE OCCUR...ISOLD
TORNADOES WILL ALSO BE POSSIBLE. GIVEN ALL THE VARIABLES INVOLVED
AND INTERACTIONS BETWEEN THE SYNOPTIC AND MESO ALPH AND MESO BETA
SCALES...ANY TORNADO THAT WOULD DEVELOP WOULD BE SHORT LIVED. FCST
SOUNDINGS INDICATE CONSIDERABLE MOISTURE ALOFT SO ANY HAIL THREAT
SHOULD BE UNDER 1 INCH.

SQUALL LINE SHOULD BE ALONG/EAST OF THE MISSISSIPPI BY SUNRISE
TUESDAY. ALL MODELS INDICATE A DEEP TROP FOLD MOVING ACROSS THE
AREA SO SUSTAINED 30 TO 40 MPH WINDS SEEM LIKELY WITH GUSTS TO 50
TO 60 MPH. WRAP AROUND PRECIP WILL CONTINUE AT LEAST THROUGH MID
MORNING BEFORE THE DRY SLOT ARRIVES.        ..08..

.LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
TUESDAY NIGHT INTO WEDNESDAY...VERY INTENSE CYCLONE STILL PROJECTED
BY LATEST 12Z RUN MODELS TO BOMB TO SUB-970 MB LEVELS TUE NIGHT JUST
NORTHEAST OF THE MN ARROWHEAD. THE DVN CWA TO BE BATHED IN FULL ON
SUBSIDING DRY SLOT...AND CLEAR SKIES AND DEVELOPING INVERSION AROUND
H9 MB SHOULD HELP SFC WINDS TEMPORARILY DECREASE BELOW WARNING AND
ADVISORY CRITERIA OVERNIGHT. IN-WRAPPING LLVL COLD CONVEYOR TO START
TO BE FELT LATE TUE NIGHT AND WED...WITH HIGHS BEING HELD IN THE
50S IN MUCH OF THE LOCAL FCST AREA DESPITE ANOTHER ROUND OF VERY
DEEP MIXING. MIXING TOOLS AND EXTENT OF DOWNWARD MOMENTUM TRANSFER
INDICATED ON BUFKIT SUGGEST THAT WED TO BE A MODERATE TO HIGH END
WIND ADVISORY DAY AGAIN WITH WIDESPREAD GUSTS OF 40 TO 50 MPH ON WED.
CHANNELED TROP FOLD ACRS THE HEART OF THE CWA AND INTO THE SOUTH
WILL MAKE UP FOR LESS GRADIENT IN THOSE AREAS. SOME SIGNALS OF
ISOLATED HIGH WIND WARNING CRITERIA GUSTS OF MID TO UPPER 50 MPH
GUSTS POSSIBLE ACRS THE NORTHERN THIRD OF THE DVN CWA...ESPECIALLY
IF WRAP-AROUND STRATUS FINALLY TRIES TO MAKE HEADWAY INTO THE
NORTHERN CWA AND ENHANCES DIFFERENTIAL HEATING MIXING ALONG AND JUST
SOUTH OF THE DECK. WRAP AROUND STRATUS MAY TRY TO SURGE SOUTH TOWARD
THE I80 CORRIDOR WED NIGHT...AND AGAIN SFC WINDS SHOULD DECREASE
DIURNALLY TO SUB-HEADLINE VALUES AS INTENSE CYCLONE FILLS ON IT/S
JOURNEY TOWARD JAMES BAY. IF SOME SPOTTY LIGHT PRECIP CAN MAKE IT
INTO THE NORTHERN CWA LATE WED NIGHT...FCST SOUNDINGS COOL ENOUGH TO
ALLOW SNOW FLAKES/FLURRIES TO REACH SFC. WILL KEEP FCST DRY FOR NOW
FOR WED NIGHT BEFORE ADDING ANY MELTING FLAKES INTO THE BOUNDARY
LAYER/SNOW MENTION.

THURSDAY AND FRIDAY...BRUNT OF CAA AND LLVL COLD POOL ON THU SHOULD
KEEP MOST OF THE CWA WITH HIGHS IN THE UPPER 40S TO LOWER 50S.
DEEPER MIXING AND STRATUS CLEARING IN THE AFTERNOON MAY ALLOW FOR
SOME MID 50S ESPECIALLY IN THE SOUTHWEST. INCOMING SFC RIDGE AXIS AND
SFC WIND DECOUPLE COULD MAKE FOR A WIDESPREAD HARD FREEZE LATE THU
NIGHT INTO EARLY FRI MORNING IF IT MAKES IT RIGHT OVER THE MS RVR.
EVEN AFTER A COLD START TO THE DAY...PASSING RIDGE WILL COMMENCE LLVL
RETURN FLOW WITH A LATE AFTERNOON THERMAL MODERATION POTENTIAL TO
AROUND 60 OR EVEN THE LOWER 60S.

SATURDAY DAY THROUGH NEXT MONDAY...MEDIUM RANGE MODEL CONSISTENCY
LACKING THIS PERIOD OVER THE PAST FEW RUNS FOR MUCH CONFIDENCE...
BUT THE ENSEMBLES SUGGEST BROAD MID-CONUS UPPER RIDGING TO COMBINE
WITH INCREASING RETURN FLOW AND LLVL TAP INTO SOUTHEAST PLAINS
THERMAL RIDGE FOR AN ABOVE NORMAL HIGH TEMP DAY NEXT SAT. THE GFS AND
NEW ECMWF HAVE SLOWED THE ARRIVAL OF THE NEXT WAVE IMPULSE OUT OF THE
GRT BSN NOW NOT UNTIL LATER SUNDAY...AND REALLY VARY WITH SOME
PHASING ISSUES WITH NORTHERN STREAM ENERGY NORTH OF THE UPPER RIDGE.
FOR NOW WILL KEEP THE FCST DRY AND SEASONABLY MODERATE THROUGH SUNDAY
AND AWAIT FURTHER MODEL CONSISTENCY WITH THE NEXT WAVE EJECT AND
RIDGE UNDERCUTTING PROCESS. SUNDAY MAY BE MILDER THAN SATURDAY WITH A
LATER IMPULSE ARRIVAL...BUT SHOWERS MAY ARRIVE IN TIME TO DAMPEN ALL
HALLOWS EVE.    ..12..

&&

.AVIATION...
VFR WX THROUGH 00Z/26. SHORTLY AFT 00Z/26 LLWS WL BE A CONCERN AS
SYNOPTIC SYSTEM RAPIDLY DEEPENS. SOUTH WINDS AOA 40KTS ARE INDICATED
AT 1.5-2KFT AGL AND HAVE INCLUDED THIS IN THE 18Z TAFS. MAIN EVENT
TO BE A SQUALL LINE ALONG THE COLD FRONT. ISOLD/SCT CONVECTION
POSSIBLE PRIOR TO 06Z/26 BUT WAA INDICATES CONVECTION TO HOLD OFF
UNTIL CLOSER TO 06Z. TEMPO GROUP IN ALL TAFS TO COVER CFP/SQUALL
LINE 06Z/12Z WITH 3-5SM AND 2KFT CIGS WITH TSRA. AFT 12Z/26...
GRADIENT WNDS TO NEGATE LLWS WITH 25-30KT SUSTAINED WITH G40-45KTS.
..08..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HIGH WIND WARNING FROM 7 AM TO 7 PM CDT TUESDAY FOR BENTON-
     BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-IOWA-JACKSON-
     JOHNSON-JONES-KEOKUK-LINN-LOUISA-MUSCATINE-SCOTT-WASHINGTON.

     HIGH WIND WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY EVENING
     FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES MOINES-
     DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-
     KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.

     WIND ADVISORY FROM 7 AM TO 7 PM CDT TUESDAY FOR DES MOINES-HENRY
     IA-JEFFERSON-LEE-VAN BUREN.

IL...HIGH WIND WARNING FROM 7 AM TO 7 PM CDT TUESDAY FOR BUREAU-
     CARROLL-HENRY IL-JO DAVIESS-MERCER-PUTNAM-ROCK ISLAND-
     STEPHENSON-WHITESIDE.

     HIGH WIND WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY EVENING
     FOR BUREAU-CARROLL-HANCOCK-HENDERSON-HENRY IL-JO DAVIESS-
     MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-STEPHENSON-WARREN-
     WHITESIDE.

     WIND ADVISORY FROM 7 AM TO 7 PM CDT TUESDAY FOR HANCOCK-
     HENDERSON-MCDONOUGH-WARREN.

MO...WIND ADVISORY FROM 7 AM TO 7 PM CDT TUESDAY FOR CLARK-SCOTLAND.

&&

<!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>