River Flood Warning 67, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
648 AM CDT WED MAY 27 2009

.SHORT TERM.../TODAY/
MAIN CONCERNS TODAY ARE PRECIP AND TEMP TRENDS.  PESKY SRN PLAINS
SHORT WAVE IS STILL OVER NRN IA WITH A SLOWER SPEED THAN ANTICIPATED
YESTERDAY.  MODELS FINALLY LIFT THIS FEATURE NEWD OUT OF FORECAST
AREA BY MIDDAY...BUT IN THE MEAN TIME HAVE CONTINUED HIGHER POPS
TOWARD MCW/ALO THIS MORNING.  ANOTHER CONCERN WILL BE NE/KS SHORT
WAVES.  MODELS BRUSH SWRN IA WITH THEIR ASSOCIATED FORCING SO HAVE
RAISED POPS SLIGHTLY IN THAT AREA TO ACCOUNT FOR POTENTIAL.
OTHERWISE DO NO EXPECT MUCH PRECIP TODAY OUTSIDE OF ISOLD LIGHT
SHOWERS.  ALTHOUGH CIGS MAY LIFT SOMEWHAT NW...BUFR SOUNDINGS ALL
SUGGEST LITTLE REBOUND TODAY IN SOLID CLOUD COVER.  GUIDANCE SEEMS
TO HAVE CAPTURED THIS OK SO HIGHS ARE STILL WITHIN THEIR ENVELOPE.

.LONG TERM.../TONIGHT THROUGH SUNDAY/
FORECAST CONCERNS IN THE LONG TERM PERIOD CONTINUE TO FOCUS ON
FRIDAY NIGHT THROUGH SUNDAY.  THE LAST OF A COUPLE OF SHORTWAVES
WILL LIFT OUT OF THE FORECAST AREA OVERNIGHT TONIGHT AND SKIES
SHOULD CLEAR BEHIND THIS.  HOWEVER...WITH ALL THE RAIN IF WE DO
CLEAR OUT...FOG SHOULD QUICKLY DEVELOP.  THE WEEKEND REMAINS
COMPLICATED AS WE HAVE A THETA-E AXIS AND A SHORT WAVE DROPPING OVER
EASTERN IOWA. DECENT FORCING ALSO EVIDENT THE ONLY INGREDIENT
LACKING IS MOISTURE WHICH WILL LIMIT THE DEGREE OF INSTABILITY WITH
THE SHORT WAVE PASSING.  I KEPT THE TOKEN POPS WE HAD GOING SINCE IT
DOES NOT MAKE SENSE TO PULL IT WITH OTHER FAVORABLE PARAMETERS BUT
THIS AREA WILL NEED TO BE WATCHED.  FOR SATURDAY AND SUNDAY...THE
MODELS ARE STILL UNCERTAIN OF FRONTAL POSITION AND SPEED AS WELL AS
TIMING OF A COUPLE OF SHORT WAVES BUT BY SATURDAY NIGHT AND SUNDAY A
FRONT IS PROGGED SOMEWHERE BETWEEN THE NORTHEAST HALF OF IA TO ALONG
THE MN BORDER.  CAPE AND SHEAR SUFFICIENT FOR SOME STORMS TO BE
STRONG BUT TRENDS ARE TOWARDS A SLOWER PROGRESSION OF THE FRONT.
NEW EURO IS MUCH LESS AGGRESSIVE WITH FROPA UNTIL SUNDAY
NIGHT/MONDAY AND GFS IS A LITTLE MORE BULLISH ON SUNDAY EVENING BUT
KEEPS THE MAIN FORCING NORTH OF THE CWA THROUGH THAT TIME.  I
TWEAKED POPS ALL PERIODS OVER THE WEEKEND BUT CONFIDENCE IS LOW ON
ANY ONE PERIOD AT THIS POINT.  LOOKING FOR A LITTLE MORE MODEL
CONTINUITY WHICH I HOPE WILL COME IN THE NEXT COUPLE OF RUNS.

&&

.HYDROLOGY...
SLOW MOVING SYSTEM HAS PRODUCED ANYWHERE FROM TWO TO FOUR INCH RAINS
OVER THE NRN HALF OF FORECAST AREA IN 24 HOUR PERIOD ENDED AT 08Z.
DUE TO ITS PROLONGED NATURE AND STARTING WITH RELATIVELY DRY
GROUND...THIS HAS HAD LITTLE EFFECT OUTSIDE OF URBAN STREET
FLOODING HOWEVER.  THERE HAS BEEN LITTLE REACTION TO RIVER FORECAST
POINTS WITH ONLY WITHIN BANK RISES ANTICIPATED AT ALL SITES.  NO
WARNINGS ARE CURRENTLY IN EFFECT OR EXPECTED.

&&

.AVIATION...27/12Z
LOW MOVING UPPER LEVEL LOW PRESSURE AREA OVER NORTHERN IA CONTINUES
TO RESULT IS A RATHER STAGNANT PATTERN WITH WIDESPREAD IFR/LIFR
CONDITIONS.  EXPECT LITTLE CHANGE THROUGH MUCH OF THE MORNING
FOLLOWED BY GRADUAL LIFTING TO IFR/MVFR LATER TODAY.  WITH THE
POSSIBLE EXCEPTION OF FOD...EXPECT CIGS TO BE NO BETTER THAN MVFR
EVEN BY THE END OF THE PERIOD.  HAVE RELATIVELY LOW CONFIDENCE IN
TIMING DETAILS HOWEVER...OR WHEN THESE CATEGORY CHANGES WILL OCCUR.

&&

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

&&

SHORT TERM/AVIATION/HYDROLOGY...SMALL
LONG TERM...FAB

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
442 AM CDT WED MAY 27 2009

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-281100-
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-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
442 AM CDT WED MAY 27 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE IS A CHANCE FOR THUNDERSTORMS THIS WEEKEND. SOME SEVERE
STORMS ARE POSSIBLE BUT SPECIFIC THREATS AND TIMING WILL BE
DETERMINED WITH FUTURE FORECASTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AT TIMES THIS WEEKEND.

FAB