Special Weather Statement, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
306 PM CDT TUE MAR 22 2011

.SYNOPSIS...
A HIGHLY DYNAMIC...BUT STRONGLY CAPPED WARM SECTOR CONTINUES TO BE
FOUND OVER IOWA...CENTRAL ILLINOIS AND POINTS SOUTH.  THE LOW LEVELS
ARE HIGHLY SHEARED...WITH DEEP LAYER SHEAR ALSO VERY FAVORABLE FOR
SUPERCELLS IN OUR CWA. HOWEVER...LOW LEVEL CAPE IS ABSENT...AND
CAPPING ALOFT SHOWS THAT WHAT SHOWERS ARE OCCURRING ARE EITHER LOW
LEVEL DRIZZLE...OR VERY ELEVATED RAIN SHOWERS.

&&

.SHORT TERM...TONIGHT AND WEDNESDAY...
AS IT STANDS...THE STORM EVOLUTION SHOULD ALLOW FOR ISOLATED TO
SCATTERED ELEVATED STORMS THIS AFTERNOON...GRADUALLY BECOMING MORE
NUMEROUS OVER THE NORTHERN 1/3 OF THE CWA WITH TIME. THE MAIN
FORCING...AS WELL AS SEVERE WEATHER POTENTIAL SHOULD MOVE FROM WEST
TO EAST BETWEEN 23Z WEST TO 05Z EAST. AS THIS OCCURS...THE POTENTIAL
SEVERE WEATHER THREATS SHOULD DECREASE WITH TIME...AS SHOULD BE THE
CASE EVEN WHEN THEY ENTER THE CWA FROM CENTRAL IOWA AND MO. BY EARLY
EVENING...THE MAIN THREAT SHOULD BE HAIL...AS THE LOW LEVELS LOOSE
WHAT LITTLE BUOYANCY IT HAS. WHILE EACH STORM MAY PRODUCE A QUICK
0.25 TO 0.5 INCH...THE NATURE OF THEM SHOULD KEEP WIDESPREAD QPF
UNDER 1 INCH...AND GENERALLY UNDER 0.5 INCH SOUTH OF HIGHWAY 30. QPF
SHOULD FALL ACROSS RIVER BASINS...VS ALONG THEM...THUS IMPACTS TO
THE TRIBUTARIES SHOULD BE MORE LIMITED THAT THEY COULD HAVE BEEN.

TEMPERATURES WILL CONTINUE TO RISE SLIGHTLY THIS EVENING...FOLLOWED
BY GRADUAL COOLING. AND WHILE TOMORROW WILL BE A MILD START DUE TO
DEEP DRY SLOT MIXING...TEMPS WILL COOL BY MID DAY...POSSIBLY TO THE
30S NORTH.
..ERVIN..

.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
OVERALL...MODEL INITIALIZATION WAS POOR IN REGARDS TO LOW LEVEL
MOISTURE. ADDITIONALLY...THE AMOUNT OF SNOW COVER THAT WAS INPUT
INTO THE MODELS CONTINUES TO BE OVERSTATED WHEN COMPARED TO GROUND
TRUTH.

THE HEMISPHERIC PATTERN IS IN THE EARLY STAGES OF COMPLETING THE
TRANSITION TO FOUR WAVES. BY WEDNESDAY LONGWAVE TROFS WILL BE OFF
THE WEST COAST AND THROUGH THE CANADIAN MARITIMES SOUTH INTO THE
ATLANTIC. THE RIDGE OVER THE CENTRAL CONUS WILL CONTINUE. STRONG JET
ENERGY MOVING ACROSS THE PACIFIC WILL DE-AMPLIFY THE PATTERN ACROSS
THE PACIFIC AND NORTH AMERICA LATE THIS WEEK WHILE A POWERFUL STORM
DEVELOPS ACROSS EASTERN EUROPE. ENERGY FROM THIS STORM WILL INDUCE A
STORM OVER THE PACIFIC EARLY NEXT WEEK THAT PRODUCES SPLIT FLOW
ACROSS NORTH AMERICA WITH TROFS ON EITHER COAST.

BY THE END OF THE MONTH THE LONGWAVE PATTERN ACROSS THE ENTIRE
HEMISPHERE TURNS TO NEAR ZONAL FLOW. THE LONGWAVE PROGNOSTIC CHARTS
HAVE BEEN SUGGESTING THIS FOR MANY DAYS NOW. THUS A MAJOR
HEMISPHERIC PATTERN CHANGE IS EXPECTED TO OCCUR IN EARLY APRIL. HOW
THE PATTERN CHANGE WILL PLAY OUT IS UNKNOWN. HOWEVER...A SIGNIFICANT
RE-AMPLIFICATION OF THE HEMISPHERIC FLOW WILL OCCUR THROUGH ONE OR
MORE MAJOR STORM SYSTEMS ACROSS THE HEMISPHERE. THE OVERALL WAVE
PATTERN MAY CHANGE FROM FOUR TO FIVE WAVES.

THE NET RESULT FOR THE AREA WILL BE AN ACTIVE WEATHER PATTERN
CONTINUING INTO EARLY NEXT WEEK. THE FLOW PATTERN SUPPORTS
PROGRESSIVE SHORTWAVES WHICH WILL LIMIT THE POTENTIAL FOR HEAVY
PRECIPITATION. THUS PRECIPITATION THROUGH THE WEEKEND SHOULD BE NEAR
OR SLIGHTLY BELOW NORMAL. PRECIPITATION NEXT WEEK WILL AVERAGE BELOW
NORMAL WITH SPLIT FLOW ACROSS THE CONUS. TEMPERATURES WILL BE
COOLING TO BELOW NORMAL THE SECOND HALF OF THIS WEEK AND INTO EARLY
NEXT WEEK. THE ENSEMBLE MEMBERS SHOW THE NAO STRONGLY CLUSTERED AND
GOING NEGATIVE. THE CLUSTERING SUGGESTS THAT A NEGATIVE NAO WILL
CONTINUE INTO THE FIRST FEW DAYS OF APRIL BUT IS TRENDING TOWARD
NEUTRAL. THUS BY LATE NEXT WEEK TEMPERATURES SHOULD BE APPROACHING
NORMAL.

THE MODELS SOLUTIONS ARE HIGHLY VARIED ESPECIALLY THE FURTHER OUT IN
TIME. THIS VARIABILITY IS TRACEABLE TO THE PATTERN CHANGE...
INDIVIDUAL MODEL PHYSICS...AND HOW EACH IS HANDLING THE RESPECTIVE
ENERGY IN THE NORTHERN/SOUTHERN STREAMS.

WED NIGHT THE OCCLUDED OR INVERTED TROF ROTATES THROUGH THE AREA.
LOW LEVEL LAPSE RATES ARE STEEP ENOUGH THAT SHRA SHOULD CONTINUE
DURING THE EVENING. EVAPORATIVE COOLING NORTH OF THE TROF WILL BE
THE KEY TO DEVELOPING A MIX AND EVENTUAL CHANGE OVER LATE WED NIGHT.
HOWEVER...SNOW AMOUNTS WILL RANGE FROM A TRACE TO A DUSTING AT
BEST.

THURS/THURS EVENING QUIET AND DRY CONDITIONS WILL BE SEEN AS
CANADIAN HIGH PRESSURE MOVES ACROSS THE AREA. TEMPERATURES WILL BE
BELOW NORMAL.

LATE THURSDAY NIGHT THROUGH FRIDAY NIGHT ANOTHER SYSTEM MOVES
THROUGH THE AREA. THE KEY WILL BE HOW DEEP THE DRY AIR IS INITIALLY
IN THE LOWER LEVELS. POPS HAVE BEEN CUT BACK TO THE SOUTHWEST THIRD
TO 40 PERCENT OF THE CWFA BUT IT IS CONCEIVABLE THAT NO PRECIP
OCCURS PRIOR TO SUNRISE FRIDAY. ON FRIDAY...CONDENSATION PRESSURE
DEFICITS COLLAPSE WITH RESPECTABLE FORCING ACROSS THE AREA. SNOW
WILL LIKELY BE SEEN IN THE MORNING BEFORE TURNING OVER TO A COLD
RASN MIX BY LATE MORNING AND THE AFTERNOON. THERE MAY BE A BRIEF
ACCUMULATION OF UP TO AN INCH ON GRASSY SURFACES BEFORE WARMER
TEMPERATURES RESULT IN MELTING.

FRIDAY NIGHT/SATURDAY IS SOMEWHAT IN QUESTION DUE TO WHERE THE
SYSTEM ACTUALLY TRACKS. THERE SHOULD BE SOME SNOW FRIDAY NIGHT WHEN
THE BETTER FORCING IS ACROSS THE AREA. HOWEVER...AMOUNTS SHOULD BE
LESS THAN AN INCH ON GRASSY SURFACES. THERE SHOULD BE SOME SNOW
LINGERING INTO SATURDAY MORNING BEFORE ENDING.

SATURDAY NIGHT/SUNDAY LOOKS TO BE DRY AS YET ANOTHER CANADIAN HIGH
PRESSURE MOVES ACROSS THE AREA.

SUNDAY NIGHT THROUGH TUESDAY IS HIGHLY IN QUESTION. ANOTHER SYSTEM
OR SYSTEMS WILL BE MOVING THROUGH THE FLOW WITH A CHANCE OF
PRODUCING PRECIP. THE GFS/GEM ARE THE FURTHEST NORTH AND GIVE PRECIP
TO THE AREA WHILE THE ECMWF/UKMET ARE FURTHER SOUTH WITH HIGH
PRESSURE HOLDING ACROSS THE GREAT LAKES. SPLIT FLOW WILL BE
DEVELOPING ACROSS THE CONUS DURING THIS TIME PERIOD AND THIS SYSTEM
WILL BE IN THE SOUTHERN STREAM. THE DIFFERENCES BETWEEN THE MODELS
IS DUE TO HOW MUCH PHASING OCCURS BETWEEN THE NORTHERN AND
SOUTHERN STREAMS. FOR NOW WILL GO WITH SCHC TO VERY LOW CHC POPS
DURING THE PERIOD. HOWEVER...THERE IS A VERY REAL POSSIBILITY THAT
THE ENTIRE TIME PERIOD WILL BE DRY.
..08..

.AVIATION...
A WARM FRONT WILL MOVE NORTH OF MLI BY LATE AFTERNOON BEFORE
STALLING OUT. THIS WILL KEEP MLI AND BRL VFR WITH OCCASIONAL MVFR
DUE TO SCATTERED SHOWERS AND THUNDERSTORMS. CID AND DBQ WILL BE
NORTH OF THE FRONT...AND REMAIN IMPACTED BY LOW STRATUS AND DRIZZLE
BETWEEN SHOWERS AND STORMS. CIGS SHOULD REMAIN BETWEEN 600 FT AND
1000 FT THROUGH LATE TONIGHT AT CID AND DBQ. SOME STRONG STORMS ARE
POSSIBLE THIS EVENING...WITH HAIL LIKELY WITH STRONG STORMS AT ALL
TAF SITES. LATE TONIGHT...AS COLD FRONT WILL BRING WEST WINDS TO ALL
SITES...AND WHEN THIS OCCURS...CIGS SHOULD BECOME VFR ALONG WITH
VISIBILITIES.
..ERVIN..

&&

.HYDROLOGY...
RECENT RAINFALL FROM THE WEEKEND HAS RESULTED IN RISES ON MANY
AREA TRIBUTARY RIVERS. ADDITIONAL PRECIPITATION IS EXPECTED THROUGH
TOMORROW. WHERE AND HOW MUCH RAIN DOES FALL WILL IMPACT THE
FORECAST RISES ON THE AREA TRIBUTARY RIVERS. ADDITIONAL RIVER FLOOD
WARNINGS MAY BE ISSUED DEPENDING ON THE AMOUNT OF RAINFALL THAT
OCCURS TONIGHT INTO TOMORROW.

THE MAINSTEM MISSISSIPPI RIVER LEVELS CONTINUE TO RISE IN RESPONSE
TO SNOW MELT ACROSS SOUTHERN MINNESOTA...WEST CENTRAL AND SOUTHERN
WISCONSIN SINCE LAST WEEK. THE LATEST RIVER MODEL INDICATIONS SHOW
THE MISSISSIPPI RIVER LEVELS TO RISE ABOVE FLOOD STAGE GENERALLY IN
THE MARCH 25TH TO MARCH 31ST TIME FRAME. THIS TIME FRAME APPLIES TO
THE MISSISSIPPI RIVER GENERALLY FROM DUBUQUE DOWNSTREAM TO GREGORY
LANDING.

THE TIMING FOR THE MISSISSIPPI RIVER TO RISE ABOVE FLOOD STAGE WILL
BE GREATLY INFLUENCED BY PRECIPITATION IN THE COMING DAYS...AS WELL
AS TEMPERATURES AND HOW QUICKLY THE WATER FROM THE MELTED SNOW MAKES
ITS WAY INTO THE MAINSTEM MISSISSIPPI RIVER. THE RISE ABOVE FLOOD
STAGE COULD OCCUR SOONER IF HEAVY PRECIPITATION OCCURS FROM EASTERN
IOWA AND NORTHWESTERN ILLINOIS AND TO THE NORTH. THE RISE ABOVE
FLOOD STAGE COULD OCCUR TOWARD THE LATTER PORTION OF THE MARCH 25TH
TO MARCH 31ST TIME FRAME IF PRECIPITATION AMOUNTS ARE LIGHT TO
MODERATE...AND COLDER TEMPERATURES ACT TO SLOW THE MOVEMENT OF THE
MELTED SNOW.    ..STOFLET..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1206 PM CDT TUE MAR 22 2011

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-231000-
BUCHANAN-DELAWARE-DUBUQUE-BENTON-LINN-JONES-JACKSON-IOWA-JOHNSON-
CEDAR-CLINTON-MUSCATINE-SCOTT-KEOKUK-WASHINGTON-LOUISA-JEFFERSON-
HENRY IA-DES MOINES-VAN BUREN-LEE-JO DAVIESS-STEPHENSON-CARROLL-
WHITESIDE-ROCK ISLAND-HENRY IL-BUREAU-PUTNAM-MERCER-HENDERSON-
WARREN-HANCOCK-MCDONOUGH-SCOTLAND-CLARK-
1206 PM CDT TUE MAR 22 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
ILLINOIS...NORTHWEST ILLINOIS...WEST CENTRAL ILLINOIS...EAST
CENTRAL IOWA...NORTHEAST IOWA...SOUTHEAST IOWA AND NORTHEAST
MISSOURI.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE OVER THE
OUTLOOK AREA THIS AFTERNOON AND EVENING...AS A WARM FRONT LIFTS
SLOWLY NORTHWARD. SOME OF THE THUNDERSTORMS COULD BE
SEVERE...MAINLY BETWEEN 3 PM AND 11 PM. LARGE HAIL WILL BE A
THREAT OVER THE ENTIRE OUTLOOK AREA...WHILE AREAS MAINLY SOUTH OF
INTERSTATE 80 WILL ALSO SEE A THREAT OF DAMAGING WINDS AND ISOLATED
TORNADOES.

THE STORM PREDICTION CENTER HAS PLACED THE ENTIRE OUTLOOK AREA
UNDER A SLIGHT RISK FOR SEVERE WEATHER THIS AFTERNOON AND EVENING.

SEVERAL ROUNDS OF RAINFALL THIS WEEK MAY PUSH SOME AREA TRIBUTARY
RIVERS NEAR OR ABOVE FLOOD STAGE. PLEASE SEE THE LATEST FLOOD
STATEMENTS AND FLOOD WARNINGS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

A LOW PRESSURE SYSTEM MOVING ACROSS THE PLAINS MAY INTERACT WITH
COLD ENOUGH AIR TO PRODUCE SOME SNOW ACROSS THE AREA ON FRIDAY.
HOW FAR NORTH OR SOUTH THIS SYSTEM TRACKS IS STILL UNCERTAIN AT
THIS TIME...BUT LATEST INDICATIONS SUGGEST THAT SOME MINOR SNOW
ACCUMULATIONS MAY BE POSSIBLE ON GRASSY AND ELEVATED SURFACES
ALONG AND NORTH OF INTERSTATE 80. MORE SNOW MAY THEN BE POSSIBLE
ACROSS PORTIONS OF THE OUTLOOK AREA ON SATURDAY. THE AMOUNT OF
SNOW AND WHERE IT IS LIKELY TO OCCUR ON SATURDAY IS STILL
UNCERTAIN AT THIS TIME.

MISSISSIPPI RIVER LEVELS CONTINUE TO RISE IN RESPONSE TO SNOW MELT
ACROSS SOUTHERN MINNESOTA AND WEST CENTRAL AND SOUTHERN WISCONSIN.
THE LATEST RIVER MODEL INDICATIONS SHOW THE MAINSTEM MISSISSIPPI
RIVER LEVELS TO RISE ABOVE FLOOD STAGE GENERALLY IN THE MARCH 25TH
TO MARCH 31ST TIME FRAME. THIS TIME FRAME APPLIES TO THE
MISSISSIPPI RIVER GENERALLY FROM DUBUQUE DOWNSTREAM TO GREGORY
LANDING. THE TIMING FOR A RISE ABOVE FLOOD STAGE WILL BE GREATLY
INFLUENCED BY PRECIPITATION IN THE COMING DAYS...AS WELL AS
TEMPERATURES AND HOW QUICKLY THE WATER FROM THE MELTED SNOW MAKES
ITS WAY INTO THE MAINSTEM MISSISSIPPI RIVER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED FOR PORTIONS OF THE
OUTLOOK AREA THIS AFTERNOON AND EVENING.

05/12/STOFLET

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
938 PM CDT TUE MAR 22 2011

IAZ040-041-051>053-063-064-076-077-087-230330-
JEFFERSON IA-DELAWARE IA-BUCHANAN IA-JONES IA-BENTON IA-LINN IA-
IOWA IA-JOHNSON IA-WASHINGTON IA-KEOKUK IA-
938 PM CDT TUE MAR 22 2011

...THUNDERSTORMS WITH SMALL HAIL...

AT 930 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR HAD A LINE OF
THUNDERSTORMS EXTENDING FROM LAMONT TO NEAR FREMONT IOWA...MOVING
EAST AT 30 MPH. ANOTHER STRONG STORM WAS AHEAD OF THIS LINE IN
SOUTHERN LINN AND NORTHERN JOHNSON COUNTIES...MOVING NORTHEAST AT 45
MPH.

THESE STORMS WILL BE CAPABLE OF PRODUCING HAIL UP TO PENNY SIZE AND
WINDS UP TO 35 MPH.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 200 AM CDT WEDNESDAY MORNING
FOR KEOKUK...WASHINGTON...JEFFERSON...HENRY...AND VAN BUREN COUNTIES
IN IOWA...AND SCOTLAND COUNTY IN MISSOURI.

&&

LAT...LON 4265 9182 4265 9115 4116 9161 4116 9242

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