AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
331 PM CDT TUE MAY 21 2013
.SYNOPSIS...
ISSUED AT 240 PM CDT TUE MAY 21 2013
A CLOSED H5 LOW WAS LOCATED OVER SOUTHEASTERN SOUTH DAKOTA AND
SOUTHWESTERN MINNESOTA EARLY THIS AFTERNOON. AT THE SURFACE
ELONGATED LOW PRESSURE EXTENDED FROM SOUTHEAST SOUTH DAKOTA INTO
WISCONSIN WITH TWO CIRCULATION CENTERS LOCATED ON THE WESTERN AND
EASTERN PORTIONS OF THE TROF. A WEAK COLD FRONT OVER EASTERN
IOWA/NORTHWEST ILLINOIS THIS AFTERNOON ORIGINATED IN THE WISCONSIN
LOW WHILE A SECONDARY FRONT WAS JUST ENTERING NORTHWEST IOWA.
ANOTHER...STRONGER...CLOSED H5 LOW WAS JUST MOVING INTO THE
PACIFIC NORTHWEST AND SHOULD ACT AS A KICKER TO DISLODGE THE MID
WEST SYSTEM.
&&
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 240 PM CDT TUE MAY 21 2013
THE SYSTEM OVER THE CENTRAL U.S. WILL STAY OVER MINNESOTA AND
SOUTH DAKOTA TONIGHT AND THEN DROP SOUTHEAST WEDNESDAY KEEPING THE
REGION IN COOL CYCLONIC FLOW THROUGH THE PERIOD.
WEAK CONVERGENCE ALONG THE MID MISSISSIPPI VALLEY COLD FRONT AND
MODEST CAPES AROUND 1000 J/KG WILL PROVIDE A CHANCE OF SOME
EVENING THUNDERSTORMS EAST OF THE MISSISSIPPI RIVER THIS EVENING. A
S/W OVER THE SOUTHERN PLAINS THIS AFTERNOON WILL LIFT NORTHEAST
TONIGHT SPREADING MORE SHOWERS INTO AREAS ALONG AND EAST OF THE
MISSISSIPPI RIVER LATE TONIGHT AND WEDNESDAY MORNING. WEDNESDAY
AFTERNOON...AS A WEAKENING SURFACE LOW MOVES SOUTHEAST THROUGH THE
REGION...WRAP AROUND SHOWERS WILL SPREAD OVER THE AREA WITH THE
BETTER CHANCES ALONG AND NORTH OF INTERSTATE 80. COOL AIR
ADVECTING IN TO THE REGION TONIGHT AND WEDNESDAY WILL BRING
TEMPERATURES IN THE 50S AND LOW 60S TONIGHT. WEDNESDAY WITH COOLER
AIR AND PLACE AND WIDESPREAD CLOUDS HIGHS WILL ONLY BE IN THE 60S
AND LOW 70S.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 240 PM CDT TUE MAY 21 2013
WEDNESDAY NIGHT AND THURSDAY...SHOWERS WILL LOOK TO PIVOT AROUND
WESTERN FLANK OF WESTERN GRT LKS TROF WED NIGHT AN MAY BE MORE
PREVALENT ALONG AND NORTH OF I80 FROM 00Z-06Z...AND THEN CONTINUE
TO ROTATE SOUTH AND EAST INTO THU MORNING. FCST SOUNDINGS SUGGEST
DEEPER SATURATED SOUNDINGS WED EVENING WITH PW/S PUSHING OVER AN
INCH...BUT FORCING AND INSTABILITY MARGINAL TO MAKE THE MOST OF THOSE
PROFILES. MOST AREAS TO GET 2 TENTHS OF AN INCH OR LESS BY THU
MORNING. WILL NOT MENTION ANY THUNDER THU EVENING WITH LIMITED
INSTABILITY PROFILES. TOP-DOWN SATURATION LATE WED NIGHT INTO THU
MORNING MAY TREND SHOWERS INTO MORE OF A DRIZZLE REGIME AFTER 3 AM
CDT. A COOL DAMP NIGHT WITH LOWS IN THE LOWER 50S WITH SOME UPPER
40S POSSIBLE. SECONDARY SATELLITE VORT SPOKE MAY KEEP SHOWERS
FESTERING ACRS THE SOUTHEASTERN HALF OF THE FCST AREA THU MORNING
BEFORE THAT ACTIVITY MOVES OUT OR DECAYS BY AFTERNOON. HIGHS HELD IN
THE 60S LATEST 12Z RUN MODELS IN GOOD AGREEMENT IN ADVERTISING
SEASONABLY STRONG BACKDOOR CANADIAN SFC HIGH DUMPING DOWN THE WESTERN
GRT LKS LATE THU AND THU NIGHT...WITH ASSOCIATED COOL PUSH AND CLOUD
CLEAR OFF SETTING THE STAGE FOR A CHILLY NIGHT THU NIGHT. CURRENTLY
PROGGED AIR MASS ADVECTING IN COULD SUPPORT WIDESPREAD LOWS BY FRI
MORNING IN THE LOWER 40S TO UPPER 30S...EXCEPT FOR MID 40S IN THE
SOUTHWESTERN CWA.
FRIDAY AND SATURDAY...AFTER COOL START TO THE DAY...FRI LOOKS TO BE
MAINLY SUNNY UNTIL SOME HIGH CLOUDS SPILL IN FROM THE WEST OFF
GATHERING CONVECTION IN RETURN FLOW ACRS THE PLAINS. WARM AIR
RETURN FLOW ALOFT ESPECIALLY AROUND THE H85 MB LAYER COULD LIMIT
MIXING DEPTH AND KEEP FRI HIGHS HELD IN THE MID 60S EVEN WITH A LOT
OF INSOLATION. FRI NIGHT SOLUTIONS START TO DIVERGE BETWEEN THE 12Z
GFS...THE ECMWF...UKMET AND GEM. THE ECMWF CONTINUES TO BE LESS
AMPLIFIED WITH MID CONUS UPPER RIDGING...ALLOWING MCS DEVELOPMENT
ACRS THE CENTRAL PLAINS TO LEE OF WESTERN CONUS TROFFINESS TO RIDGE-
RIDE AND PROPAGATE EASTWARD ALONG H85 MB BOUNDARY ACRS PORTIONS OR
ALL OF THE DVN CWA LATER FRI NIGHT AND INTO SAT MORNING. THE NEW 12Z
ECMWF FAVORS HEAVIER ELEVATED CONVECTION FED ON H85 THTA-E PLUME ACRS
THE SOUTHERN HALF TO THIRD OF THE DVN CWA FRI NIGHT..WHERE AREAS
COULD GET UP TO AN INCH OF RAINFALL BY SAT MORNING. THIS IN CONTRAST
TO THE MORE AMPLIFIED RIDGE AND FURTHER WE AXIS PLACEMENT OF THE
12Z GFS...WHICH KEEPS FRI NIGHT AND SAT MORNING BASICALLY DRY UNTIL
ELEVATED PRECIP SYSTEM MOVES IN FROM THE WEST BY LATE SAT AFTERNOON.
THE GFS THEN SUGGESTS LLJ AND WARM MOIST CONVEYOR INCREASING OFF THE
WESTERN GULF WILL FUEL A NOCTURNAL MCS TYPE FEATURE SAT NIGHT INTO
SUNDAY MORNING ACRS MOST OF THE LOCAL FCST AREA. THIS WHILE THE
CONSISTENT ECMWF IS FURTHER SOUTH WITH LLVL BAROCLINIC RIBBON LAY
OUT AS WELL AS SOUTHWESTERN GRT LKS LLVL RIDGE AND NORTHEAST BOUNDARY
LAYER PUSH KEEPING THE DVN CWA MAINLY DRY EXCEPT FOR SOME
OVERRUNNING SHOWERS ACRS THE FAR SOUTH SAT NIGHT. THE CANADIAN MORE
SIMILAR TO THE GFS FOR SAT NIGHT AND ADVERTISES UP TO 1.5 INCHES OF
RAIN ACRS THE HEART OF THE CWA BY 12Z SUNDAY. WITH UNCERTAINTIES...
WILL HAVE TO KEEP CHC POPS FOR ALMOST EVERY PERIOD WHICH WILL BE AN
UNFORTUNATE THEME THAT WILL LOOK TO REOCCUR THROUGH THE REST OF THE
LONG RANGE. BOUNDARY PLACEMENT...PRECIP EPISODES AND OUTFLOW/CLOUD
DEBRIS TO PLAY HAVOC WITH TEMP FCST/S THROUGH THE HOLIDAY WEEKEND.
SUNDAY THROUGH NEXT TUESDAY...AS STATED ABOVE...LARGE DIFFERENCES IN
MID CONUS RIDGE PLACEMENT OF THE MAIN AXIS AND AMPLIFICATION...AS
WELL AS NORTH-SOUTH LAY OUT DIFFERENCES OF WEST-TO-EAST ORIENTED LLVL
BOUNDARY OR H85 FRONT BETWEEN THE MEDIUM RANGE MODELS WILL AVERAGE
OUT TO DAILY CHC POPS THOUGH MOST OF THIS PERIOD. THE NEW EURO
CONTINUES TO BE FURTHER SOUTH WITH THE QUASI-STATIONARY LLVL
THERMAL RIBBON THAT PRECIP WILL FOCUS ON AND OVER AND KEEP MOST OF
THE CWA DRY UNTIL TUE...JUST BATHED IN SEASONABLY COOL NORTHEAST
OR EASTERLY FLOW WITH JUST THE FAR SOUTHERN CWA GETTING CLIPPED BY
OVERRUNNING SHOWERS. THIS WHILE THE GFS AND GEM ARE FURTHER NORTH
WITH THE LLVL CONVERGENT AXIS AN BREAK OUT PERIODIC EPISODES OF
ELEVATED SHOWERS OR EVEN POSSIBLE MCS TYPE PRECIP COMPLEXES THROUGH
THE HOLIDAY WEEKEND OVER THE REGION. CLIMATOLOGY SUGGESTS A
COMPROMISE BETWEEN THE TWO CAMPS OF MODELS THAT THE SOUTHERN THIRD TO
HALF OF THE DVN CWA WILL BE UNDER THE GUN FOR A SOGGY HOLIDAY
WEEKEND. BELOW NORMAL TEMPS NORTH OF ANY BOUNDARY THAT SETS UP
ALONG OR JUST SOUTH OF THE CWA...POSSIBLY IN THE LOW 60S OR EVEN 50S
IF OVERRUNNING RAINS WIN OUT WHILE LAKE ENHANCED NORTHEAST SFC FLOW
SPILLS ACRS THE AREA ESPECIALLY ON SUNDAY. DIFFERENCES CONTINUE INTO
TUE AS THE GFS TRENDS DRIER SHIFTING THE MCS TRACK TO THE NORTH ACRS
MN AND WI FOR THE MID WEEK PERIOD...WHILE THE ECMWF ALSO TRENDS
NORTH BUT THAT TARGETS IA AND NORTHERN IL FOR A FAVORED MCS TRACK
FOR THE MID WEEK PERIOD. ..12..
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1208 PM CDT TUE MAY 21 2013
STALLED LOW PRESSURE OVER MN WILL WILL DROP SOUTHEAST THROUGH
EASTERN IA AND WEAKEN LATE TONIGHT AND WEDNESDAY MORNING.
WIDESPREAD CU BASED AROUND 35HND FEET THIS AFTERNOON WILL
DISSIPATE WITH LOSS OF HEATING BY EARLY THIS EVENING. AN AREA OF
SHOWERS WILL LIFT NORTHEAST BRUSHING LOCATIONS NEAR AND EAST OF
THE MISSISSIPPI RIVER LATE TONIGHT AND WEDNESDAY. AT THIS TIME IT
APPEARS FLIGHT CONDITIONS WILL REMAIN VFR IN THE SHOWERS EXCEPT AT
KDBQ WHERE CIGS COULD DROP BELOW 3KFT. FURTHER WEST...AN AREA OF
MVFR CLOUDS AND SCATTERED SHRA WILL ACCOMPANY THE WEAKENING LOW
PRESSURE AS IT MOVES THROUGH THE REGION. MVFR CIGS SHOULD REACH KCID
AFTER 12Z WEDNESDAY.
DLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...DLF
SHORT TERM...DLF
LONG TERM...12
AVIATION...DLF
