River Flood Warning 221, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
321 PM CDT TUE AUG 10 2010

.SYNOPSIS...
AN UPPER RIDGE REMAINS IN PLACE OVER THE NORTH CNTRL U.S. WITH A
S/W OVER THE CENTRAL/NORTHERN PLAINS LIFTING NE OVER THE RIDGE.
AT THE SURFAC...LOW PRESSURE WAS LOCATED OVER THE DAKOTAS WITH A
TRF/WARM FRONT EXTENDING SE ALONG THE MO RIVER THEN INTO NRN MO.
HOT/HUMID AIR COVERED MUCH OF THE REGION. THE NERN CWFA THOUGH WAS
BENEFITING FORM SELY WINDS WHICH WERE HELPING HOLD TEMPS IN THE
MID/UPPER 80S. THE ONLY PCPN IN THE AREA WAS OF BAND OF TSRA AHEAD
OF THE PLAINS S/W FROM ERN NE INTO CNTRL MN. SOME ISOLATED TSRA
HAS ALSO POPPED OVER NORTHERN/CENTRAL MO ALONG A WEAK CONVERGENCE
AXIS.

&&

.SHORT TERM...TONIGHT AND WEDNESDAY...
HEAT AND PCPN CHANCES CONTINUE TO DOMINATE THE FORECAST DURING
THIS PERIOD. HIGH PW/S REMAINING OVER THE AREA CONTINUE TO SUGGEST
POTENTIAL FOR HEAVY RAINS. FEEL THE BEST POTENTIAL FOR ORGANIZED
HEAVY RAINS IS ACROSS THE NORTH LATE TONIGHT INTO WEDNESDAY
MORNING AS TAIL END OF NORTHERN PLAINS/NCNTRL U.S. VORT MOVES
THROUGH. FORCING IN THE LOW LEVELS THOUGH REMAINS WEAK WITH LLJ
ONLY PROGGED TO REACH 15 TO 20KTS OVERNIGHT AND WEAK SURFACE WINDS
NEAR THE FRONT STALLED OVER OUR SOUTH. WITHOUT A CLEAR SIGNAL FOR
ORGANIZED HEAVY RAINS WILL HOLD OFF ON A FLASH FLOOD WATCH FOR
TONIGHT...BUT WILL GO WITH LIKELY POPS OVER THE NRN 1/4 AND
MENTION HEAVY RAINS. TO THE SOUTH WILL GO WITH CHANCE OR SLIGHT
CHANCE POPS OVERNIGHT. WITH THE RIDGE OVER THE AREA TONIGHT WOULD
EXPECT SLOW MOVING STORMS WHICH IN COMBINATION WITH THE HIGH P/WS
WILL CONTRIBUTE TO ISOLATED HEAVY RAIN AMOUNTS OVER THE CWFA.
POTENTIAL FOR SEVERE STORMS ALSO EXISTS WITH THE BETTER THREAT
AGAIN NORTH WITH THE SUPPORT FROM THE S/W. AS HAS BEEN THE CASE
RECENTLY WARM MID LEVEL TEMPS SHOULD LIMIT ANY HAIL SO DAMAGING
WIND WILL BE THE MAIN THREAT.

WILL GO WITH PERSISTENCE ON LOWS TONIGHT RANGING FROM NEAR 70 NE TO
THE MID 70S SOUTH AND WEST. ANY ONGOING PCPN OVER THE CWA
WEDNESDAY MORNING IS EXPECTED TO END OR DIMINISH BY LATE MORNING
ALLOWING TEMPS IN THE SOUTH TO RECOVER INTO THE LOW 90S...SO HAVE
EXTENDED THE HEAT ADVISORY THROUGH WEDNESDAY. ..DLF..

.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...
WEDNESDAY NIGHT...WILL GRADUALLY END THE THUNDERSTORM CHANCES AS
IMPULSE MOVES OFF TO THE EAST.

THURSDAY...HOT AND VERY HUMID WITH STRENGTHENING CAP SO NOT
EXPECTING CONVECTION. SHOULD BE PLENTY OF SUNSHINE WITH MAX TEMPS
SOARING INTO AT LEAST THE LOWER TO MID 90S WITH DEWPOINTS WELL INTO
THE 70S WILL CREATE HEAT INDICIES OF 100 TO 110 OVER MUCH OF MY CWA.
THEREFORE WILL CONTINUE THE HEAT ADVISORY THROUGH THURSDAY EVENING.

FRIDAY THROUGH SATURDAY...OPERATIONAL MODELS AGREE ON DIGGING TROUGH
INTO THE MIDWEST. THIS IS AN IMPRESSIVE FOR MID AUGUST 2 TO 3
STANDARD DEVIATIONS BELOW NORMAL H5 TROUGH. DPROG/DT SUGGESTS THIS
TROUGH AMPLIFYING EVEN MORE ON EACH SUCCESSIVE RUN. STRONG COLD
FRONT SHOULD BE ADVANCING INTO THE CWA FRIDAY NIGHT WITH
THUNDERSTORMS LIKELY ACCOMPANYING THE FRONT. MODELS HAVE BIG TIMING
DIFFERENCES ON THE ARRIVAL OF THE FRONT WITH THE NAM/GFS BRINGING
STORMS IN ALREADY IN THE AFTERNOON WITH THE ECM NOT UNTIL SATURDAY
MORNING. THE TIMING WOULD HAVE GREAT IMPACTS ON THE MAX TEMPS AND ON
THE POTENTIAL FOR SEVERE WEATHER.

IF THE FRONT CAN ARRIVE AT PEAK HEATING ON FRIDAY THEN A SIGNIFICANT
SEVERE WEATHER EVENT WOULD BE MORE LIKELY. DEEPENING LOW
PRESSURE...DIGGING TROUGH AND STRENGTHENING MID LEVEL WINDS FAVOR A
WIDESPREAD SEVERE EVENT. THERE IS THE POTENTIAL THE EVENT COULD
CONTINUE WELL AFTER DARK. TORRENTIAL RAINS WOULD ALSO BE A THREAT.
HOWEVER IF THE ECM IS CORRECT THEN THE SEVERE WEATHER THREAT WOULD
BE VERY LOW WITH CONVECTION HOLDING OFF UNTIL EARLY SATURDAY. SO
STAY TUNED. HOT AND HUMID AHEAD OF THE FRONT ON FRIDAY SO MAY NEED
TO EVENTUALLY EXTEND THE HEAT ADVISORY THROUGH FRIDAY. HOWEVER IF
CLOUDS OR STORMS ROLL IN SOONER THEN TEMPS MAY NOT BE AS WARM AS
CURRENTLY IN THE GRIDS.

LATE WEEKEND THROUGH EARLY NEXT WEEK...A COOLER AND MUCH LESS HUMID
PERIOD. MEX GUIDANCE MAY NOT BE GRASPING THE IMPACT OF THIS AIRMASS
THIS FAR OUT SO IF TRENDS CONTINUE THEN TEMPS MAY NEED TO BE
LOWERED...BUT FOR NOW HAVE STARTED THE DOWNWARD TREND. GRIDS WILL
INDICATE MAX TEMPS IN THE UPPER 70S FAR NORTH TO MID 80S SOUTH WITH
MIN TEMPS IN THE UPPER 50S FAR NORTH TO MID 60S SOUTH. BUT AGAIN
THIS MAY BE TOO WARM IF THE AMPLIFYING TREND CONTINUES. IF THE 12Z
ECM RUN IS CORRECT MUCH COOLER AIR ARRIVES MID TO LATE NEXT WEEK AS
DEEP VORTEX DEVELOPS NEAR HUDSON BAY. THIS IS AN INTERESTING CHANGE
FROM THE 00Z RUN WHICH HAD OUR REGION BACK IN THE HEAT AND HUMIDITY.

..HAASE..

&&

.AVIATION...
TSRA THREAT WILL BE DIFFICULT TO PIN DOWN AT TAFS SITES TONIGHT.
HOWEVER S/W WILL MOVE JUST TO OUR NORTH OVER NIGHT SHOULD PROVIDE
BEST SUPPORT FOR TSRA OVER THE NRN TAF SITES. THEREFORE HAVE
INCLUDED VCTS OVERNIGHT AT ALL TAF SITES WITH A TEMPO GROUP FOR
TSRA AT KCID/KDBQ. SOME TSRA MAY LINGER INTO WEDNESDAY MORNING AT
KDBQ/MLI/KBRL. ..DLF..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HEAT ADVISORY UNTIL 9 PM CDT THURSDAY FOR DES MOINES-HENRY IA-
     JEFFERSON-KEOKUK-LEE-LOUISA-VAN BUREN-WASHINGTON.

IL...HEAT ADVISORY UNTIL 9 PM CDT THURSDAY FOR HANCOCK-HENDERSON-
     MCDONOUGH-MERCER-WARREN.

MO...HEAT ADVISORY UNTIL 9 PM CDT THURSDAY FOR CLARK-SCOTLAND.

&&

DLF/HAASE