Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 010547
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1247 AM CDT MON SEP 1 2014

.UPDATE...
ISSUED AT 820 PM CDT SUN AUG 31 2014

EVENING UPDATE FOR TIMING/INTENSITY OF THUNDERSTORMS INTO THE
FORECAST AREA LATE TONIGHT INTO MONDAY MORNING.

LATEST RADAR TRENDS...MODELED WELL BY THE HRRR/RAP...INDICATE
STORMS PUSHING INTO THE WESTERN FRINGE OF THE FORECAST AREA NEAR
AND AFTER 11 PM CDT. HAVE UPDATED FORECAST GRIDS TO ADJUST TIMING
AND BRING HIGHER POPS IN EARLIER. DESPITE THE COOLING BOUNDARY
LAYER...THE COMPLEX MOVING INTO CENTRAL IOWA MAY BE ABLE TO
SUSTAIN A DAMAGING WIND THREAT UNTIL 2 OR 3 AM CDT. CONVECTION
STILL EXPECTED TO WEAKEN OVERNIGHT AND DECREASE IN COVERAGE NEAR
AND EAST OF THE MISSISSIPPI RIVER. HAVE UPDATED THE HAZARDOUS
WEATHER OUTLOOK TO REFLECT FORECAST CHANGES.

&&

.SYNOPSIS...
ISSUED AT 313 PM CDT SUN AUG 31 2014

A WARM...MID SUMMER-LIKE DAY IS FOUND OVER OUR CWA TODAY AS WE
REMAIN WELL EAST OF THE COLD FRONT APPROACHING IOWA THIS AFTERNOON.
THE COLD FRONT IS SLOWLY MOVING EAST...AND HAS ALREADY SPAWNED A FEW
HIGH BASED THUNDERSTORMS FROM SOUTHERN MN TO FAR EASTERN NE.
TEMPERATURES WITH FULL SUN TODAY HAVE REACHED THE MID 80S AS OF 2
PM...AND APPEAR SET FOR HIGHS IN THE MID TO UPPER 80S BEFORE CLOUDS
INTERRUPT THE HEATING LATER THIS AFTERNOON. SURFACE BASED STORMS
REMAIN CAPPED FOR NOW...THOUGH CAPE VALUES ARE SHOWN ON RAP DATA TO BE
2000 TO 4000 J/KG.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 313 PM CDT SUN AUG 31 2014

THERE IS LITTLE DOUBT THERE WILL BE AN IMPRESSIVE CONVECTIVE EVENT
TONIGHT. THERE IS PLENTY OF DOUBT THAT IT WILL STRONGLY AFFECT MORE
THAN JUST THE WESTERN MOST PORTION OF OUR CWA.  THE SLOW MOVING
FRONT SHOULD BE ENOUGH TO FOCUS STORMS WITH PLENTY OF CAPE AND
MOISTURE AVAILABLE TO THE WEST...LIKELY NEAR THE MISSOURI RIVER.
THEY SHOULD MOVE EAST...SLOWLY. THIS PLACES THE WEAKENING PHASE OF
THE COMPLEX INTO EASTERN IOWA BETWEEN MIDNIGHT AND 9 AM MONDAY. THIS
POOR DIURNAL TIMING COMBINED WITH LESS THAN IDEAL MOISTURE TRANSPORT
DURING THAT TIME FRAME SUGGESTS BOTH INTENSITY AND COVERAGE OF
STORMS WILL BE ON THE WANE IN THAT PERIOD. I HAVE CONFINED HIGH POPS
TO ONLY THE WESTERN CWA LATE TONIGHT...AND LOWERED TO CHANCE FOR
MONDAY MORNING SINCE MOST MODELS SUGGEST A FRAGMENTED LINE...AND
THAT SEEMS MOST LIKELY TO ME AS WELL. QPF SHOULD BE IMPRESSIVE TO
THE WEST...BUT MAY BE INSIGNIFICANT IN OUR CWA...GENERALLY 0.25 OR
LESS IN ALL BE THE FAR WEST...WHERE 0.5 TO 1.0 IS POSSIBLE.

MONDAY WILL SEE FAR BETTER DYNAMICS...THUS THE SPC OUTLOOK FOR
SEVERE WEATHER. HOWEVER...THE CONVERGENT OUTFLOW BOUNDARY WILL
LIKELY BE WELL IN ADVANCE OF THE COLD FRONT...WHICH SHOULD ALSO
DEFLECT THE STRONGEST HEATING WELL EAST OF THE CWA AS WELL.
THUS...THE WEAKENING CONVECTIVE DEBRIS SHOULD INHIBIT OUR MONDAY
SEVERE POTENTIAL...AS WELL AS WIDESPREAD RAIN POTENTIAL AGAIN. SURE
SEEMS THIS EVENT SHOULD PRODUCE THE MAJORITY OF ITS RAIN WEST AND
SOUTHEAST OF OUR CWA.

ERVIN

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 313 PM CDT SUN AUG 31 2014

THE FRONT WILL CLEAR THE SOUTHEAST HALF OF THE AREA LATE MONDAY
EVENING. THE SOUTHEAST HALF OF THE AREA SHOULD SEE PRECIPITATION
ONGOING AT SUNSET THAT ENDS FROM NORTHWEST TO SOUTHEAST AFTER
MIDNIGHT. DRIER AIR MOVING INTO THE AREA SHOULD RESULT IN LOWS NEAR
OR SLIGHTLY BELOW NORMAL BY SUNRISE TUESDAY.

TUESDAY/TUESDAY NIGHT DRY CONDITIONS ARE EXPECTED AS HIGH PRESSURE
MOVES THROUGH THE MIDWEST. TEMPERATURES SHOULD BE CLOSE TO NORMAL.

WEDNESDAY MORNING LOOKS TO BE DRY ACROSS THE AREA AS THE HIGH MOVES
TOWARD THE EAST COAST. A WEAK DISTURBANCE WILL MOVE THROUGH THE AREA
WEDNESDAY AFTERNOON. THE OVERALL FORCING IS NOT STRONG AND MOISTURE
AVAILABILITY IS IN QUESTION. IF PRECIPITATION DOES OCCUR IT WOULD BE
ISOLATED IN NATURE WITH THE SOUTH HALF BEING FAVORED.

WEDNESDAY NIGHT ON...
THE MODEL CONSENSUS HAS SLIGHT CHANCE TO CHANCE POPS IN EACH 12 HR
PERIOD FROM WEDNESDAY NIGHT THROUGH SATURDAY.

THERE IS A WEAK DISTURBANCE MOVING THROUGH THE AREA WEDNESDAY
NIGHT/THURSDAY. MOISTURE AVAILABILITY WILL BE ON THE INCREASE BUT
THE OVERALL FORCING IS NOT STRONG. THE POSSIBILITY DOES EXIST THERE
WILL BE PERIODS OF DRY WEATHER WEDNESDAY NIGHT/THURSDAY.

THE MODELS DIFFER SOMEWHAT ON THE TIMING BUT AGREE THAT ANOTHER COLD
FRONT WILL MOVE THROUGH THE AREA IN THE THURSDAY NIGHT THROUGH
FRIDAY NIGHT TIME FRAME.

SEVERAL MODELS ARE PUSHING A SIGNIFICANT HIGH INTO THE WESTERN GREAT
LAKES ON SATURDAY. THE CURRENT MODEL CONSENSUS HAS SLIGHT CHANCE
POPS ACROSS THE SOUTH QUARTER OF THE AREA BUT THE OVERALL TREND IS
SUGGESTING DECREASING PRECIPITATION CHANCES.

SATURDAY NIGHT THROUGH SUNDAY THE MODEL CONSENSUS HAS DRY CONDITIONS
WITH HIGH PRESSURE OVER THE GREAT LAKES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1237 AM CDT MON SEP 1 2014

LINEAR MESOSCALE CONVECTIVE SYSTEM WILL CONTINUE TO MOVE ACROSS THE
REGION OVERNIGHT WHILE SLOWLY WEAKENING. GUSTY WINDS WITH MVFR TO
LOCALLY IFR CONDITIONS EXPECTED IN THE STORMS... WITH AN ISOLATED
SEVERE WIND GUST TO 60 MPH POSSIBLE NEAR TO SOUTHWEST OF QUAD CITIES.
WAKE LOW FOLLOWING MAY RESULT IN GUSTY EAST/SOUTHEAST WINDS DEVELOPING
INTO EASTERN IA ESPECIALLY AT KCID TERMINAL. COLD FRONT ANTICIPATED
TO PASS THROUGH THE TERMINALS THIS AFTERNOON. REDEVELOPMENT OF SOME
SHOWERS AND STORMS IS POSSIBLE AHEAD OF THE FRONT FAVORING KMLI AND
KBRL...BUT NOT CONFIDENT TO INTRODUCE AT THIS TIME DUE TO POSSIBLE
LINGERING DEBRIS CLOUDS FROM AM CONVECTION AND WEAK FRONTAL CONVERGENCE.

&&

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

$$

UPDATE...RP KINNEY
SYNOPSIS...ERVIN
SHORT TERM...ERVIN
LONG TERM...08
AVIATION...05





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