539
FXUS63 KDVN 150456
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1156 PM CDT SAT SEP 14 2019
..AVIATION UPDATE
UPDATE
ISSUED AT 614 PM CDT SAT SEP 14 2019
ALL OUR FOCUS WILL BE ON THE ONSET OF THE STORMS FROM CENTRAL IOWA
LATER THIS EVENING IN THE WEST/NORTHWEST. ON THE LATEST RAP DATA
ON SPC'S MESOPAGE, WE STILL SEE A CUT OFF MUCAPE TO NIL OVER
EASTERN IOWA, THUS, DESPITE THE STORMS CLOSE PROXIMITY TO EASTERN
IOWA, I DON'T EXPECT A RAPID INTENSIFICATION, NOR WIDESPREAD
DEVELOPMENT OF STORMS INTO OUR AREA QUITE YET. LATER TONIGHT, THE
STORMS SHOULD EXPAND INTO AN MCS WITH HEAVY RAIN OVER OUR AREA,
WHICH STILL IN SOMEWHAT IN QUESTION ON HOW FAR NORTH OR SOUTH THIS
TRACKS.
SYNOPSIS
ISSUED AT 312 PM CDT SAT SEP 14 2019
18Z SURFACE DATA HAS A WEAK WARM FRONT RUNNING FROM EASTERN IOWA
BACK INTO THE EASTERN DAKOTAS. DEW POINTS WERE IN THE 50S ACROSS
THE GREAT LAKES WITH 60S AND 70S FROM THE MISSISSIPPI VALLEY INTO
THE PLAINS.
SHORT TERM
(THIS EVENING THROUGH SUNDAY)
ISSUED AT 312 PM CDT SAT SEP 14 2019
HEADLINE CHANGES...THE FLASH FLOOD WATCH FOR JO DAVIESS,
STEPHENSON AND CARROLL COUNTIES HAS BEEN EXTENDED UNTIL 10 AM
SUNDAY MORNING.
THROUGH LATE THIS AFTERNOON...
A PERSISTENT DECAYING STORM COMPLEX ACROSS IOWA WILL LIKELY PUSH
SPRINKLES OR SOME ISOLATED SHOWERS SOUTH OF I-80 AND NORTH OF
HIGHWAY 34 THROUGH LATE AFTERNOON IN EASTERN IOWA.
TONIGHT AND SUNDAY...
THE PERSISTENT COMPLEX ACROSS IOWA TODAY RAISES QUESTIONS AS TO HOW
STORMS WILL DEVELOP AND EVOLVE TONIGHT.
TWO SCENARIOS ARE POSSIBLE TONIGHT. WHAT IS COMMON BETWEEN EITHER
SCENARIO IS HIGH MOISTURE LEVELS, UNSTABLE AIR ALOFT AND FORCING
FROM A PASSING UPPER LEVEL DISTURBANCE THAT WILL RESULT IN HEAVY
RAINFALL.
SCENARIO 1 INVOLVES NEW STORM INITIATION ALONG THE IA/MN BORDER
DURING THE EVENING THAT MOVES SOUTHEAST OVERNIGHT AND EXITS THE AREA
LATE SUNDAY MORNING.
IF THIS SCENARIO OCCURS THEN THE INTERNAL SIGNAL POINTS TO THE
HEAVIEST RAINFALL OCCURRING BETWEEN HIGHWAY 20 AND HIGHWAY 30
GENERALLY NORTH OF AN INDEPENDENCE, IA TO STERLING, IL LINE.
SCENARIO 1 IS WHAT THE CURRENT FORECAST IS BASED UPON.
SCENARIO 2 WOULD HAVE NEW CONVECTION DEVELOP WITH THE REMNANTS OF
THE CURRENT SYSTEM ACROSS IOWA. IF THIS OCCURS THEN THE HEAVIER
RAINFALL WOULD OCCUR ACROSS SOUTHEAST IOWA INTO WEST CENTRAL
ILLINOIS.
IF SCENARIO 2 OCCURS THEN THE OVERALL FORECAST MESSAGE WOULD NEED TO
BE CHANGED CONSIDERABLY.
LONG TERM
(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 312 PM CDT SAT SEP 14 2019
TARTING THE PERIOD OFF WITH ADDING SOME PRECIPITATION CHANCES TO
THE SOUTHERN AREAS FOR SUNDAY EVENING. THE FRONT WILL BE SITUATED
ACROSS THE FAR SOUTHERN PART OF THE FORECAST AREA AND WITH SOME
CONVERGENCE AND MOISTURE POOLING ALONG THE FRONT, FELT THERE IS
ENOUGH OF A CHANCE FOR SHOWERS AND THUNDERSTORMS TO ADD A SLIGHT
CHANCE IN FOR THE EVENING HOURS.
HIGH PRESSURE BUILDS IN AT THE SURFACE THROUGH THE DAY MONDAY WITH
RETURN FLOE BEING SEEN OVER THE PLAINS INTO WESTERN IOWA AS THE
UPPER LEVEL RIDGE IS CENTERED UP AND DOWN THE MISSISSIPPI RIVER
VALLEY. THE SETUP LOOKS GOOD FOR PATCHY TO EVEN AREAS OF FOG WITH
GOOD MOISTURE AT THE SURFACE UNDER THE INVERSION AND MOSTLY CLEAR
SKIES SUNDAY NIGHT INTO MONDAY. THE AREAS WITH THE WEAKEST LOW LEVEL
FLOW TO SUPPORT FOG DEVELOPMENT WILL BE ACROSS THE NORTHEAST
QUADRANT OF THE FORECAST AREA SO HAVE LIMITED THE MENTION OF FOG DO
THOSE AREAS.
TEMPERATURES ON MONDAY WILL BE A BIT WARMER THAN ON SUNDAY AND WILL
BE WELL ABOVE NORMAL IN THE 80S. THINK THAT EVEN IF FOG DOES FORM
AND HOLDS ON LONGER INTO THE MORNING, TEMPERATURES SHOULD RECOVER
RATHER QUICKLY TO GET THOSE AREAS INTO THE 80S.
THE BIG STORY FOR THE WEEK WILL BE HOT AND HUMID. THE UPPER LEVEL
RIDGE SITS IN PLACE THROUGH THE WEEK. TEMPERATURES MONDAY THROUGH
WEDNESDAY WILL BE WARMEST WITH HIGHS IN THE MID TO UPPER 80S AND
WITH DEWPOINTS IN THE UPPER 60S TO LOW 70S, IT WILL BE QUITE
UNCOMFORTABLE FOR THIS TIME OF YEAR.
A FEW SHORTWAVE TROUGHS WILL MOVE THROUGH THE FLOW TO PROVIDE
CHANCES FOR THUNDERSTORMS BEGINNING ON WEDNESDAY AND CONTINUING
THROUGH THE WEEK. THE CHANCES FOR WIDESPREAD THUNDERSTORMS IS
HIGHEST WEDNESDAY NIGHT AS THE PRIMARY WAVE OF SHORTWAVE ENERGY
MOVES ACROSS THE AREA. TIMING COULD CHANGE THIS TO EARLIER OR
LATER, WHICH WILL NEED TO BE WATCHED FOR ANY STRONGER STORM
POTENTIAL OR HEAVY RAIN/FLOODING POTENTIAL. MOVING THROUGH THE
REMAINDER OF THE WEEK, THERE WILL BE MINOR WEAK SHORTWAVE ENERGY
MOVING THROUGH THE SOUTHWEST FLOW ACROSS OUR AREA PERIODICALLY,
BUT TIMING THOSE PIECES OF ENERGY IS NOT ANYTHING THAT CAN BE DONE
AT THIS POINT WITH HIGH CONFIDENCE. ALSO, WITH HIGH DEWPOINTS
PROVIDING DECENT INSTABILITY WILL LIKELY LEAD TO AT LEAST SOME
DAILY DIURNAL CONVECTION. THEREFORE THUNDERSTORM CHANCES ARE IN
THE FORECAST THROUGH ALL PERIODS.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1153 PM CDT SAT SEP 14 2019
ACTIVE NEXT 6 HOURS FOR THE TAF SITES WITH SHOWERS AND
THUNDERSTORMS AFFECTING MANY OF THE SITES. EARLY IN THE MORNING,
WE MAY SEE SOME IFR AND HAVE STARTED TO TREND THAT WAY WITH LOW
END MVFR. AFTER THE RAIN AND STORMS TONIGHT, EXPECT VFR CONDITIONS
FOR THE REST OF THE PERIOD.
HYDROLOGY
ISSUED AT 1129 AM CDT SAT SEP 14 2019
ROUTED WATER MOVING THROUGH THE RIVER SYSTEMS ALONG WITH
ADDITIONAL HEAVY RAIN POTENTIAL TONIGHT IS CAUSING FORECAST RISES,
MANY WITHIN BANK RISES, ACROSS THE AREA.
THE HARDEST HIT LOCAL BASINS HAVE BEEN THE PECATONICA AND ROCK
RIVER BASINS AND WE ARE GETTING A BETTER HANDLE ON THE FLOWS FROM
RAINS THAT ALREADY FELL, HOWEVER THERE DOES REMAIN A BIT OF
UNCERTAINTY ON HOW HIGH THE CRESTS WILL BE. THE PECATONICA IN
FREEPORT IS CRESTING CURRENTLY AND WILL FALL LESS THAN A FOOT
BEFORE STARTING TO GO UP AGAIN AS MORE WATER MOVES DOWN FROM
UPSTREAM.
ON THE ROCK, THE FORECAST FOR THE GAGE AT COMO HAS GONE DOWN THIS
MORNING AND THE RATE OF RISE HAS SLOWED, GIVING LESS CONFIDENCE
THAT THE RIVER WILL HIT THE FLOOD STAGE OF 12.5 FT EVEN THOUGH
IT'S ONLY A HALF FOOT FROM THAT LEVEL CURRENTLY. BECAUSE OF THIS,
OPTED TO HOLD ONTO THE FLOOD WATCH AND WILL RE-EVALUATE THIS
AFTERNOON. DOWNSTREAM AT JOSLIN, IT MAY BE NOTICED THAT THE
HYDROGRAPH IS NOW SHOWING THE RIVER TO RISE TO 14.1 FEET. THINK
THE RISE IS GOING TO BE VERY NEAR 14 FT, BUT DON'T HAVE ENOUGH
CONFIDENCE THAT IT WILL REACH OR EXCEED 14 FT TO PUT OUT A NEW
FLOOD WARNING FOR MODERATE FLOODING YET. WILL CONTINUE TO MONITOR.
THERE IS A CHANCE FOR HEAVY RAINS TONIGHT, IF HEAVIER RAINS FALL
THAN IS EXPECTED, ADDITIONAL RIVER FLOODING COULD OCCUR.
DVN WATCHES/WARNINGS/ADVISORIES
IA...FLASH FLOOD WATCH UNTIL 7 AM CDT SUNDAY FOR BUCHANAN-DELAWARE-
DUBUQUE-JACKSON-JONES.
IL...FLASH FLOOD WATCH UNTIL 10 AM CDT SUNDAY FOR CARROLL-JO DAVIESS-
STEPHENSON.
MO...NONE.
UPDATE...ERVIN
SYNOPSIS...08
SHORT TERM...08
LONG TERM...BROOKS
AVIATION...GIBBS
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