Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 250425
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1125 PM CDT SUN AUG 24 2014

.UPDATE...
ISSUED AT 934 PM CDT SUN AUG 24 2014

WITH A MOISTURE RICH LLJ TRANSPORTING ELEVATED INSTABILITY INTO THE
UPPER MIDWEST...AND NEW CONVECTION FIRING FROM WESTERN IOWA
THROUGH SOUTHEAST MN...IT NOW APPEARS THE CHANCES FOR LATE
NIGHT/EARLY MORNING STORMS FOR OUR CWA HAVE INCREASED. I HAVE
BUMPED UP POPS TO HIGH CHANCE FOR OUR NORTHWEST 1/3...AND
INCREASED SLIGHTS THROUGH THE QUAD CITIES. IF THE NAM AND GFS ARE
CORRECT...WE MAY NEED TO INCREASE FURTHER AS THEY BOTH SUGGEST
ORGANIZED CONVECTION THROUGH ABOUT 15Z.

ERVIN

&&

.SYNOPSIS...
ISSUED AT 342 PM CDT SUN AUG 24 2014

THE STREAK OF THE LATEST 90 DEG READINGS AT BOTH BRL AND CID ASOS
HAS ENDED. FULL SUNSHINE AND SOUTHERLY WINDS HAS BOOSTED TEMPS
INTO THE UPPER 80S AND LOWER 90S THIS AFTERNOON... WHICH COMBINED
WITH DEWPTS IN THE 70S MAKING FOR VERY HOT AND HUMID CONDITIONS THE
LIKES OF WHICH WE HAVE NOT REALLY SEEN THIS SUMMER... WITH
HEAT INDEX READINGS AROUND 100 OR IN THE LOWER 100S. IMPRESSIVE
OCCLUDING CYCLONE WAS LOCATED OVER THE NORTHERN PLAINS USHERING IN
UNSEASONABLY COLD AIR RESPONSIBLE FOR SOME LIGHT ACCUMULATING SNOW
IN HIGHER ELEVATIONS OVER PORTIONS OF MT/WY. FRONTAL BOUNDARY
EXTENDS FROM THE LOW SWD THROUGH FAR NORTHWEST IA THEN CONTINUING
THROUGH CENTRAL KS...AND LIKELY TO SERVE AS FOCAL POINT FOR SOME
SHOWERS AND STORMS TONIGHT AS UPPER LEVEL ENERGY RIDING UP BACKSIDE
OF MID-LOWER MISSISSIPPI VLY HEAT DOME INTERACTS WITH FRONT AND
POOLING MOISTURE.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 342 PM CDT SUN AUG 24 2014

FRONTAL BOUNDARY INTO WESTERN IA TO MOVE SLOWLY TONIGHT AND REMAIN
WEST OF CWA DUE TO NEAR PARALLEL ALIGNMENT WITH SOUTHWEST FLOW
ALOFT. THIS BOUNDARY WILL BE FOCUS FOR SOME SHOWERS AND STORMS
TONIGHT. ANTICIPATE WILL SEE AT LEAST SCATTERED SHOWERS AND POSSIBLY
FEW STORMS DEVELOP INTO NORTHEAST IA AND NORTHWEST IL LATE TONIGHT
WITH ELEVATED THETA-E ADVECTION WITH VEERING BRANCH OF LOW LEVEL
JET. THIS ACTIVITY WILL LIKELY PERSIST THROUGH MID AM ON MONDAY
MAINLY NORTH OF I-80 BEFORE DIMINISHING WITH WEAKENING JET AND
THETA-E ADVECTION. MAY SEE SOME REDEVELOPMENT BY MID TO LATE
AFTERNOON ACROSS NORTHWEST THIRD AGAIN WITH FRONT SAGGING IN...BUT
WITH WEAK FRONTAL CONVERGENCE AND LACK OF OTHER COHERENT TRIGGER
OR FORCING MECHANISM FOR NOW I KEPT ONLY SLIGHT CHANCE POPS.

LOWS TONIGHT NEAR TO A BIT WARMER WITH LIGHT S/SE WINDS SHOULD
RESULT IN LOWS OF 68-74F.

MONDAY LOOKS TO BE THE LAST DAY OF THE HOT WEATHER BEFORE FRONT
MOVES INTO THE REGION. ANTICIPATE WIDESPREAD LOWER 90S ESPECIALLY
FROM AROUND QUAD CITIES ON SOUTH AND EAST... WHICH COMBINED WITH
DEWPTS IN THE 70S SHOULD RESULT IN DANGEROUS AFTERNOON HEAT INDICES
ONCE AGAIN OF 100-105. AS RESULT...HAVE EXPANDED HEAT ADVISORY UP
THROUGH THE QC METRO. BIT MORE UNCERTAINTY ON HEAT HEADLINES EXIST
ACROSS NORTHEAST IA INTO NORTHWEST IL DUE TO LIKELIHOOD OF CONVECTIVE
DEBRIS...THUS HAVE HELD OFF THERE FOR NOW.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 342 PM CDT SUN AUG 24 2014

INCREASING LIKELIHOOD OF EPISODES OF SIGNIFICANT AND LOCALLY HEAVY TO
VERY HEAVY RAINS WITH POSSIBLE WATER ISSUES BY NEXT WEEKEND AND
COOLER TEMPERATURES THE MAIN FORECAST ISSUES.

LONG TERM FORECAST CONFIDENCE...FAIR TO GOOD (AVERAGE TO ABOVE
AVERAGE) ON SIGNIFICANT RAINS AND COOLER THE NEXT SEVERAL DAYS.  POOR
TO VERY POOR (BELOW TO WELL BELOW AVERAGE) ON LOCATIONS...TIMING AND
AMOUNTS.  TEMPERATURES LIKELY WILL NEED LOWERING FOR HIGHS MIDDLE
TO LATE NEXT WEEK AT LEAST A FEW MORE DEGREES...POSSIBLY 5 PLUS.

OVERVIEW...INITIALIZATION AND VERIFICATION SHOWS COLDER AND STRONGER
UPPER LEVEL AND SURFACE SYSTEM IN NW NORTH AMERICA.  THE RUN TO RUN
VARIANCE INTER AND INTRA-MODEL IS GREATER THAN NORMAL BUT ALL SUPPORT
FAVORABLE TO VERY FAVORABLE REGIME OF STALLED BOUNDARY NEAR TO JUST
SOUTH OF AREA WITH UPPER LOW TO THE WEST FOR SEVERAL DAYS OF
CLOUDS...RAIN IN FORM OF SHOWERS AND STORMS...POSSIBLY HEAVY RAIN AT
TIMES. LOCAL TOOLS SUGGEST GOING WITH A STRAIGHT MIX THE BEST COURSE
OF ACTION (25 PERCENT EACH GFS/UKMET/GEM-NH/UKMET) AS LATENT HEAT
FEEDBACK WILL BE IMPORTANT TO ASSESS FOR MIDDLE/LATE NEXT WEEK. BASED
ON PAST CASES THE BIASES OF SOLUTIONS USED...NEXT 24-36 HRS BETTER
CONFIDENCE ON THE RISK...TIMING...LOCATION AND AMOUNTS.

MONDAY NIGHT...RAISED POPS NW SECTIONS AS MATURING AREA OF SHOWERS
AND EMBEDDED THUNDERSTORMS TRAVELS ALONG ADVANCING COLD FRONT.
LOCAL FORCING AND QPF TOOLS SUGGEST LIGHT TO MODERATE AMOUNTS ARE
SUGGESTED WITH SOME RAIN TOTALS OF UP TO AN INCH POSSIBLE NW
SECTIONS FOR LATER SHIFTS TO ASSESS.  HAVE LIKELY POPS NW TO LOW
CHANCE SE SECTIONS WITH BEST CHANCES OF RAIN...PROBABLY WELL AFTER
MIDNIGHT.   MINS...UPPER 60S FAR NW TO LOWER 70S ELSEWHERE.

TUESDAY...QUITE A CHALLENGE AS SEASONALLY STRONG BUT MODERATELY SLOW
MOVING FRONT PASSES WITH USING 40-50 POPS ALONG AND MOSTLY BEHIND
FRONT. LOCAL FORCING TOOLS SUGGEST HIGHER POPS WILL BE NEEDED WITH
AREAS OF LIGHT TO MODERATE RAINS MOST LOCATIONS AND AGAIN ISOLATED
AMOUNTS UP TO AN INCH POSSIBLE.  HIGHS IN THE UPPER 70S MAY BE
POSSIBLE FAR NW SECTIONS WITH AROUND 90 DEGREES IF LOTS OF SUNSHINE
OCCURS THERE WITH NEAR HEAT ADVISORY POSSIBLE.  TRENDS SUGGEST THIS
FRONT WILL BE FASTER AND IF SO HIGHS WILL NEED MORE TRIMMING LOWER BY
1-2 CATEGORIES OVER NW 1/2 TO 2/3 OR MORE OF THE FORECAST AREA.

TUESDAY NIGHT THROUGH THURSDAY...NORTHEAST TO EAST FLOW BEHIND THE
FRONT AND OFF LAKE MICHIGAN...COUPLED WITH OVERRUNNING FROM UPPER
LOW TO THE WEST SUPPORTS HIGH CHANCE TO LIKELY POPS WITH TRENDS
SUGGESTING HIGHER POPS WILL BE NEEDED WHEN TIMING OF DISTURBANCES
ARE BETTER KNOWN. TEMPERATURES LIKELY MOST AREAS STILL TOO MILD MOST
PERIODS BY 1 TO 2 CATEGORIES WITH HIGHS STRUGGLING TO MAKE 70 DEGREES
POSSIBLE NORTH ON THURSDAY.  RAIN TOTALS OVER THIS 48 HOUR PERIOD
SHOULD END UP WITH WIDESPREAD MODERATE TO HEAVY IN THE .5 TO 1.5 INCH
RANGES. KEEP IN MIND THIS WOULD BE ON TOP OF THE MONDAY NIGHT INTO
TUESDAY.

THURSDAY NIGHT INTO FRIDAY...EVIDENCE OF GREATEST FORCING FOR HEAVY
TO VERY HEAVY RAINS AS SW FORCING COLLIDES WITH EASTERLY FLOW OFF
LAKE MICHIGAN WHICH IS A FAVORED VERY RAIN SITUATION.  PW/S 1.5 TO
NEAR 2 INCHES AND GENERAL SUSTAINED FORCING SUGGEST RAIN TOTALS OF 2
TO 3 INCHES APPEAR POSSIBLE.  TEMPERATURES WILL BE A CHALLENGE WITH
TRACK OF FRONT AND SURFACE WAVE THE KEY AS HIGHS MAY STILL BE TOO
WARM. CURRENT POPS APPEAR TOO LOW BY AT LEAST 10-20 PERCENT FOR LATER
SHIFTS.

FRIDAY NIGHT THROUGH SUNDAY...UPPER LOW TRACK AND SPEED KEY TO HOW
QUICKLY CLOUDS AND POPS END FROM NW TO SE.  TRENDS SUGGEST LIGHT TO
MODERATE AMOUNTS WITH HIGHS 75 TO 85 AND LOWS MOSTLY IN THE 60S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1122 PM CDT SUN AUG 24 2014

AN APPROACHING FRONT BRINGS THE THREAT FOR SHOWERS AND
THUNDERSTORMS TO EASTERN IOWA AFTER 08Z LATE TONIGHT.  IT IS NOT
CERTAIN THAT THEY WILL IMPACT THE AREA...AND A VCSH IS CONTINUED
TO BE USED TO DESCRIBE THIS LATE NIGHT THREAT WITH TEMPORARY 5SM
TSRA POSSIBLE AT BOTH CID AND DBQ. IF THE LINE OF STORMS VERIFY
OVERNIGHT IN EASTERN IOWA...MVFR CONDITIONS ARE LIKELY TO OCCUR
ESPECIALLY AT CID AND DBQ AND POSSIBLY AT MLI. OTHERWISE...LATE NIGHT
AND EARLY MORNING MVFR FOG IS LIKELY AT ALL SITES DUE TO THE VERY
MOIST AIR MASS IN PLACE IN THE REGION. AFTER 15Z MONDAY...A RETURN
TO HOT VFR WEATHER IS EXPECTED. SOUTH TO SOUTHEAST WINDS OF 5 TO 9
KTS ARE EXPECTED THROUGH THE PERIOD. ANOTHER THREAT FOR A SHOWER
OR STORM WILL ARRIVE BY LATE AFTERNOON MONDAY AND CONTINUE INTO
MONDAY NIGHT.
ERVIN


&&

.HYDROLOGY...
ISSUED AT 342 PM CDT SUN AUG 24 2014

MONDAY NIGHT THROUGH AT LEAST FRIDAY...A SLOWLY MOVING
FRONT WILL STALL NEARBY PRODUCING EPISODES OF SHOWERS AND STORMS.
THIS PATTERN IS HISTORICALLY FAVORABLE TO VERY FAVORABLE FOR
WIDESPREAD SIGNIFICANT TO HEAVY RAINFALL OVER A SEVERAL DAY PERIOD
OVER THE FORECAST AREA. LOCAL TOOLS AND TECHNIQUES OF AREA MOISTURE
LEVELS AND FORCING DURATION SUGGEST 2 TO LOCALLY UP TO 5 INCHES OR
MORE OF RAIN APPEARS REASONABLE...MAINLY ALONG AND NORTH OF HIGHWAY
34 CORRIDOR. BASED ON CURRENT SOIL MOISTURE LEVELS...ADDITIONAL RAIN
TOTALS OF OVER 2 INCHES COULD RESULT IN LOWER END WATER ISSUES. TOTAL
RAIN AMOUNTS OF 4 INCHES OR MORE SHOULD RESULT IN SIGNIFICANT RIVER
FLOODING CONCERNS AND IF OCCURS IN SHORTER PERIOD OF TIME...FLASH
FLOODING. THE RISK OF THIS HYDROLOGICAL EVENT WILL AGAIN BE BETTER
KNOWN IN THE NEXT 24 TO 36 HOURS.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HEAT ADVISORY FROM NOON TO 8 PM CDT MONDAY FOR LOUISA-MUSCATINE-
     SCOTT.

     HEAT ADVISORY UNTIL 8 PM CDT MONDAY FOR DES MOINES-HENRY IA-LEE-
     VAN BUREN.

IL...HEAT ADVISORY FROM NOON TO 8 PM CDT MONDAY FOR BUREAU-HENRY IL-
     MERCER-PUTNAM-ROCK ISLAND-WHITESIDE.

     HEAT ADVISORY UNTIL 8 PM CDT MONDAY FOR HANCOCK-HENDERSON-
     MCDONOUGH-WARREN.

MO...HEAT ADVISORY UNTIL 8 PM CDT MONDAY FOR CLARK-SCOTLAND.

&&

$$

UPDATE...ERVIN
SYNOPSIS...05
SHORT TERM...05
LONG TERM...NICHOLS
AVIATION...ERVIN
HYDROLOGY...NICHOLS





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