Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 201140
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
640 AM CDT WED AUG 20 2014

.SYNOPSIS...
ISSUED AT 251 AM CDT WED AUG 20 2014

ANALYSIS AT 230 AM SHOWS A DEVELOPING ELEVATED BAND OF SHOWERS AND
THUNDERSTORMS JUST STARTING TO DEVELOP FROM SIOUX CITY IOWA TO WEST
OF MEMPHIS MISSOURI. THIS BAND BASED ON TRENDS SUGGEST WILL INTENSIFY
NEXT FEW HOURS AND SLIDE SOUTHEAST. PRESSURE FALL PATTERNS AND LOW
LEVEL JET SUGGEST WITH DAYBREAK THIS BAND WILL WEAKEN AND STRATIFY
TO SHOWERS. BL MOISTURE TOO WET BIAS AND UPSTREAM ENERGY ALL SUGGEST
RISK OF SHOWERS AND STORMS AND WARMER AND HUMID THROUGH THIS WEEKEND
WITH POOR CONFIDENCE OF ANY ORGANIZED EVENT ATTM.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 251 AM CDT WED AUG 20 2014

SHORT TERM FORECAST CONFIDENCE...FAIR TO POOR (AVERAGE TO BELOW
AVERAGE)...ALL SOLUTIONS HAVING PROBLEMS WITH ELEVATED CONVECTION
IMPACTING HIGH TEMPERATURES WITH RISK OF HIGHER CLOUD LEVELS AND
POPS OF MOSTLY LIGHT SHOWERS. TONIGHT... SUBTLE EVIDENCE OF MCS TO
SLIDE OVER NORTH SECTIONS WILL TAKE ANOTHER 12+ HOURS TO BETTER
ASSESS AS TODAY/S PRECIPITATION WILL AFFECT LOW LEVEL JET TONIGHT.

TODAY...PARTLY CLOUDY WITH MATURE AND DISSIPATING SHOWERS AND ISOLATED
STORMS TO SLIDE NORTHEAST ALONG ELEVATED WARM FRONT. HIGHS TO BE GREATLY
IMPACTED BY CLOUDS WITH NORTH SECTIONS POSSIBLY A FEW DEGREES TOO HIGH
IF CLOUDS HANG IN. SOUTH SECTIONS...HEATING AND MIXING WITH WINDS OVER
10 KTS SUGGESTS HIGHS MAY BE UP TO 3 DEGREES TOO LOW...OR LOWER 90S.
SLIGHT CHANCE POPS LATE MORNING ON A BEST FIT FOR DYING PRECIPITATION
BAND FOR NOW.

TONIGHT...LOCAL MCS GENERATION TOOL SUPPORTS SOME SOLUTIONS OF AN MCS
TO DEVELOP OVER NORTHERN IOWA IN EVENING AND TRACK SOUTHEAST OVER NORTH
SECTIONS. LOCAL TECHNIQUES SUGGEST LOCALLY HEAVY RAIN TOTALS OF 1 INCH
OR MORE POSSIBLE WITH GUSTY WINDS AND GOOD OUTFLOW BOUNDARY. HIGH CHANCE
TO LOW LIKELY POPS NORTH REASONABLE WITH LOWS POSSIBLY 3 PLUS DEGREES
TOO HIGH WITH DECENT RAINS FOR LATER SHIFTS DUE TO EVAPORATIVE COOLING.

.LONG TERM...(THURSDAY THROUGH NEXT TUESDAY)
ISSUED AT 251 AM CDT WED AUG 20 2014

THURSDAY AND FRIDAY...ASSESSING THE LATEST 00Z MODEL RUNS AND
ONGOING RUN-TO-RUN ADJUSTMENTS...ANY SCTRD SHOWERS/THUNDERSTORMS OR
LINGERING CLUSTERS SHOULD MIGRATE NORTH AND EAST OUT OF THE DVN CWA
BY NOON THU IF NOT EARLIER...WITH THE TAP INTO BUILDING SOUTHEASTERN
PLAINS THERMAL RIDGE BY SOUTHWESTERLY LLVL FLOW STRENGTHENING BY
AFTERNOON. IF CONVECTIVE DEBRIS CAN CLEAR IN TIME LIKE CURRENTLY
EXPECTED...MOST OF THE CWA SHOULD WARM INTO THE UPPER 80S TO LOWER
90S WITH MAYBE JUST THE NORTHEASTERN THIRD OR QUARTER OF THE CWA
REMAINING IN THE MID 80S WHERE LLVL COOL POOL OR RAIN COOLED SFC
LAYER NEEDS TO BE MODERATED. HEAT INDEX AROUND 100 SOUTH OF I80.
BROAD UPPER RIDGE AXIS AND WARM DOME IMPLANTS ITSELF ACRS THE MS RVR
VALLEY BY LATE IN THE DAY...WITH ONGOING QUESTION OF WHERE/HOW FAR
NORTH OR SOUTH/ THU NIGHT RING OF FIRE PATTERN SETS UP. MCS FORCING
TOOLS AND LOOKING AT WHERE THE MODELS SUGGEST THE MAIN WAVE TO ROLL
ALONG WESTERN FLANK OF THE RIDGE SUGGEST MORE SUBSTANTIAL CONVECTION
TO OCCUR ACRS THE NORTHWESTERN HIGH PLAINS AND DAKOTAS THU
NIGHT...BUT SECONDARY CONVECTIVE FORMATION AXIS MAY OCCUR ALONG THE
IA/MN BORDER EAST SOUTHEASTWARD INTO SOUTHERN WI AND NORTHEASTERN
IL...VERY CLOSE TO IF NOT MAKING IT INTO THE NORTHERN CWA. THE 00Z
GFS AND NAM HAVE TRENDED BACK SOUTH WITH FORCING AND FAVORABLE H85
MB THERMAL GRADIENT THU NIGHT THE NORTH HALF OF THE CWA MAY BE IN
THE CROSS HAIRS FOR NOCTURNAL DEVELOPMENT. FOR NOW WILL KEEP LOW CHC
POPS ACRS MUCH OF THE CWA INTO FRI MORNING...BUT THESE MAY HAVE TO BE
INCREASED OVER THE NEXT FEW FCST PACKAGES IF TRENDS CONTINUE. PWAT
FEED OF 1.8 TO OVER 2 INCHES SUGGEST VERY HEAVY BUT LOCALIZED
RAINFALL POSSIBLE INTO EARLY FRI AM IF CONVECTION CAN MAKE IT OR FORM
ACRS PORTIONS OF THE CWA. MARGINALLY SVR STORM CELLS POSSIBLE WITH
NEAR 1 INCH HAIL AND ISOLATED WIND DOWNBURSTS OF 50-60 MPH...BUT
VERTICAL COLUMN SATURATION WILL HAVE A SAY ON THAT AND PROBABLY BE A
LIMIT. IF UPPER RIDGE AND HEAT DOME CAN AMPLIFY ACRS THE AREA ENOUGH
ON FRI...THE WARMEST DAY OF THE SUMMER SO FAR POSSIBLE WITH MANY MID
90S IF CONVECTIVE DEBRIS/OUTFLOWS CAN CLEAR OR MIX OUT EARLY ENOUGH.
A GOOD BET FOR A HEAT ADVISORY HEADLINE THAT DAY WITH SFC DPTS IN
THE LOW TO MID 70S. THE 00Z RUN ECMWF THE MOST BULLISH IN HANDLING
UPPER RIDGE AMPLIFICATION OVER THE LOCAL AREA AND SHUNTING MAIN RING
OF FIRE TO THE WEST/NORTH/NORTHEAST BY THE END OF THE WEEK. AGAIN
THE NAM AND GFS ARE FURTHER SOUTH AND MAY BE ENOUGH SO THAT NEW MCS
DEVELOPMENT OR AT LEAST SOME STORM CLUSTERS FRI EVENING AND
OVERNIGHT MAY OCCUR IN NORTHERN PORTIONS OF THE CWA.

SATURDAY AND SUNDAY...MORE OF THE SAME WITH TEMPORARY BLOCKED
UPPER RIDGE ACRS THE UPPER MS RVR VALLEY AND WESTERN GRT LKS...
CLUSTERS OF THUNDERSTORMS PROPAGATING AROUND A SUBSTANTIAL HEAT DOME.
THE EURO KEEPS US MAINLY DRY AND HOT...PORTIONS OF THE AREA NEEDING
HEAT HEADLINES...WHILE THE GFS SAYS A FEW COMPLEXES OR STORMS MAKE
IT INTO AT LEAST THE NORTHERN CWA LATE SAT INTO SAT NIGHT...AND
AGAIN LATER ON SUNDAY. LOW CHC POPS WILL RIDE ACRS THE NORTH HALF
TO COVER THIS POTENTIAL.

MONDAY AND NEXT TUESDAY...LONG RANGE INDICATIONS CONTINUE WITH
INCOMING UPPER TROFFINESS AND JET ENERGY TO DAMPEN THE UPPER RIDGE
AND PUMMEL IT OFF TO THE EAST SOME. MORE ROUNDS OF SHOWERS/STORMS
POSSIBLE IN THIS SCENARIO/TRANSITION EARLY NEXT WEEK...WITH A
TEMP COOL DOWN FROM THE NORTHWEST BACK CLOSER TO NORMAL VALUES BY
NEXT TUE.    ..12..

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 636 AM CDT WED AUG 20 2014

GENERALLY VFR CONDITIONS THROUGH THE NEXT 24 HOURS. ISOLATED TO
WIDELY SCATTERED THUNDERSTORMS AND SHOWERS MAY IMPACT CID/BRL
TERMINALS THROUGH AT LEAST 20/14Z AS WEAK UPPER BOUNDARY MOVES NE.
THIS IS HANDLED AS A TEMPO GROUP WITH BRIEF HI MVFR CONDITIONS
POSSIBLE. THEN...PARTLY CLOUDY WITH THUNDERSTORMS IN VICINITY
AFTER 21/02Z AS ANOTHER CONVECTIVE COMPLEX MAY FORM AND IMPACT
SOME OF THE TERMINALS. EXPECT LIGHT SOUTH TO SOUTHWEST WINDS.

&&

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

&&

$$

SYNOPSIS...NICHOLS
SHORT TERM...NICHOLS
LONG TERM...12
AVIATION...NICHOLS





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