Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 261143
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
643 AM CDT TUE AUG 26 2014

.UPDATE...
ISSUED AT 546 AM CDT TUE AUG 26 2014

MCS OVER CENTRAL IA IS ADVANCING EAST AND WILL REACH BENTON AND
BUCHANAN COUNTIES WITHIN THE HOUR. MAIN THREAT LOOKS TO BE HEAVY
RAINFALL. WELL DEFINED OUTFLOW BOUNDARIES OR GRAVITY WAVES ON DMX
RADAR MAY TRIGGER ADDITIONAL STORMS FURTHER SOUTH AS THEY ADVANCE
INTO THE MORE UNSTABLE ENVIRONMENT WITH STEEPER MID LEVEL LAPSE
RATES AND MUCAPES OVER 2000 J/KG IN EASTERN IA AND NW IL AROUND
SUNRISE. MORE ISOLATED CELLS CONTINUE TO FESTER NORTH OF THE QUAD
CITIES TO STERLING CORRIDOR.

HAVE UPDATED THE FORECAST FOR LIKELY TO CATEGORICAL POPS FOR THE
ORGANIZED STORM CLUSTER LIKELY TO IMPACT AREAS ALONG AND NW OF A
CID TO DBQ AXIS OVER THE NEXT SEVERAL HOURS. HEAVY RAINFALL RATES
ARE LIKELY AND WILL NEED TO MONITOR CLOSELY FOR POSSIBLE CELL
TRAINING AND POTENTIAL FLASH FLOODING AS THIS COMPLEX WILL MOVE
OVER THE AREA THAT HAD RADAR INDICATED WIDESPREAD RAINFALL TOTALS
OF 1 TO 2 PLUS INCHES JUST 24 HOURS AGO.

&&

.SYNOPSIS...
ISSUED AT 333 AM CDT TUE AUG 26 2014

THE SURFACE FRONT CONTINUES TO SLOWLY ADVANCE SOUTHEAST ACROSS THE
FORECAST AREA EARLY THIS MORNING. UP UNTIL ROUGHLY 230 AM...
CONVECTION HAS BEEN PRIMARILY CONFINED TO A LARGE...NEARLY
STATIONARY MCS OVER EASTERN NEB INTO WESTERN IA. ISOLATED...FAST
DEVELOPING CELLS HAVE BEEN FORMING AHEAD OF THE FRONT IN THE PAST
HALF HOUR...THAT RAN ROUGHLY FROM JO DAVIESS COUNTY SW TO
FAIRFIELD. TEMPERATURES AND DEWPOINTS WERE IN THE 70S ALONG AND
AHEAD OF THIS BOUNDARY...WHILE READINGS IN THE UPPER 60S HAD
REACHED INDEPENDENCE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 333 AM CDT TUE AUG 26 2014

PRIMARY FOCUS IS CONVECTIVE TRENDS THROUGHOUT. BASED ON RAP
CONVERGENCE FIELDS IN THE 800-850 MB LAYER THAT CORRELATE WELL WITH
THE DEVELOPING CONVECTION JUST WEST OF THE QC METRO...A SMALL MCS IS
LIKELY TO DEVELOP IN THIS AREA EXTENDING E-SE EARLY THIS MORNING.
WITH THE LINGERING DEEP MOISTURE-RICH AIRMASS...THE PRIMARY
THREAT FROM THESE STORMS WILL BE HEAVY RAINFALL RATES AND POSSIBLE
SMALL HAIL AND STRONG GUSTY WINDS. THE SEVERE POTENTIAL APPEARS TO
BE LIMITED BY THE WEAK SHEAR VALUES EARLY THIS MORNING. THE
QUESTION THEN TURNS TO THE TRENDS WITH THE UPSTREAM MCS...WHICH IS
TIED TO A SEPARATE SHORTWAVE ROUNDING THE UPPER HIGH TO OUR
SOUTH...AND BETTER ELEVATED CONVERGENCE. AT THIS TIME...MOST
MODELS HAVE THIS REACHING INTO AT LEAST THE WEST AND DISSIPATING
THIS MORNING...WHICH IS HOW THE FORECAST IS TRENDED.

LATER TODAY...WILL KEEP AT LEAST SLIGHT CHANCES FOR THUNDERSTORMS
GOING ALONG AND BEHIND THE FRONT...WHICH IS EXPECTED TO REACH AN
AXIS FROM SOUTHERN LAKE MI TO CENTRAL MO BY EVENING. HIGH PRESSURE
BUILDING INTO SOUTHERN MN AND NORTHERN IA SHOULD KEEP THE FAR NORTH
DRY...AND USHER DRIER AIR INTO THE REGION ON LIGHT NORTHERLY WINDS.
THIS SHOULD HOLD HIGHS IN THE 70S ACROSS THE NW...WHILE THE FAR
SOUTH COULD AGAIN REACH THE UPPER 80S BEFORE THE MIDDAY FROPA.

TONIGHT...MCS PARAMETERS ARE LOOKING MORE FAVORABLE FOR AN
ORGANIZED COMPLEX TO MOVE INTO THE FORECAST AREA THAN THE CURRENT
SETUP AND HAVE KEPT LIKELY POPS GOING ACROSS MUCH OF THE AREA
AFTER MIDNIGHT. WILL HAVE A CONTINUED THREAT OF HEAVY RAINFALL...
WHICH WILL NEED TO BE WATCHED CLOSELY AS IT MAY AFFECT AREAS
SATURATED BY RECENT HEAVY RAINS...ESPECIALLY IN THE NORTH. WITH
THE LOW LEVELS FIRMLY ON THE COOL SIDE OF THE SURFACE FRONT...LOW
TEMPERATURES WILL RETURN CLOSER TO LATE AUGUST NORMALS...FROM THE
UPPER 50S NORTH TO UPPER 60S SOUTH.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 333 AM CDT TUE AUG 26 2014

THE OVERALL WEATHER PATTERN IS SUPPORTIVE OF NOCTURNAL THUNDERSTORM
COMPLEXES ACROSS THE MIDWEST. WHERE EACH DEVELOPS AND MOVES AFFECTS
SUBSEQUENT DEVELOPMENT. AS A RESULT...THERE WILL BE PERIODS OF DRY
WEATHER THAT MAY BE 6-12 HOURS IN DURATION.

BASED ON INTERNAL SIGNALS...THERE SHOULD BE A NOCTURNAL THUNDERSTORM
COMPLEX ACROSS CENTRAL IOWA AT SUNRISE WEDNESDAY THAT SLOWLY MOVES
INTO THE AREA AND DISSIPATES DURING THE MORNING. BOUNDARIES LEFT
OVER FROM THIS COMPLEX WILL PROVIDE THE FOCUS FOR DIURNAL
DEVELOPMENT WEDNESDAY AFTERNOON/EVENING. THE DIURNAL DEVELOPMENT IS
EXPECTED TO BE ISOLATED TO WIDELY SCATTERED IN NATURE.

ANOTHER NOCTURNAL THUNDERSTORM COMPLEX WILL DEVELOP WEDNESDAY
EVENING IN WESTERN/NORTHWEST IOWA AND MOVE EAST NORTHEAST OVERNIGHT.
THE NORTHWEST THIRD TO HALF OF THE AREA HAS THE BEST CHANCE OF
SEEING RAIN. DUE TO HIGH MOISTURE LEVELS...LOCALLY HEAVY RAINFALL IS
POSSIBLE.

THE WEDNESDAY NIGHT STORM COMPLEX IS EXPECTED TO MOVE INTO WISCONSIN
AND DISSIPATE THURSDAY MORNING. BOUNDARIES FROM THIS COMPLEX WILL
PROVIDE THE FOCUS FOR ISOLATED TO SCATTERED DIURNAL CONVECTION
THURSDAY AFTERNOON/EVENING.

ALTHOUGH THE SIGNAL IS WEAKER...YET ANOTHER NOCTURNAL THUNDERSTORM
COMPLEX SHOULD DEVELOP THURSDAY NIGHT ACROSS NORTHERN IOWA AND MOVE
GENERALLY EAST NORTHEAST. THE NORTHWEST HALF OF THE AREA HAS THE
BETTER CHANCE AT SEEING RAIN.

FRIDAY ON...
OTHER THAN SUNDAY NIGHT WERE THE MODEL CONSENSUS HAS SLIGHT CHANCE
POPS...THERE ARE CHANCE POPS IN EACH 12 HOUR PERIOD FROM FRIDAY
THROUGH MONDAY. TEMPERATURES SHOULD BE NEAR TO SLIGHTLY ABOVE NORMAL.

THE LARGE SCALE PICTURE CONTINUES TO SUGGEST AN ACTIVE WEATHER
PATTERN WITH A FRONT MOVING THROUGH THE AREA. IT WILL NOT RAIN
CONTINUOUSLY THE ENTIRE TIME. THERE WILL BE PERIODS OF DRY WEATHER
THAT MAY LAST 6 OR 12 HOURS. ONE POSSIBLE PERIOD OF DRY WEATHER MAY
BE SATURDAY NIGHT INTO SUNDAY NIGHT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 642 AM CDT TUE AUG 26 2014

CLUSTER OF THUNDERSTORMS WITH HEAVY RAINFALL MOVING INTO EASTERN
IA EARLY THIS MORNING WILL LIKELY IMPACT ALL TAF SITES BEFORE
MID MORNING WITH MVFR CONDITIONS AND A PERIOD OF NORTHWEST WINDS
GUSTING 25 TO 30 KTS. THIS SHOULD MOVE OUT BY MIDDAY WITH VFR
CONDITIONS AS MORE STABLE AIR MOVES IN BEHIND THE SOUTHEAST MOVING
COLD FRONT. ANOTHER STORM COMPLEX IS EXPECTED LATE TONIGHT.
CURRENT INDICATIONS POINT TOWARD THUNDERSTORMS LIKELY AFFECTING
CID...DBQ AND MLI BETWEEN MIDNIGHT AND SUNRISE...WITH SLIGHTLY
LOWER CHANCES FOR BRL.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...08
AVIATION...SHEETS






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