Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 202027
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
327 PM CDT SAT SEP 20 2014

.SYNOPSIS...
ISSUED AT 326 PM CDT SAT SEP 20 2014

COLD FRONT AT 3 PM WAS EVIDENT ON VISIBLE SATELLITE AND SURFACE
PRESSURE FIELDS FROM LAKE SUPERIOR SW ACROSS CENTRAL WI INTO CENTRAL
IA. IN THE LOCAL AREA...THE BOUNDARY WAS ROUGHLY FROM MANCHESTER TO
BELLE PLAINE. THE FRONT WAS PRIMARILY A WIND SHIFT LINE...WITH
DEWPOINTS TRAILING OFF FROM WIDESPREAD 60S AHEAD OF THE BOUNDARY TO
THE 50S OVER NW IA AND SOUTHERN MN. SCATTERED SHOWERS AND
THUNDERSTORMS WERE WELL AHEAD OF THE BOUNDARY...PRIMARILY ACROSS
NORTHERN IL WITH ISOLATED CELLS IN SE IA. THE HIGH PRESSURE CENTER
OF THIS INCOMING AIRMASS WAS WELL TO THE NW OVER THE NORTHERN
ROCKIES. ALOFT...A SHORTWAVE WAS EVIDENT ON SATELLITE WV IMAGERY
FROM WI SOUTH ALONG THE MS RIVER...HELPING FOCUS THIS CONVECTION.
A DEEPENING...STRONGER SHORTWAVE WAS FURTHER UPSTREAM IN THE NW
FLOW OVER EASTERN ND...PRODUCING A LARGE LINEAR MCS MOVING THROUGH
FAR NE SE AND WESTERN MN.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 326 PM CDT SAT SEP 20 2014

POTENTIAL FOR SEVERE THUNDERSTORMS AHEAD OF THE APPROACHING COLD
FRONT LATE THIS AFTERNOON/EVENING IS THE INITIAL CONCERN...
FOLLOWED BY TEMPERATURES AND POSSIBLE SHOWERS SUNDAY AS THE
NORTHERN PLAINS SYSTEM PASSES TO THE NORTH. MAIN AREA OF CONCERN
IS W CENTRAL IL WHERE ROUGHLY 50 KTS OF 0-6 KM SHEAR AND 30 PLUS
FROM 0-3 KM IS PROGGED TO BUILD INTO THE AREA WHERE MUCAPES ARE IN
A RANGE OF 1500 TO 2000 J/KG. BASED ON CURRENT TRENDS...WITH
CONVECTION PRIMARILY FOCUSED ALONG A PREFRONTAL SURFACE TROUGH AND
AHEAD OF THE MID LEVEL SHORTWAVE MOVING INTO MI AND IN...THE LOCAL
SEVERE POTENTIAL APPEARS TO BE WANING AND MAY BE ABLE TO CANCEL
THE SEVERE THUNDERSTORM WATCH FOR THIS AREA EARLY.

THROUGH THE REST OF TONIGHT INTO TUESDAY...POST FRONTAL NW WINDS ADVECTING
DEWPOINTS IN THE 50S UNDER CLEAR SKIES WILL LEAD TO LOWS IN THE
LOWER TO MID 50S. THE EXCEPTION WILL BE IN THE FAR NORTH AND
NORTHEAST...WHERE SLIGHT CHANCE ARE CONTINUED FOR POSSIBLE SHOWERS
ASSOCIATED WITH THE UPPER LEVEL SHORTWAVE AND TRAILING SURFACE
TROUGH SHOWN REACHING WEST FROM THE GREAT LAKES SUNDAY. HIGHS FROM
THE MID 60S NORTH TO LOWER 70S SOUTH...AT THE LOW END OF
GUIDANCE...LOOK REASONABLE LOOKING AT UPSTREAM VALUES THIS AFTERNOON
IN THE NORTHERN PLAINS.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 326 PM CDT SAT SEP 20 2014

SUNDAY NIGHT THROUGH WEDNESDAY... A LONGWAVE UPPER LEVEL TROF WILL
DIG OVER THE NORTHEASTERN CONUS AS A LONGWAVE RIDGE BUILDS OVER THE
WEST. SURFACE HIGH PRESSURE WILL MOVE INTO THE UPPER MID WEST DURING
THIS TIME FRAME. QUIET FALL WEATHER WILL RESULT WITH NEAR NORMAL
TEMPERATURES. DAYTIME HIGHS WILL RANGE IN THE LOW TO MID 70S WITH
OVERNIGHT LOWS IN THE UPPER 40S TO LOW 50S. OVERNIGHT WEDNESDAY A
WEAK UPPER LEVEL SHORTWAVE WILL UNDERCUT THE UPPER LEVEL RIDGE AND
MOVE ACROSS THE UPPER MISSISSIPPI VALLEY. THE BEST UPPER LEVEL
FORCING WILL BE WEAKENING AS THE WAVE APPROACHES AND IS EXPECTED TO
REMAIN WEST OF THE REGION. HOWEVER THERE WILL STILL BE A CHANCE OF
SHOWERS OR THUNDERSTORM OVER THE NORTHWESTERN PART OF THE FORECAST
AREA. PLEASANT FALL WEATHER CONTINUES THROUGH NEXT WEEKEND WITH
HIGHS IN THE UPPER 70S AND LOWS AROUND 50.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1218 PM CDT SAT SEP 20 2014

SCATTERED SHOWERS AND THUNDERSTORMS WILL IMPACT ALL TERMINALS UNTIL
A COLD FRONT MOVES THROUGH IN THE LATE AFTERNOON HOURS. MVFR TO
BRIEFLY IFR CONDITIONS CAN BE EXPECTED WITH THUNDERSTORMS AND
THERE IS A POSSIBILITY THAT A FEW COULD PRODUCE STRONG WINDS AND
SMALL HAIL. THIS FRONT WILL SHIFT WINDS TO MORE NORTHWESTERLY BY
EVENING...FOLLOWED BY PREVAILING VFR CONDITIONS OVERNIGHT THROUGH
SUNDAY.

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...KUHL
AVIATION...SHEETS





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