Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 220349
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1049 PM CDT MON APR 21 2014

.UPDATE...
ISSUED AT 948 PM CDT MON APR 21 2014

HAVE UPDATED THE FORECAST TO REMOVE MENTION OF SHOWERS IN THE CWA
AS THE COLD FRONT CONTINUES TO MAKE PROGRESS THROUGH OUR FAR
EASTERN AND SOUTHERN COUNTIES. ELSEWHERE...SKIES HAVE ALREADY
CLEARED ACROSS OUR NW HALF AND I MIGHT ADD RIGHT ON SCHEDULE. HIGH
PRESSURE CENTERED IN THE EASTERN DAKOTAS WILL TRACK INTO EASTERN
IOWA TUESDAY AFTERNOON. THIS WILL PROVIDE PLEASANT WEATHER UNTIL
THE NEXT ACTIVE WEATHER ARRIVES BEGINNING ON WEDNESDAY.

UPDATE ISSUED AT 647 PM CDT MON APR 21 2014

COLD FRONT CONTINUES TO MAKE PROGRESS ACROSS THE CWA WITH PRESSURE
RISES OCCURRING OVER THE UPPER MIDWEST. ALONG THE FRONT A LINE OF
WEAKENING SHOWERS/ISOLATED WEAK THUNDERSTORMS WAS MOVING THROUGH
OUR FAR SOUTHERN CWA. BEHIND THE FRONT NORTHWEST WINDS WERE
BRINGING COOLER/DRIER AIR INTO THE AREA WITH CLEARING SKIES. VERY
PLEASANT SPRING WEATHER IS IN STORE TONIGHT AND TUESDAY.

&&

.SYNOPSIS...
ISSUED AT 320 PM CDT MON APR 21 2014

LATEST SFC ANALYSIS AND CLOUD PATTERN ON THE LATEST VIS SATELLITE
LOOP WERE INDICATING THE MAIN INCOMING COLD FRONT DRAPED FROM NORTH
CENTRAL WI...THROUGH NORTHEASTERN INTO SOUTHWESTERN IA...AND INTO
THE SOUTHERN PLAINS. SECONDARY COLD PUSH NOTED BEHIND THAT ONE
PLUNGING DOWN THE DAKOTAS AND SOUTHERN MN. ENOUGH LIFT AHEAD/ALONG
THE FRONT INTO ADEQUATE AFTERNOON DIURNALLY ADJUSTED MUCAPES TO KEEP
SHOWERS AND SOME THUNDERSTORMS FESTERING ACRS EASTERN IA INTO IL. A
FEW STRONGER CELLS MAY EVEN BE ABLE TO PRODUCE SOME HAIL AND WIND
GUSTS TO 40 MPH OVER THE NEXT 1-3 HRS. CANADIAN SFC HIGH NOTED
NOSING DOWN THE NORTHWESTERN HIGH PLAINS WITH EYES ON SHIFTING TOWARD
THE MS RVR VALLEY THROUGH TOMORROW.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 320 PM CDT MON APR 21 2014

TONIGHT...WILL WALK OUT ANY LINGERING SHOWERS AND STORMS ALONG AND
JUST POST-FRONTAL POSITIONING OUT OF THE EASTERN/SOUTHEASTERN CWA
THROUGH 03Z OR SO...MOST GONE BY 01Z. THEN EXPECT CLEARING AND AN
INCREASE IN NORTHWEST WINDS FROM NORTHWEST TO SOUTHEAST AFTER 02Z...
WITH SOME ISALLOBARIC PRESSURE RISE ENHANCEMENT IN INCOMING RIDGE
GRADIENT TO MAKE FOR SOME TEMPORARY GUSTS OVER 20 KTS. LLVL COLD AIR
ADVECTION WILL BE ON...AS WELL AS DRIER/LOWER SFC DPTS FROM THE
NORTHERN PLAINS. LOWS TONIGHT TO BE IN THE LOW TO MID 40S...WITH
EVEN SOME UPPER 30S POSSIBLE ALONG THE HWY 20 CORRIDOR. WOULD BE
COLDER IF IT WERE NOT FOR THE WINDS AND INHERENT MIXING MAINTAINING
OVERNIGHT INTO EARLY TUE MORNING IN INCOMING SFC RIDGE PRESSURE
GRADIENT.

TUESDAY...INCOMING CANADIAN RIDGE SLATED TO ENGULF THE MID AND
UPPER MS RVR VALLEY...WITH LEE-SIDE PRESSURE GRADIENT STILL LINGERING
ENOUGH FOR MID MORNING NORTHWEST WIND GUST INCREASE...BEFORE WINDS
RELAX AGAIN LATER IN THE AFTERNOON. VERY STEEP LLVL LAPSE RATES OVER
9 C/KM PRODUCED BY DAYTIME HEATING...BUT LITTLE AMBIENT MOISTURE TO
PRODUCE MUCH OF ANY CU. DEEP MIXING UP TO H85 MB OR EVEN HIGHER
NEEDED TO ATTAIN THE FCST HIGHS FOR TUE WHICH MAY GET CLOSE TO OR
JUST UNDER NORMAL FOR THIS TIME OF YEAR.   ..12..

.LONG TERM...(TUESDAY NIGHT THROUGH NEXT MONDAY)
ISSUED AT 320 PM CDT MON APR 21 2014

RAIN AND THUNDERSTORMS LOOK LIKELY LATE WEDNESDAY NIGHT INTO
THURSDAY WITH THE NOW CONSISTENT LATE WEEK SYSTEM. CONSIDERABLE
LARGE SCALE MODEL DIFFERENCES REMAIN FOR THE WEEKEND AND ESPECIALLY
INTO NEXT WEEK...WITH A CHANGE TO MUCH COOLER AND WETTER WEATHER
LOOKING MORE LIKELY.

TUESDAY NIGHT...A COOL DRY EASTERLY FLOW OUT OF THE RIDGE DEPARTING
OVER THE GREAT LAKES SUPPORTS GUIDANCE LOW TEMPERATURES IN THE MID
30S OVER NW MO INTO FAR EASTERN IA....WHILE INCREASING CLOUDS AND
DEWPOINTS HOLDING A BIT HIGHER SHOULD KEEP THE REST OF THE AREA IN
THE UPPER 30S TO LOWER 40S.

WEDNESDAY...A WEAK UPPER LEVEL RIDGE RUNNING SHORTWAVE IS SHOWN BY
NEARLY ALL MODELS INTERACTING WITH ELEVATED MOISTURE RETURN TO
PRODUCING QPF DURING THE DAY OVER PORTIONS OF THE FORECAST AREA.
HOWEVER...THIS MOISTURE RETURN REMAINS ELEVATED ABOVE A DRY LOW
LEVEL SOUTHEAST FLOW. OVERALL...THE SYNOPTIC SETUP REMAINS
UNFAVORABLE FOR ORGANIZED CONVECTION AND LACKING A COHESIVE LOW LEVEL
FOCUSING BOUNDARY....WILL KEEP ONLY LOW CONFIDENCE CHANCE POPS FOR
GOING THROUGH THE DAY WITH HIGHS IN THE 60S,

WEDNESDAY NIGHT THROUGH THURSDAY...A STRONG LOW LEVEL JET AND THETAE
ADVECTION WILL SETUP ELEVATED THUNDERSTORMS...ESPECIALLY IN THE WEST
TOWARD MORNING. THE MAIN SURFACE FRONT PUSHES THROUGH THURSDAY AND
HAVE HIGH END LIKELY POPS FOR WHAT SHOULD A WIDESPREAD LIKELY TO
MODERATE RAIN EVENT. THE POTENTIAL FOR ANY STRONG OR SEVERE STORMS
WILL BE DEPENDENT ON WHETHER ANY BREAKS CAN DEVELOP TO ALLOW FURTHER
DESTABILIZATION AHEAD OF THE FRONT. EVEN WITH CLOUDS...WARM
ADVECTION SHOULD PUSH HIGHS INTO THE MID 60S TO POSSIBLY LOWER
70S...SIMILAR TO TODAY. LOW CHANCE POPS HANG ON INTO THE THU
EVENING...FOLLOWED BY CLEARING SKIES AND TEMPERATURES COOLING BACK
INTO THE 40S.

A MUCH MORE AMPLIFIED AND BLOCKY TYPE PATTERN DEVELOPS OVER THE
WEEKEND INTO EARLY NEXT WEEK WITH MAJOR LARGE SCALE DIFFERENCES
ESPECIALLY BETWEEN THE GFS AND ECMWF LEADING TO A LOW CONFIDENCE
FORECAST PERIOD. THE GFS REMAINS THE MOST AMPLIFIED...WITH A LARGE
UPPER LOW DEVELOPING OFF NEW ENGLAND THAT HOLDS AN UPSTREAM BLOCKING
RIDGE OVER THE CENTRAL U.S....FLANKED BY A DEEPER LOW OVER THE
SOUTHERN PLAINS. OTHER OPERATIONAL MODELS ARE MUCH LESS AGGRESSIVE
WITH THESE FEATURES AND A BIT MORE PROGRESSIVE. AT THE SURFACE...
THERE IS SOME AGREEMENT WITH A LARGE HIGH OVER CANADA INTO THE UPPER
MS VALLEY DEVELOPING A STRENGTHENING LOW LEVEL EASTERLY FLOW NORTH
OF THE MAIN SYNOPTIC FRONT SUPPRESSED WELL TO THE SOUTH. THIS WOULD
BE A COOL REGIME FOR THE LOCAL AREA WITH TEMPERATURES COOLING DOWN
FROM NEAR NORMAL FRIDAY TO WELL BELOW NORMAL BY EARLY NEXT WEEK. LOW
CONFIDENCE RAIN CHANCES RUN FROM SATURDAY NIGHT THROUGH MONDAY AS A
SERIES OF WAVES MAY MOVE ALONG THE MAIN FRONT THAT STALLS TO THE
SOUTH. DETAILS WILL BECOME MORE CLEAR IN LATER FORECASTS AS THE
MODELS GET A BETTER HANDLE ON WHERE THE FRONT LAYS OUT...ALONG WITH
HOW MUCH COLD AIR SPILLS INTO THE UPPER MIDWEST.    ..11..

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1049 PM CDT MON APR 21 2014

VFR CONDS WITH SKC THROUGH THIS TAF CYCLE AS HIGH PRESSURE BUILDS
INTO THE AREA. NORTHWEST TO NORTH WINDS 10 TO 15 KNOTS.

&&

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

$$

UPDATE...HAASE
SYNOPSIS...12
SHORT TERM...12
LONG TERM...11
AVIATION...HAASE






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