Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 191712
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1212 PM CDT SUN APR 19 2015

.UPDATE...
ISSUED AT 1111 AM CDT SUN APR 19 2015

MODELS AGAIN HAVING A TOUGH TIME WITH MOISTURE PROFILES AS 12Z
SOUNDINGS WERE MUCH DRIER THAN ANTICIPATED. 12Z ANALYSIS SUGGESTED
THAT GULF MOISTURE IS BECOMING INCREASINGLY CONFINED AND CUT OFF
OVER THE MID MS AND OHIO VALLEY REGIONS WITH THE DEVELOPING SURFACE LOW
THAT WILL BECOME THE PRIMARY SURFACE FEATURE BY TONIGHT. THE
BOTTOM LINE IS THAT THIS WILL RESULT IN A MUCH LESS PESSIMISTIC
FORECAST THAN PREVIOUSLY ADVERTISED FOR THIS AFTERNOON.

TODAY...PRECIPITATION CHANCES OVER THE FORECAST AREA APPEARS TO BE
FOCUSED ON TWO PRIMARY MECHANISMS. ONE IS THE DEFORMATION AXIS OF
LIGHT RAIN NORTH AND NORTHWEST OF THE DEVELOPING SURFACE LOW OVER
THE MO BOOTHEEL...WHICH IS EXPECTED TO LIFT N-NE IN RESPONSE TO
THE SHORTWAVE LIFTING OUT OF THE CENTRAL PLAINS LONGWAVE TROUGH.
THE OTHER IS A BROAD AREA OF WEAK UPGLIDE AND MID LEVEL LIFT THAT
CONTINUES TO RESULT IN ISOLATED TO SCATTERED SHOWERS WEST OF A
LINE FROM MOUNT PLEASANT TO MONTICELLO THIS MORNING. THIS LATTER
FORCING WILL CONTINUE IN THE WEST WITH MARGINAL MUCAPES HIGH
ENOUGH TO WARRANT A MENTION OF ISOLATED THUNDERSTORMS. THE
DEFORMATION AXIS AROUND THE LOW LIFTING INTO IL WILL GRADUALLY
SPREAD INTO THE FAR SE AND EAST BY MID AFTERNOON. THIS PROCESS MAY
LEAVE PORTIONS OF THE CENTRAL AND NORTHEAST DRY THROUGH MID
AFTERNOON...AND POSSIBLY KEEP NW IL ZONES FREE OF RAIN THROUGH THE
DAY.

HAVE UPDATED THE FORECAST TO ADJUST POPS ACCORDINGLY AND REDUCE
THE CLOUD COVER OVER ESPECIALLY THE CENTRAL AND EAST. RESULTING
SUNSHINE AND LACK OF PRECIPITATION WILL ALLOW TEMPERATURES TO
RECOVER AT LEAST INTO THE LOWER 70S AND HAVE TWEAKED HIGHS AS
WELL.

&&

.SYNOPSIS...
ISSUED AT 345 AM CDT SUN APR 19 2015

MODELS CONTINUE TO STRUGGLE WITH THE EASTERLY FEED OF DRY AIR INTO
OUR NORTHEAST CWA AND AT SOME LOCATIONS DEWPOINTS WERE 10 DEGREES
LOWER THAN ANY GUIDANCE. IN OUR WESTERN CWA GUIDANCE WAS CLOSE TO
REALITY AS WINDS WERE MORE SOUTHEAST. SPC MESO ANALYSIS SHOWED
DECENT 850 MB MOISTURE TRANSPORT ALONG WITH PRECIPITABLE WATERS
OVER AN INCH IN OUR WESTERN CWA. AND SURE ENOUGH DOPPLER RADAR HAS
SHOWN POCKETS OF SHOWERS AND ISOLATED THUNDERSTORMS ALL NIGHT.
RAINFALL ESTIMATES INDICATE 1/4 TO 3/4 OF AN INCH HAS FALLEN IN
SOME SPOTS IN OUR WEST SINCE LAST EVENING.

3 AM TEMPERATURES RANGED FROM 50 AT FREEPORT TO 61 AT MACOMB.
ELSEWHERE...CANADIAN HIGH PRESSURE WAS CENTERED NORTHEAST OF LAKE
SUPERIOR AND SOME SITES IN NW WI WERE REPORTING DEWPOINTS IN THE TEENS.

UPPER LEVEL TROUGH WAS DIGGING INTO THE NORTHERN PLAINS WHILE
ANOTHER TROUGH WAS PUSHING INTO THE CENTRAL/SOUTHERN PLAINS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 345 AM CDT SUN APR 19 2015

FORECAST FOCUS ON INCREASING RAIN AND TEMPERATURES.

TODAY...UPPER LEVEL TROUGH APPROACHES FROM THE WEST AND THIS WILL PROVIDE
LARGE SCALE ASCENT ALONG WITH BETTER MOISTURE TRANSPORT AS THE DAY PROGRESSES.
THE MORE WIDESPREAD RAIN APPEARS TO DEVELOP THIS AFTERNOON WITH THE
ARRIVAL OF STRONGER FORCING...AS A SHORT WAVE PUSHES ACROSS IA AHEAD
OF THE MAIN TROUGH. MEANWHILE...PHASING BEGINS TO OCCUR AND MODELS LIFT
A DEEPENING CYCLONE OUT OF THE LOWER MS VALLEY INTO FAR WESTERN INDIANA
BY 00Z. INTERESTING THAT THE NAM/ECMWF KEEP NW IL DRY MUCH OF THE DAY
AND THEY MAY BE ON TO SOMETHING WITH SUCH A DRY EASTERLY FEED INTO THAT
AREA. I WILL MENTION ISOLATED THUNDERSTORMS THIS AFTERNOON AS DEEP LAYER
SHEAR IS WEAK AND MUCAPE IS 500 J/KG OR LESS. WITH MORE CLOUDINESS TODAY
MAXIMUM TEMPERATURES SHOULD BE COOLER THAN THAN THE PAST COUPLE OF DAYS.
I AM EXPECTING HIGHS IN THE UPPER 60S TO LOWER 70S AT MOST LOCATIONS.

TONIGHT...PHASING IS NEARLY COMPLETE AND A LONG WAVE TROUGH PUSHES
ACROSS THE MIDWEST WITH DECENT FORCING AND GOOD MOISTURE IN PLACE.
IN THE MEANTIME...THE SLOWLY DEEPENING CYCLONE LIFTS INTO NORTHERN
LOWER MI BY 12Z. MODELS INDICATE WIDESPREAD RAIN OVER THE CWA MUCH
OF THE NIGHT. THIS LOOKS TO BE MORE OF A STRATIFORM/DEFORMATION TYPE
RAIN RATHER THAN ALL OUT CONVECTIVE/MCS TYPE SO WILL NOT MENTION THUNDER
AS INSTABILITY IS VERY LIMITED...AND THE ENTIRE COLUMN IS VERY SATURATED.
A COLD FRONT WILL PUSH ACROSS THE CWA DURING THE NIGHT USHERING MUCH
COOLER TEMPERATURES INTO THE AREA BY MORNING. MINIMUM TEMPERATURES
WILL RANGE FROM THE LOWER 40S AT INDEPENDENCE TO THE UPPER 40S AT
PRINCETON AND MACOMB IN ILLINOIS.

RAINFALL AMOUNTS TODAY THROUGH TONIGHT SHOULD BE 0.3 TO 0.7 INCHES OVER
MUCH OF THE CWA.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 345 AM CDT SUN APR 19 2015

COOLER AND MAINLY DRY FOR MUCH OF UPCOMING WEEK WITH FROST/FREEZE
POTENTIAL LATER IN THE WEEK.

MUCH OF THE UPCOMING WEEK AHEAD WILL FEATURE A LARGE AND SLOW
MOVING UPPER LOW FROM THE GREAT LAKES TO EASTERN CANADA DUE TO
HIGHLY AMPLIFIED RIDGING OVER THE EASTERN ATLANTIC AND GREENLAND.
OUR CWA WILL BE GOVERNED BY NORTHWEST FLOW ON BACKSIDE OF THE
LARGE UPPER LOW WHICH WILL USHER IN REINFORCING BOUTS OF CANADIAN
AIR RESULTING IN COOLER HIGHS IN THE 50S AND 60S... WITH LOWS
MAINLY IN THE 30S. THE COOLER AIR WILL ALSO BE ACCOMPANIED BY
WINDY CONDITIONS MONDAY AND TUESDAY WITH THE POTENTIAL TO BE
NEAR WIND ADVISORY CRITERIA GIVEN JUXTAPOSITION OF TIGHT PRESSURE
GRADIENT... COLD ADVECTION AND DEEP MIXING. AFTER SOME LINGERING
SHOWERS POSSIBLE EARLY MONDAY AM... WILL HAVE THE POTENTIAL
FOR AFTERNOON POPCORN SHOWERS ACROSS MAINLY THE NORTHERN CWA BOTH
MONDAY AND TUESDAY WITH STEEP MID LEVEL LAPSE RATES... COLD
AIR ALOFT... AND SKINNY CAPE NOTED ON FORECAST SOUNDINGS. WILL
NEED TO WATCH FOR ENHANCED WIND GUSTS WITH ANY SHOWERS VIA
EVAPORATIVE COOLING OF PCPN IN LARGE... DRY SUB-CLOUD LAYER WITH
CLASSIC INVERTED V SOUNDINGS.

CANADIAN SURFACE RIDGE AXIS BUILDING IN THURSDAY INTO FRIDAY WILL
BRING POTENTIAL FOR FROST AND POSSIBLY FREEZING TEMPS ONE OR BOTH
MORNINGS. MIN TEMPS MAY NEED LOWERING BY 3-5 DEGS SOME LOCATIONS
ESPECIALLY THURSDAY AM BASED ON 850 MB TEMPS -4C TO -7C WITH MORE
WIDESPREAD 20S POSSIBLE WITH ANY DURATION OF CLEAR SKIES AND LIGHT
WINDS.

RAIN CHANCES LOOK TO RETURN BY EITHER LATE IN THE WEEK AND/OR NEXT
WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1212 PM CDT SUN APR 19 2015

VFR CONDITIONS ARE NOW EXPECTED TO PREVAIL THROUGH THE AFTERNOON
BEFORE LOWER CIGS AND MORE WIDESPREAD SHOWERS DEVELOP THIS EVENING
AHEAD OF A PASSING UPPER LEVEL SYSTEM. THERE IS POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY AT CID AND BRL THIS AFTERNOON...WHICH IS TOO
LOW TO INCLUDE IN THE FORECASTS. WIDESPREAD MVFR AND POSSIBLE
PERIODS OF IFR ARE EXPECTED OVERNIGHT DUE TO RAIN AND LOW CLOUDS.
A COLD FRONT MOVING THROUGH OVERNIGHT WILL VEER WINDS TO THE
WEST/NORTHWEST WITH SPEEDS INCREASING TO 20 TO 30 MPH WITH HIGHER
GUSTS POSSIBLE LATE MONDAY MORNING.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...HAASE
SHORT TERM...HAASE
LONG TERM...MCCLURE
AVIATION...SHEETS






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