Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 260846
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
346 AM CDT SUN APR 26 2015

.SYNOPSIS...
ISSUED AT 308 AM CDT SUN APR 26 2015

THE LATEST SFC ANALYSIS WAS INDICATING A BROAD RIDGE OCCUPYING
MUCH OF THE UPPER MIDWEST...HOLDING FRONTAL SYSTEMS AT BAY ACRS
THE NORTHWESTERN HIGH PLAINS AND DOWN ACRS THE SOUTHERN PLAINS TO
TN VALLEY REGIONS. THIS SYSTEM ALSO SQUEEZING NORTHEASTERLY
DRYING COOLING FLOW ACRS THE LOCAL AREA...WITH LOWER STRATOCU
CONTINUING TO GET SHUNTED TO THE SOUTH AS THE EARLY MORNING
PROGRESSES. ALOFT...MID/UPPER LEVEL MOISTURE FLOW PATTERNS ON THE
LATEST WATER VAPOR LOOP INDICATING A DEEP TROF ACRS THE SOUTHERN
GRT BSN...WITH OMEGA BLOCKING UPPER RIDGE AXIS HOLDING FIRM ACRS
THE PLAINS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 308 AM CDT SUN APR 26 2015

TODAY...THERE MAY BE SOME PATCHY FROST IN LOW LYING AREAS OF THE
NORTHEASTERN THIRD OF THE CWA EARLY THIS MORNING...BUT ENOUGH
NORTHEAST SFC WINDS TO KEEP IT AT A MINIMUM DESPITE LOW/DRY DPTS
ADVECTING INTO THOSE AREAS OUT OF WI. AFTER THE CLOUDS GET ERODED
OUT OF THE SOUTHERN CWA THIS MORNING...EXPECT A MAINLY SUNNY DAY
TODAY. BUT WITH DEEPENING NORTHEAST FETCH OFF THE GRT LKS/LK
MI...SOME MOISTURE DRAW MAY HELP FUEL AT LEAST SCTRD CU
DEVELOPMENT ACRS MUCH OF THE NORTHEASTERN HALF OF IL AND POSSIBLY
WESTWARD TO THE MS RVR. CU RULE PARAMETERS ALSO PICKING UP ON THIS
SCENARIO. OTHERWISE...FCST SOUNDINGS SHOWING DEEP MIXING IN AN
UNSEASONABLY COOL AIRMASS...POSSIBLY UP OVER H85 MB WHICH WOULD
SUPPORT WIDESPREAD HIGHS IN THE UPPER 50S TO AROUND 60 ESPECIALLY
TAKING INTO ACCOUNT LATE APRIL INSOLATION.

TONIGHT...SFC RIDGE MAINTAINS ACRS THE UPPER MIDWEST INTO THE
WESTERN GRT LKS MAKING FOR MAINLY CLEAR SKIES AS LONG AS THERE
ARE NOT ANY LK FETCH STRATOCU GETTING TRAPPED NOCTURNALLY UNDER AN
INVERSION. BULK OF SHORT RANGE MODELS KEEP SOME TYPE OF WIND
COMPONENT/NORTHWEST TO NORTHEAST/ GOING OF AT LEAST 3 TO 6 MPH
INTO THE EARLY MON MORNING HOURS AND KEEP GUIDANCE LOW TEMPS
MAINLY IN THE MID 30S TONIGHT. BUT DRY DOWN-MIXED SFC DPTS
POSSIBLY LOWER THAN WHAT THE MODELS SUGGEST WILL HAPPEN...AS WELL
AS THE POSSIBLY OF SFC WINDS DECOUPLING UNDER AN INVERSION
WARRANT A LEAN TOWARD THE COOLEST OF GUIDANCE LOWS OR EVEN
UNDERCUTTING THOSE VALUES A FEW DEGREES. FOR NOW WILL GO WITH LOW
TO MID 30S NORTH OF I80 WITH PATCHY FROST POSSIBLE...AND MID 30S
TO AROUND 37 DEGREES TO THE SOUTH.


.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 308 AM CDT SUN APR 26 2015

MAIN CHALLENGE IS TEMPERATURES AS A SURFACE RIDGE AXIS KEEPS A
SEASONABLY DRY AIRMASS IN PLACE UNDER A SPLIT FLOW UPPER LEVEL
PATTERN FOR MUCH OF THIS WEEK. A WARMING TREND IS STILL ON TRACK FOR
LATE WEEK INTO THE WEEKEND...WHEN RETURNING GULF MOISTURE WILL BRING
THE NEXT CHANCES FOR RAIN.

MONDAY AND TUESDAY...LIGHT NORTHEAST WINDS OUT OF A RIDGE OVER
CENTRAL CANADA CONTINUE TO CHANNEL A SOMEWHAT COOL AND DRY GREAT
LAKES AIRMASS INTO THE REGION...WHILE SHORTWAVE RIDGING ALOFT KEEPS
SKIES MOSTLY CLEAR. THE RESULT WILL BE AN EXTENDED PERIOD OF DRY
WEATHER WITH LARGE DIURNAL TEMPERATURE SWINGS. VERIFICATION OF
CURRENT DEWPOINTS AND FORECAST TRENDS SUGGEST MODELS MAY OVERALL BE
A BIT TOO MOIST AT THE LOW LEVELS. HAVE THUS UNDERCUT LOWEST MODEL
DEWPOINTS AND TRENDED TOWARD THE COLD SIDE FOR OVERNIGHT LOWS AND
WARMER GUIDANCE FOR DAYTIME HIGHS. HIGHS SHOULD REACH THE LOWER TO
MID 60S MONDAY...THEN MID TO UPPER 60S TUESDAY. MONDAY NIGHT INTO
EARLY TUESDAY MORNING...TEMPERATURES WILL DROP INTO THE 30S...WITH
FAR NW IL POSSIBLY NEAR OR JUST BELOW FREEZING AS CENTER OF THE
PASSING RIDGE AXIS SUGGESTS LIGHT AND VARIABLE WINDS. LATER
FORECASTS WILL NEED TO MONITOR THIS AREA FOR A POTENTIAL LATE SEASON
FROST.

WEDNESDAY THROUGH SATURDAY...AN EASTWARD MIGRATING WESTERN U.S.
UPPER LEVEL RIDGE WILL RESULT IN A GRADUAL WARMING TREND WITH
TEMPERATURES RISING FROM THE LOWER 70S MID WEEK TO AT LEAST THE MID
AND POSSIBLY UPPER 70S BY SATURDAY WITH LOWS IN THE 40S...REACHING
THE 50S BY THE WEEKEND. SLIGHT TO LOW END CHANCE POPS FOR SHOWERS
AND THUNDERSTORMS WERE BROUGHT IN FOR FRIDAY NIGHT INTO SATURDAY.
ECMWF AND GFS AGREE WITH A DEVELOPING LOW LEVEL SOUTHERLY FLOW AND
MOISTURE RETURN IN THIS TIMEFRAME...BUT THERE REMAIN SIGNIFICANT
DIFFERENCES WITH THE TIMING AND PLACEMENT OF WEAK SURFACE FRONTS AND
UPPER LEVEL SHORTWAVES...KEEPING FORECAST CONFIDENCE LOW AT THIS
TIME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1120 PM CDT SAT APR 25 2015

LOW PRESSURE WILL CONTINUE TO MOVE AWAY FROM THE REGION TONIGHT...
WITH NORTHEAST WINDS DECREASING TO AROUND 8 KTS...AND CONTINUING
THROUGH THE PERIOD. DRY AIR WILL CONTINUE TO SCATTER OUT OR CLEAR
ANY REMAINING MVFR CIGS IN SOUTHEAST IOWA. AFTER 08Z/26 ALL SITES
WILL BE VFR/CLEAR THROUGH THE REST OF THE PERIOD AS HIGH PRESSURE
BUILDS INTO THE NORTHERN GREAT LAKES.  ERVIN

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...SHEETS
AVIATION...ERVIN


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