Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 180839
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
339 AM CDT SAT APR 18 2015

.SYNOPSIS...
ISSUED AT 330 AM CDT SAT APR 18 2015

A QUIET NIGHT OVER THE CWA WITH MAINLY THIN CIRRUS CLOUDS AND
CURRENT TEMPERATURES RANGING FROM THE LOWER 50S TO LOWER 60S.
REGIONAL DOPPLER RADAR DATA INDICATED A FEW SHOWERS AND ISOLATED
THUNDERSTORMS IN CENTRAL IOWA IN AN AREA OF WEAK WARM AIR ADVECTION/
850 MB TRANSPORT. HOWEVER...THESE SHOWERS WERE MOVING NORTH.

ELSEWHERE...HIGH PRESSURE WAS SITUATED JUST NORTH OF MN AND IN THE
UPPER OHIO VALLEY. WATER VAPOR LOOPS SHOWED A FILLING UPPER LOW IN
EXTREME SOUTHERN CO MOVING SLOWLY EAST.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT SAT APR 18 2015

FORECAST FOCUS ON SHOWER CHANCES...CLOUDS AND TEMPERATURES.

TODAY...OPERATIONAL MODELS STRUGGLING WITH THE DRY EASTERLY FEED
FROM HIGH PRESSURE TO OUR NORTH AND EAST. THE MODELS ARE NOW
KEEPING OUR EASTERN CWA DRY WHILE BRINGING SOME SHOWERS INTO OUR
WESTERN COUNTIES MAINLY THIS AFTERNOON. FORCING LOOKS WEAK AND THE
AIRMASS IS STABLE SO MODELS MAY STILL BE GENERATING TOO MUCH QPF.
THEREFORE HAVE CONFINED CHANCE POPS TO WEST OF THE MS RIVER TODAY.
MODELS SEEM TO ALSO DEVELOP TOO MUCH CLOUDINESS ESPECIALLY THE
FARTHER EAST YOU GO INTO THE CWA. TEMPERATURES WILL BE A CHALLENGE
WITH AN EAST TO SOUTHEAST WIND BUT PROBABLY NOT AS MUCH CLOUD
COVER AS GUIDANCE SUGGESTS. THE RESULT SHOULD BE AFTERNOON HIGHS
IN THE 70S...SEVERAL DEGREES LOWER THAN YESTERDAY. RAINFALL
AMOUNTS IN OUR FAR WEST WILL BE UP TO A TENTH OF AN INCH.

TONIGHT...FILLING UPPER LOW IN CO BECOMES AN OPEN WAVE AS IT LIFTS
INTO THE CENTRAL/SOUTHERN PLAINS...AND BEGINS PHASING WITH A
NORTHERN STREAM TROUGH. BETTER FORCING AND INCREASING MOISTURE
TRANSPORT SHOULD LEAD TO LIKELY POPS AFTER MIDNIGHT IN OUR WESTERN
COUNTIES. HOWEVER...EAST OF THE MS RIVER THE DRY AIR SHOULD CONTINUE
TO WIN OUT AND I WILL KEEP THAT AREA RAIN-FREE. THE AIRMASS STILL
LOOKS TOO STABLE TO MENTION THUNDER. RAINFALL AMOUNTS WILL RANGE
FROM 1/4 TO 1/2 INCH WEST TO LITTLE IF ANY EAST. MINIMUM TEMPERATURES
SHOULD BOTTOM OUT MAINLY IN THE LOWER TO MID 50S.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT SAT APR 18 2015

PERIOD OF RAIN LIKELY THROUGH SUNDAY NIGHT...THEN COOLER AND MAINLY DRY
THROUGH MID-WEEK.

MODELS REMAIN IN GOOD AGREEMENT THAT THE CLOSED UPPER LOW EMERGING
INTO THE CENTRAL PLAINS ON SUNDAY WILL DEAMPLIFY INTO OPEN WAVE
WHILE LIFTING THROUGH THE MID-MISSISSIPPI VALLEY SUNDAY NIGHT.
THIS ENERGY WILL PHASE WITH SOUTHERN CANADA SHORTWAVE TO FORM
SLOW MOVING CLOSED LOW OVER THE WESTERN GREAT LAKES EARLY NEXT WEEK.

THE MAIN CHALLENGES WILL BE POPS... AND QPF AMOUNTS SUNDAY AND
SUNDAY NIGHT. THE REMNANTS OF SOUTHERN STREAM CUTOFF LOW
EMERGING INTO THE PLAINS ON SUNDAY LOOK TO BE THE PRIMARY FORCING
MECHANISM FOR PCPN WHILE LIFTING THROUGH THE MID-MISSISSIPPI VALLEY.
POSITIVE VORTICITY ADVECTION AT 500 MB AND SOME MID LEVEL
FRONTOGENETICAL FORCING AND MOISTURE APPEAR SUFFICIENT FOR LIKELIHOOD
OF A PERIOD OF RAIN OVER MUCH OF CWA. HOWEVER... DRIER LOW LEVEL
EASTERLY FLOW INITIALLY ON SUNDAY SHOULD SLOW OR MAY INHIBIT ARRIVAL
OF ANY MEASURABLE RAIN OVER NORTHWEST IL AND POSSIBLY FAR NORTHEAST
TO EAST CENTRAL IA UNTIL LATE SUNDAY AND SUNDAY EVENING WHEN THE
BETTER FORCING ARRIVES. HIGHEST RAINFALL AMOUNTS THROUGH SUNDAY NIGHT
(GENERALLY 0.2 INCH TO 0.5 INCH) FAVOR WESTERN AND SOUTHERN SECTIONS
OF CWA GIVEN CLOSE PROXIMITY TO BETTER LIFT AND 850 MB THETA-E AXIS.
AMOUNTS OF GENERALLY UP TO 0.2 INCH LOOK REASONABLE ACROSS THE
REST OF THE CWA. MARGINAL LAPSE RATES AND LIMITED MUCAPE SHOULD
PRECLUDE MUCH IN THE WAY OF THUNDER WITH PCPN MOSTLY RAIN OR SHOWERS.
HIGHS ON SUNDAY WILL BE CHALLENGING DUE TO CLOUDS AND SOME PCPN
AROUND... AND COOLER WITH MAINLY 60S. WARMEST READINGS MAY BE
OVER PORTIONS OF EAST CENTRAL INTO NORTHEAST IA AND FAR NORTHWEST IL
WHERE DRIER CONDITIONS ANTICIPATED FOR MUCH OF SUNDAY.

THE MID-MISSISSIPPI VALLEY SHORTWAVE IS EXPECTED TO PHASE WITH SOUTHERN
CANADA SHORTWAVE TO FORM LARGE NEARLY CUTOFF UPPER LOW OVER THE WESTERN
GREAT LAKES EARLY NEXT WEEK. THIS SYSTEM WILL BE SLOW MOVING AND THUS
HAVE INFLUENCE ON OUR WEATHER FOR MUCH OF NEXT WEEK WITH FLOW ALOFT
GENERALLY NORTHWESTERLY USHERING IN COOLER TEMPS (HIGHS IN THE 50S/60S
AND LOWS IN THE 30S/40S). SOME PATCHY FROST MAY BE POSSIBLE ON ONE
OR TWO NIGHTS FROM MONDAY THROUGH WEDNESDAY IF SKIES CLEAR AND WINDS GO
LIGHT. OUTSIDE OF SOME QUICK PASSING LIGHT RAIN SHOWERS MONDAY AND TUESDAY
MAINLY NORTHERN CWA... EXPECT GENERALLY DRY CONDITIONS THROUGH MID-WEEK.
STILL QUITE A BIT OF VARIABILITY IN MODELS OVER THE LATTER HALF OF WEEK
TIED TO MOVEMENT OF UPPER LOW. TRIMMED POPS TO SLIGHT CHANCES MUCH OF THE
PERIOD FROM WEDNESDAY NIGHT THROUGH FRIDAY... AS TRENDS SUGGEST SLOWER
MOVEMENT OF UPPER LOW AND THUS MORE CONTINUATION OF DRIER NORTHWEST FLOW
WITH MUCH IF NOT ALL OF PCPN FOCUSING OVER PORTIONS OF THE CENTRAL/SOUTHERN
PLAINS INTO LOWER MISSISSIPPI VALLEY IN LINE WITH PATTERN OF LATE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1151 PM CDT FRI APR 17 2015

VERY SLOW MOVING LOW PRESSURE ALOFT WILL CONTINUE TO DRIFT TOWARDS
THE UPPER MIDWEST THROUGH SATURDAY. DRY AIR IN PLACE OVER EASTERN
IOWA AND NORTHWEST ILLINOIS...WILL KEEP CONDITIONS DRY...VFR...AND
MAINLY SCATTERED TO BROKEN MID AND HIGH CLOUDS...AT LEAST THROUGH
LATE AFTERNOON SATURDAY. BY SATURDAY NIGHT...RAIN SHOWERS MAY
BEGIN MOVING INTO EASTERN IOWA...WITH SOME POSSIBLE MVFR CIGS
ACCOMPANYING THEM AFTER 00Z. WINDS WILL BE LIGHT EAST TO SOUTHEAST
THROUGH THE PERIOD. ERVIN

&&

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

$$

SYNOPSIS...HAASE
SHORT TERM...HAASE
LONG TERM...05
AVIATION...ERVIN




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