Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 201219
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
719 AM CDT MON APR 20 2015

.UPDATE...
ISSUED AT 718 AM CDT MON APR 20 2015

DOPPLER RADAR INDICATED THE WEST (BACK) EDGE OF THE DEFORMATION ZONE
PRODUCING LIGHT RAIN AND SPRINKLES EXTENDED FROM ABOUT MANCHESTER IA
TO THE QUAD CITIES AND WAS MOVING EAST AT ABOUT 20 MPH. THIS PUTS THE
BACK EDGE EXITING THE DVN CWA BY AROUND 10 AM OR SO. NORTHWEST
WINDS HAVE BEEN GUSTING TO 30 TO 40 MPH THE PAST SEVERAL HOURS AND
EARLIER I ISSUED A SPECIAL WEATHER STATEMENT FOR THE MORNING COMMUTE.
HOWEVER...WINDS WILL REMAIN STRONG FOR MUCH OF THE DAY AND THEN
DIMINISH QUICKLY TOWARDS SUNSET.

THE LATEST HRRR AND WRF MODELS HAVE COME IN A BIT MORE AGGRESSIVE
WITH THE SHOWERS ACROSS THE CWA. THEREFORE HAVE RAISED POPS TO 30
PERCENT AND DESCRIBED IT AS "ISOLATED TO SCATTERED SHOWERS".

&&

.SYNOPSIS...
ISSUED AT 335 AM CDT MON APR 20 2015

DEEPENING CYCLONE (987 MB) WAS LOCATED IN EXTREME WESTERN LOWER MI
AND BROUGHT WIDESPREAD RAIN TO THE DVN CWA LAST EVENING AND OVERNIGHT.
A COLD FRONT HAS SWEPT THROUGH THE AREA WITH NORTHWEST WINDS GUSTING
TO 35 MPH. DOPPLER RADAR INDICATED LIGHT RAIN STILL FALLING ROUGHLY
ALONG AND NORTH OF HIGHWAY 30 IN IA AND IL AND WAS GRADUALLY LIFTING
NORTHWARD. CURRENT TEMPERATURES RANGED FROM THE LOWER 40S TO MID 50S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 335 AM CDT MON APR 20 2015

FORECAST FOCUS ON RAIN CHANCES...WIND AND TEMPERATURES.

TODAY...THIS WILL BE A VERY WINDY AND MUCH COOLER DAY AS THE DEEPENING
CYCLONE TRACKS NORTHWARD TO JUST NORTH OF LAKE SUPERIOR. THE STRATIFORM
RAIN SHIELD SHOULD LIFT OUT OF THE DVN CWA BY MID TO LATE MORNING.
OTHERWISE PARTLY SUNNY SKIES ARE EXPECTED WITH FORECAST SOUNDINGS
INDICATING DEEP MIXING TO ABOUT 700 MB BRINGING DOWN 35 TO 40 MPH
WIND GUSTS...WHICH IS BELOW ADVISORY CRITERIA. NONETHELESS HANG ONTO
YOUR HAT AND THE STEERING WHEEL! STEEP LAPSE RATES AND ENOUGH MOISTURE
SHOULD ALLOW FOR ISOLATED HIGH-BASED RAIN SHOWERS ANYWHERE IN THE CWA
LATER THIS MORNING THROUGH THE AFTERNOON. THE HRRR AND WRF MODELS DEPICT
THIS SCENARIO QUITE WELL. TEMPERATURES WILL BE A CHALLENGE AGAIN AS
WE HAVE COLD AIR ADVECTION BUT THERE WILL ALSO BE SOME SUNSHINE TO
OFFSET THIS SOMEWHAT. THEREFORE A GOOD COMPROMISE SEEMS TO BE HIGHS
IN THE UPPER 50S TO LOWER 60S.

TONIGHT...DEEP CYCLONE (980 MB) WILL BE ANCHORED NORTH OF LAKE SUPERIOR
DUE TO A STRONG GREENLAND BLOCK. SKIES SHOULD BE PARTLY CLOUDY AND GUSTY
WEST WINDS WILL DIMINISH BY SUNSET WITH DECOUPLING. HOWEVER... THE WINDS
SHOULD STAY AT 10 TO 15 MPH MUCH OF THE NIGHT. MINIMUM TEMPERATURES
IN THE 35 TO 40 RANGE SHOULD BE COMMON. A FEW SHOWERS MAY LINGER INTO
THE EARLY EVENING HOURS FOR LATER SHIFTS TO CONSIDER...BUT FOR NOW I
WILL CONTINUE A DRY FORECAST FOR TONIGHT.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 335 AM CDT MON APR 20 2015

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

NORTHWEST FLOW PATTERN WILL GOVERN MUCH OF THE LONG TERM PERIOD AS
BLOCKING DEVELOPS OVER EASTERN ATLANTIC AND GREENLAND RESULTING IN
SLOW EASTWARD PROGRESSION OF GREAT LAKES UPPER LOW. SERIES OF
IMPULSES WILL ROTATE AROUND THE CYCLONE WITH NORTHERN CWA IN CLOSER
PROXIMITY AND THUS FAVORED FOR MORE DIURNAL DRIVEN CLOUD COVER ON
TUESDAY ALONG WITH SPRINKLES AND SOME LIGHT POPCORN SHOWERS GIVEN
STEEP LAPSE RATES...COLD AIR ALOFT AND PRESENCE OF SKINNY CAPE NOTED
ON FORECAST SOUNDINGS. MAIN ITEM ON TUESDAY WILL BE WINDY CONDITIONS
WITH POTENTIAL FOR WIND ADVISORY AS NAM/GFS BUFR SOUNDINGS SHOWING
30-35 KTS OF WIND ON AVERAGE THROUGH THE MIXED LAYER WITH 50-55 KTS
SITTING ATOP DEEP MIXED LAYER TO NEAR 650 MB. POSSIBLE AS WELL THAT
ANY SHOWERS COULD ENHANCE WIND GUSTS VIA EVAPORATIVE COOLING OF
PCPN IN LARGE... DRY SUB-CLOUD LAYER WITH CLASSIC INVERTED V TYPE
SOUNDINGS.

CANADIAN SURFACE RIDGE AXIS WILL BUILD IN OVER THE LATTER HALF OF THE
WEEK AS THE UPPER LOW PLODS EASTWARD FROM GREAT LAKES. THIS WILL
BRING DIMINISHING WINDS WEDNESDAY THROUGH FRIDAY BUT ALSO REINFORCE
COOL... DRY AIR WITH MORE IDEAL RADIATIONAL COOLING SETUP LEADING TO
INCREASING RISK FOR AREAS OF FROST AND FREEZING TEMPS POSSIBLY AS
EARLY AS WEDNESDAY AM... BUT MORE LIKELY THURSDAY/FRIDAY AM. FREEZE
HIGHLIGHTS ARE ACTIVE IF NEEDED WITH FRUIT TREES NOW SUSCEPTIBLE
TO TEMPS AT/BELOW 28F PER FEEDBACK FROM ISU EXTENSION COMMERCIAL
HORTICULTURE SPECIALIST. NURSERIES AND STORES ALSO MOVING
STOCK OUTDOORS... AND RECENT WARM SPELL AND MOISTURE HAS CAUSED YARDS
TO ADVANCE QUICKLY.

TOWARD SATURDAY AND INTO THE FIRST HALF OF THE WEEKEND THERE IS THE
POTENTIAL FOR RAIN CHANCES WITH ANOTHER STORM SYSTEM. CONFIDENCE IS
LOW AS MODEL VARIANCE QUITE HIGH. DPROG/DT... OR COMPARISON OF MODELS
RUN TO RUN... SHOWS BETTER CONSISTENCY EXISTS WITH ECMWF WHICH IS
SLOWER AND FAVORS SOUTHERN CWA FOR BETTER RAIN CHANCES DUE TO MORE
SOUTHERLY TRACK OF SYSTEM AND INCREASING EASTERLY FLOW. GFS ENSEMBLE
MEANS SIMILAR LINES OF ECMWF AND ACTUALLY SUGGEST MUCH IF NOT ALL OF
RAIN STAYING TO OUR SOUTH FROM PARTS OF MID TO LOWER MISSISSIPPI VLY
WHICH ALSO FITS WITH PATTERN OF LATE. AS RESULT... HAVE ADJUSTED POPS
TO LOWER OR REMOVE ACROSS THE NORTH/EAST FRIDAY NIGHT AND SATURDAY AND
PLACE THE BEST CHANCES ACROSS THE SOUTHERN CWA.

TEMPS THROUGHOUT THE ENTIRE PERIOD LOOK TO REMAIN SEASONABLY COOL WITH
HIGHS 50S/60S... AND LOWS MAINLY IN THE 30S WITH SOME 20S IN FAVORED
DRAINAGE LOCATIONS WEDNESDAY THROUGH FRIDAY MORNINGS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 648 AM CDT MON APR 20 2015

MVFR CIGS THIS MORNING THEN VFR CIGS THIS AFTERNOON AND VFR NO CIGS
TONIGHT. ISOLATED TO SCATTERED SHOWERS LATE THIS MORNING THROUGH THE
AFTERNOON. NORTHWEST WINDS SUSTAINED 15 TO 20 KNOTS WITH GUSTS TO
30 KNOTS TODAY THEN WEST 10 TO 15 KNOTS TONIGHT.


&&

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

$$

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






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