Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 301250
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
750 AM CDT SAT MAY 30 2015

.SYNOPSIS...
ISSUED AT 330 AM CDT SAT MAY 30 2015

A SLOW MOVING COLD FRONT STILL SITUATED ACROSS CENTRAL IOWA INTO
SOUTHEAST MINNESOTA HAS ALLOWED A STRATIFORM AREA OF RAIN TO FLOW
NORTHWARD INTO THE SOUTHEAST HALF OR SO OF THE FORECAST AREA OVER
THE PAST FEW HOURS VIA SOUTHWEST WINDS AHEAD OF THE BOUNDARY.
OTHERWISE...TEMPS WERE MILD IN THE 60S WITH HUMID CONDITIONS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT SAT MAY 30 2015

TODAY...UNSEASONABLY COOL AND BLUSTERY WITH TEMPS IN THE 60S THIS
MORNING FALLING INTO THE 50S THROUGH THE AFTN. SFC CYCLOGENESIS
WILL OCCUR OVER S ILLINOIS TODAY AS A 500MB VORTICITY MAX LIFTS
NORTHEASTWARD OUT OF N ARKANSAS. THIS FEATURE WILL HAVE AN IMPACT
ON THE SENSIBLE WEATHER ACROSS E IOWA/W ILLINOIS/NE MISSOURI IN
THE FORM SHOWERS AND BREEZY NORTHEAST WINDS BETWEEN 15-30 MPH
THAT WILL DEVELOP AS THE SFC PRESSURE GRADIENT INCREASES.

ADDITIONALLY...HIGH SFC-850MB MOISTURE MEANS LOW-LEVEL STRATUS
CLOUDS ARE NOW FORECAST TO HANG AROUND LONGER INTO THE AFTN.
COOLING TEMPS AT 925MB BEHIND THE COLD FRONT WILL HELP TO MAINTAIN
THE HIGH DEGREE OF LOW-LEVEL SATURATION BEFORE SIGNIFICANT DRY AIR
ADVECTION RESULTS IN DECREASING CLOUD COVER LATE THIS AFTN OR THIS
EVENING. NAM TIME-HEIGHT SECTIONS HIGHLIGHT THE DEEPEST 1000-500MB
COLUMN MOISTURE TO OCCUR THROUGH THE AFTN AS WELL.

PRECIP PLACEMENT AND TIMING LOOKS FAIRLY CONSISTENT AMONG THE HI-
RES MODELS...NAM12/RAP/HRRR/NMM...WHICH RAISES CONFIDENCE FOR THE
STEADY RAIN ESPECIALLY ALONG AND EAST OF A MEMPHIS MISSOURI TO
FREEPORT ILLINOIS LINE.

WHILE THERE IS SOME UPPER DIVERGENCE THROUGH THE DAY LOW- LEVEL
CONVERGENCE IN THE SFC-850MB IN THE TROUGH AXIS WILL PROVIDE LIFT
THROUGH THE LATE MORNING INTO THE AFTN. SINCE THE SFC LOW WILL
TRACK WELL SOUTHEAST OF THE FORECAST AREA OVER SOUTHERN
ILLINOIS...THE SOUTHEASTERN THIRD OF THE DVN CWA WILL RECEIVE THE
STEADIEST RAIN AND THE HIGHEST TOTALS. EAST OF THE MISSISSIPPI
RIVER EXPECT TOTALS BETWEEN 0.25 TO 1.25 INCHES ON AVG WITH A
TIGHT WEST TO EAST GRADIENT.

SOUTH OF DUBUQUE COUNTY....THE TIER OF COUNTIES TO THE IMMEDIATE
WEST SIDE OF THE RIVER WILL BE ON THE WESTERN EDGE OF THE STEADIER
SHIELD OF RAIN BUT COULD STILL PICK UP LIGHT AMOUNTS OF RAINFALL.
MENTIONED SLIGHT CHANCES FOR THUNDER WITH A FEW EMBEDDED STORMS
POSSIBLE BUT NOTHING WIDESPREAD IS ANTICIPATED.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT SAT MAY 30 2015

UNSEASONABLY COOL AND DRY WEATHER TO START OUT THE NEW WEEK AS THE
REGION WILL BE DOMINATED BY HIGH PRESSURE THAT MIGRATES FROM CANADA
TO THE GREAT LAKES. HAVE STAYED CLOSE TO GUIDANCE BLEND AND PREVIOUS
FORECAST WITH HIGHS ONLY IN THE 60S SUNDAY AND MONDAY...WITH SUNDAY
NIGHT LOWS ONLY IN THE 40S. BASED ON THE SURFACE RIDGE AXIS SHOWN
POSITIONED OVER NW IL TOWARD 12Z MONDAY WITH ITS LIGHT EASTERLY
WINDS AND COLDEST TEMPERATURES AT 850 MB...SOME SHELTERED AREAS OF
FAR NW IL AND POSSIBLY FAR EASTERN IA COULD DIP INTO THE UPPER 30S.
THIS WOULD REQUIRE CLEAR SKIES...WHICH IS QUESTIONABLE LOOKING AT
THE POTENTIAL FOR HIGH LEVEL RH IN THE NW FLOW ALOFT AND WEAK MID
LEVEL SHORTWAVES.

LATEST MODEL RUNS HAVE SLOWED THE ONSET OF A PREVIOUSLY ADVERTISED
MORE AMPLIFIED UPPER LEVEL PATTERN AND DEVELOPING SW UPPER LEVEL
FLOW...AND INSTEAD NOW KEEP A TROUGH WELL TO THE WEST WITH A BROAD
FLAT RIDGE OVER THE CENTRAL U.S. WITH EMBEDDED SHORTWAVES POSSIBLY
IMPACTING THE REGION AS EARLY AS WEDNESDAY. THIS LEADS TO A
CONTINUED LOW CONFIDENCE FORECAST...WITH A POTENTIALLY ACTIVE
WEATHER PERIOD FROM MID TO LATE WEEK AND A PROLONGED PERIOD OF
SLIGHT TO LOW END CHANCES FOR SHOWERS AND THUNDERSTORMS IN THE
FORECAST FROM TUE NIGHT THROUGH FRIDAY. WHILE CONFIDENCE IN THE
TIMING OF MID LEVEL SHORTWAVE TRIGGERS IS LOW...THE SETUP WILL
RESULT IN RETURNING GULF MOISTURE WEDNESDAY WHICH WILL CONTINUE TO
FEED INTO THE AREA THROUGH FRIDAY. MORE FAVORABLE CONVERGENCE FROM
AN APPROACHING FRONTAL SYSTEM WILL KEEP THE HIGHEST POPS FOCUSED ON
THE FRIDAY PERIOD. WARM ADVECTION COMMENCES TUESDAY TO RETURN HIGHS
TO THE 70S WHILE LOWS RECOVER FROM THE 50S TO THE 60S BY WEDNESDAY
MORNING. WEDNESDAY INTO THURSDAY WILL LIKELY ALSO SEE RISING
DEWPOINTS...RETURNING HUMIDITY LEVELS TO MORE TYPICAL EARLY JUNE
VALUES. MODEL CONSENSUS KEEPS HIGHS FROM AROUND 80 TO THE LOWER 80S
WEDNESDAY THROUGH FRIDAY WITH OVERNIGHT LOWS IN THE 60S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 735 AM CDT SAT MAY 30 2015

A SOUTHWARD MOVING COLD FRONT WILL BRING A BIG DROP IN
TEMPS IN THE 925-850MB LAYER WHICH WILL HELP TO MAINTAIN A
HIGH DEGREE OF SATURATION AND LOW CIGS INTO THIS AFTN.

IN FACT IFR CIGS HAVE DEVELOPED AT ALL TERMINALS EXCEPT
KMLI. IT WILL LIKELY TAKE SEVERAL HOURS...POSSIBLY 2-4
HOURS BEFORE CIGS IMPROVE TO LOW-END MVFR. SCT -SHRA ARE
MOST LIKELY AT KBRL AND A LITTLE LESS SO AT KMLI INTO
THE EARLY AFTN BUT THE THREAT FOR THUNDER IS LOW.

BREEZY NE WINDS WILL DEVELOP THROUGH THE MORNING GUSTING
UP TO 25 KTS INTO THE AFTN. EXPECT A GRADUAL RETURN TO VFR
DURING THE EVENING HOURS.

&&

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

$$

SYNOPSIS...UTTECH
SHORT TERM...UTTECH
LONG TERM...SHEETS
AVIATION...UTTECH



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