Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 300002
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
702 PM CDT FRI APR 29 2016

...AVIATION UPDATE...

.SYNOPSIS...
ISSUED AT 330 PM CDT FRI APR 29 2016

THE LATEST SFC ANALYSIS WAS INDICATING RIDGING ACRS THE UPPER MS RVR
VALLEY INTO THE GRT LKS...WHILE CYCLOGENESIS AND INVERTED TROFFINESS
CONTINUED TO ORGANIZE ACRS THE SOUTHERN PLAINS. ALOFT...CURRENT
WATER VAPOR LOOP WAS INDICATING AN UPPER LOW OVER NORTHEASTERN NM/
SOUTHEASTERN CO BECOMING INCREASINGLY NEGATIVELY TILTED. BUT LEE
SIDE UPPER RIDGE LOBE WAS STILL HOLDING FIRM FROM THE NORTHERN
PLAINS DOWN INTO THE SOUTHEASTERN CONUS. EXCEPT FOR A FEW BREAKS
FROM TIME TO TIME...STRATOCU DECK HAS BEEN STUBBORN TO MIX OUT SOME
AND REALLY HAS KEPT A LID ON HIGH TEMPS THIS AFTERNOON.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 330 PM CDT FRI APR 29 2016

TONIGHT...TAKING INTO ACCOUNT THE STRENGTH OF THE MID AND UPPER
LEVEL RIDGE JUST WEST OF THE GRT LKS AND INITIAL DRY SUBSIDENT
AIRMASS IN PLACE...WILL SIDE WITH THE SLOWER TO SATURATE THE COLUMN
MODELS FOR ADVANCING THE PRECIP UP INTO THE REGION FROM THE
SOUTH/SOUTHWEST AS NEGATIVELY TILTED CYCLONE COMPLEX ROLLS UP ACRS
THE EAST CENTRAL PLAINS BY SAT MORNING. WILL KEEP THINGS DRY THROUGH
06Z SAT...AND THEN INCREASE ACRS THE SOUTHWESTERN HALF OR A BIT MORE
THROUGH 12Z SAT. ACTUALLY THINK THE 12Z HIRES ARW WHICH KEEPS MOST
PRECIP SOUTH OF I80 THRU 12Z SAT/EXCEPT WEST OF THE IOWA CITY AREA
TAKING INTO ACCOUNT THE DELAY IN SATURATION AND EAST-NORTHEAST DRY
FETCH HANDLING THE BEST. SURE THERE WILL BE INITIAL ELEVATED PRECIP
BANDS/RADAR RETURNS BEFORE THIS AND FURTHER TO THE NORTH OVERNIGHT...
BUT SHOULD REMAIN IN VIRGA FORM AND DECAY AS THEY TRY TO MAKE IT
TO THE NORTHEAST. BUT SSW 40-50 KT LLJ AND ROBUST ELEVATED THTA-E
FEED/WARM MOIST CONVEYOR OFF THE WESTERN GULF WILL BE REALIZED BY
SAT MORNING. ACTUALLY A STRONG THTA-E ADVECTION AND CONVERGENT
SIGNATURE ACRS THE SOUTHERN HALF OF THE CWA SAT MORNING. PWAT/S
PROGGED TO INCREASE TO NEAR AN INCH NORTH OF I80 BY 12Z SAT...AND
UP TO 1.2 INCHES IN THE SOUTH. WILL KEEP ISOLATED THUNDER SOUTH OF
I80 BY LATE TONIGHT...BUT MID LAYER LAPSE RATES AND MUCAPES APPEAR
MARGINAL SOUTH OF I80 EXCEPT THE FAR SOUTHERN TIER OR TWO OF DVN
CWA COUNTIES. LOWS AROUND 40 OR IN THE LOW 40S NORTH...TO THE
UPPER 40S IN THE SOUTH.

SATURDAY...EXTENT OF SATURATION OF THE VERTICAL COLUMN AND DEEP
LAYER SHEAR TO WRING OUT THE PRECIP LIKE A HAND SQUEEZING A SPONGE
SHOULD MAKE FOR A DECENT RAIN EVENT ON SATURDAY. ALREADY ADVERTISED
WIDESPREAD 0.50 TO 1+ INCHES STILL LOOKS IN LINE BY 00Z SUNDAY...
AND WITH THE MAIN BAND OF PRECIP MIGRATING NORTH AS THE DAY
PROGRESSES INTO THE NORTHERN TO NORTHEASTERN THIRD OF THE FCST AREA
BY MID TO LATE AFTERNOON...SHOULD HELP KEEP QPF TOTALS FROM REACHING
MORE WIDESPREAD 1-2 INCHES. CLOUD COVER AND EXTENSIVE PRECIP MAY
KEEP MANY AREAS NORTH OF I80 IN THE 40S DURING THE DAY SATURDAY.

ATTENTION THEN SHIFTS TO THE SOUTHERN CWA BY LATE AFTERNOON WHERE
THE MAIN RAIN BAND LIFTS NORTHWARD OUT OF. BULK OF THE LATEST 12Z
RUN MODEL SOLUTIONS SET UP WARM FRONT AND NORTHERN FRINGE OF DEEPER
CONVECTIVE INDEX/INSTABILITY ZONE FROM WEST OF THE STL AREA IN
CENTRAL MO...EAST-NORTHEASTWARD ACRS EAST CENTRAL IL INTO INDIANA.
THUS ISOLATED TO WDLY SCTRD AFTERNOON THUNDERSTORM DEVELOPMENT
SHOULD OCCUR ALONG THIS SWATH AND REMAIN JUST TO THE SOUTH AND
SOUTHEAST OF THE DVN CWA THROUGH 00Z SUNDAY. SOME OF THESE SLIGHTLY
ELEVATED STORMS COULD PRODUCE SEVERE SIZE HAIL NOT ALL THAT FAR AWAY
FROM THE LOCAL AREA...AND THE 12Z 4KM NAM HINTS AT THIS ESPECIALLY
ACRS WEST CENTRAL IL. BUT AGAIN...BULK OF OTHER SOLUTIONS ARE FURTHER
TO THE SOUTH MAKING THE 4KM NAM A BIT OF AN OUTLIER. BUT AS
ALWAYS... THE WEATHER WATCH WILL HAVE TO BE ON TO SEE HOW FAR NORTH
THE WARM FRONT AND HEATING CAN RETREAT NORTHWARD ON SAT AFTERNOON
AND IF THE SOUTHERN CWA WILL BE AT RISK FOR STRONG TO SVR STORMS
LIKE THIS PAST WED EVENING.    ..12..

.LONG TERM...(SATURDAY NIGHT THROUGH NEXT FRIDAY)
ISSUED AT 330 PM CDT FRI APR 29 2016

COOL AND RATHER DAMP WEATHER WILL BALANCE OUT THE WEEKEND...THEN
NEXT WEEK LOOKS LARGELY DRY WITH NEAR NORMAL TEMPERATURES. THE
SYSTEM THIS WEEKEND APPEARS TO BE TRENDING TOWARD A SLOWER...DEEPER
SYSTEM THAT WILL KEEP UNSETTLED CONDITIONS GOING WELL INTO SUNDAY.

SATURDAY NIGHT...MODELS GENERALLY SUGGEST THE INITIAL WAVE OF
ORGANIZED SHOWERS AND POTENTIAL THUNDERSTORM WILL BE ROTATING
NORTHEAST OUT OF NE IA AND NORTHERN IL EARLY. THE FRONT AROUND 850
MB LAYS OUT E-NE FROM SE NEB THROUGH S CENTRAL IA...ERN IA INTO N
CENTRAL IL THROUGH MUCH OF THE NIGHT. THIS...AND THE NEXT LOBE OF
UPPER LEVEL LIFT ROTATING NE THROUGH THE AREA MAY PROVIDE SUPPORT
FOR SUBSEQUENT WAVES OF AT LEAST SCATTERED SHOWERS THROUGH THE REST
OF THE NIGHT. THUNDERSTORMS WILL BE LIKELY IN THE FAR SOUTH CLOSEST
TO THE SURFACE BOUNDARY THAT STAYS JUST SOUTH OF THE FORECAST AREA.
IF THIS BOUNDARY TRENDS CLOSER TO THE FARTHEST NORTH GEM POSITION...
THERE WOULD BE A POTENTIAL FOR SEVERE STORMS WITH PRIMARILY A HAIL
THREAT IN OUR NE MO AND SOUTHERN IL COUNTIES IN THE EVENING.
FURTHER NORTH...STEEP MID LEVEL LAPSE RATES AND MUCAPES AS HIGH AS
150 TO NEAR 1000 J/KG...DEPENDING ON THE MODEL...WILL WARRANT
MENTION OF AT LEAST ISOLATED THUNDERSTORMS AS FAR NORTH AS THE I-80
CORRIDOR THROUGH THE EVENING. QPF AMOUNTS ARE KEPT WELL BELOW .10
FOR THE OVERNIGHT PERIOD...BUT GIVEN THE ENVIRONMENT WITH AN AXIS OF
PW VALUES OVER .75 SHOWN WRAPPING W-NW INTO THE REGION...STRONGER
CONVECTIVE CELLS WOULD EASILY GENERATE LOCALIZED QUARTER TO HALF
INCH AMOUNTS. TEMPERATURES SHOULD AGAIN COOL BACK INTO THE 40S FOR
OVERNIGHT LOWS WITH BRISK NE SURFACE WINDS.

SUNDAY...THE SLOWER AND LIKELY DEEPER UPPER SYSTEM EJECTING NE
THROUGH THE AREA WILL KEEP A RISK OF SHOWERS GOING THROUGH THE
DAY...ESPECIALLY ACROSS THE CENTRAL AND SOUTH. THE SETUP FAVORS
CLOUD COVER LINGERING THROUGH MUCH OF THE DAY SIMILAR TO THE PAST
SEVERAL DAYS HOLDING TEMPERATURES IN THE 50S. THE INITIALLY TIGHT
PRESSURE GRADIENT AROUND THE LOW EXITING INTO THE OHIO VALLEY WILL
PROVIDE RESULT IN BRISK NE WINDS OF 15 TO 25 MPH. CLEARING SKIES AND
IN-BUILDING SURFACE RIDGE WILL LEAD TO A COOL NIGHT WITH UPPER 30S
OR POSSIBLY COOLER MINS ALONG THE HIGHWAY 20 CORRIDOR AND LOWER 40S
ELSEWHERE.

MONDAY THROUGH FRIDAY OVERALL LOOKS TO BE A DRY AND MILD PERIOD WITH
A SERIES OF WEAK FRONTAL SYSTEMS. FOR THE MOST PART...THESE APPEAR
TO LACK SUFFICIENT FORCING OR MOISTURE AVAILABILITY TO JUSTIFY GOING
WITH ANYTHING MORE THAN SLIGHT CHANCE POPS AT THIS TIME. HIGHS ARE
KEPT IN A RANGE FROM THE MID 60S TO LOWER 70S WITH LOWS PRIMARILY IN
THE 40S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 657 PM CDT FRI APR 29 2016

00Z TAFS FOCUSED ON FINE TUNING TIMING OF RAIN ONSET OVERNIGHT
INTO SATURDAY MORNING. BASED ON RADAR TRENDS AND SOME OF THE HIGH
RESOLUTION MODELS...HAVE BROUGHT THE RAIN IN A COUPLE HOURS
SOONER. EXPECT MVFR TO LOW VFR CEILINGS...WITH IFR CONDITIONS IN
PERIODS OF MODERATE RAIN THROUGH SATURDAY MORNING. SHOWERS WILL
BECOME MORE SCATTERED IN NATURE SATURDAY AFTERNOON.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...SHEETS
AVIATION...RP KINNEY



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