Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 010121
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
821 PM CDT SAT APR 30 2016

.UPDATE...
ISSUED AT 821 PM CDT SAT APR 30 2016

CURRENT RADAR TRENDS SHOWING THUNDERSTORMS FIRING AND MOVING EAST
ALONG THE FRONT NOW WELL SOUTH ROUGHLY FROM A QUINCY TO LINCOLN IL
AXIS SUGGESTS THE POTENTIAL FOR THUNDERSTORMS IN THE FORECAST AREA
HAS ENDED FOR THIS EVENING. FURTHER NORTH...THE MAIN AXIS OF
SHOWERS HAS LIFTED WELL TO THE NORTHEAST...LEAVING WIDESPREAD LOW
CLOUDS...DRIZZLE AND AVIATION IMPACTING FOG OVER THE AREA. BRISK
NORTHEAST WINDS HAVE KEPT TEMPERATURES IN THE LOWER TO MID 40S
NORTH OF I-80 WITH UPPER 40S TO LOWER 50S IN THE SOUTH.

HAVE UPDATED THE FORECAST TO REMOVE THUNDER CHANCES THIS EVENING
IN THE FAR SOUTH AND MENTION VERY LIGHT RAIN OR DRIZZLE THROUGH
THE OVERNIGHT AS THE NEARLY SATURATED LAYER BELOW 850 MB ON THE
00Z/01 KDVN SOUNDING REMAINS IN PLACE. BASED ON ADVECTION...
TEMPERATURES IN THE NORTH AND NE WILL HOLD IN THE LOWER
40S...WHILE THE SOUTH CONTINUES TO FALL REACHING THE MID AND UPPER
40S BY SUNRISE. FOG STILL LOOKS MOST LIKELY SOUTH OF I-80 WHERE
WINDS FIELDS WILL BE SLIGHTLY WEAKER AND MORE CONVERGENT.

&&

.SYNOPSIS...
ISSUED AT 340 PM CDT SAT APR 30 2016

THE LATEST SFC ANALYSIS WAS INDICATING OCCLUDED SFC WAVE AND TROF
SYSTEM FROM SOUTHEASTERN NEB....DRAPING EAST-SOUTHEASTWARD INTO
SOUTH CENTRAL IL. SFC PRESSURE FALLS INCREASING ALONG THE MAIN WARM
FRONT FROM FAR NORTH CENTRAL MO...TO JUST EAST OF THE STL AREA.
CLEARING AND HEATING IN THESE AREAS HAS ALLOWED FOR SFC BASED CAPES
TO GROW UP INTO THE 1K-2K J/KG RANGE IN THESE AREAS. OTHERWISE THE
MAIN RAIN BAND IS MIGRATING NORTHWARD ACRS THE NORTHEASTERN HALF OF
THE DVN CWA ATTM...WITH LIGHTER ACTIVITY FESTERING ALONG AND JUST
SOUTH OF I80.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 340 PM CDT SAT APR 30 2016

TONIGHT...WITH THE CLEARING TO THE SOUTH EDGING EVER CLOSER TO THE
SOUTHERN CWA ALONG WITH THE NORTHERN EDGE OF INSTABILITY GRADIENT...
WILL HAVE TO WATCH FOR ISOLATED TO WDLY SCTRD CONVECTION IN THE FAR
SOUTHERN CWA THROUGH AT LEAST 8 PM CDT. A FEW OF THE LATEST RUN
HIRES SOLUTIONS HAVE PICKED UP ON THIS...AND RAPID SCAN SUPER HIRES
VIS IMAGE SHOWING ENHANCED LINEAR CU FIELD EXTENDING FROM FAR NW
MO...EAST-SOUTHEASTWARD TOWARD THE STL AREA. IF A STRONG OR SEVERE
STORM WERE TO MANAGE TO FORM AN MAKE IT INTO THE FAR SOUTHERN CWA
THIS EVENING...HAIL WOULD BE THE MAIN THREAT BUT LLVL VEERING WIND
PROFILES MAY SUPPORT SECONDARY THREATS OF DOWNBURST WIND AND A
WEAKER SIDE TORNADO. OTHERWISE...FURTHER TO THE NORTH ACRS THE REST
OF THE CWA THE MAIN RAIN BAND WILL BE PRETTY MUCH TO THE NORTH OF
THE AREA BY THE START OF THE 1ST PERIOD. ONGOING LIFT WILL ALLOW FOR
A FEW SCTRD SHOWERS OR PATCHY LIGHT RAIN TO FORM AND PUSH NORTH ACRS
THE AREA...BUT MOST OF THE PRECIP MAY TRANSITION MORE TO DRIZZLE OR
SPRINKLES OVERNIGHT. AS WEAKENING LLVL OCCLUSION AND SFC WAVE ROLL
EAST ACRS THE SOUTHERN CWA BY EARLY SUNDAY MORNING... LIGHTER
CONVERGENT FLOW IN THE VCNTY OF THIS FEATURE MAY ALLOW FOR SOME FOG
DEVELOPMENT MAINLY SOUTH OF I80 FROM MIDNIGHT ON INTO SUNDAY
MORNING. FURTHER TO THE NORTH A MORE SUSTAINED NORTHEAST SFC BREEZE
SHOULD MAKE ANY FOG TOO LIGHT TO MENTION IN THE GRIDS/ZONES. LOWS IN
THE LOW TO MID 40S NORTH OF I80...TO THE MID UPPER 40S IN THE SOUTH.

SUNDAY...UPSTREAM UPPER LEVEL WAVE/LOW WILL LOOK TO PROPAGATE RIGHT
ACRS THE CWA BY SUNDAY EVENING. WITH LINGERING LOW TO MID LEVEL
MOISTURE FIELDS IN PLACE...EXPECT AN UPTREND IN SHOWER ACTIVITY TO
DEVELOP AND MOVE IN FROM THE WEST. SEVERAL MODEL SOLUTIONS EVEN
DEVELOP A TYPE OF DEF ZONE PRECIP BAND ACRS THE NORTHERN CWA BY
SUNDAY AFTERNOON...AND EXTENT OF LIFT AND SATURATION ON FCST
VERTICAL PROFILES SUGGEST ONE OR TWO TENTHS OF AN INCH OF ADDITIONAL
RAINFALL POSSIBLE IN THESE AREAS BY 00Z MON. WITH ONGOING NORTHERLY
UNDERCUTTING LLVL FLOW...WILL KEEP HIGHS MAINLY IN THE 50 TO 55
RANGE EXCEPT IN THE FAR SOUTHEAST WHERE A SLOWER PRECIP ARRIVAL MAY
ALLOW FOR SOME MID TO UPPER 50S. BUT LIKE THE PAST FEW DAYS...AN
EARLIER ONSET OF RAIN FROM THE WEST AND THICK CLOUD COVER COULD MAKE
IT HARD FOR SOME AREAS TO GET OUT OF THE 40S AGAIN.   ..12..

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 340 PM CDT SAT APR 30 2016

MAIN FORECAST CONCERN FOR THE LONG TERM ARE DIFFERENCES IN MODEL
SOLUTIONS IN THE DAY 3 THROUGH DAY 5 TIME FRAME. THE ECMWF AND GFS
DIFFER IN A NW FLOW SYSTEM. THESE DIFFERENCES AFFECT OUR AREA
DIFFERENTLY. BESIDES THIS...A RATHER QUIET LONG TERM IS FORECAST
WITH COOLER TEMPERATURES THE END OF THE NEXT WEEK IN THE NW FLOW.

CWA WILL BE ON THE TRANSITION ZONE BETWEEN THE NW FLOW AND A HIGH
AMPLITUDE RIDGE THROUGH THE EXTENDED.  A NW FLOW WAVE IS FORECAST TO
DIVE SOUTH ACROSS THE AREA ON TUESDAY INTO WEDNESDAY. AT THIS TIME
THE GFS KEEPS THE WAVE IN THE FLOW WHILE THE ECMWF HAS THE WAVE DIVE
SOUTH INTO THE PLAINS.  IN THE ECMWF SCENARIO THE RIDGE TO THE WEST
IS STATIONARY WHEREAS THE GFS IS MORE PROGRESSIVE...KEEPING THE WAVE
EAST OF THE CWA.  AT THIS TIME DECIDED THAT THE GFS SEEMS MORE
REASONABLE AS OFFSHORE PACIFIC SYSTEM WILL LIKELY HELP THE RIDGE
MOVE EAST.  IF THE ECMWF IS CORRECT THIS RUN...THEN THE FORECAST FOR
NEXT WEEK WOULD INCLUDE MORE POPS AND COOLER TEMPS. WHILE I AM NOT
CONFIDENT IN THIS SOLUTION...THE MAJOR DIFFERENCES BETWEEN THE
MODELS MAKE WE FEEL LESS CONFIDENT IN THE GFS AS WELL. REGARDLESS
OF THIS...H85 TEMPS WED NIGHT INTO THURSDAY ARE NEAR
0C...SUGGESTING THAT COLD TEMPS WILL BE POSSIBLE. THESE TEMPS LOOK
TO BE THE ONLY SENSIBLE WEATHER IN THE LONG TERM THAT LOOK TO HAVE
IMPACT ON THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 645 PM CDT SAT APR 30 2016

IFR CONDITIONS DUE TO LINGERING LOW CLOUDS...FOG AND DRIZZLE WILL
BE THE RULE OVERNIGHT THROUGH SUNDAY AS A LOW PRESSURE SYSTEM
PASSES TO THE SOUTH. INITIALLY GUSTY EAST TO SOUTHEAST SURFACE
WINDS WILL DIMINISH TO LESS THAN 10 KTS AFTER MIDNIGHT TONIGHT.
SUNDAY...LINGERING MOISTURE AND A PASSING UPPER LEVEL SYSTEM WILL
KEEP IFR TO LOW MVFR CONDITIONS IN PLACE AS ANOTHER ROUND OF LIGHT
RAIN...DRIZZLE AND OVERSPREADS OVER THE AREA. CONDITIONS SHOULD
IMPROVE SOME IN THE AFTERNOON...BUT OVERALL CONFIDENCE IN THE
TIMING OF CIGS LIFTING ABOVE IFR THRESHOLDS IS LOW. BRL IS THE
SITE MOST LIKELY TO SEE IMPROVEMENT...AND HAVE TRENDED CONDITIONS
TOWARD MVFR THERE SUNDAY MORNING.


&&

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

$$

UPDATE...SHEETS
SYNOPSIS...12
SHORT TERM...12
LONG TERM...GIBBS
AVIATION...SHEETS


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