Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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656
FXUS63 KDVN 170843
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
343 AM CDT SUN MAY 17 2015

.SYNOPSIS...
ISSUED AT 340 AM CDT SUN MAY 17 2015

SYNOPSIS...HUGE SQUALL LINE OF SEVERE STORMS AND EMBEDDED TORNADOES
EXTENDED ALL THE WAY FROM NORTHERN MO TO CENTRAL TX. HOWEVER...THE
FAR NORTHERN PORTION OF THE LINE APPROACHING NORTHEAST MO AND
SOUTHCENTRAL IA WAS RAPIDLY WEAKENING AS IT RUNS INTO MUCH MORE
STABLE AIR WITH MINIMAL CAPE. ALSO...IR SATELLITE SHOWS RAPIDLY
WARMING TOPS. MEANWHILE BACK AT THE RANCH...LOW STRATUS HAS FORMED
OVER MUCH OF THE CWA DUE TO CONTINUED MOISTURE TRANSPORT FROM THE
SOUTH. 3 AM TEMPERATURES RANGED FROM THE MID 60S TO AROUND 70 WITH
DEWPOINTS IN THE MID 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CDT SUN MAY 17 2015

FORECAST FOCUS ON SEVERE POTENTIAL AND COVERAGE OF THUNDERSTORMS.

TODAY...SPC HAS SHIFTED THE ENHANCED SEVERE RISK NORTH OF THE CWA
CLOSER TO THE STRONGEST SHEAR AND TRIPLE POINT OF THE OCCLUDING
CYCLONE WITH A SLIGHT RISK OVER ALL OF THE CWA. SPC HAS A 5%
PROBABILITY FOR TORNADOES IN NORTHEAST IA AND NORTHERN IL WITH A 15%
PROBABILITY OF WIND AND HAIL OVER THE ENTIRE CWA. THIS IS A LOW
CONFIDENCE FORECAST OF EXACTLY HOW THE CONVECTION WILL PLAY OUT AS
MODELS DIFFER GREATLY...RANGING FROM NUMEROUS TO ONLY ISOLATED
STORMS.

FIRST OF ALL IS THIS MORNING WITH THE RAPIDLY DECAYING SQUALL LINE
WHICH WILL BE MOVING INTO OUR WESTERN AND SOUTHERN CWA EARLY THIS
MORNING...SO WILL HAVE LIKELY POPS FOR THOSE AREAS. THE HRRR MODEL
TAKES THIS WEAK LINE OVER ALL OF EASTERN IA TO ABOUT THE MS RIVER
THEN FADES IT BY MID MORNING...SO WILL HAVE CHANCE POPS THE FARTHER
EAST YOU GO INTO THE CWA. THEN WE HAVE THE LOW STRATUS FOR MUCH OF
THE MORNING WITH THE AVIATION GFS-LAMP GUIDANCE INDICATING THIS TO
DISSIPATE BY LATE MORNING/EARLY AFTERNOON SIMILAR TO YESTERDAY.

THIS AFTERNOON...COVERAGE OF THUNDERSTORMS IS PROBLEMATIC AS MODELS
HAVE DIFFERING SOLUTIONS. MODELS STILL INDICATE STRONG DEEP LAYER
SHEAR WITH 0-6KM OF 40-45 KTS AIDED BY CYCLONICALLY CURVED JET FROM
MID MISSISSIPPI VALLEY INTO GREAT LAKES. TEMPERATURES IN THE LOWER
TO MID 80S AND DEWPTS IN THE MID TO UPPER 60S SHOULD YIELD MODERATE
INSTABILITY WITH MLCAPES OF 1000-2000 J/KG. THIS IS CERTAINLY
SUFFICIENT TO SUPPORT ALL MODES OF SEVERE WEATHER. HOWEVER...WITH
THE OCCLUDING CYCLONE WE ARE ALSO LOSING THE FORCING/LOW LEVEL
CONVERGENCE TO GET STORMS TO DEVELOP...EXCEPT IN OUR FAR EASTERN
COUNTIES EARLY THIS AFTERNOON. THIS WILL BE INTERESTING TO SEE HOW
THIS PLAYS OUT BUT FOR NOW WILL HAVE THE HIGHEST POPS IN THE EAST
AND ONLY SLIGHT POPS IN THE SW. MAXIMUM TEMPERATURES SHOULD GET INTO
THE LOWER TO MID 80S AT MOST LOCATIONS.

TONIGHT...I WILL MAINTAIN THE SMALL POPS FOR EARLY THIS EVENING
ALONG AND EAST OF THE MS RIVER BUT WE COULD JUST AS EASILY BE DRY.
OPERATIONAL MODELS INDICATE DRY SLOT TO SPREAD OVER ALL THE CWA AS
THE OCCLUDING CYCLONE TRACKS INTO THE MN ARROWHEAD. SKIES WILL BE
CLEARING OR CLEAR WITH COOLER AND DRIER AIR BEGINNING TO PUSH INTO
THE NW CWA OVERNIGHT. MINIMUM TEMPERATURES WILL RANGE FROM THE MID
50S NW TO THE LOWER TO MID 60S SE.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 340 AM CDT SUN MAY 17 2015

COOL BUT NICE MID MAY WEATHER FOR THE UPCOMING WORK WEEK WITH SOME
LIGHT RAIN POSSIBLE WEDNESDAY.

LONG TERM FORECAST CONFIDENCE ASSESSMENT...GOOD OR ABOVE AVERAGE WITH
LITTLE SENSIBLE WEATHER ISSUES. MAIN ISSUE IS DIURNAL TEMPERATURE RANGES
WITH MOST DAYS SUGGESTION OF WIDER RANGES OF HI/LO BY A DEGREE OR SO
MOST LOCATIONS SUPPORTED.

OVERVIEW...INITIALIZATION AND VERIFICATION IS GOOD WITH SLIGHTLY TOO
MOIST BL ISSUES NOTED THAT ARE IMPACTING NORMAL MODEL FIELDS CURRENTLY
AS TOO WIDESPREAD EXCEPT FOR LINEAR FEATURES UNDERDONE. THIS WILL HAVE
NO IMPACT MONDAY ONWARD. RUN TO RUN VARIANCES SUGGEST LITTLE DIFFERENCES
EXCEPT TEMPERATURES BY A CATEGORY OR SO WITH A MEAN TAKEN FOR LATER
SHIFTS TO REASSESS AS AGAIN PROBABLE A DEGREE OR TWO TO COOL/MILD FOR
HIGHS/LOWS MOST DAYS.

MONDAY...STRONG CAA TO RESULT IN BREEZY WEATHER WITH MANY LOCATIONS
TO HAVE NEARLY STEADY TEMPERATURES WITH 15 TO 25+ MPH WITH SOME GUSTS
TO 30 MPH NORTH HALF OF FORECAST AREA. STRONG GRADIENT WITH LOWER 60S
FAR NW TO UPPER 70S FAR SE SECTIONS. MONDAY NIGHT...WINDS MAY BE UP
ENOUGH TO PRECLUDE FROST RISK WITH UPPER 30S NW TO MID 40S SOUTH SECTIONS.

TUESDAY...BELOW NORMAL TEMPERATURES BY 10 TO 15 DEGREES WITH CONTINUED
CAA WITH LOW LEVEL THERMAL FIELDS SUPPORTIVE OF NEAR 60F FAR NORTH TO
MIDDLE 60S SOUTH SECTIONS DESPITE NEARLY FULL TO FULL SUNSHINE.
TUESDAY NIGHT...LIGHT WINDS MAY ALLOW FOR BL DECOUPLING NORTH 1/2
AND PATCHY FROST RISK FOR LATER SHIFT TO RECONSIDER. LOCAL TECHNIQUES
DO SUGGEST WITH FAIR SKIES AND BL DECOUPLING SOME MID 30S POSSIBLE
ALONG AND NORTH OF HIGHWAY 30 CORRIDOR FAVORED LOW LYING LOCATIONS.

WEDNESDAY...INCREASING CLOUDS WITH RISK OF SPRINKLES MOSTLY CENTRAL
SECTIONS AND SOME LIGHT RAIN SOUTH 1/3 OF AREA. HIGHS SHOULD WITH CLOUDS
BE MOSTLY LOWER 60S WITH UPPER 50S POSSIBLE IN HEAVIEST CLOUDS AND
POSSIBLE LIGHT RAIN. WEDNESDAY NIGHT...ANY LIGHT PRECIPITATION SHOULD
END AROUND MIDNIGHT WITH CLEARING SKIES BY MORNING ALL BUT FAR SE
SECTIONS. MINS LOWER TO MIDDLE 40S ARE REASONABLE.

THURSDAY THROUGH SATURDAY...MORE NICE WEATHER WITH UPPER 60S MOST LOCATIONS
FOR HIGHS ON THURSDAY AND LOWER 70S A GOOD REFERENCE POINT FRIDAY/SATURDAY
WITH LOW DEWPOINTS. MINS 40S RISING INTO THE 50S SATURDAY AND SUNDAY
AM WITH PROBABLE MOST LOCATIONS MINS ARE 2 TO 3 PLUS DEGREES TOO MILD
FOR LATER SHIFTS TO CONSIDER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1153 PM CDT SAT MAY 16 2015

THE DISSIPATING REMNANTS FROM A LINE OF STRONG THUNDERSTORMS
ADVANCING FROM THE PLAINS WILL LIKELY MOVE INTO THE EASTERN IOWA
TERMINALS AS LIGHT RAIN WITH MVFR CONDITIONS DUE TO STRATUS AND
FOG TOWARD MORNING. BEYOND...THE FORECAST REMAINS LOW CONFIDENCE
WITH RESPECT TO THE POTENTIAL FOR STRONG TO SEVERE STORMS AS AN
UPPER LEVEL TROUGH MOVES THROUGH LATER IN THE DAY. FOR NOW...THIS
POTENTIAL IS LIMITED TO HIGHER CONFIDENCE CHANCE FOR SHOWERS IN
THE LATE MORNING OR EARLY AFTERNOON. GUSTY SOUTH WINDS WILL
GRADUALLY VEER TO MORE SOUTHWEST TOWARD SUNDAY EVENING WITH
PREVAILING VFR CONDITIONS.


&&

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

&&

$$

SYNOPSIS...HAASE
SHORT TERM...HAASE
LONG TERM...NICHOLS
AVIATION...SHEETS



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