Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 261812
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
112 PM CDT SUN JUL 26 2015

.UPDATE...
ISSUED AT 1251 PM CDT SUN JUL 26 2015

WELL DEFINED OUTFLOW BOUNDARY SAGGING SOUTH OF CID-MLI ATTIM.
RESIDUAL COOL POOL AND CLOUDS COMBINED WITH EASTERLY FLOW
HOLDING TEMPS DOWN NORTH OF BOUNDARY AND WILL BE UPDATING TO
TRIM HIGHS A BIT PORTIONS OF NORTHEAST IA INTO NORTHWEST IL.
OTHERWISE... AFFORMENTIONED BOUNDARY(IES) WILL PROVIDE CONTINUED
FOCUS FOR REDEVELOPMENT OF SHOWERS AND STORMS THROUGH THE
AFTERNOON. WILL HAVE TO MONITOR FOR A FEW STRONG TO POSSIBLE
ISOLATED SEVERE STORMS LATER THIS AFTERNOON WITH INSTABILITY
INCREASING WITH CONTINUED FILTERED SUNSHINE. CURRENTLY SBCAPE
AND MLCAPES RUNNING AROUND 1000-1500+ J/KG ALONG MOIST
AXIS/BOUNDARY WITH 0-6KM SHEAR AROUND 30 KTS. KEEPING EYE
ESPECIALLY ON POTENTIAL FOR NON-SUPERCELL TORNADO OR SPIN-UP
WITH ANY CELL INTERACTION WITH BOUNDARY. SOME UNCERTAINTY ON
EXTENT OF DEVELOPMENT WITH WARM EML ADVANCING INTO REGION IN WAKE
OF PASSING SHORTWAVE... THUS PLANNING TO SEND UP A 19Z BALLOON TO
SAMPLE ENVIRONMENT. WILL HAVE UPDATED GRIDS/ZFP/PFM OUT SOON.

UPDATE ISSUED AT 643 AM CDT SUN JUL 26 2015

SQUALL LINE IN ADVANCE OF AN UPPER LEVEL TROUGH MOVING ACROSS THE
MIDWEST EXTENDED FROM THE NORTHEAST CORNER OF IA TO EAST OF DES
MOINES AND THEN INTO FAR NW MO. THIS LINE WAS MOVING SOUTHEAST AT
ABOUT 30 MPH AND IN ISOLATED SPOTS HAS PRODUCED WINDS TO 50 MPH.
THE STRONGER SHEAR...LOW LEVEL MOISTURE TRANSPORT AND INSTABILITY
WAS LOCATED ACROSS MO AND THE STRONGEST PORTION OF THE LINE SHOULD
PUSH SOUTHEAST INTO NORTHERN MO THIS MORNING. THE NORTHERN PORTION
OF THE LINE WILL CONTINUE TO TRACK ACROSS THE DVN CWA BUT IS EXPECTED
TO GRADUALLY WEAKEN AS THE MORNING PROGRESSES. REMAINS TO BE SEEN
IF ANY REDEVELOPMENT OF THUNDERSTORMS OCCURS LATER THIS AFTERNOON.

I HAVE UPDATED THE GRIDS TO GO LIKELY POPS IN OUR WESTERN CWA TO
COVER THE APPROACHING SQUALL LINE. HOWEVER...KEPT THE SCATTERED
WORDING ELSEWHERE AS THE LINE IS EXPECTED TO WEAKEN IS IT TRACKS
FARTHER EASTWARD INTO THE DVN CWA.

&&

.SYNOPSIS...
ISSUED AT 335 AM CDT SUN JUL 26 2015

DOPPLER RADAR INDICATED AN AREA OF THUNDERSTORMS IN NORTHEAST MO
NEAR AN OUTFLOW BOUNDARY AND AIDED BY AN UPPER LEVEL TROUGH MOVING
ACROSS THE UPPER MS VALLEY. SHEAR IS RATHER WEAK BUT PWAT`S ARE
NEAR 2 INCHES SO HEAVY RAINFALL HAS BEEN THE MAIN FEATURE IN THE
DVN CWA SO FAR. THIS TROUGH WAS ALSO TRIGGERING A LARGER MCS IN
THE FORM OF A SQUALL LINE THAT EXTENDED FROM SOUTHERN MN TO
WESTERN IA AND WAS MOVING SOUTHEAST. UP TO 50 MPH WIND GUSTS HAVE
BEEN NOTED WITH THIS LINE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 335 AM CDT SUN JUL 26 2015

FORECAST FOCUS ON CONVECTION AND TEMPERATURES.

TODAY...OPERATIONAL MODELS INCLUDING THE CONVECTION-ALLOWING HRRR
MODEL CONTINUES TO STRUGGLE WITH THE EVOLUTION OF THE ONGOING
CONVECTION. THE ONLY MODEL THAT CAPTURES THE MCS IN NW IA WAS THE
SPC 4KM WRF-NMM WHICH TAKES THE STRONGEST PORTION OF THE MCS INTO
NORTHERN AND CENTRAL MO THIS MORNING. THIS SEEMS TO MAKE SENSE
CONSIDERING THE HIGHER CAPE/PWAT`S WERE LOCATED THERE. THE
NORTHERN PORTION OF THE MCS STILL SHOULD TRACK ACROSS PORTIONS OF
THE DVN CWA THIS MORNING SO HIGHER POPS THEN. I WILL MAINTAIN
CHANCE POPS THIS AFTERNOON AS THE TROUGH SWINGS ACROSS THE CWA.
HOWEVER...CONFIDENCE LOW IN REGARDS TO COVERAGE OF THE STORMS.
TEMPERATURES WILL BE TRICKY DEPENDING ON CLOUD TRENDS BUT FOR NOW
HIGHS SHOULD PUSH INTO THE MID TO UPPER 80S. WITH DEWPOINTS IN THE
MID 70S THIS SHOULD ALLOW HEAT INDEX VALUES TO RISE INTO THE MID
TO UPPER 90S. ONCE AGAIN TEMPERATURES MAY NEED TO BE ADJUSTED UP
OR DOWN DEPENDING ON AMOUNT OF CLOUDINESS...OR LACK THEREOF. THIS
MAY IMPACT THE HEAT INDEX VALUES.

TONIGHT...WITH THE PASSAGE OF THE UPPER LEVEL TROUGH TO OUR EAST
THIS ALLOWS A RIDGE TO BEGIN BUILDING INTO THE MIDWEST. THIS SHOULD
LESSEN CONVECTION WITH TIME SO I WILL HAVE DECREASING POPS. HOWEVER...
SOME OF THE MODELS ESPECIALLY THE GFS/NAM DISAGREE AND INDICATE MCS
DEVELOPMENT OVER THE CWA. I DON`T SEE MUCH IN THE WAY OF FORCING
SUCH AS A LOW LEVEL JET. THEREFORE...LOW CONFIDENCE IN CONVECTIVE
TRENDS. LOWS TONIGHT WILL BE IN THE UPPER 60S TO LOWER 70S.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 335 AM CDT SUN JUL 26 2015

MODELS ARE IN GOOD OVERALL AGREEMENT WITH THE SYNOPTIC PATTERN BUT
STRUGGLE WITH TIMING ESPECIALLY EARLY IN THE PERIOD. THE MAIN
FORECAST CONCERNS ARE THE CHANCES OF PRECIPITATION AS WELL AS
TEMPERATURES ON MONDAY AND TUESDAY.

WE BEGIN THE LONG TERM PERIOD WITH ZONAL FLOW ACROSS THE CONUS ON
MONDAY. A SHORTWAVE TROUGH IN THE GULF OF ALASKA WILL MOVE INTO THE
INTERMOUNTAIN WEST ON MONDAY WHILE HIGH PRESSURE SITS ACROSS EASTERN
OKLAHOMA...AND KANSAS. THE RIDGE AXIS WILL SHIFT EASTWARD AS ENERGY
EJECTS OUT OF THE INTERMOUNTAIN WEST TROUGH TOWARDS THE PLAINS. THIS
WILL BRING THE RISK OF SHOWERS AND THUNDERSTORMS TO THE REGION LATER
IN THE DAY ON MONDAY. THE HANDLING OF A FRONTAL BOUNDARY ACROSS THE
UPPER MIDWEST ON MONDAY WILL HAVE A BIG IMPACT ON TEMPERATURES AND
DEWPOINTS ACROSS THE REGION. THE GFS AND NAM ARE MUCH FARTHER TO THE
NORTH WITH THE WARM FRONT THAN THE ECWMF AND GEM DESPITE HAVING
NEARLY IDENTICAL SURFACE PRESSURE PATTERNS. BECAUSE THIS WARM FRONT
IS MUCH FARTHER TO THE NORTH WITH THE GFS AND NAM HE TEMPERATURES
AND DEWPOINTS ARE MUCH HIGHER ACROSS A BROAD PART OF THE UPPER
MIDWEST. THEREFORE WE BLENDED THE MODELS FOR THE TIME BEING TO
ACCOUNT FOR THE DIFFERENT SOLUTIONS UNTIL THE MODELS COME INTO
BETTER AGREEMENT. CLOUD COVER ON MONDAY MAY ALSO WORK TO INHIBIT
TEMPERATURES ON MONDAY BUT THERE IS SOME CONCERN THAT AT LEAST PART
OF THE AREA WILL HAVE HEAT INDICES APPROACHING 100 ON MONDAY.

THE 500 HPA RIDGE AXIS WILL SHIFT TO THE EAST MONDAY NIGHT INTO
TUESDAY AS THE MODELS DEPICT WARM SOUTHERLY FLOW ACROSS THE
REMAINDER OF THE FORECAST AREA AND EXTENDING NORTHWARD ACROSS THE
UPPER MIDWEST. 850 HPA TEMPERATURES ARE NEAR 22*C AND AFTERNOON
SOUNDINGS DEPICT AT LEAST MIXING TO AROUND 850 HPA WHICH WILL YIELD
TEMPERATURES IN THE LOWER TO MID 90S ACROSS THE REGION AND POSSIBLY
ANOTHER DAY WITH HIGH HEAT INDEX VALUES.

AT 500 HPA...THE INTERMOUNTAIN WEST TROUGH WILL LIFT FROM THE LEE OF
THE NORTHERN ROCKIES AND INTO SOUTHERN CANADA ALONG WITH ITS
ATTENDANT SURFACE LOW. THE BEST LIFT ON TUESDAY WILL PASS TO OUR
NORTH DURING THE DAY WHICH WILL LIMIT THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS. MODELS DEPICT THE COLD FRONT MOVING ACROSS THE REGION
TUESDAY NIGHT INTO WEDNESDAY WITH THE BEST CHANCES ASSOCIATED WITH
THE COLD FRONT AND STRONGER CONVERGENCE.

AFTER WEDNESDAY...MODELS DEPICT SURFACE HIGH PRESSURE BUILDING INTO
THE PLAINS WHILE AT 500 HPA RIDGING REBOUNDS OVER THE WESTERN US AND
A DEEP CYCLONE RESIDES ACROSS ONTARIO AND QUEBEC. THIS WILL PLACE
THE REGION UNDER NORTHWEST FLOW ALOFT. THIS WILL BRING QUIET WEATHER
WEDNESDAY INTO FRIDAY NIGHT WITH NEAR TO SLIGHTLY BELOW NORMAL
TEMPERATURES. ANOTHER DISTURBANCE...MOVING ACROSS SOUTHERN CANADA
WILL DRAG ANOTHER COLD FRONT ACROSS THE AREA LATE FRIDAY INTO
SATURDAY MORNING BRINGING A CHANCE OF SCATTERED SHOWERS AND THUNDERSTORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1251 PM CDT SUN JUL 26 2015

WELL DEFINED OUTFLOW BOUNDARY NEAR CID TO MLI TO SAG SOUTH THROUGH
EARLY AFTERNOON BEFORE STALLING NEAR BRL. BEHIND THE OUTFLOW
BOUNDARY WILL BE CHARACTERIZED BY CU WITH IFR TO MVFR CIGS
IMPROVING TO VFR BY LATE AFTERNOON WITH NE/E WINDS AROUND 10 KTS
AND GUSTING OCCASIONALLY TO NEAR 20 KTS. BRL WILL SEE CU WITH
PERIODS OF IFR TO MVFR CIGS WITH MOISTURE POOLING AHEAD OF
BOUNDARY WITH ANY CIGS LIFTING TO VFR BY LATE AFTERNOON. THERE
WILL BE A CHANCE OF A SHOWER OR STORM THIS AFTERNOON AT ALL THE
TAF SITES...BUT CONFIDENCE ON OCCURRENCE AT TERMINAL IS TOO LOW
FOR MENTION BUT WILL MONITOR RADAR AND AMEND IF NEEDED.
OUTFLOW BOUNDARY OR EFFECTIVE WARM FRONT DUE TO DIFFERENTIAL
HEATING WILL SLOWLY LIFT BACK NORTH TONIGHT THROUGH MONDAY.
WITH MOISTURE POOLING IN VICINITY OF BOUNDARY ALONG WITH EAST TO
SOUTHEAST FLOW SHOULD FAVOR LOW CLOUD AND FOG DEVELOPMENT WITH
MVFR TO IFR CONDITIONS LATE TONIGHT INTO MONDAY MORNING...WITH
CHANCE FOR LIFR/VLIFR CONDITIONS. CHANCE FOR A SHOWER OR STORM
WILL EXIST UNTIL THE FRONT PASSES LATER MONDAY... BUT AGAIN TOO
LOW CONFIDENCE FOR MENTION.

&&

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

$$

UPDATE...05
SYNOPSIS...HAASE
SHORT TERM...HAASE
LONG TERM...COUSINS
AVIATION...05



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