Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 260837
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
337 AM CDT SUN JUL 26 2015

.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 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1159 PM CDT SAT JUL 25 2015

LIGHT SURFACE WINDS AND HUMID SURFACE CONDITIONS WILL LIKELY LEAD
TO MVFR FOG AT MOST SITES OVERNIGHT INTO THE EARLY MORNING HOURS.
WIDELY SCATTERED THUNDERSTORMS DEVELOPING OVER CENTRAL IOWA...AND
A LARGER COMPLEX MOVING OUT OF THE DAKOTAS WILL PUSH INTO THE
TERMINALS SUNDAY MORNING. DUE TO LOW CONFIDENCE IN TRENDS WITH
THESE SYSTEMS...ONLY PROB30 WORDING WAS USED FOR POSSIBLE STORMS
ARRIVING MID MORNING ONWARD AT CID...MLI AND DBQ...WHILE
CONFIDENCE IS HIGHER THAT THE BRL AREA SHOULD SEE STORMS CLOSER TO
SUNRISE. FROM MID TO LATE SUNDAY AFTERNOON...HAVE GONE WITH NO
SIGNIFICANT WEATHER IN THE TAFS...BUT THERE IS A POTENTIAL FOR AT
LEAST WIDELY SCATTERED THUNDERSTORMS THAT MAY BE ADDED IN LATER UPDATES.

&&

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

$$

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


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