Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 242043
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
343 PM CDT FRI JUL 24 2015

.SYNOPSIS...
ISSUED AT 342 PM CDT FRI JUL 24 2015

MCS THAT ROLLED SOUTH ALONG THE WESTERN FORECAST AREA BORDER TODAY
HAS MODIFIED THE ENVIRONMENT AND IS NOW THE DOMINANT WEATHER FEATURE
IN THE IMMEDIATE SHORT TERM. WHILE THE STRONGEST STORMS HAVE NOW
DIVED SOUTH INTO NE MO WITH SHOWERS EXTENDING NE INTO W CENTRAL
IL...THE ASSOCIATED ANVIL CLOUD COVER AND RELATED IMPACTS OF
THERMAL/PRESSURE FIELDS HAS HELD TEMPERATURES IN THE 70S TODAY OVER
ALL BUT THE FAR SOUTH. A RESULTING WAKE LOW OVER FAR NE IA WAS
PRODUCING GUSTY S-SW WINDS...REACHING NEAR 30 TO NEAR 40 MPH AT
TIMES...ACROSS THE FORECAST AREA. ON A LARGER SCALE...A MID LEVEL
SHORTWAVE THAT TRIGGERED TODAY/S MCS WAS PUSHING EASTWARD FROM
THE WESTERN GREAT LAKES SOUTH INTO SOUTHERN IL...WHILE A RIDGE
AXIS REMAINED OVER THE CENTRAL PLAINS. AT THE SURFACE...A WEAK
SURFACE TROUGH REACHED FROM WESTERN LAKE SUPERIOR INTO THE MO
RIVER VALLEY. MOISTURE POOLING OUT AHEAD WAS RESULTING IN
DEWPOINTS EDGING INTO THE MID TO UPPER 70S ACROSS WESTERN MO AND
WESTERN IA. DEWPOINTS OVER THE LOCAL AREA WERE SOMEWHAT LESS
OPPRESSIVE...FROM THE LOWER 60S EAST AND NE TO AROUND 70 SOUTH AND
WEST.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 342 PM CDT FRI JUL 24 2015

CHALLENGES CONTINUE TO FOCUS ON THUNDERSTORM CHANCES AND BUILDING
HEAT AND HUMIDITY THAT COULD RESULT IN HAZARDOUS HEAT INDEX VALUES
SATURDAY. OVERALL...FORECAST CONFIDENCE IS BELOW AVERAGE DUE TO
WEAKLY FORCED CONVECTIVE TRENDS THAT HAVE NOT BEEN WELL HANDLED
WELL BY THE MODELS...WHICH AFFECTS CRITICAL TEMPERATURE FIELDS.

LATE THIS AFTERNOON INTO TONIGHT...THE AIRMASS WILL SLOWLY RECOVER
AS THE CLOUD COVER FROM THE MO STORMS DROPS S-SE GIVING WAY LATE DAY
SUNSHINE AND SURFACE WIND FIELDS RETURNING TO LIGHT SOUTHERLY
AHEAD OF THE TROUGH ADVANCING FROM THE WEST. AN ELEVATED WARM
MIXED LAYER ADVANCING FROM THE SOUTHWEST SHOULD EFFECTIVELY CAP
ADDITIONAL CONVECTION IN THE NEAR TERM...AND FOCUS FOR
REDEVELOPMENT WILL BE ALONG POSSIBLE OUTFLOW BOUNDARIES IN WESTERN
IA AND NE MO...AND A WEAK MID LEVEL SHORTWAVE TOPPING THE UPPER
RIDGE TRIGGERING STORMS OVER CENTRAL NEB. WILL CARRY CHANCE POPS
FOR LATE THIS EVENING OVER ESPECIALLY THE SOUTH...RAMPING UP TO
HIGH CHANCE TO LOW LIKELY TOWARD MORNING ACROSS THE SOUTH...WHERE
THE MID LEVEL WAVE SHOULD TRACK. ALTHOUGH MOISTURE LEVELS WILL BE
HIGH TO SUPPORT LOCALLY HEAVY RAINFALL...THE LACK OF STRONG DEEP
SHEAR SHOULD PRECLUDE A SIGNIFICANT SEVERE WEATHER THREAT. THE
INCREASING MOISTURE SHOULD LIMIT LOWS TO THE UPPER 70S NORTH TO
LOWER 70S SOUTH.

SATURDAY...TRENDS FROM OVERNIGHT CONVECTION WILL DETERMINE THE
POTENTIAL FOR SUBSEQUENT CONVECTIVE REDEVELOPMENT DURING THE DAY.
THE WEAK SURFACE BOUNDARY IS STILL SHOWN DROPPING SOUTH INTO
NORTHERN MO INTO CENTRAL IL BY MIDDAY...THEN WASHING OUT DURING THE
AFTERNOON. HAVE CONTINUED HIGHER CHANCE POPS CLOSEST TO THIS
BOUNDARY. THE MAIN THREAT FROM STORMS APPEARS TO BE LOCALLY HEAVY
RAINFALL. HIGHER DEWPOINTS...IN THE LOWER TO MID 70S WILL OVERSPREAD
AND POOL INTO THE AREA OVERNIGHT INTO SATURDAY...POTENTIALLY
REACHING THE UPPER 70S DURING THE DAY. THE AMOUNT OF CLOUD COVER AND
ASSOCIATED MIXING AND INSOLATION WILL BE CRITICAL TO BOTH MAX
TEMPERATURES AND HEAT INDEX READINGS AND CONFIDENCE IS TOO LOW TO
ISSUE ANY HEADLINES. FOR NOW...OUR FORECAST HAS 90S SOUTH OF
I-80...REACHING NEAR 102 IN FAR NE MO AND W CENTRAL IL MID TO LATE
AFTERNOON.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 342 PM CDT FRI JUL 24 2015

FORECAST FOCUS IN THE EXTENDED IS ON STORM CHANCES SATURDAY NIGHT
THROUGH SUNDAY WITH SEVERE POTENTIAL...ALONG WITH INCREASING HEAT
AND HUMIDITY DURING THE START OF NEXT WEEK.

SATURDAY NIGHT-SUNDAY...AN MCS WILL LIKELY BE ONGOING ACROSS
NE/IA/MO WITH STORMS LIKELY MOVING EAST SOUTHEAST. NOCTURNAL
LLJ...INCREASED  LOW LEVEL CONVERGENCE...AND ANY BOUNDARIES LEFT
OVER FROM SATURDAY MORNING...SHOULD ALLOW THESE STORMS TO MOVE
ACROSS THE SOUTH HALF OF CWA WHEREAS THE NORTHERN HALF WILL POSSIBLY
SEE SHOWERS AND THUNDERSTORMS FROM COMPLEX MOVING SOUTHEAST OUT OF
SOUTH DAKOTA AND MINNESOTA. HAVE KEPT POPS IN THE HIGH CHANCE
RANGE DUE TO VARYING MODEL DISCREPANCIES IN STRENGTH AND
PLACEMENT OF SHORTWAVE.

REGARDING SEVERE POTENTIAL...A VERY MOIST AIR MASS INDICATIVE OF
PWATS OVER 2 INCHES AND DEWPOINTS IN THE 70S WILL CREATE A MODERATE
TO STRONG UNSTABLE ATMOSPHERE SUNDAY.  THERE IS LITTLE TO NO
SYNOPTIC FORCING...BUT MODELS ARE STILL SHOWING A WEAK VORT MAX
TRAVERSING THE FLOW THAT MAY BE JUST ENOUGH FOR STORM DEVELOPMENT. 0-
6 KM SHEAR VALUES OVER 35 KTS SUNDAY AFTERNOON MAY SUPPORT A FEW
ISOLATED SEVERE STORMS WITH DAMAGING WIND THE PRIMARY THREAT.
FORECAST SOUNDINGS INDICATE THE CAP SHOULD BREAK DURING THE LATE
AFTERNOON ON SUNDAY. THE ONE CAVEAT TO THIS POTENTIAL IS THE
RESIDUAL CLOUDS AND PRECIPITATION FROM THE MORNING MAY LIMIT
DESTABILIZATION IN THE AFTERNOON. IN ANY CASE...IT WILL STILL BE A
HOT AND HUMID DAY SUNDAY...WITH HEAT INDICES IN THE UPPER 90S IN
THE AFTERNOON.

MONDAY-TUESDAY...THIS PERIOD WILL LIKELY SEE MORE DRY THAN WET HOURS
AS THE UPPER LEVEL RIDGE BUILDS ACROSS THE AREA...PUSHING THE STORM
TRACK FURTHER TO THE NORTH AND WEST OF THE CWA. HIGHS WILL BE IN THE
MID TO UPPER 80S AND HEAT INDICES IN THE UPPER 90 AND EVEN A FEW 100
DEGREE VALUES WILL BE POSSIBLE. THE HOTTEST DAY WILL BE TUESDAY.

WEDNESDAY NIGHT-FRIDAY...850 AND SURFACE COLD FRONT WILL BRING
RELIEF TO THE HEAT AND HUMIDITY DURING THIS PERIOD. MODELS DIFFER ON
TIMING OF THE FRONT BUT GENERALLY AGREE THAT IT WILL PASS SOMETIME
WEDNESDAY AFTERNOON/EVENING. A FEW SCATTERED SHOWERS AND STORMS WILL
BE POSSIBLE AHEAD OF FRONT AND MODEL CONSENSUS HAS SLIGHT CHANCE
POPS AT THIS TIME. DRY WEATHER IS EXPECTED THURSDAY AND
FRIDAY...WITH DEWPOINTS DROPPING INTO THE UPPER 50S AND LOWER 60S
MAKING FOR MORE COMFORTABLE CONDITIONS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1237 PM CDT FRI JUL 24 2015

CLUSTER OF THUNDERSTORMS DROPPING SOUTH THROUGH EAST CENTRAL IA
WILL MOVE OUT OF CID AND DBQ EARLY AFTERNOON...AFFECTING MLI AND
BRL WITH WEAKER SHOWERS AND ISOLATED THUNDERSTORMS AROUND MID
AFTERNOON. OTHERWISE...LIGHT WIND FIELDS WILL EXIST WITH VFR
CONDITIONS. THERE IS A LOW POTENTIAL FOR ADDITIONAL THUNDERSTORMS
TONIGHT THROUGH SATURDAY MORNING AS A WEAK SURFACE FRONT MOVES
THROUGH...BUT WITH A HIGH LEVEL OF UNCERTAINTY AND EXPECTED LOW
COVERAGE...THESE ARE NOT MENTIONED IN THE FORECASTS. INCREASING
LOW LEVEL MOISTURE WILL LIKELY LEAD TO AT LEAST MVFR FOG INCLUDED
AT ALL SITES FOR THE OVERNIGHT PERIOD.


&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...GROSS
AVIATION...SHEETS



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