Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 241746
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1246 PM CDT SUN AUG 24 2014

.SYNOPSIS...
ISSUED AT 330 AM CDT SUN AUG 24 2014

ALOFT...HIGHLY AMPLIFIED UPPER RIDGE SPANS THE EASTERN CONUS...AND A
CLOSED UPPER LOW CENTERED OVER THE NORTHERN ROCKIES DOMINATES THE
WEST. AT THE SURFACE...TROUGH OVER THE PLAINS WITH A WARM FRONT
EXTENDING ACROSS NORTHERN MO AND SOUTHERN IL.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT SUN AUG 24 2014

INITIAL FORECAST CONCERN IN THE SHORT TERM IS POTENTIAL FOR HEAT
TODAY.

WARM FRONT IS PROGGED TO LIFT RAPIDLY NORTH TODAY...REACHING THE
HIGHWAY 20 CORRIDOR BY 18Z.  850 MB THERMAL RIDGE EXTENDS FROM THE
PLAINS NORTHWARD INTO WESTERN IA...WITH 850MB TEMPS FROM 22-24C
PROGGED TO EXTEND INTO THE CWFA THROUGH THE PERIOD.  WITH MUCH LESS
CLOUD COVER TODAY LEADING TO AMPLE MIXING...AND THE SURGING WARM
FRONT...LOOK FOR TEMPS TO APPROACH 90F BY MIDDAY AND FINALLY TOP OUT
IN THE LOWER 90S.  ADD TO THAT DEW POINTS IN THE LOWER 70S...AND WE
CAN EXPECT TO SEE HEAT INDICES IN THE UPPER 90S TO AROUND 100 BY
EARLY AFTERNOON.  WILL HOIST HEAT ADVISORY FOR SOUTHERNMOST COUNTIES
FOR THIS AFTERNOON WHERE HEAT INDEX IS PROGGED TO BE IN THE 100-102
RANGE FOR A FEW HOURS.

FOR TONIGHT...THE MAIN CONCERN IS POTENTIAL FOR PRECIP. COLD FRONT
PROGGED TO STALL IN WESTERN IA...AND MCS DEVELOPMENT ONCE AGAIN
EXPECTED.  ACTIVITY SHOULD STAY NORTH OF THE CWFA OVER MN CLOSER TO
BETTER LIFT...BUT CANNOT RULE OUT THE POSSIBILITY THAT THE SOUTHERN
END COULD BRUSH NORTHERNMOST COUNTIES BEFORE 12Z. THUS HAVE INCLUDED
LOW POPS LATE TONIGHT NORTH OF HIGHWAY 20 CORRIDOR FOR THIS SCENARIO.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 330 AM CDT SUN AUG 24 2014

THE UPPER LEVEL RIDGE IS EXPECTED TO BREAK DOWN MONDAY...LEADING TO
AN ACTIVE WEATHER PATTERN FOR MUCH OF THE WORK WEEK. THE RESULTING
ZONAL UPPER FLOW...INTERACTING WITH A SLOW MOVING SURFACE BOUNDARY
OVER THE REGION WILL REQUIRE AT LEAST DAILY CHANCES FOR RAIN AND
THUNDERSTORMS.

MUCH LIKE THE PAST SEVERAL DAYS...MONDAY/S FORECAST WILL HINGE ON
THE TRACK AND TIMING OF A DISSIPATING NOCTURNAL MCS OVER THE REGION.
IF A COMPLEX MOVES ACROSS THE CENTRAL AND NORTH IN THE MORNING AS
SUGGESTED...IT WOULD HOLD TEMPERATURES THERE IN THE 70S IN THE
MORNING...FOLLOWED BY A RECOVERY INTO THE 80S BY AFTERNOON. AT THE
SAME TIME...THE SOUTH MAY BE IN A SIMILAR AIR MASS AS SUNDAY...AND
WITH SUNSHINE WOULD REACH INTO THE LOWER 90S BY AFTERNOON. WITH
DECENT MODEL CONSENSUS SUGGESTING THIS MCS TRACK...AND HOLDING THE
SYNOPTIC FRONT MAINLY NW OF THE FORECAST AREA THROUGH THE DAY...HAVE
TRENDED THE FORECAST THIS DIRECTION WITH CHANCE POPS MAINLY IN THE
NORTH AND TEMPERATURES RANGING FROM THE MID 80S NORTH TO LOWER 90S
SOUTH. WITH DEW POINTS STILL IN THE 70S...THIS WOULD LEAD TO HEAT
INDEX READINGS AS HIGH AS 100 TO 103 OVER NE MO...SE IA AND W
CENTRAL IL...AND A HEAT ADVISORY WILL NEED TO BE CONSIDERED.

MONDAY NIGHT THROUGH WEDNESDAY NIGHT...THE AREA WILL LIKELY SEE
SEVERAL ROUNDS OF MCS ACTIVITY AS THE SURFACE BOUNDARY SETTLES SOUTH
THROUGH THE AREA AND HAVE CHANCE POPS THROUGHOUT. POPS INCREASE TO
LIKELY ACROSS THE NORTH FOR WED INTO WED NIGHT AS IT WILL BE IN
A MORE FAVORED LOCATION FOR RAIN AS ONE OR MORE WAVES MOVE ALONG THE
BOUNDARY THAT IS EXPECTED TO SETTLE SOMEWHERE ALONG THE IA/MO BORDER
INTO CENTRAL IL BY THIS TIME. TEMPERATURES WILL CONTINUE TO BE A
CHALLENGE. FOR NOW...WILL BANK ON CLOUD COVER AND PRECIPITATION TO
LIMIT HIGHS TO THE 80S TUESDAY WHILE HIGH DEW POINTS HOLD MINS IN THE
70S MONDAY NIGHT...FOLLOWED BY MID 60S NORTH TUE NIGHT AS WINDS GO
NORTHERLY BEHIND THE BOUNDARY. DEPENDING ON CONVECTIVE TRENDS...THE
CURRENT FORECAST APPARENT TEMPERATURE TRENDS MAY AGAIN PUSH HEAT
ADVISORY CRITERIA OVER THE FAR SOUTH TUESDAY AFTERNOON. HIGHS FROM
THE UPPER 70S NORTH TO UPPER 80S SOUTH FOR WED MAY BE TOO OPTIMISTIC
IF THE MORE SOUTHERLY ECMWF AND GEM SURFACE FRONTAL PLACEMENT
VERIFIES.

THE LATEST MODELS CONTINUE TO DIVERGE INTO TWO SEPARATE CAMPS BY
LATE WEEK. THE GFS IS FASTER WITH THE STRONGEST SHORTWAVE AND
SURFACE WAVE PUSHING THROUGH WED AND THU...FOLLOWED BY HIGH PRESSURE
AND DRY CONDITIONS SUGGESTED FOR FRIDAY AND SATURDAY. THE ECMWF AND
CANADIAN MODELS MAINTAIN MUCH SLOWER TIMING OF THE WEEK/S STRONGEST
SYSTEM...WHICH WOULD IMPACT THE AREA WITH GOOD RAIN CHANCES THU INTO
AT LEAST FRIDAY NIGHT. UNTIL A PREFERENCE CAN BE WORKED OUT...OUR
BLENDED APPROACH WILL CONTINUE RAIN AND THUNDERSTORM CHANCES LATE
WEEK INTO SATURDAY.

SEASONABLY HIGH PW VALUES PROGGED TO REMAIN IN PLACE THROUGH THE
WEEK MAY LEAD TO A THREAT OF AT LEAST LOCALLY HEAVY RAINFALL WITH
THE THUNDERSTORM COMPLEXES THROUGH AT LEAST MID WEEK. EACH EVENT MAY
BE CAPABLE OF PRODUCING AT LEAST LOCALIZED TOTALS OF 1 TO 3
INCHES..AS SEEN THE OVER PAST SEVERAL DAYS. THIS MAY LEAD TO AN
INCREASING THREAT OF FLASH FLOODING AS SUCCESSIVE RAINFALL EVENTS
SATURATE AREA SOILS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1234 PM CDT SUN AUG 24 2014

VFR CONDITIONS EXPECTED TO GENERALLY DOMINATE THE TAF CYCLE.
ABUNDANT LOW LEVEL MOISTURE AND DECREASING SOUTHERLY WINDS WILL
LIKELY PROMOTE SOME LIGHT FOG DEVELOPMENT LATE TONIGHT AND EARLY
MONDAY AM WITH VISIBILITIES 3-6SM. ALSO ANTICIPATE SCATTERED
SHOWERS AND POSSIBLY A FEW STORMS TO MOVE OR DEVELOP INTO
NORTHEAST IA OVERNIGHT AND MONDAY AM WITH WEAKENING BRANCH OF LOW
LEVEL JET AHEAD OF FRONTAL BOUNDARY... AND HAVE INCLUDED VCSH AT
BOTH CID AND DBQ TERMINALS.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR DES MOINES-HENRY
     IA-LEE-VAN BUREN.

IL...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR HANCOCK-HENDERSON-
     MCDONOUGH-WARREN.

MO...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR CLARK-SCOTLAND.

&&

$$

SYNOPSIS...DMD
SHORT TERM...DMD
LONG TERM...SHEETS
AVIATION...05





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