Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 211748
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1248 PM CDT MON JUL 21 2014

.SYNOPSIS...
ISSUED AT 243 AM CDT MON JUL 21 2014

A BROAD RIDGE IS SET UP OVER THE WESTERN AND CENTRAL U.S. WITH
MONSOONAL MOISTURE WORKING AROUND ITS WESTERN PERIPHERY ALONG THE
AZ-NM BORDER INTO CO. MEANWHILE THE POLAR JET AND ASSOCIATED
SURFACE BOUNDARY ARE LOCATED ALONG THE U.S.-CANADIAN BORDER WITH A
COUPLE OF SHORT WAVE TROUGHS RIDING THE BOUNDARY SETTING OFF
THUNDERSTORMS. MOISTURE HAS INCREASED OVER THE AREA WITH DEW
POINTS NOW MOSTLY IN THE 60S AND A PW ON THE OOZ DVN SOUNDING UP
OVER AN INCH.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 243 AM CDT MON JUL 21 2014

MAIN AREAS OF INTEREST THROUGH TONIGHT ARE THE CONTINUED HEAT-
MOISTURE ADVECTION AND THE POTENTIAL FOR THUNDERSTORMS IN THE
NORTH LATE TONIGHT.

REGARDING THE LATTER...THE NAME AND GFS HAVE BEEN SOLELY
AGGRESSIVE WITH BRINGING HIGH POPS TO THE AREA LATE TONIGHT. GIVEN
THE TRACK OF UPPER LEVEL SUPPORT AND THE CAP FORECAST TO BE IN
PLACE...HAVE OPTED FOR A DRIER SOLUTION LIKE THE ECMWF AND GEM.
THUS WILL HAVE ONLY LOW POPS IN THE NORTH AFTER MIDNIGHT TO
ACCOUNT FOR THE POTENTIAL OF A FEW STORMS THAT MAY BRUSH THE AREA
AS THE VORT WORKS ITS WAY ACROSS THE UPPER MIDWEST.

DESPITE WARM ADVECTION SUNDAY...MAX TEMPS ONCE AGAIN FAILED TO
REACH GUIDANCE FORECASTED HIGHS. SMOKE MAY HAVE BEEN A LIMITING
FACTOR AS WELL AS A MIXING HEIGHT ONLY UP TO ABOUT 5 KFT. THUS
HAVE AGAIN TRENDED BELOW MOST GUIDANCE TODAY...BUT HAVE REFLECTED
A DECENT WARMUP AS 850 MB TEMPS POKE INTO THE LOWER 20S C BY 00Z.
DEW POINTS SHOULD ALSO TREND GRADUALLY UPWARD THROUGH THE DAY...
BUT HEAT INDEX VALUES WILL REMAIN BELOW LEVELS OF CONCERN.
HOWEVER...IT WILL BE A NOTICEABLY WARMER AND MORE HUMID DAY...AND
NIGHT. WOLF

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 243 AM CDT MON JUL 21 2014

TUESDAY THROUGH SUNDAY

VERY WARM AND HUMID CONDITIONS EARLY IN THE WEEK WILL GIVE WAY TO
SLIGHTLY COOLER AND LESS HUMID CONDITIONS BY MID TO LATE WEEK AS
HIGH PRESSURE DROPS DOWN SOUTHEAST OUT OF CANADA. RAIN CHANCES
RETURN FOR THE WEEKEND...BUT FORECAST CONFIDENCE IS LOW DUE TO
CONTINUED INCONSISTENCY IN MODEL TIMING AND PLACEMENT OF CRITICAL
SYNOPTIC FEATURES THIS FAR OUT.

THE DOME OF HOT AIR BUILDING UNDER THE LARGE UPPER RIDGE CENTERED
OVER THE SOUTHERN HIGH PLAINS WILL GET NUDGED NORTHEASTWARD TUESDAY
BY AN UPPER LEVEL SHORTWAVE MOVING INTO THE PACIFIC NW. THE STRONG WARM
AIR ADVECTION WILL DRIVE TEMPERATURES WELL INTO THE LOWER 90S OVER
MOST OF THE AREA TUESDAY. WILL GO CLOSE TO A GFS/ECMWF BLEND FOR
HIGHS...IGNORING THE COOLER NAM...WHICH APPEARS TO BE AFFECTED BY
LINGERING CLOUD COVER AND RAIN FROM A DISSIPATING MCS IT DEVELOPS
MONDAY NIGHT...WHICH DOES NOT LOOK LIKELY DUE TO THE CAPPING AND IS
IGNORED. FORECAST SOUNDINGS AND 700 MB THERMAL FIELDS INDICATE A
STRONG CAP OVER THE FORECAST AREA DURING THE DAY...WHICH SHOULD
SUPPRESS ANY THUNDERSTORM DEVELOPMENT EVEN AS THE SURFACE FRONT
DROPS INTO THE NW BY AFTERNOON. WILL LEAVE LOW CONFIDENCE SLIGHT
CHANCES IN THE AFTERNOON FOR THE SMALL POTENTIAL THAT SOMETHING
COULD OVERCOME THE CAP ALONG THE ADVANCING SURFACE BOUNDARY BY LATE
AFTERNOON. THIS BOUNDARY WILL LIKELY RESULT IN LOW LEVEL MOISTURE
CONVERGENCE IN AN ALREADY VERY MUGGY AIR MASS THAT WILL ADVECT INTO
THE AREA FROM THE CENTRAL PLAINS. BY AFTERNOON...DEWPOINTS SHOULD BE
WELL INTO THE 70S...LIKELY PRODUCING HEAT INDEX VALUES IN THE 100 TO
105 RANGE OVER MOST OF THE AREA. A HEAT ADVISORY WILL LIKELY BE
NEEDED FOR AT LEAST THE SOUTH AND WEST FOR AT LEAST THE AFTERNOON
HOURS.

TUESDAY NIGHT...THE SHORTWAVE TROUGH ROUNDING THE UPPER RIDGE DRIVES
THE SURFACE FRONT SOUTHEAST THROUGH THE AREA BY MORNING...AND SHOULD
BE ABLE TO TRIGGER AT LEAST SCATTERED THUNDERSTORMS DUE TO ITS
FORCING AND NUDGING OF THE CAP SOUTHWARD. THIS APPEARS MOST LIKELY
OVER THE SOUTH IN THE EVENING TO PERHAPS AFTER MIDNIGHT...WHERE
LIKELY POPS ARE MAINTAINED. THE INITIAL HIGH CAPE...BUT MARGINAL
SHEAR ENVIRONMENT MAY SUPPORT AT LEAST ISOLATED PULSE TYPE SEVERE
STORMS WITH DAMAGING WIND AND HEAVY RAINFALL THE PRIMARY THREAT.
ELSEWHERE...IT IS PLAUSIBLE THAT THE FRONT MAY MOVE THROUGH WITHOUT
ANY PRECIPITATION DUE TO THE CURRENT TIMING OF THE CAPPING...SURFACE
FRONT AND MID LEVEL FORCING. FOR NOW...HAVE MAINTAINED SLIGHT TO LOW
END OVERNIGHT POPS CENTRAL AND NW.

HIGH PRESSURE THEN FOLLOWS...DROPPING SOUTH OUT OF CANADA INTO THE
UPPER MS VALLEY WEDNESDAY THROUGH THURSDAY NIGHT. THIS WILL RETURN A
MUCH DRIER AIR MASS TO THE REGION AND RETURN A MORE COMFORTABLE RANGE
OF DAYTIME HIGHS IN THE UPPER 70S AND LOWER 80S WITH OVERNIGHT LOWS
IN THE MID 50S TO LOWER 60S.

FRIDAY INTO NEXT WEEKEND...MEDIUM RANGE MODELS CONTINUE TO HAVE
RATHER POOR CONTINUITY OR CONSISTENCY WITH THE STRENGTH OF A MID
LEVEL SHORTWAVE DIVING SOUTHEAST OUT OF CANADA IN THE DEVELOPING NW
FLOW...ALONG WITH THE ASSOCIATED FRONTAL SYSTEMS IN THE LOCAL AREA.
HOWEVER...THERE IS SOME CONSENSUS IN THE 00Z RUNS OF A MUCH WEAKER
FEATURE WITH A CONTINUED SUGGESTION OF A WAVE OF WARM AIR ADVECTION
JUSTIFYING THE CONSENSUS FOCUSING OF THE HIGHER POPS ON THE FRIDAY
NIGHT PERIOD. LOW CONFIDENCE CHANCE POPS THEN ABOUND FOR THE WEEKEND
WITH TEMPERATURES TRENDING NEAR NORMAL AS VERY WARM AIR REMAINS
ENTRENCHED UNDER THE UPPER RIDGE THAT RETREATS TO THE WESTERN U.S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1239 PM CDT MON JUL 21 2014

VFR CONDITIONS EXPECTED OVER AT LEAST THE NEXT 24 HOURS WITH WARM
SOUTH WINDS OF 5 TO 10+ MPH AHEAD OF AN APPROACHING COOL FRONT.
AFTER 21/13Z...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
POSSIBLE AHEAD OF THE COOL FRONT WITH COVERAGE ENOUGH TO WARRANT
PROB30 GROUP AT DBQ/CID/MLI TERMINALS. ANY STORMS MAY RESULT IN
BRIEF MVFR CONDITIONS DUE TO RAIN. WINDS WILL SHIFT TO THE SOUTHWEST
AT 10+ MPH BY MID DAY.

&&

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

&&

$$

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





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