Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 271121
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
621 AM CDT MON APR 27 2015

.SYNOPSIS...
ISSUED AT 358 AM CDT MON APR 27 2015

A LARGE SURFACE RIDGE OVER THE NORTHERN PLAINS...UPPER MS VALLEY
INTO SOUTHERN CANADA CONTINUED TO PROVIDE CLEAR SKIES AND SEASONABLY
COOL TEMPERATURES OVER THE FORECAST AREA EARLY THIS MORNING. UPPER
AIR ANALYSIS SHOWED THIS RIDGE BEING HELD IN PLACE BY AN UPPER LEVEL
RIDGE...SITUATED OVER THE NORTHERN PLAINS ABOVE A STRONGER NEARLY
STATIONARY LOW OVER NEW MEXICO...FORMING A PSEUDO-REX BLOCK.
RESULTING SUBSIDENCE AND LIGHT N-NE WINDS CHANNELING A DRY GREAT
LAKES AIRMASS WERE RESULTING IN DEWPOINTS ONLY IN THE UPPER 20S TO
MID 30S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 358 AM CDT MON APR 27 2015

TEMPERATURES AND THE POTENTIAL FOR EARLY MORNING FROST ARE THE MAIN
SHORT TERM CHALLENGES. THE UPPER LEVEL BLOCKING PATTERN IS EXPECTED
TO SLOWLY BREAK DOWN THROUGH THE PERIOD...ALLOWING THE SURFACE RIDGE
AXIS TO MIGRATE EASTWARD. THIS WILL RESULT IN LARGELY A PERSISTENCE
FORECAST AS LITTLE CHANGE IN THERMAL AND MOISTURE FIELDS IS EXPECTED
OUTSIDE MINOR AIRMASS MODIFICATION. WITH NEAR FULL SUNSHINE AND DEEP
MIXING...HIGHS SHOULD REACH A RANGE FROM AROUND 60 NORTH TO THE MID
60S SOUTH. THIS IS CLOSE TO PERSISTENCE PLUS A FEW DEGREES AND AT
THE WARMER SIDE OF MOS GUIDANCE. PERSISTENCE WILL ALSO BE THE RULE
FOR OVERNIGHT. THE NORTHEAST WILL AGAIN BE THE COOLEST AND THE MOST
LIKELY TO SEE AT LEAST PATCHY FROST AND HAVE KEPT COVERAGE GOING
FROM THE PREVIOUS FORECAST FOR NW IL INTO FAR E CENTRAL IA FROM
MIDNIGHT TIL SUNRISE. WILL CONTINUE TO UNDERCUT GUIDANCE BY NEARLY A
CATEGORY...WITH LOWS RANGING FROM THE LOWER 30S NORTHEAST TO AROUND
40 IN THE SOUTHWEST.

.LONG TERM...(TUESDAY THROUGH NEXT SUNDAY)
ISSUED AT 358 AM CDT MON APR 27 2015

TUESDAY AND WEDNESDAY...UPPER RIDGE LOBE WILL LOOK TO DROP ACRS THE
NORTHWESTERN GRT LKS EARLY IN THE PERIOD...WITH TROFFINESS THEN
FOLLOWING IT BY TUE EVENING. SOUTHERN STREAM SYSTEM ALMOST ACTING
LIKE A CUT-OFF ROLLING UP TOWARD THE TN VALLEY OUT OF THE DEEP
SOUTHERN PLAINS TRYING TO INTERACT WITH THE NW GRT LKS WAVE. THE NET
RESULT OF THE LOCAL AREA WHICH WILL REMAIN IN-BETWEEN THESE
PROCESSES WILL BE A DRY SFC TROF PASSING THRU THE CWA FROM THE
NORTHWEST LATE TUE INTO EARLY WED MORNING. THIS FEATURE MAY WASH OUT
AS LARGER SCALE PHASING TAKES OVER ALONG AND EAST OF THE REGION BY
WED...ALLOWING RE-ENFORCING NORTH-TO-NORTHEAST LLVL FLOW AND RIDGING
TO DUMP DOWN THE UPPER MS RVR VALLEY INTO THE WESTERN GRT LKS FOR
THE MID WEEK PERIOD. STILL WITH INSOLATION AND SOME AIRMASS
MODIFICATION ON TUE WILL GO WITH HIGHS IN THE MID 60S...WITH SOME
AREAS PUSHING THE UPPER 60S. COOL DIURNAL SWING INTO THE LOWER 40S
BY WED MORNING IN ONGOING DRY BOUNDARY LAYER...SOME UPPER 30S
POSSIBLE IN THE NORMAL COOL AIR DRAINAGE LOCATIONS. TEMP GUIDANCE
GOES A FEW DEGREES WARMER FOR WED THAN WHAT OCCURS ON TUE...BUT N-NE
FETCH MAY LIMIT HIGHS BACK CLOSER TO WHAT OCCURS ON TUE...THE NEW
00Z EURO ONLY SUPPORTS MID 60S FOR WED. WILL LEAN TOWARD THE 00Z
ECMWF FOR A DRY WED NIGHT AS WELL...AS THE GFS SEEMS TO REV UP A
CLOSED UPPER LOW OVER LK MI TOO MUCH LOOKING AT MID TO UPPER LEVEL
JET DYNAMICS. THE GFS AND THIS BULLISH MID UPPER TROF DEVELOPMENT
WOULD TRY TO ROTATE SOME INSTABILITY SHOWERS INTO THE EASTERN DVN CWA
BY LATE WED AND WED EVENING.

THURSDAY AND FRIDAY...ANOTHER UPSTREAM UPPER RIDGE LOBE GETS PRESSED
ACRS THE UPPER MIDWEST ON THU INTO THE FIRST PART OF FRI FOR A
CONTINUED MAINLY FAIR WX REGIME. CONTINUED COOLING NORTH TO
NORTHEAST LLVL FETCH TO THE WEST OF EASTERN GRT LKS TROF PHASING
WARRANTS A TRIM BACK ON THU HIGHS...MID TO UPPER 60S MAY STILL BE A
BIT OPTIMISTIC ACCORDING TO THICKNESSES ADVECTED IN BY THE LATEST
RUNS...PLUS WORRIES OF LK STRATOCU INTO PORTIONS OF THE NORTH/EAST.
THU NIGHT POSSIBLY COOLER THAN ADVERTISED AS WELL. MORE ACTIVE WAVE
TRAIN OFF THE NORTHEASTERN PACIFIC WILL DAMPEN UPPER RIDGING AND
RIDE THE DECREASING BULGE OF HIGH PRESSURE ALONG AND JUST TO THE
NORTH OF THE WESTERN U.S./CANADIAN BORDER REGION INTO THE END OF THE
WEEK. SEVERAL OF THE LATEST RUN MEDIUM RANGE MODELS VARY ON TIMING
OF A POTENTIAL INCOMING SFC FRONT ASSOCIATED WITH A LEAD RIDGE-
RIDING UPPER TROF...THE 00Z ECMWF PUSHES A FROPA THRU THE CWA FRI
NIGHT BEFORE IT STALLS ALIGNING UNDER FLATTENING STEERING FLOW...
THE GFS MORE TOWARD SAT MORNING IN A MORE WEAKENING FASHION. THE
EURO IS MORE AGGRESSIVE WITH PRE-FRONTAL SHOWERS AND SOME STORMS BY
FRI EVENING..,THE GFS NOT UNTIL AFTER MIDNIGHT INTO EARLY SAT MORNING
SUGGESTING WEAKENING SHOWER/STORM CLUSTERS FROM THE NORTHWEST. FOR
NOW JUST LOW POPS FOR FRI NIGHT...PRE-FRONTAL WARMING EARLIER IN THE
DAY FRI FOR A REBOUND INTO THE 70S.

NEXT SATURDAY AND SUNDAY...THE GENERAL IDEA OF THE MREF PATTERN LAY-
OUT FOR THE UPCOMING WEEKEND IS THAT THE BOUNDARY WILL LOOK TO LAY
OUT PARALLEL TO FLATTENING MORE WESTERLY STEERING FLOW ACRS THE
UPPER MIDWEST...IT/S JUST THE DETAILS WHERE/HOW FAR NORTH OR SOUTH/
IT WILL DO SO AS WELL AS ROUNDS OF SOUTHERLY LLVL FLOW IMPINGING ON
THE BOUNDARY AND AMOUNT OF MOISTURE FEED TO FUEL OCCASIONAL
SHOWERS/ STORMS. EMBEDDED WAVE PULSES RIPPLING THRU THIS MORE ZONAL
FLOW REGIME ALSO WILL BE A PRECIP WINDOW DEFINER...BUT DIFFICULT TO
DETERMINE AT THIS POINT SO LOW CHC POPS THRU THE WEEKEND WILL RIDE.
MORE OF THE CURRENT MODEL SOLUTIONS SUGGEST THE BOUNDARY LAYING OUT
IN SUCH A WAY THE THE SOUTH HALF OF THE DVN CWA WILL HAVE A BETTER
CHC FOR OCCASIONAL BOUTS OF RAIN FROM SAT NIGH THRU SUNDAY NIGHT.
NOCTURNAL LLJ MAY MAKE FOR ALMOST A TYPE OF NOCTURNAL MCS POTENTIAL
LAT IN THE PERIOD WITH MORE ORGANIZED FORCING/ELEVATED THTA-E FEED
SUNDAY NIGH INTO EARLY MON MORNING...BUT AGAIN THESE TYPE OF
DETAILS THAT FAR OUT HARD TO COUNT ON AT THIS POINT. BOUNDARY
PLACEMENT A BIG DETERMINATOR ON HIGH TEMP POTENTIAL AS WELL BUT WILL
HAVE TO USE GENERAL TEMP MODIFICATION AND PERIODS OF DRY WX DURING
THE DAY FOR THE FCST HIGHS THAT WILL BE IN THIS FCST PACKAGE...COULD
BE TOO WARM IF THE BOUNDARY GETS LAID OUT FURTHER TO THE SOUTH LIKE
THE LATEST TRENDS SUGGEST ALONG WITH CONVECTIVE DEBRIS POSSIBILITY.
 ..12..

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 621 AM CDT MON APR 27 2015

VFR CONDITIONS WILL CONTINUE AS HIGH PRESSURE PROVIDES CLEAR
SKIES AND LIGHT NORTH TO NORTHEAST WINDS TODAY AND TONIGHT.

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...12
AVIATION...SHEETS



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