Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 280012
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
712 PM CDT SAT JUN 27 2015

.SYNOPSIS...
ISSUED AT 330 PM CDT SAT JUN 27 2015

OUTSIDE OF A COUPLE SMALL SHOWERS W AND SW OF MACOMB...THE ENTIRE
FORECAST AREA WAS FREE OF PRECIPITATION THIS AFTERNOON AS THE REGION
WAS IN A BREAK BETWEEN SYNOPTIC WEATHER SYSTEMS. A DEPARTING LOW...
BOTH AT THE SURFACE AND ALOFT...WAS OVER OHIO AT 12Z THIS MORNING.
TO THE WEST...A RIDGE AXIS REACHED FROM THE CENTRAL PLAINS NORTHEAST
INTO THE UPPER GREAT LAKES. OVER THE LOCAL AREA...A WEAK LOW LEVEL
CONVERGENCE BOUNDARY SETUP BY LIGHT NORTHEASTERLIES OUT OF THE GREAT
LAKES WAS SITUATED FROM FAR EAST CENTRAL IA SOUTH ALONG THE MS RIVER
VALLEY TO NORTH OF ST LOUIS. SUBSIDENCE FROM THE INCOMING SURFACE
RIDGE AND SHORTWAVE RIDGING ALOFT WAS LIKELY PREVENTING MODERATE TO
TOWERING CU ALONG THIS BOUNDARY OVER MOST OF THE FORECAST AREA FROM
FURTHER EVOLVING INTO SHOWERS. THE DRIER CANADIAN AND GREAT LAKES
AIRMASS WAS PROVIDING LOWER HUMIDITY WITH AFTERNOON DEWPOINTS ONLY
IN THE LOWER TO MID 50S NORTH AND NORTHEAST...WHILE HIGHER SURFACE
MOISTURE LEVELS FURTHER WEST AND SOUTH HELD READINGS IN THE LOWER
60S. FURTHER UPSTREAM...WATER VAPOR IMAGES AND REGIONAL RADAR MOSAIC
SHOWED A STRONG SHORTWAVE IN THE NW FLOW MOVING S-SE OUT OF MANITOBA
TRIGGERING THUNDERSTORMS AS FAR SOUTH AS FAR NE ND AND NORTHERN MN
THIS AFTERNOON. THIS FEATURE WILL BRING THUNDERSTORMS BACK INTO THE
LOCAL AREA LATE TONIGHT AND SUNDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 330 PM CDT SAT JUN 27 2015

MAIN FOCUS IS ON THE INCOMING SHORTWAVE AND DEVELOPING SURFACE LOW
THAT WILL RETURN WIDESPREAD THUNDERSTORMS...POSSIBLY SEVERE...INTO
THE AREA AS IT ROTATES THROUGH SUNDAY. AHEAD OF THIS...MOST OF
TONIGHT WILL HAVE QUIET CONDITIONS WITH COMFORTABLY LOW HUMIDITY AND
SLIGHTLY BELOW NORMAL TEMPERATURES. ANY SHOWERS THAT FORM THIS
AFTERNOON SHOULD QUICKLY DISSIPATE EARLY THIS EVENING.

TONIGHT...MID AND UPPER LEVEL FORCING AND MOISTURE CONVERGENCE AHEAD
OF THE INCOMING SHORTWAVE AND ASSOCIATED SURFACE TROUGH APPEARS TO
HAVE SLOWED SOME FROM PREVIOUS RUNS AND HAVE THUS BACKED OFF ON LATE
NIGHT/EARLY SUNDAY MORNING POPS IN THE FAR NW. VERY LOW MUCAPE
VALUES AND H5 TO H7 LAYER LAPSE RATES POSSIBLY ONLY 6 C/KM POINT
TOWARD MAINLY SHOWERS AND ISOLATED THUNDERSTORMS AS THIS MOVES IN
LATE TONIGHT.

SUNDAY...THE PRIMARY WAVE OF UPPER LEVEL FORCING AHEAD OF THIS SYSTEM
AND LOW LEVEL CONVERGENCE WITH THE SURFACE TROUGH MOVING THROUGH IN
THE AFTERNOON REQUIRES WIDESPREAD LIKELY TO CATEGORICAL POPS. AS
MENTIONED IN PREVIOUS DISCUSSIONS...THE AMOUNT OF CLOUD COVER
OUTSIDE OF THE THUNDERSTORMS WILL BE CRITICAL FOR HIGH TEMPERATURES
AND ALSO THE AMOUNT OF INSTABILITY. ADJUSTING FOR POSSIBLY A TOO
HIGH BIAS WITH MODEL SURFACE DEWPOINTS AND ASSOCIATED CAPE...WILL
ANTICIPATE MUCAPES OF 1500 TO 2000 J/KG OR POSSIBLY HIGHER IN THE
AFTERNOON OVER PRIMARILY THE SOUTH IF ENOUGH BREAKS DEVELOP IN THE
CLOUD COVER. IN THIS SAME AREA...0-6 KM SHEAR VALUES MAY REACH 45 TO
NEAR 50 KTS. THIS COMBINATION MAY SUPPORT A FEW SEVERE STORMS WITH
BOTH A HAIL AND WIND THREAT...AS OUTLINED BY SPC/S DAY 2 SLIGHT RISK
SW OF A LINE FROM NEAR WASHINGTON TO MACOMB. CONSIDERING THE
POTENTIAL FOR MOST OF THE AREA TO HAVE MOSTLY CLOUDY CONDITIONS...
HAVE CONTINUE TO TREND ON THE COOL SIDE OF GUIDANCE WITH HIGHS FROM
THE MID 70S NORTH TO AROUND 80 SOUTH.

.LONG TERM...(SUNDAY NIGHT THROUGH NEXT SATURDAY)
ISSUED AT 330 PM CDT SAT JUN 27 2015

SUNDAY NIGHT AND MONDAY...BULK OF 12Z MODEL RUNS SUGGEST VIGOROUS
CLIPPER-LIKE LOW WILL STILL BE DIGGING SOUTHEASTWARD INTO NORTHERN
IL SUNDAY NIGHT...WILL HAVE TO KEEP HIGH CHC TO LIKELY POPS GOING
WELL INTO SUNDAY EVENING WITH ASSOCIATED SHOWERS/LINGERING STORMS
ROTATING AROUND THIS FEATURE ESPECIALLY EAST OF THE MS RVR. ACTIVITY
SHOULD REALLY WANE WITH LOSS OF HEATING IN THE LATE EVENING AND INTO
THE OVERNIGHT HOURS. WIDESPREAD LOWS IN THE LOW TO MID 60S SUNDAY
NIGHT INTO EARLY MON MORNING. THE MEDIUM RANGE SOLUTIONS THEN
SUGGEST A SECONDARY SATELLITE VORT OR VORT SPOKE ROTATING DOWN
EMBEDDED IN ENHANCED NORTHWESTERLIES ALOFT ON MONDAY. IF WE CAN WARM
INTO THE UPPER 70S TO LOWER 80S WITH SFC DPTS AT LEAST IN THE LOW TO
MID 60S...1000 TO NEAR 2000 J/KG CAPES COULD BUILD BY AFTERNOON.
THUS ANOTHER SET-UP FOR DIURNAL SCTRD SHOWERS AND STORMS MONDAY
AFTERNOON ACRS MUCH OF THE CWA. DEEP SHEAR PROFILES NOT AS ROBUST AS
ON SUNDAY AND CONVECTION MON AFTERNOON APPEARS WILL BE MORE OF THE
PULSE TYPE. LOCALLY HEAVY DOWNPOURS POSSIBLE THOUGH WHERE THE STORMS
OCCUR UNTIL THE CELLS COLLAPSE ON THEMSELVES. ACTIVITY SHOULD
DIURNALLY WANE AGAIN AS MON EVENING PROGRESSES.

TUESDAY THROUGH NEXT FRIDAY...LATEST RUN MEDIUM RANGE SOLUTIONS AND
MREF CONTINUE WITH THE IDEA OF WESTERN CONUS UPPER RIDGING AND
GENERAL L/W TROFFINESS ACRS THE EASTERN GRT LKS AND APPALACHIA
REGIONS FOR MUCH OF THIS PERIOD. THUS ALMOST A DAILY CHC FOR AT
LEAST ISOLATED TO WDLY SCTRD PRECIP WITH SUBTLE RIPPLES DROPPING
DOWN IN PERSISTENT NORTHWEST FLOW. BUT SOME OF THE 12Z RUNS ARE
MORE BULLISH WITH STRENGTH AND SOUTHWESTERLY IMPRESSION OF WESTERN
GRT LKS BACK-DOOR TYPE LLVL HIGH PRESSURE THAT COULD MAKE FOR A
MAINLY DRY TUE NIGHT THROUGH EARLY THU...ESPECIALLY ACRS THE
NORTHEASTERN HALF OF THE DVN CWA. BUT THE NEW 12Z ECMWF CONTINUES
WITH A STRONGER VORT ALOFT THAT WOULD SPREAD OVERRUNNING SHOWERS AND
SOME STORMS ACRS MOST OF THE CWA WED AND WED NIGHT...WITH IT/S SMALL
DRY WINDOW THU INTO THU EVENING WITH WAKE SYSTEM RIDGE LOBE ARCS THE
AREA THAT PERIOD. WILL HAVE TO KEEP ALMOST DAILY CHC POPS GOING WITH
TEMPS BELOW NORMAL FOR THE MOST PART FOR MUCH OF THE UPCOMING WEEK.

LONG RANGE LOOK AT THE 4TH OF JULY SATURDAY...THE NEW 12Z RUN ECMWF
IS ADVERTISING A PATTERN CHANGE TO MORE OF A FLATTER MEAN WESTERLY
FLOW PATTERN OR EVEN A TYPE OF BROAD LOW AMPLITUDE UPPER RIDGE BULGE
ACRS MUCH OF THE MID CONUS...WITH MAIN UPPER JET MIGRATING ALONG OR
NORTH OF THE U.S./CANADIAN BORDER. THIS WOULD MAKE FOR A WARMING AND
MAINLY DRY FIRST HALF TO THE WEEKEND WITH LACK OF A CONVECTIVE FOCAL
POINT FOR THE LOCAL AREA...WITH MAYBE SOME ISOLATED AIR MASS TYPE
PRECIP BY SUNDAY AFTERNOON. THIS IN CONTRAST TO THE 12Z RUN GFS
WHICH MAINTAINS BROAD NORTHWESTERLIES ACRS THE UPPER MIDWEST AND
JUST SO HAPPENS TO BE TIMING AN EMBEDDED WAVE IN THIS FLOW TO KICK
UP SCTRD SHOWERS AND STORMS SATURDAY AFTERNOON AND INTO THE EVENING
TO MAKE FOR A DICEY HOLIDAY. THE EURO WOULD HAVE TEMPS WARMING WELL
UP IN THE 80S BY NEXT SATURDAY...WHILE THE GFS IS ADVERTISING MORE
IN THE WAY OF UPPER 70S TO LOWER 80S. WILL HAVE TO WATCH LONG RANGE
MODEL TRENDS OVER THE NEXT FEW DAYS...BUT TELECONNECTION HINTS LEAN
MORE TOWARD THE GFS SOLUTION FOR THE WEEKEND ANYWAYS...WITH THE
PATTERN FLATTENING NOT COMING UNTIL THE FOLLOWING WEEK.    ..12..

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 701 PM CDT SAT JUN 27 2015

00Z TAFS UPDATED TO TIME IN A PREVAILING GROUP OF -SHRA VCTS FROM
13Z TO 15Z SUNDAY WITH INITIAL SURGE OF COMPLEX DROPPING SOUTH
INTO THE REGION. ADDITIONAL CONVECTION IS EXPECTED TO REDEVELOP
SATURDAY AFTERNOON...WHICH IS COVERED BY VCTS GROUPS. SOME LIGHT
FOG IS MOST FAVORED AT KBRL DURING THE EARLY MORNING.

&&

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

$$

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



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