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000
FXUS63 KDVN 240822
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
322 AM CDT FRI MAY 24 2013

.SYNOPSIS...
ISSUED AT 245 AM CDT FRI MAY 24 2013

HIGH PRESSURE CENTERED OVER THE LAKE SUPERIOR REGION WAS PROVIDING
CLEAR AND COOL CONDITIONS ACROSS THE AREA EARLY THIS MORNING. CLOSER
TO THE CENTER OF THE HIGH...TEMPERATURES ACROSS NORTHERN WI WERE IN
THE 30S WITH POCKETS OF UPPER 20S. FURTHER SOUTH...A NORTHEAST
BREEZE IN THE LIGHT ANTICYCLONIC FLOW WAS HOLDING TEMPERATURES IN
THE 40S WITH A FEW POCKETS OF UPPER 30S FROM NORTHERN IL INTO
EASTERN IA. FURTHER AWAY FROM LAKE MI...SOUTHEAST IA AND WEST
CENTRAL IL WERE IN THE LOWER 50S. IN THE UPPER LEVELS...00Z ANALYSIS
SHOWED A LONGWAVE TROUGH FROM EASTERN CANADA INTO THE GREAT
LAKES...A RIDGE TO THE WEST ACROSS THE CENTRAL AND NORTHERN
PLAINS...WHILE A CLOSED LOW WAS FURTHER WEST OVER THE PACIFIC NW. AT
850 MB...GULF MOISTURE WAS FEEDING N-NW INTO THE HIGH PLAINS IN THE
SOUTHERLY FLOW BETWEEN A RIDGE OVER THE UPPER MS VALLEY AND A LOW
OVER THE INTERMOUNTAIN WEST. THIS RETURN FLOW IS EXPECTED TO VEER
MORE N-NE BY TONIGHT IN RESPONSE TO A SERIES OF UPPER LEVEL
SHORTWAVES THAT WILL BEGIN TO FLATTEN THE 500 MB RIDGE IN THE
CENTRAL CONUS. THE ELEVATED THETAE ADVECTION WILL LIKELY LEAD TO MCS
FORMATION THAT SHOULD SPILL INTO THE LOCAL AREA BY SATURDAY
MORNING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 245 AM CDT FRI MAY 24 2013

INITIAL FOCUS IS ON TEMPERATURES TODAY...FOLLOWED BY THE POTENTIAL
FOR SHOWERS AND THUNDERSTORMS LATE TONIGHT. BLOCKY PATTERN ALOFT WILL
KEEP HIGH PRESSURE ANCHORED JUST EAST OF THE FORECAST AREA THROUGH
TODAY. THIS...ALONG WITH A VERY DRY AIR MASS IN PLACE AND UPPER LEVEL
SUBSIDENCE DOWNSTREAM FROM THE UPPER LEVEL RIDGE SHOULD PROVIDE
CLEAR SKIES. AFTER STARTING OUT IN THE UPPER 30S IN A FEW LOCATIONS
THIS MORNING...THE DRY AIR WILL PERMIT A LARGER THAN NORMAL DIURNAL
RANGE. CONSIDERING THE LIGHT SOUTHEAST FLOW OUT OF THE GREAT
LAKES AND MIXING TO JUST ABOVE 900 MB...A BLEND OF MOS GUIDANCE
HIGHS FROM THE LOWER 60S NORTHEAST TO THE UPPER 60S WEST LOOKS
REASONABLE. THIS AIR MASS TRAJECTORY WILL KEEP DEW POINTS IN THE 30S
THROUGH MOST OF THE DAY...PROVIDING COMFORTABLY LOW HUMIDITY.

TONIGHT...THE DEPARTING SURFACE RIDGE WILL CONTINUE TO PROVIDE A
WEAK LOW LEVEL EAST TO SOUTHEAST FLOW OF DRY AIR. HOWEVER...THIS
WILL BE OVERRUN BY WARM ADVECTION AND THEN INCREASING MOISTURE AT
850 MB TOWARD SATURDAY MORNING. AN MCS WILL LIKELY DEVELOP ON THIS
THETAE ADVECTION WELL TO THE WEST TO NORTHWEST OF THE FORECAST AREA
LATE IN THE EVENING. THIS WOULD THEN FOLLOW PROPAGATION VECTORS
EAST TO SOUTHEAST INTO EASTERN IA BY 12Z...IN A DISSIPATING MODE AS
IT MOVES AWAY FROM A MORE FAVORABLE MOISTURE FEED AND ENCOUNTERS DRY
AIR IN THE LOW LEVELS. AT THE SAME TIME...WEAK ELEVATED CONVERGENCE
ALONG WITH INCREASING MID LEVEL TEMPERATURE LAPSE RATES AND THETAE
LAPSE RATES MAY LEAD TO ISOLATED TO WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS...FOCUSED OVER SOUTHEAST IA OR EAST CENTRAL AND
NORTHEAST IA...DEPENDING ON THE MODEL TOWARD SUNRISE. CONSIDERING
THE ABOVE...HAVE GONE WITH LIKELY POPS ROUGHLY WEST OF THE HIGHWAY
218 CORRIDOR AFTER 1 AM...WITH POPS DIMINISHING TO CHANCE TO SLIGHT
CHANCES IN IL. INCREASING CLOUDS AND SLIGHTLY STRONGER SURFACE WINDS
WILL HOLD MINS WARMER THAN THIS MORNING...BUT STILL BELOW NORMAL...
FROM THE LOWER 40S EAST AND NORTHEAST TO THE LOWER 50S IN SE IA AND
NE MO. SHEETS

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 245 AM CDT FRI MAY 24 2013

THE LONG TERM TIME FRAME LOOKS LIKE AN UNSETTLED PERIOD WITH
PLENTY OF OPPORTUNITIES FOR RAIN AND DRY WEATHER...THOUGH LITTLE
IN THE WAY OF SEVERE WEATHER POTENTIAL. MODELS ARE IN GENERAL
AGREEMENT THROUGH DAY 5 BUT THEN DIVERGE FOR DAYS 6 AND 7.

WHILE THE RIDGE MAINTAINS ITSELF OVER THE CENTRAL U.S.THROUGH
MONDAY...SEVERAL WEAK WAVES EMBEDDED IN THE RIDGE ARE PROBLEMATIC
FOR PINPOINTING PRECIP CHANCES. IN ADDITION THE LOCATION OF THE
SURFACE AND 850 FRONTS WILL ALSO BE KEY PLAYERS.

DECAYING MCS SATURDAY WILL PRECEDE A WEAK SHORT WAVE TROUGH
PASSAGE SATURDAY NIGHT INTO SUNDAY. THIS SHOULD FOCUS STORM
CHANCES ALONG THE 850MB FRONT MOVING INTO OUR CWA...WITH ANOTHER
NOCTURNAL MCS INITIATING TO OUR WEST AND PERSISTING INTO SUNDAY.

ON MONDAY...THE SURFACE WARM FRONT SHIFTS CLOSER TO THE CWA
PROVIDING ANOTHER FOCUSING MECHANISM FOR STORMS. HOWEVER...OVERALL
THIS HOLIDAY WEEKEND INSTABILITY IS LIMITED AND FORCING...BOTH
MID LEVEL SHORTWAVE TROUGHS AND LOW-LEVEL JET INTERACTIONS WITH
THE 850MB BOUNDARY ARE WEAK.  SO I WANT TO AVOID THE IMPRESSION OF
A TOTAL WASHOUT FOR THE WEEKEND...AS THERE SHOULD BE PLENTY OF
DRY WEATHER IN BETWEEN THE RAIN CHANCES. THE CHALLENGE IS TRYING
TO PIN THOSE PERIODS...AND IT IS DIFFICULT TO DO SO WITH SUCH
SUBTLE FEATURES. BUT THE PATTERN SEEMS TO FAVOR NOCTURNAL
INITIATION AND DECAY EARLY THE NEXT DAY.

BY MID WEEK THE ACTIVITY MOSTLY SHIFTS TO THE NORTH THOUGH NOT
COMPLETELY OUT OF THE AREA...SO POP CHANCES WILL DIMINISH AS TEMPS
MODERATE.

MODELS DIVERGE LATE IN THE WEEK WITH THE GFS BRINGING A PACIFIC
TROUGH INTO THE NORTHERN ROCKIES/PLAINS INDICATING A LITTLE MORE
ENERGETIC WEATHER FOR US...WHILE THE 12Z ECMWF CUTS OFF A LOW TO
OUR SOUTHWEST ALLOWING THE RIDGE TO DOMINATE AND TREND US TOWARD
QUIET WEATHER. THE 00Z GFS RUN IS WELL WITHIN THE MEAN OF THE 12Z
ENSEMBLE...AND THE 00Z ECMWF SEEMS TO BE TRENDING THIS WAY TOO. SO
OPTED FOR THE MORE ENERGETIC PATTERN WHICH IS REFLECTED IN POPS.
WOLF

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1139 PM CDT THU MAY 23 2013

VFR CONDITIONS EXPECTED THE NEXT 24 HOURS. LIGHT AND VARIABLE WINDS
OVERNIGHT WILL SLOWLY INCREASE OUT OF THE SOUTHEAST FRIDAY MORNING BUT
STILL AT OR BELOW 10 KTS. FRIDAY EVENING THUNDERSTORMS ARE
EXPECTED TO GENERATE OUT OVER THE PLAINS WHICH WILL MOVE TOWARDS
THE TERMINALS. THESE WILL SPREAD HIGH CLOUDS ABOVE 10KFT AFTER
00Z...BUT NO THUNDERSTORM ACTIVITY IS EXPECTED TO AFFECT THE TERMINALS
UNTIL AFTER 06Z. LE


&&

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

$$

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