Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 112354
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
654 PM CDT FRI APR 11 2014

.SYNOPSIS...
ISSUED AT 348 PM CDT FRI APR 11 2014

ANOTHER BREEZY...DRY AND MILD DAY OVER THE AREA UNDER A MOSTLY ZONAL
FLOW ALOFT. WATER VAPOR IMAGERY SHOWED A SHORTWAVE MOVING INTO THE
WESTERN GREAT LAKES. A WEAK SURFACE TROUGH TRAILED W-SW ACROSS
NORTHERN IA TO FAR SE SD. A MORE SIGNIFICANT BOUNDARY WAS NEARLY
STATIONARY FROM NORTHERN TX REACHING E-NE ALONG THE OHIO VALLEY.
THIS BOUNDARY WAS THE NORTHERN REACHES OF A GULF AIRMASS WITH MIDDAY
DEWPOINTS IN THE 50S TO LOWER 60S TO ITS SOUTH. TO THE NORTH...DEEPER
MIXING INTO A VERY DRY PLAINS AIRMASS HAS LOWERED DEWPOINTS INTO THE
20S AND 30S...WHILE DRY BULB TEMPERATURES WERE WELL INTO THE 70S
OVER MOST OF THE FORECAST AREA. UPSTREAM...A COMPLEX OF SHORTWAVES
IN THE NORTHERN STREAM FROM THE PACIFIC NW INTO MT AND WY IS EXPECTED
TO LEAD TO LEE CYCLOGENESIS TONIGHT. THIS SYSTEM WILL THEN EVOLVE
EASTWARD INTO THE PLAINS ALONG A NEW DEVELOPING PRIMARY WARM FRONT
SETTING UP JUST TO OUR NORTH FROM SD...ALONG THE IA/MN BORDER..INTO
SOUTHERN WI.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 348 PM CDT FRI APR 11 2014

ACTIVE WEATHER DAY SETTING UP FOR SATURDAY WITH CONCERNS CENTERED ON
BOTH SEVERE WEATHER AND FIRE WEATHER. THE FIRE WEATHER CONCERNS ARE
OUTLINED IN THE SEPARATE FIRE WEATHER DISCUSSION BELOW.

THE DEVELOPING LEE TROUGH AT 850 MB SETS UP A RETURN S-SW LOW LEVEL
JET OF 40 TO 50 KTS THAT IS SHOWN REACHING IA AND NW IL BY MORNING.
THIS EFFECTIVELY WASHES OUT THE SOUTHERN PLAINS/MID MS VALLEY
BOUNDARY...OPENING THE DOOR FOR THE GULF AIRMASS AND SURFACE
DEWPOINTS AT LEAST IN THE 50S TO EXPAND NORTHWARD INTO THE FORECAST
AREA SATURDAY. CONFIDENCE IN HOW FAST THIS TAKES PLACE IS LOW DUE TO
THE CONTINUED POOR HANDLING BY OPERATIONAL MODELS OF THE LOW LEVEL
MOISTURE OVER THE LOCAL AREA AND IN OUR SOURCE REGION TO THE SOUTH.

TONIGHT...THE WEAK SURFACE PRESSURE GRADIENT IN PLACE WILL ALLOW
WINDS TO BECOME LIGHT AFTER SUNSET. COMBINED WITH THE INITIALLY
CLEAR SKIES AND VERY DRY AIR...TEMPERATURES SHOULD COOL TO LOWS FROM
AROUND THE MID 40S TO NEAR 50 BEFORE RETURN SOUTHERLY WINDS HIGH
CLOUDS SPILL IN TOWARD MORNING. THE LOW LEVEL JET AND THETAE
CONVERGENCE WILL SET UP A FAVORABLE AREA FOR SCATTERED SHOWERS AND
THUNDERSTORMS JUST TO OUR NORTH...ESPECIALLY TOWARD MORNING AND HAVE
MAINTAINED LOW CHANCE POPS. THERE WILL BE A LOW POTENTIAL FOR SOME
OF THESE STORMS TO PRODUCE LARGE HAIL...BUT THE CURRENT EXPECTED
LOCATION OF THE ELEVATED WARM FRONT SUGGESTS THIS WOULD BE WELL
NORTH OR NW OF THE FORECAST AREA.

SATURDAY...HAVE GONE WITH THE DRIEST...MOST CONSERVATIVE GUIDANCE
SLOWING THE ADVANCEMENT OF DEWPOINTS IN THE LOWER TO MID 50S UNTIL
LATE MORNING AND AFTERNOON. AFTER A LEAD UPPER LEVEL SHORTWAVE AND
POSSIBLY AN ORGANIZED THUNDERSTORM COMPLEX PASSES TO THE NORTH IN
THE MORNING...THE PRIMARY SURFACE LOW ADVANCES EAST ALONG THE
BOUNDARY INTO SOUTHERN MN THROUGH THE DAY. THIS WILL PLACE THE
LOCAL AREA IN AN INCREASINGLY UNSTABLE WARM SECTOR THROUGH THE DAY.
THE DRIER AND MORE REASONABLE LOOKING WRF/NAM SOUNDINGS INDICATE
DEVELOPING MUCAPES OF 1500 TO 2000 J/KG SE IA AND NE MO BY AFTERNOON
UNDER A WEAK CAP AROUND 750 MB. THIS...COMBINED WITH LARGELY
UNIDIRECTIONAL DEEP LAYER SHEAR MAY LEAD TO CLUSTERS OF SEVERE
STORMS AS CONVECTIVE TEMPERATURES WELL INTO THE 70S ARE REACHED
BY AFTERNOON. SPC HAS OUTLOOKED THIS CONCERN IN ITS LATEST DAY 2
SLIGHT RISK THAT ENCOMPASSES NEARLY THE ENTIRE FORECAST AREA. THE
PRIMARY RISKS WILL BE LARGE HAIL AND DAMAGING WIND. HIGHEST POPS FOR
THUNDERSTORMS ARE KEPT OVER THE NORTH AND WEST CLOSER TO THE
ADVANCING LOW LEVEL BOUNDARIES AND MID LEVEL SHORTWAVES LATE IN THE DAY.

.LONG TERM...(SATURDAY NIGHT THROUGH NEXT FRIDAY)
ISSUED AT 348 PM CDT FRI APR 11 2014

SATURDAY NIGHT...AN ACTIVE WEEKEND CONTINUES. ASSESSING ALL THE
LATEST 12Z RUN GUIDANCE...THE GENERAL IDEA IS MAIN SFC BOUNDARY TO
BE IN ALMOST QUASI-STATIONARY MODE ALONG OR JUST NORTHWEST OF THE
CWA AT 00Z SUN...LLVL CONVERGENT AND FORCING PROGS SUGGEST
CONVECTION ALONG THIS FEATURE SHOULD BE ONGOING OR DEVELOPING AT
THIS TIME ON NORTHERN FRINGE OF 100-1500 J/KG SBCAPE FIELDS. BUT
CONVECTION TO BE MORE FED BY ELEVATED THTA-E ADVECTION AND
CONVERGENT FIELDS AND POSSIBLY ROOTED OFF THE SFC. STRONGER LLVL
THTA-E ADVECTION AND CONVERGENT FIELDS AND MORE PRIME MCS
DEVELOPMENT FIELDS STILL LOOK TO TAKE PLACE IN THE NEB/KS/IA/MO QUAD-
STATE REGION SAT EVENING. IF THIS SYSTEM TAKES OFF FIRST AND
DOMINATES...SOME POTENTIAL TO ROB FROM THE NORTHEAST IF LLJ
SOUTHWESTERLY DIRECTION IS VALID. BUT CHANCES ARE THAT DEVELOPING
STORMS JUST TO THE NORTHWEST OR IN THE NORTHERN AND NORTHWESTERN CWA
TO CLUSTER OR EVEN EVOLVE INTO A SECONDARY MCS-TYPE SYSTEM BLEEDING
DOWN ACRS MUCH OF THE NORTHWESTERN HALF OF THE DVN CWA AS SAT NIGHT
PROGRESSES. SHEAR...FORCING AND THERMODYNAMIC PROFILES STILL SUPPORT
SOME STORMS POSSIBLE WITH LARGE HAIL BEING THE DOMINATE THREAT...BUT
CAN/T RULE OUT DOWNBURST DAMAGING WINDS WITH STRONGER CELLS. WHERE
THE STORM CLUSTERS PERSIST...HALF INCH TO AN INCH OF RAIN POSSIBLY
BY LATE SAT NIGHT. SOME OF THE LATEST HIRES PROGS SUGGEST STORMS TO
FIRE FURTHER SOUTH THAN CURRENTLY ANTICIPATED MAYBE FROM A FREEPORT
IL...TO WEST OF MUSCATINE...AND TO SIGOURNEY AXIS AT AROUND 7 PM CDT
SAT EVENING. BETTER INSTABILITY/CAPE FIELDS IN THESE AREAS AT THAT
TIME BUT LESS CONVERGENT FORCING/FOCAL POINTS...SO FOR NOW WILL
STICK TO FURTHER NORTHWEST DEVELOPMENT AND THEN PUSH SOUTH TO
SOUTHEASTWARD.

SUNDAY...TAKING MODEL BLEND/ENSEMBLE SOLUTIONS OF SFC FRONT SAGGING
SOUTHEAST AND BI-SECTING THE CWA FROM NE-TO-SW BY EARLY SUNDAY
MORNING...IF NOT PUSHED FURTHER SOUTH BY STORM OUTFLOW...FEATURE
SHOULD GET HING UP BY NEXT AND MORE SUBSTANTIAL APPROACHING ROUND
OF LIFT FROM THE SOUTHWEST AS UPSTREAM L/W TROF SHIFTS ACRS THE
PLAINS. RESULTANT LLVL CYCLOGENESIS TO FORM A LOW THAT WILL RIPPLE UP
THE SW-TO-NE ORIENTED THERMAL BOUNDARY AND TARGET CENTRAL IL BY
SUNDAY EVENING. CURRENT PROGS SUGGEST IMPRESSIVE ELEVATED THTA-E
ADVECTION AND CONVERGENT FEED IN LLVL WARM MOIST CONVEYOR UP OFF
THE WESTERN GULF TO FUEL A SIGNIFICANT PRECIP EVENT...DEF ZONE TYPE
SYSTEM ACRS MUCH OF THE LOCAL FCST AREA OFF THE PASSING LOW TO THE
SOUTHEAST/EAST. MAYBE AFTER A MORNING LULL OR JUST LINGERING LIGHT
RAIN PATCHES SUNDAY MORNING...THIS DEF ZONE TO ENGULF THE CWA FROM
THE SOUTHWEST FROM LATE MORNING AND THE AFTERNOON. DEEP SATURATED
FCST SOUNDINGS WITH PRECIPITAL WATER PROFILES OF 1-1.3 INCHES
SUGGEST ROUNDS OF SEASONABLY MODERATE TO HEAVY RAINFALL SUNDAY
AFTERNOON AND WELL INTO THE EVENING. SOME LINGERING ELEVATED MUCAPE
ENOUGH TO KEEP AT LEAST ISOLATED THUNDER WORDING GOING CWA-WIDE...
ALTHOUGH MAY BE MORE PREVALENT CLOSER TO PASSING LOW IN THE
SOUTHEASTERN THIRD OF THE DVN CWA. SATURATED SOUNDINGS MAY
PRECLUDE MUCH MIXING FRICTION/THUNDER LATER IN THE DAY. STRENGTH OF
PASSING JET TO HELP BOOST L/W TROF ALONG SUGGESTS THE MORE
PROGRESSIVE 12Z RUN GFS MAY BE MORE IN LINE WITH PRECIP DECREASING
IN INTENSITY AFTER MIDNIGHT AND EXITING MOST OF THE CWA BY 12Z-13Z
MON MORNING. BUT BY THEN...WIDESPREAD 1-2 INCH RAINFALL AMOUNTS MAY
BE CONSERVATIVE...SOME SWATHS OF 3 INCHES APPEAR LIKELY. THESE SUN-
SUN NIGHT AMOUNTS NOT TAKING INTO ACCOUNT THE SAT NIGHT PRECIP
AMOUNTS WHICH COULD MEAN SOME SPOTS WELL OVER 3 INCHES FOR A
WEEKEND TOTAL. DRY THAWED OUT GROUND SHOULD ABSORB MUCH...AND
DURATION OF PRECIP TO HELP AS WELL. BUT STILL...THESE TYPE OF
AMOUNTS WILL EVENTUALLY LEAD TO DECENT TRIBUTARY RIVER/STREAM RISES
BY EARLY NEXT WEEK. SUNDAY HIGH TEMPS NOT MUCH WARMER THAN
SAT OVERNIGHT LOWS IN THE NORTHWEST HALF...POST FRONTAL AREAS. BACK
TO SUNDAY NIGHT...IN-WRAPPING POST-FRONTAL LLVL COLD CONVEYOR AS
WELL AS TOP-DOWN COOLING STILL ENOUGH TO SWITCH NORTHWEST FLANK OF
DEF ZONE TO RAIN/SNOW MIX OR ALL SNOW BY MIDNIGHT IN THE FAR
NORTHWEST...BUILDING EAST AND SOUTH INTO EARLY MON MORNING. BUT EVEN
WITH A TOTAL WET SNOW SWITCH OVER ALONG AND NORTH OF I80...SNOW
INTENSITY NOT ENOUGH TO OVERCOME MILD GROUND TEMPS. 1-2 INCHES OF
SNOW MAY INDEED FALL ALONG AND NORTH OF THE HWY 30 CORRIDOR LAST
SUNDAY NIGH INTO EARLY MONDAY MORNING...BUT MUCH WILL MELT AND
MAYBE A WET HALF INCH OR EVEN LESS MEASURED ON ELEVATED AND
GRASSY SFCS. LOWS BY MON MORNING WILL GET WELL DOWN IN THE 30S
LOOKING AT THE EXTENT OF SFC COLD AIR ADVECTION.

MONDAY THROUGH NEXT FRIDAY... PRECIP EXITS MON MORNING...MAKING FOR
BRISK COOL NORTHWEST WINDS AND A RAW DAY...HIGHS IN THE 40S. GFS EVEN
BREAKS OUT INSTABILITY SNOW SHOWERS NORTH OF I80 DURING THE
AFTERNOON UNDER COLD CORE UPPER TROF AXIS. IF CLOUDS CAN THIN/CLEAR
ENOUGH WITH DECREASING WINDS...LOWS IN THE 20S POSSIBLE MON NIGHT.
RE-ENFORCING COLD SURGE ON TUE POSSIBLE...THE 12Z RUN ECMWF HAS A
RIDICULOUS -12C H85 MB ISOTHERM INTO THE NORTHERN CWA BY TUE
MORNING...-10C TO THE SOUTH. THIS MAY BE TOO COLD...BUT IF TO VERIFY
HIGHS MAY BE LIMITED TO THE UPPER 30S OR AROUND 40 ON TUE. ANOTHER
UNSEASONABLY COOL NIGHT TUE NIGHT INTO EARLY WED IF CLOUDS CAN
CLEAR...ANOTHER NIGHT FOR THE POTENTIAL TO DIP DOWN IN THE 20S
POSSIBLY SOME LOWER 20S NORTH OF I80....NEAR RECORD COLD IN SOME
SPOTS. SOME TEMP REBOUND BACK INTO THE UPPER 40S TO MID 50S ON WED...
FLATTENING FLOW RELOADS OFF TO THE WEST WITH TROFFINESS ACRS THE GRT
BSN...INCREASING RETURN FLOW AHEAD OF THIS PROCESS TO HELP TEMPS
MODERATE NEXT THU AND FRI. NEXT UPSTREAM SYSTEM TO ENCROACH UPON THE
MIDWEST BY NEXT THU...BUT MANY DETAILS TO WORK OUT BETWEEN NOW AND
THEN.    ..12..

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 645 PM CDT FRI APR 11 2014

VFR CONDITIONS UNTIL 13/00Z. WINDS WILL DIMINISH AND SHIFT TO THE
SOUTH AROUND 5 KTS BY 12/02Z AS A LOW PRESSURE SYSTEM DEVELOPS IN
THE PLAINS. STRONGER WINDS 1000 TO 2000 FT AGL MAY RESULT IN LOW
LEVEL WIND SHEAR CONDITIONS DEVELOPING...ESPECIALLY NEAR DBQ AND
CID AFTER 12/09Z. CONFIDENCE IN ACHIEVING LLWS CONDITIONS IS NOT
HIGH ENOUGH TO INCLUDE IN THE CURRENT FORECASTS...BUT WILL BE
MONITORED FOR LATER UPDATES. RETURNING MOISTURE ON THESE STRONGER
WINDS ALOFT MAY ALSO LEAD TO ISOLATED SHOWERS AND THUNDERSTORMS
EARLY SATURDAY MORNING NEAR DBQ AND CID TERMINALS. THIS POTENTIAL
WILL ALSO BE MONITORED...AND MAY BE ADDED IN 12/06Z TAF FORECAST
AS WELL. AFTER 12/21Z...CONVECTIVE TEMPERATURE MAY BE REACHED WITH
THUNDERSTORMS FIRING NW OF CID/DBQ TERMINALS WITH BETTER CHANCES
AFTER 13/00Z. SINCE THIS IS VERY UNCERTAIN...WILL HOLD OFF UNTIL
06Z TAF PACKAGE TO PROVIDE MORE CERTAIN TIMING OF INITIATION.

&&

.FIRE WEATHER...
ISSUED AT 348 PM CDT FRI APR 11 2014

THIS EVENING...WINDS SHOULD DIMINISH SIGNIFICANTLY TOWARD SUNSET...
WHILE RH VALUES RECOVER INTO THE 30S AND 40S THIS EVENING. THIS WILL
SIGNIFICANTLY DIMINISH THE FIRE THREAT.

SATURDAY...STRONG SOUTH WINDS AS HIGH AS 20 TO 30 MPH WILL DEVELOP
IN THE AFTERNOON. HOWEVER...AN INCOMING MOIST AIRMASS ORIGINATING
FROM THE GULF COAST REGION WILL HOLD RELATIVE HUMIDITY VALUES MUCH
HIGHER THAN TODAY. WHILE THERE IS SOME UNCERTAINTY IN HOW FAST THIS
MOISTURE RETURNS...IT IS LIKELY THAN MINIMUM RH VALUES WILL DROP NO
LOWER THAN 40 PERCENT. THIS WOULD STILL PLACE GFDI IN THE VERY HIGH
RANGE OVER MUCH OF EAST CENTRAL IA INTO NW IL...PRESENTING A CONTINUE
THREAT OF GRASS FIRES...ALBEIT NOT AS HIGH AS THE PAST FEW DAYS.

&&

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

&&

$$

SYNOPSIS...11
SHORT TERM...11
LONG TERM...12
AVIATION...NICHOLS
FIRE WEATHER...11







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