Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 281755
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1155 AM CST WED JAN 28 2015

.UPDATE...
ISSUED AT 1155 AM CST WED JAN 28 2015

AS EXPECTED THE LOW STRATUS HAS LIFTED NORTHWARD OUT OF THE DVN CWA
ON STRENGTHENING SURFACE/LOW LEVEL WINDS/STRONG WARM AIR ADVECTION.
IN THE MEANTIME...OPAGUE CIRRUS WAS SPREADING OVER THE CWA AND THIS...
ALONG WITH SNOW COVER IN ROUGHLY OUR NE HALF...WAS KEEPING TEMPERATURES
COOLER THAN FORECAST. HAVE ALREADY UPDATED THE GRIDS TO LOWER MAXIMUM
TEMPERATURES BY AT LEAST 5 DEGREES AT SOME LOCATIONS AND WILL CONTINUE
TO MONITOR. REMAINDER OF THE GRIDS UNCHANGED AT THIS TIME.

UPDATE ISSUED AT 501 AM CST WED JAN 28 2015

CLEARING IS SPREADING NORTH FASTER THAN FORECAST...AND WILL HAVE A
MAJOR IMPACT TO TODAYS HIGHS. I HAVE CLEARED SKIES TO MOSTLY SUNNY
IN THE SOUTH 1/2 THIS MORNING AND INCREASED HIGHS TO UPPER 40S TO
LOWER 50S OVER MUCH OF THAT AREA. OVER SNOW...I RETAINED HIGHS
CLOSER TO THE LOWER 40S. MORE UPDATES MAY BE NEEDED AS THE CLOUDS
ARE ERASED FROM THE SKY...MEANWHILE...MODELS HAVE NO IDEA THIS IS
HAPPENING.

&&

.SYNOPSIS...
ISSUED AT 326 AM CST WED JAN 28 2015

YESTERDAYS PERSISTENT PROBLEMATIC CLOUDS CONTINUE TO BE IN PLACE OVER
THE CWA THIS MORNING. HOWEVER...UNLIKE YESTERDAYS NORTHEAST LOW
LEVEL FLOW REINFORCING THIS CLOUD COVER AND COLDER TEMPERATURES...
WE NOW SEE SOUTHEAST LOW LEVEL FLOW WAA...AND FOR THE MOMENT...
RELATIVE DRY LOW LEVEL ADVECTION. THIS AIS ALLOWING THE STRATUS TO
CLEAR FROM THE SOUTHEAST OVER ILLINOIS DURING THE EARLY MORNING
HOURS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 326 AM CST WED JAN 28 2015

THE CLOUDS COULD NOT BE MORE CHALLENGING TODAY. IN ONCE SENSE...
STEADY CLEARING IS OCCURRING IN REALITY...BUT NOT IN COMPUTER
MODEL DATA. THIS SHOULD CONTINUE FOR THE TIME BEING...AND
IMPROVEMENT HAS BEEN PLACED INTO THE SOUTHEAST CWA COUNTIES
THROUGH 12Z TO SHOW CLEARING. HOWEVER...THE FLOW WILL BECOME MORE
SOUTHERLY DURING THE DAY TODAY...AND WITH LIFT AND INCREASING
MOIST ADVECTION TAKING PLACE OVER COOL AIR...WE MAY GENERATE MORE
CLOUDS... EFFECTIVELY HOLDING THE EDGE OF CLOUDS IN PLACE. THE
QUESTION IS WHERE...SOUTH? I-80? NORTH? SNOW COVER DOES NOT EXIST
OVER OUR WEST 1/2 OR OUR SOUTH...SO I AM INCLINED TO THINK THE
PERSISTENT CLOUDS ARE GOING TO HOLD NORTH OF INTERSTATE 80...BUT
THAT COULD EASILY BE OFF BY SEVERAL COUNTIES...IN A WAY...I AM
CERTAIN AN EARLY MORNING UPDATE WILL BE REQUIRED TO FINE TUNE THIS
FORECAST. AS THE CLOUDS GO...SO WILL TEMPERATURES. THE ATMOSPHERE
SUPPORTS 40S AND EVEN 50S WITH ANY SUNSHINE. HOWEVER...WITH 100%
CLOUDS AND WIND TRAJECTORY OVER SNOW COVER...THE FAR NORTH MAY
ONLY REACH THE MID 30S...VERY LATE IN THE AFTERNOON.

TONIGHT...LOW PRESSURE WILL MOVE OVER HEAD...ROUGHLY CENTERED AROUND
THE MIDNIGHT HOUR. SOUTH WINDS AHEAD OF THIS LOW COMBINED WITH
CLOUDS DEVELOPING IN ADVANCE IF NOT ALREADY IN PLACE...WILL KEEP
TEMPERATURES HOLDING IN THE MID 30S TO LOWER 40S MOST OF THE NIGHT.
AS THE LOW PASSES...A SLIGHT CHANCE OF SHOWER SEEMS WARRANTED...BUT
AS MID LEVELS DRY OUT...A MORE LIKELY SCENARIO IS A FEW WAVES OF
DRIZZLE BEHIND THE LOW. IT SHOULD TAKE UNTIL NEARLY DAWN BEFORE CAA
DRAGS OUR TEMPERATURES BACK BELOW FREEZING...SO I AM THINKING THAT
WE SEE LITTLE IF ANY FREEZING DRIZZLE THREAT...BUT IF IT OCCURRED IT
WOULD BE ONLY POSSIBLE IN THE FAR NORTHWESTERN COUNTIES.

ERVIN

.LONG TERM...(THURSDAY THROUGH NEXT TUESDAY)
ISSUED AT 326 AM CST WED JAN 28 2015

THURSDAY AND FRIDAY...WILL WALK OUT A FEW SNOW SHOWERS OR FLURRIES
OUT OF THE EASTERN HALF OR EVEN THIRD OF THE DVN CWA JUST THROUGH 15Z
THU IN WAKE OF EXITING CYCLONE ACRS THE SOUTHWESTERN GRT LKS.
TOP-DOWN COOLING ONGOING MAY STILL ALLOW FOR A MIX OF RAIN/SNOW OR
EVEN SOME ICE PELLET MIX IN THE FAR EAST THRU MID MORNING. BUT THE
MAIN WX STORY FOR THU WILL BE THE NORTHWEST SFC WIND SURGE...WITH
MIXING-DOWNWARD MOMENTUM TRANSFER PROFILES IN TIGHT LLVL PRESSURE
GRADIENT BETWEEN EXITING LOW AND PLAINS RIDGE LOBE...SUGGESTING WIND
GUSTS POSSIBLY EXCEEDING 40 MPH AT TIMES. DESPITE AN IN-RUSH OF
COOLING AIR MASS AS THE DAY PROGRESSES...DEEP MIXING AND SOME DELAY
IN THE REAL COOLER PROFILES WILL ALLOW FOR MOST OF THE CWA SEEING
HIGHS IN THE 35-40 DEGREE RANGE. EXPECT SOME CLEARING FROM THE
WEST AS THE DAY PROGRESSES. THE UPSTREAM SFC RIDGE AXIS WILL SLIDE
OVERHEAD THU NIGHT FOR A SFC WIND DECREASE/DECOUPLE...IF SKIES
REMAIN MAINLY CLEAR EXTENT OF INCOMING AIRMASS WILL SUPPORT LOWS
WELL DOWN IN THE TEENS IN THE NORTH HALF OR MORE...AROUND 20 IN
THE SOUTHERN CWA. DESPITE SOME INSOLATION UNDER PASSING HIGH
COMPLEX ON FRI...WEAK MIXING SOUNDINGS AND COOL START TO THE DAY
SHOULD LIMIT HIGHS TO THE UPPER 20S IN THE NORTHEASTERN HALF...TO
MID 30S IN THE SOUTHWESTERN FCST AREA. QUICK TEMP DROP OFF FRI
EVENING AFTER SUNSET...THEN IT WILL BE UP TO THE TIMING OF THE
START OF BL RETURN FLOW INCREASING FROM THE SOUTHEAST TO ALLOW FOR
A STEADY TO SLOW TEMP RISE INTO SAT MORNING. ANY FURTHER DELAY IN
THAT PROCESS WILL MAKE THE ADVERTISED LOWS STILL TOO MILD.

SATURDAY AND SUNDAY...MANY OF THE 00Z RUN MEDIUM RANGE SOLUTIONS
INCLUDING THE HEAVILY USED GFS AND ECMWF...PHASE THE NORTHERN
STREAM DIGGING UPPER TROF ENERGY WITH THE SOUTHERN STREAM GRT BSN
UPPER LOW ACRS THE SOUTHERN AND CENTRAL PLAINS SAT INTO SAT NIGHT.
IF THIS WERE TO VERIFY...IT WOULD MAKE FOR A MORE DEVELOPED LLVL
LOW AND INVERTED TROF COMPLEX EJECTING OUT OF THE SOUTHERN PLAINS
AND ROLLING UP TOWARD THE OH RVR VALLEY INTO SUNDAY. THE LATEST MODEL
SOLUTIONS ALSO HAVE TRENDED WETTER WITH AN ENHANCED MILD/MOIST
CONVEYOR STREAMING UP AHEAD OF THE SYSTEM AND OVERRUNNING IT ACRS
THE MID TO UPPER MS RVR VALLEY LATE SAT INTO SUNDAY. BESIDES MAYBE
A BRIEF PERIOD OF RAIN/SNOW MIX IN THE SOUTH SAT AFTERNOON...BULK OF
THERMAL PROFILES ALTHOUGH NOT ALL THAT FRIGID...STILL COLD ENOUGH TO
ALLOW FOR A WET SNOW EVENT. POSSIBLY A HEAVY WET SNOW EVENT AT
TIMES...AS WELL AS A RATHER LONG DURATION/SAT AFTERNOON THROUGH EARLY
SUNDAY EVENING/BEFORE EXITING OFF TO THE EAST. BOTH THE 00Z RUN
ECMWF AND GFS PRODUCE SEVERAL INCHES OF SNOW ACRS THE DVN CWA
DURING THIS PERIOD...ENOUGH SO TO MAKE FOR A LONG DURATION ADVISORY
OR EVEN A 24 HR WARNING CRITERIA EVENT. DEEPENING ON THE MAIN SFC LOW
TRACK...THE MODELS ARE ALSO SUGGESTING BRISK NORTH TO NORTHEAST
SFC WINDS ON SUNDAY INTO SUNDAY EVENING COMPOUNDING THE WINTERY
SCENARIO. WILL CONTINUE TO RAISE POPS THRU THE PERIOD...AND MUCH
ATTENTION WILL HAVE TO BE FOCUSED ON THE COMING MODEL RUNS OVER THE
NEXT 24-36 HRS FOR SYSTEM EVOLUTION...PHASING AND TIMING ISSUES TO
BE WORKED OUT. ALSO AFTER WHATEVER TYPE OF SYSTEM DEVELOPS AND THEN
EXITS THE REGION...ALL SIGNS POINT TO A STRONG CANADIAN HIGH WITH
ARCTIC AIR DUMPING DOWN THE UPPER MIDWEST SUNDAY NIGH INTO MONDAY.
WITH FRESH AND POSSIBLY SUBSTANTIAL NEW SNOW COVER...A COLD WINDOW
APPEARS TO BE BREWING FOR EARLY NEXT WEEK.

NEXT MONDAY AND TUESDAY...AGAIN POINTING TO THE ABOVE DISCUSSION...
MONDAY MAY BE A COLD CANADIAN HIGH PRESSURE DAY WITH HIGHS HELD IN
THE TEENS OR EVEN UPPER SINGLE DIGITS IN SOME LOCATIONS. BUT THE
COLD TO BE TEMPORARY...AS THE MEDIUM RANGE ENSEMBLE AND UPPER JET
ENERGY EVOLUTION SUGGEST SOMEWHAT FLATTENING FLOW BY TUE WITH
SOME TEMP MODIFICATION INTO MID WEEK. THERE MAY BE A LIGHT SNOW
EVENT EMBEDDED IN THAT TUE TIME-FRAME AS WELL WITH A CLIPPER TYPE
SYSTEM AND ELEVATED WAA PUSH.     ..12..

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1155 AM CST WED JAN 28 2015

VFR CONDS THIS AFTERNOON AND EVENING THEN MVFR/POSSIBLE IFR CONDS
BEHIND A COLD FRONT ARRIVING AFTER 06Z/29. SOUTHEAST TO SOUTH
WINDS SUSTAINED 15 TO 20 KNOTS WITH GUSTS TO AROUND 25 KNOTS THIS
AFTERNOON THEN DIMINISHING THIS EVENING. NORTHWEST WINDS BEHIND
THE COLD FRONT WILL BE SUSTAINED AROUND 20 KNOTS WITH GUSTS TO
AROUND 30 KNOTS.

&&

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

$$

UPDATE...HAASE
SYNOPSIS...ERVIN
SHORT TERM...ERVIN
LONG TERM...12
AVIATION...HAASE





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