000
FXUS63 KDVN 010541
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1141 PM CST SAT JAN 31 2015

.UPDATE...
ISSUED AT 857 PM CST SAT JAN 31 2015

FORECAST REMAINS ESSENTIALLY ON TRACK AND THE RECENTLY SENT WSW
PRODUCT HAS ONLY MINOR WORDING TWEAKS. SNOWFALL AMOUNTS WERE
UNCHANGED.

AT 8 PM...THE COLD FRONT HAS SETTLED INTO THE HIGHWAY 20 CORRIDOR...
WHERE E-NE WINDS WERE ADVECTING COLDER AIR WITH DEWPOINTS IN THE
UPPER 20S...HELPING THE PRECIPITATION MAKE A SOLID TRANSITION TO
SNOW. FURTHER SOUTH...I-80 APPEARS TO BE A ROUGH DIVIDING LINE
FOR A RAIN AND SNOW MIX NORTH TO MAINLY RAIN SOUTH. THE KDVN
SOUNDING SHOWED THE FREEZING LEVEL AT 00Z ROUGHLY AROUND 900 FT.
UPSTREAM OVER NORTHERN MO INTO SOUTH CENTRAL IA...DYNAMIC COOLING
FROM STRONGER FORCING SPREADING IN FROM SW HAS CHANGED THE
PRECIPITATION PRIMARILY OVER TO ALL SNOW...WHICH HAS LIKELY
REACHED INTO SCOTLAND COUNTY MO AND VAN BUREN CO IA. THIS
TRANSITION WILL CONTINUE TO SPREAD NORTHEAST AND AT THE CURRENT RATE...
THE REMAINING AREAS OF RAIN...OR MIXED PRECIPITATION SHOULD
CHANGE OVER TO ALL SNOW BY 10 OR 11 PM.

SNOW HAS BEGUN TO ACCUMULATE AT THE NWS OFFICE OVER THE PAST
HOUR...WITH JUST OVER A HALF INCH MEASURED AT 845 PM. THIS
SUGGESTS THAT MOST AREAS SHOULD BEGIN TO ACCUMULATE WITHIN AN HOUR
AFTER THE TRANSITION AND LIKELY REACH OR EXCEED THE 1 INCH MARK
BEFORE MIDNIGHT.

&&

.SYNOPSIS...
ISSUED AT 356 PM CST SAT JAN 31 2015

WINTER STORM WITH SIGNIFICANT SNOWFALL ACCUMS FOR THE AREA STILL ON
TRACK NEXT 24+ HRS... AS ENERGY EJECTING FROM SOUTHERN STREAM
CLOSED LOW OVER THE SOUTHWEST PHASES WITH DIGGING NORTHERN STREAM
TROUGH. COMBINATION OF THE STRONG FORCING AND ANOMALOUSLY HIGH
MOISTURE (PACIFIC AND GULF ORIGINS) BEING ENTRAINED INTO SYSTEM
WITH PWATS 3-4 SIGMA OR STANDARD DEVIATIONS ABOVE NORMAL SUPPORT
LEND SUPPORT FOR THE SIGNIFICANT SNOW ACCUMS.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 356 PM CST SAT JAN 31 2015

CONFIDENCE IS HIGH ON WIDESPREAD SIGNIFICANT SNOWFALL ACCUMS WITH
NORTH 1/2 OF CWA FAVORED FOR THE HEAVIEST AMOUNTS. CONFIDENCE
THOUGH REMAINS MODERATE ON EXACT AMOUNTS.

TIMING...RAIN/DRIZZLE CONTINUE INTO EARLY THIS EVENING BEFORE
CHANGING OVER TO SNOW FROM NORTH TO SOUTH... WITH SOME AREAS FAR
SOUTH POSSIBLY WAITING UNTIL AFTER MIDNIGHT TO CHANGE.

SNOWFALL AND AMOUNTS...SNOW MODERATE TO LOCALLY HEAVY AT TIMES
OVERNIGHT THROUGH SUNDAY AM WITH VISIBILITIES BELOW 1 MILE IN
THE HEAVIER SNOW. CHARACTER OF SNOW TO CHANGE WITH INITIALLY TONIGHT
MAINLY A WET SNOW THEN TURNING MORE POWDERY ON SUNDAY WITH ARRIVAL
OF COLDER AIR. TRACK OF SFC LOW JUST SOUTH OF CWA WITH 850/700 LOW
TRACKS ACROSS THE SOUTHERN CWA IS FAVORABLE FOR HEAVIEST SNOW
ACCUMS OVER ROUGHLY THE NORTHERN 1/2 OR SO OF CWA WHERE STRENGTH
AND DURATION OF MOISTURE AND FORCING SUPPORT 6-11 INCHES. ACROSS
THE SOUTHERN CWA STILL EXPECT SIGNIFICANT ACCUMS OF 6 INCHES OR
MORE (ESPECIALLY NEAR HWY 34) WITH POTENTIAL FOR DECENT GRADIENT
OR CUTOFF IN AMOUNTS FAR SOUTHERN CWA. SNOW SHOULD BEGIN TO TAPER
OFF IN INTENSITY SUNDAY AFTERNOON.

WINDS...LIGHT WINDS THIS EVENING TO TURN MORE EASTERLY OVERNIGHT
AT 5-10 MPH. ON SUNDAY WINDS WILL INCREASE FROM NORTHEAST AT
15-30 MPH WHICH WITH MORE POWDERY NATURE OF SNOW MAY MAKE FOR SOME
DRIFTING AND PATCHY TO AREAS OF BLOWING SNOW MAKING SNOW REMOVAL
CHALLENGING. VISIBILITIES COULD ALSO LOWER BELOW 1 MILE AT TIMES.

TEMPS... DROPPING INTO THE 20S TO AROUND 30 TONIGHT. STEADY EARLY ON
THEN FALLING INTO THE LOWER 20S AND TEENS IN THE AFTERNOON.

WIND CHILLS..DROPPING INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO
SUNDAY AFTERNOON.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 356 PM CST SAT JAN 31 2015

FORECAST FOCUS ON BELOW NORMAL TEMPERATURES DURING THIS EXTENDED
ALONG WITH A COUPLE OF CLIPPERS POTENTIALLY BRINGING LIGHT SNOW
ACCUMULATIONS.

SUNDAY NIGHT...DEFORMATION ZONE WILL CONTINUE TO PRODUCE SNOW OVER
THE CWA DURING THE EVENING. ADDITIONAL ACCUMULATIONS WILL BE UP TO
2 INCHES. THE CYCLONE WILL BE MOVING INTO SOUTHERN OH WITH A TIGHT
GRADIENT STILL OVER THE CWA DURING THE EVENING...WITH NORTH WINDS
CONTINUING TO GUST TO 30 TO 35 MPH. CONSIDERABLE DRIFTING AND SOME
BLOWING SNOW DUE TO THE DRY FLUFFY NATURE OF THE FALLING SNOW. AFTER
MIDNIGHT...THE CYCLONE TRACKS FARTHER AWAY AND HIGH PRESSURE BEGINS
TO BUILD INTO THE AREA. THE SNOW WILL BE ENDING AND WINDS WILL BE
DIMINISHING. STRONG SUBSIDENCE AND COLDER/DRIER AIR WILL ALLOW
CLOUDS TO DECREASE OVERNIGHT. THIS COMBINED WITH DEEP SNOW COVER
SHOULD DROP MINIMUM TEMPERATURES INTO THE SINGLE DIGITS BELOW AND
SINGLE DIGITS ABOVE ZERO.

MONDAY THROUGH SATURDAY...A COLD WEEK WITH BELOW NORMAL TEMPERATURES
BASICALLY REMAINING BELOW FREEZING. THE COLDEST DAYS WILL BE ON
MONDAY AND THURSDAY WITH HIGHS ONLY IN THE TEENS. THE COLDEST NIGHT
IS EXPECTED TO BE WEDNESDAY NIGHT WHERE MINIMUM TEMPERATURES DROP TO
ZERO TO 8 BELOW OVER ROUGHLY OUR NORTHERN HALF...ALONG WITH WIND
CHILLS OF 15 TO 20 BELOW ZERO. OUR SOUTHERN HALF SHOULD SEE LOWS IN
THE SINGLE DIGITS ABOVE ZERO.

THERE LOOKS TO BE A COUPLE OF OPPORTUNITIES FOR ALBERTA CLIPPERS
BRINGING SOME LIGHT SNOW TO PORTIONS OF THE CWA. HOWEVER...CONFIDENCE
IS LOW IN REGARDS TO TIMING/INTENSITY AND TRACK OF THESE SYSTEMS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1140 PM CST SAT JAN 31 2015

SNOW FALLING AT ALL TERMINALS THIS EVENING WILL CONTINUE THROUGH
THE FORECAST PERIOD AS A SLOW MOVING WINTER STORM AFFECTS THE
REGION OVERNIGHT THROUGH SUNDAY. IFR TO LIFR CONDITIONS WILL
CONTINUE WITH VERY LOW IFR CONDITIONS LIKELY AT TIMES AS SNOW
BECOMES HEAVY OVERNIGHT INTO SUNDAY MORNING REDUCING VISIBILITIES
TO ONE HALF MILE OR LESS WITH VERTICAL VISIBILITIES DOWN TO A FEW
HUNDRED FEET. SUNDAY...AS THE STORM CENTER PASSES TO THE
SOUTH...WINDS WILL RAMP UP TO 15 TO 25 MPH FROM THE NORTHEAST TO
NORTH WITH EVEN HIGHER GUSTS DURING THE AFTERNOON. CONTINUED
SNOWFALL...ALONG WITH BLOWING AND DRIFTING WILL KEEP VISIBILITIES
LIKELY BELOW IFR AND LIKELY VERY LOW IFR THROUGH THE AFTERNOON.
FORECAST SNOWFALL TOTALS FOR THE REGION ARE IN THE RANGE OF 8 TO
11 INCHES. HEAVY SNOWFALL RATES FOLLOWED BY DRIFTING SNOW SUNDAY
MAY CREATE CHALLENGING CONDITIONS FOR AIRPORT GROUND OPERATIONS.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WARNING UNTIL 9 PM CST SUNDAY FOR BENTON-BUCHANAN-
     CEDAR-CLINTON-DELAWARE-DES MOINES-DUBUQUE-HENRY IA-IOWA-
     JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LEE-LINN-LOUISA-
     MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.

IL...WINTER STORM WARNING UNTIL 9 PM CST SUNDAY FOR BUREAU-CARROLL-
     HANCOCK-HENDERSON-HENRY IL-JO DAVIESS-MCDONOUGH-MERCER-
     PUTNAM-ROCK ISLAND-STEPHENSON-WARREN-WHITESIDE.

MO...WINTER STORM WARNING UNTIL 9 PM CST SUNDAY FOR CLARK-SCOTLAND.

&&

$$

UPDATE...SHEETS
SYNOPSIS...05
SHORT TERM...05
LONG TERM...HAASE
AVIATION...SHEETS