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000
FXUS63 KDVN 311817
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1217 PM CST SAT JAN 31 2015

.SYNOPSIS...
ISSUED AT 355 AM CST SAT JAN 31 2015

SYNOPSIS...FORECAST CONFIDENCE IS HIGH FOR WIDESPREAD SIGNIFICANT
SNOW ACCUMULATIONS ACROSS E IOWA/W ILLINOIS/NE MISSOURI SO ISSUED A
WINTER STORM WARNING FOR THE ENTIRE DVN FORECAST AREA. BUCHANAN AND
DELAWARE COUNTIES ARE INCLUDED IN THE WARNING AS WELL...EVEN THOUGH
THEY WERE NOT IN THE WATCH. THE WARNING IS IN EFFECT FROM 7 PM THIS
EVENING UNTIL 9 PM SUNDAY. DUE TO A SLOWER TRANSITION FROM RAIN TO
SNOW...THE START TIME IS 9 PM THIS EVENING IN CLARK/LEE/HANCOCK/MC
DONOUGH/DES MOINES/HENDERSON/WARREN COUNTIES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 355 AM CST SAT JAN 31 2015

THE WINTER STORM WARNING IS FOR 6 TO 11 INCHES OF SNOW. THE LIGHTEST
VALUES WILL BE SOUTH OF BURLINGTON WITH THE HEAVIEST IN A SWATH
+/- 40 MILES ALONG A LINE FROM CEDAR RAPIDS TO PRINCETON.

TODAY...EXPECT INCREASING CLOUDS THROUGH THE DAY AHEAD OF
COMPLEX/EVOLVING MID-LEVEL PATTERN. A LARGE SHIELD OF LIGHT TO
MODERATE PRECIP WILL MOVE INTO THE FORECAST AREA FROM SW TO NE THIS
AFTN...REACHING AREAS SW OF BURLINGTON AROUND MIDDAY AND AREAS NEAR
DUBUQUE AND FREEPORT IN THE 5-7 PM TIME FRAME.

THIS INITIAL PUSH OF MOISTURE/WAA WILL BEGIN AS RAIN GIVEN A
RELATIVELY MILD AND SATURATED BOUNDARY LAYER. FOR THIS REASON NOT
EXPECTING MUCH SNOW ACCUMULATION PRIOR TO 6 PM. SREF P-TYPE
PROBABILITIES AND NAM/GFS P-TYPE ALGORITHMS SUGGEST A TRANSITION TO
SNOW ACROSS THE NORTHERN HALF OF THE FORECAST AREA BETWEEN 4-6 PM.

AS THE PRECIP INTENSITY INCREASES DURING THE EVENING...DYNAMICAL
COOLING WILL RESULT IN A TRANSITION TO ALL SNOW ACROSS THE CWA. THIS
CHANGEOVER WILL LIKELY TAKE UNTIL AT LEAST 9 OR 10 PM OVER THE SE
FORECAST AREA AS TEMPS REMAIN STEADY IN THE MID 30S DOWN THERE.

850 MB LOW WILL TAKE A FAVORED TRACK FOR SIGNIFICANT SNOWFALL TO
OCCUR GOING FORM SE NEBRASKA AT 12 AM SUN TO EAST-CENTRAL IL BY 6 PM
SUN REMAINING JUST SOUTH OF THE DVN CWA.

TIME-HEIGHT SECTIONS DISPLAY DEEP OMEGA INTERSECTING THE DENDRITIC
GROWTH ZONE WITHIN A HIGHLY SATURATED ENVIRONMENT FROM THE SFC UP TO
300 MB. HEAVIEST SNOW WILL FALL BETWEEN 9 PM TONIGHT TO 6 AM SUNDAY.
AREA OF 0-1 KM CONVERGENCE/850 FRONTOGENESIS WILL COINCIDE WITH DEEP
ASCENT VIA UPPER DIVERGENCE IN RIGHT ENTRANCE REGION OF A 300 MB JET
STREAK. MOIST ADIABATIC LAPSE RATES IN THE 900-750 MB LAYER WILL
DEVELOP ABOVE THE AREA OF LOW-LEVEL FORCING LEADING TO THE POTENTIAL
FOR SOME MESOSCALE CONVECTIVE BANDING. GIVEN THIS SCENARIO DUE
EXPECT A PERIOD OF SNOWFALL RATES NEAR 1-1.5 INCHES PER HOUR.

IMPACTS...MODEL QPF FORECASTS IN FAIRLY GOOD AGREEMENT BETWEEN 0.70
INCHES NEAR DUBUQUE WITH WIDESPREAD AMOUNTS NEAR 1 INCH FURTHER
SOUTH. SHOULD BE A RATHER WET SNOW FOR THE FIRST PORTION OF THE
EVENT TRANSITIONING TO A DRIER SNOW ON SUNDAY.

WINDS WILL FIRST BEGIN TO PICK UP ACROSS THE NORTHERN THIRD OF THE
CWA AFTER 3 AM SUN...BLOWING/DRIFTING OF SNOW WILL BECOME MUCH
MORE OF AN ISSUE LATER ON INTO SUN. SNOW RATIOS WILL LIKELY BEGIN
AROUND 10-12:1 THEN TRANSITION CLOSER TO 15:1 PER NAM COBB OUTPUT
ACROSS THE NORTHERN TWO-THIRDS OF THE FORECAST AREA BY LATE SAT
NIGHT WHERE THE DGZ WILL AVG AROUND 150 MB. ACROSS THE
SOUTH...RATIOS SHOULD STAY MAINLY BELOW 15:1 BECAUSE THE DGZ WILL
AVG CLOSER TO 50 MB IN THIS AREA AND SFC TEMPS WILL BE NEAR FREEZING
DURING THE BULK OF THE SNOWFALL.

GENERALLY...ABOUT 4-6" OF SNOW ACCUMULATION BY 6 AM SUNDAY WITH
ADDITIONAL ACCUMULATION FORECAST THROUGH THE DAY.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 355 AM CST SAT JAN 31 2015

LONG TERM FORECAST ASSESSMENT CONFIDENCE...GOOD OR ABOVE AVERAGE WITH
POSSIBLE HEAVIEST SNOW AXIS A BIT FURTHER SOUTH ALONG OR JUST SOUTH
OF I-80 CORRIDOR. ALSO...FRESH SNOW COVER OF 6+ INCHES SUPPORTS TEMPERATURES
MANY TIME PERIODS COULD BE 2 TO 5+ DEGREES TOO MILD...ESPECIALLY MINS
WITH CLEAR SKIES AND LIGHT WINDS. AREA SNOW TOTALS WEEKEND EVENT OF
WIDESPREAD 6+ INCHES TO LOCALLY UP TO 11 INCHES WITH DRIFTING SNOW
AND PATCHY BLOWING SNOW TO MAKE FOR A MODERATE TO LOWER END HIGH IMPACT
WINTER STORM WHICH FORTUNATELY WILL OCCUR ON THE WEEKEND.

OVERVIEW...INITIALIZATION AND VERIFICATION ARE GOOD WITH MINOR BL MOISTURE
ISSUES WHICH ARE TERTIARY TO WINTER STORM THAT WILL AFFECT AREA. COMBINATION
OF RUN TO RUN VARIANCES AND VERIFICATION AT 2 AM SUPPORTS A 70/30 BLEND
OF GFS AND HI-RES ECMWF FORCING. SLIGHTLY ABOVE AVERAGE OR LOW INTER-
MODEL DIFFERENCES ALSO SUGGEST GOOD CONFIDENCE ON MAIN IMPACTS OF STORM
THIS WEEKEND.

SUNDAY...MODERATE SNOW TO SLOWLY DIMINISH TO LIGHT SNOW BY THE AFTERNOON
WITH STEADY TO SLOWLY FALLING TEMPERATURES ALL DAY WITH NORTHERLY WINDS
INCREASING TO 15 TO 25 MPH WITH GUSTS 30 MPH AND POSSIBLY TO NEAR 35
MPH AT TIMES. COMBINE THIS WITH SEVERAL INCHES OF SNOW WITH MORE POWDERY
NATURE ON SUNDAY SUPPORTS CONSIDERABLE DRIFTING AND PATCHY BLOWING OF
SNOW IN OPEN FIELDS. TO MAKE TRAVEL MORE CHALLENGING. TEMPERATURES SHOULD
DROP 4 TO 8 DEGREES DURING THE DAY WITH THE INCREASING NORTH WINDS.

SUNDAY NIGHT...LIGHT SNOW TO END WEST TO EAST BY MID TO LATE EVENING
WITH MINOR ACCUMULATIONS BUT POSSIBLY STILL SOME DRIFTING SNOW AS WINDS
DIMINISH TO 10 TO 20 MPH AFTER DARK. SKIES SHOULD CLEAR FROM NW TO
SE AFTER 2 AM AND ENTIRE AREA BY SUNRISE TO ALLOW FOR CRASHING TEMPERATURES
WITH NORTHWEST WINDS OF 5 TO 10 MPH TO SINGLE DIGITS AND NEAR TO
AROUND ZERO IN NW SECTIONS AND WIND CHILLS OF 5 TO 15 BELOW ZERO.

MONDAY...FAIR SKIES AND QUITE COLD AND WENT WITH HIGHS BELOW GUIDANCE
PER LOCAL TOOLS WITH LIGHT WINDS AN LIMITED MIXING SUPPORTING 12 TO
18 DEGREES ABOVE ZERO. MONDAY NIGHT...FAST MOVING UPPER DISTURBANCE
MAY PRODUCE SOME LIGHT SNOW OR FLURRIES WITH SOUTH WINDS ALLOWING
FOR RISING TEMPERATURES BY DAWN INTO THE MID TO UPPER TEENS.

TUESDAY THROUGH FRIDAY...MOSTLY DRY AND COLD WITH LINGERING RISK OF
LIGHT SNOW TUESDAY/WEDNESDAY FROM NW UPPER LEVEL DISTURBANCES. IF AREA
DOES RECEIVE WIDESPREAD 6 PLUS INCHES OF SNOW...THEN TEMPERATURES MANY
PERIODS ARE LIKELY 2 TO 5 PLUS DEGREES TOO MILD...ESPECIALLY LOWS WHERE
HAVE LIGHT WINDS AND FAIR SKIES...THURSDAY AND FRIDAY MORNING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1204 PM CST SAT JAN 31 2015

WINTER STORM TO IMPACT REGION THROUGH SUNDAY WITH CONDITIONS
DETERIORATING TO MVFR AND IFR THROUGH EARLY EVENING WITH LIGHT RAIN
OR LIGHT RAIN AND SNOW MIX DEVELOPING. THIS EVENING THE PRECIPITATION
IS EXPECTED TO TRANSITION TO ALL SNOW...WITH PERIODS OF MODERATE TO
AT TIMES LOCALLY HEAVY SNOW CONTINUING THROUGH SUNDAY AM WITH IFR
TO AREAS OF LIFR/VLIFR CONDITIONS. SOUTHWEST WINDS AROUND 10 KTS
TO BECOME LIGHT THIS EVENING WHILE GRADUALLY BACKING TO E/SE THEN
TURN GUSTY FROM NORTHEAST BY SUNDAY AM POSSIBLY LEADING TO SOME
ADDITIONAL REDUCTION IN VISIBILITY FROM BLOWING AND DRIFTING SNOW.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-HENRY IA-
     IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LINN-LOUISA-
     MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.

     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR DES MOINES-LEE.

IL...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR BUREAU-CARROLL-HENRY IL-JO DAVIESS-MERCER-PUTNAM-ROCK
     ISLAND-STEPHENSON-WHITESIDE.

     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR HANCOCK-HENDERSON-MCDONOUGH-WARREN.

MO...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR SCOTLAND.

     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 9 PM CST SUNDAY
     FOR CLARK.

&&

$$

SYNOPSIS...UTTECH
SHORT TERM...UTTECH
LONG TERM...NICHOLS
AVIATION...05