Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 070015
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
613 PM CST SAT FEB 6 2016

.SHORT TERM /TONIGHT/...
ISSUED AT 353 PM CST SAT FEB 6 2016

LITTLE SENSIBLE WEATHER OF CONCERN INTO THE NIGHT. SHORT WAVE/PV
ANOMALY MOVING FROM MT INTO THE DAKOTAS HAS ALREADY SPREAD WEAK TO
MODERATE KINEMATIC AND THERMODYNAMIC FORCING INTO IA BUT IS
QUITE MOISTURE STARVED WITH LITTLE IN THE WAY OF PRECIP AND EVEN
CEILING REDUCTIONS. A WEDGE OF STRATUS STILL LINGERS FROM CENTRAL
INTO NERN IA AT 21Z BUT IS MOVING OUT AND/OR ERODING AND SHOULD
NOT BE A FACTOR INTO THE EVENING. THE AFOREMENTIONED VERTICAL
MOTION WILL CROSS IA TONIGHT...WITH RISE/FALL COUPLET REACHING THE
SERN QUARTER THIRD OF THE FORECAST AREA BY 12Z...BUT SUFFICIENT
MOISTURE WILL NOT MATERIALIZE FOR PRECIP. THUS HAVE A DRY FORECAST
WITH NOTHING BEYOND MID CLOUDS TONIGHT.

20Z SURFACE ANALYSIS SHOWS WIDESPREAD PRESSURE FALLS THROUGH THE
PLAINS AHEAD OF THE SYSTEM ALSO REFLECTING THE WARM ADVECTION
ALOFT SO EXPECT TEMPS TO BE FAIRLY STEADY TO SLOWING RISING
THROUGH MUCH OF THE NIGHT.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 353 PM CST SAT FEB 6 2016

MAIN FOCUS WAS ON THE POTENTIAL BLIZZARD CONDITIONS SUNDAY
AFTERNOON THROUGH MONDAY. A POTENT CLIPPER PUNCHES INTO THE STATE
LATE SUNDAY AFTERNOON AND BRINGS VERY STRONG WINDS AND CAA INTO
THE THE CWA SUNDAY NIGHT INTO MONDAY. MODELS ARE IN GOOD AGREEMENT
WITH THE OVERALL SYNOPTIC AND MESOSCALE FEATURES AND LEANED
TOWARD A BLEND ATTM...WITH A LITTLE MORE EMPHASIS ON THE NAM/GFS
FOR WINDS.

SUNDAY THROUGH MONDAY...STRONG PV ANOMALY AND UPPER LEVEL TROUGH
EJECT OUT OF SOUTHERN CANADA WITH THE SURFACE LOW SLIDING OVER
THE ARROWHEAD OF MN BY 00Z MONDAY AND THEN INTO THE WESTERN GREAT
LAKES BY 12Z MONDAY.

SEVERAL CONCERNS WRT TO THE POTENTIAL BLIZZARD CONDITIONS.
FIRST...WINDS ATOP THE MIXED LAYER RANGE FROM 40 TO 45
KNOTS...WITH STEEP LOW LEVEL LAPSE RATES AND DEEP MIXING
DEVELOPING LATE TOMORROW NIGHT AND CONTINUES INTO MONDAY. THE
MAJORITY OF THESE LOOK TO MATERIALIZE AT THE SURFACE DUE TO THE
EFFICIENT MOMENTUM TRANSFER. HOWEVER THE KEY COMPONENT WITH THIS
SYSTEM IS THE FALLING SNOW TOMORROW NIGHT INTO MONDAY. SOUNDINGS
BECOME DEEPLY SATURATED...AT LEAST UP TO 700MB...B/T 21Z SUNDAY
THROUGH 03Z MONDAY ALONG AND NORTH OF INTERSTATE 80 AND DEEPEN
EVEN FURTHER OVERNIGHT INTO MONDAY MORNING. CONFIDENT THERE WILL
BE ICE INTRODUCTION ICE INTO THE COLUMN TO PRODUCE FALLING SNOW
BY SUNDAY EVENING. PLUS WITH THE CAA...SOUNDINGS COOL TO NEARLY
ENTIRELY INTO THE DENDRITIC ZONE B/T 06-12Z MONDAY. ALBEIT...THE
OMEGA IS WEAK WITHIN THE DENDRITIC LAYER BUT WITH THE STEEP LAPSE
RATES AND EVEN WEAK UNSTABLE THETA-E LAPSE RATES...THIS SHOULD BE
ENOUGH TO PRODUCE SOME CONVECTIVE ROLLS. THE HIRES
MODELS...ARW/NMM/SPC 4KM WRF ALL HINTING ON CONVECTIVE BANDS
SETTING UP TOMORROW NIGHT INTO MONDAY. THE DEEPLY SATURATED
SOUNDINGS WITHIN THE DENDRITIC LAYER CONTINUE THROUGH MUCH OF THE
DAY MONDAY...THUS EXTENDED THE WATCH THROUGH 00Z TUESDAY AS
EXPECTING FALLING SNOW TO PERSIST MUCH OF THE DAY. CERTAINLY HAVE
A HIGH CONFIDENCE IN THE FALLING SNOW...BUT THE WIDESPREAD NATURE
OF IT STILL IN LOW CONFIDENCE...KEPT WITH BLIZZARD WATCH ATTM AND
ANY COUNTIES BORDERING THE WATCH WILL LIKELY NEED WINTER WX
ADVISORY FOR BLOWING SNOW TOMORROW NIGHT INTO MONDAY. THE OTHER
CAVEAT IS THE CURRENT SNOW PACK. THERE IS LIKELY A DECENT CRUST IN
PLACE WITH THE SLIGHTLY ABOVE FREEZING TEMPS AND REFREEZE TODAY
AND A LITTLE MELTING LOOKS POSSIBLE TOMORROW BEFORE THE CAA
BEGINS IN THE AFTERNOON. BELIEVE THE WINDS SHOULD BE STRONG ENOUGH
TO BREAK THROUGH SOME OF THE CRUST OVER NORTHERN IOWA AND AID IN
THE VISIBILITY RESTRICTIONS.

TUESDAY THROUGH SATURDAY...THE NEXT WEATHER MAKER LOOKS TO MOVE
ACROSS THE STATE WEDNESDAY NIGHT INTO THURSDAY. ONLY LIGHT SNOW IS
POSSIBLE OVER NORTHERN AND EASTERN PORTIONS OF THE FORECAST AREA.
OTHERWISE...A LARGE SURFACE HIGH BUILDS INTO THE REGION LATE IN
THE WEEK.

&&

.AVIATION...07/00Z
ISSUED AT 613 PM CST SAT FEB 6 2016

VFR EXPECTED THROUGH SUN EARLY AFTERNOON BUT A WINTER STORM WILL
BEGIN TO IMPACT TAFS ACROSS NW IA WITH WINDS BECOMING NW AND
INCREASING TO 20G30KTS.  -SHSN MAY DEVELOP TOWARDS 00Z ALONG WITH
AREAS OF BLSN.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY AFTERNOON
FOR AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CERRO
GORDO-CRAWFORD-DALLAS-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-
HAMILTON-HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-MARSHALL-PALO ALTO-
POCAHONTAS-SAC-STORY-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...SMALL
LONG TERM...PODRAZIK
AVIATION...FAB


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