Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 071751
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1151 AM CST SUN FEB 7 2016

.SHORT TERM /TODAY/...
ISSUED AT 400 AM CST SUN FEB 7 2016

QUIET MORNING TO SET THE STAGE FOR BLOWING SNOW/BLIZZARD
POTENTIAL IN OUR NORTH FOR SUNDAY NIGHT. WEAK AREA OF MID-LEVEL
FRONTOGENETICAL FORCING AND Q-VECTOR CONVERGENCE YIELDED SLIGHT
ASCENT IN OUR NORTH. LACK OF MOISTURE HAS PREVENTED PRECIP FROM
REACHING THE SFC. RIBBON OF WAA PASSING THROUGH CENTRAL IOWA HAS
KEPT DIURNAL RANGE TO A MINIMUM THIS MORNING.

UPPER LEVEL TROUGH WORKING ITS WAY TOWARDS THE U.S. FROM SOUTHERN
CANADA. SFC LOW NEARING THE U.S./CANADA BORDER ALONG FAR NORTH-
CENTRAL MN. ATTENDANT COLD FRONT TO PASS THROUGH SUNDAY MORNING.
POST-FRONTAL SUBSIDENCE WILL HELP BRING SUNSHINE TO THE DMX CWA
SUNDAY AFTERNOON. WITH CONFIDENCE OF SUNSHINE INCREASED...HAVE
BUMPED UP MAX TEMPS FOR SUNDAY TO LOW TO MID 40S ACROSS SOUTH.
THESE VALUES MAY STILL BE A FEW DEGREES TOO COOL...ESPECIALLY FOR
LOCATIONS WITH LITTLE TO NO SNOW DEPTH REMAINING AS SFC ALBEDO
RELATIVELY MUCH LOWER. SFC WINDS TO BE HIGH ALL DAY AS PRESSURE
GRADIENT APPROACHES 3MB/100KM IN ADVANCE OF NEARING CYCLONE.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 400 AM CST SUN FEB 7 2016

...BLIZZARD CONDITIONS ACROSS NORTHERN IOWA TONIGHT INTO
MONDAY...

A DEEPENING LOW PRESSURE SYSTEM MOVING ACROSS WISCONSIN TOWARD THE
GREAT LAKES TONIGHT WILL SEND TWO LOW PRESSURE TROUGHS SWEEPING
ACROSS IOWA FROM NORTHWEST TO SOUTHEAST. THE FIRST WILL CROSS OUR
AREA AROUND THE LATE AFTERNOON AND THE SECOND BETWEEN ABOUT SUNSET
AND MIDNIGHT. THE PASSAGE OF THESE TROUGHS WILL BE ASSOCIATED WITH
A SIGNIFICANT INCREASE IN WIND SPEEDS AND GUSTINESS...ALONG WITH
INCREASING COVERAGE OF SNOW SHOWERS. FORECAST SOUNDINGS SHOW SOME
MODEST INSTABILITY AND COMBINED WITH THE TURBULENT FLOW AND STRONG
FORCING ALOFT...IT IS LIKELY THAT STREAKS OF SNOW SHOWERS WILL
MOVE ACROSS THE AREA FOR MUCH OF TONIGHT INTO MONDAY MORNING.
MEANWHILE WIND SPEEDS AT THE TOP OF THE NEAR-SURFACE MIXED LAYER
WILL PEAK BETWEEN ABOUT MIDNIGHT AND MID MORNING MONDAY...DURING
WHICH TIME SURFACE WIND SPEEDS WILL PROBABLY REACH 25 TO 35 MPH
WITH GUSTS TO AROUND 45 MPH OR EVEN HIGHER IN SNOW SHOWERS.
COMBINED WITH THE DEEP SNOW PACK AND FLATTER TERRAIN PRESENT IN
OUR NORTHERN COUNTIES...THERE IS A SIGNIFICANT LIKELIHOOD OF
BLIZZARD CONDITIONS EITHER BEING WIDESPREAD OR AT LEAST OCCURRING
WITHIN THE BANDS OF SNOW SHOWERS...AND THE BLIZZARD WATCH HAS BEEN
UPGRADED TO A WARNING BEGINNING LATE TODAY AND CONTINUING THROUGH
MONDAY. THERE ARE STILL SOME UNCERTAINTIES PERTAINING TO THE
CHARACTER OF THE SNOW PACK ALREADY IN PLACE...WHETHER IT WILL BE
CRUSTED OVER OR MORE EASILY LOFTED...AND ALSO TO THE COVERAGE OF
SNOW SHOWERS...WHETHER THEY WILL BE WIDELY SCATTERED OR MORE
NUMEROUS AT ANY GIVEN TIME...HOWEVER THE NUMBER OF FACTORS
POINTING TO BLIZZARD CONDITIONS EASILY OUTWEIGHS THE NUMBER OF
FACTORS AGAINST...ESPECIALLY AFTER MIDNIGHT TONIGHT. DURING THE
DAY ON MONDAY THE SNOW SHOWERS WILL SLOWLY DIMINISH FROM WEST TO
EAST ALONG WITH GRADUALLY EASING WINDS IN THE AFTERNOON. IT IS
UNCLEAR AT WHAT POINT BLIZZARD CONDITIONS WILL BECOME
UNLIKELY...SO THE WARNING HAS BEEN MAINTAINED UNTIL 6 PM MONDAY
WITH THE EXPECTATION THAT SOME PORTIONS MAY NEED TO BE CANCELLED A
BIT EARLY.

FROM MONDAY NIGHT ONWARD THE FORECAST IS OVERALL QUIETER AND MORE
STRAIGHTFORWARD. COOLER WEATHER WILL PREVAIL THROUGH THE MIDDLE OF
THE WEEK WITH PERSISTENT NORTHWEST WINDS UNTIL A RIDGE PASSES OVER
AROUND WEDNESDAY NIGHT. THERE HAS BEEN AN INCONSISTENT SIGNAL FOR
SOME LIGHT SNOW AT TIMES BETWEEN AROUND WEDNESDAY AND
FRIDAY...BUT GIVEN THE HIGH VARIABILITY OF THE MODEL SOLUTIONS
AND LITTLE TO NO EXPECTED IMPACT THE FORECAST REMAINS DRY FOR
NOW.

&&

.AVIATION...07/18Z
ISSUED AT 1151 AM CST SUN FEB 7 2016

VFR CONDITIONS WILL PERSIST THROUGH MUCH OF THE AFTERNOON ALTHOUGH
MVFR/IFR CONDITIONS DUE TO A COMBINATION OF CLOUDS...SNOW AND
BLOWING SNOW WILL PROGRESS NW-SE THROUGH THE AREA INTO THE
EVENING. CONFIDENCE IS LOW IN VISIBILITY DETAILS DUE TO SNOW
SHOWER INTENSITY AND THE EFFICIENCY OF BLOWING SNOW DUE TO
RELATIVELY WET EXISTING SNOWPACK...BUT THE GENERAL CONSENSUS IS
FOR IFR VSBYS DUE TO BLOWING SNOW FOR PROLONGED PERIOD THROUGH THE
NIGHT AND INTO MONDAY MORNING. VSBYS MAY DIP TO LIFR DURING BURSTS
OF HEAVIER SNOW SHOWERS...BUT DID NOT WANT TO INCLUDE FOR 12 PLUS
HOURS. SIMILAR THINKING WITH WIND. GUSTS MAY REACH 40KTS OR MORE
FROM KDSM NORTH AND WEST...BUT DEPICTED MORE OF A LONG TERM
AVERAGE RATHER THAN PEAK.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING FROM 7 PM THIS EVENING TO 6 PM CST MONDAY FOR
AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CERRO GORDO-DALLAS-
FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-HARDIN-MARSHALL-
STORY-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

BLIZZARD WARNING FROM 4 PM THIS AFTERNOON TO 6 PM CST MONDAY FOR
CALHOUN-CARROLL-CRAWFORD-EMMET-HUMBOLDT-KOSSUTH-PALO ALTO-
POCAHONTAS-SAC.

&&

$$

SHORT TERM...KOTENBERG
LONG TERM...LEE
AVIATION...SMALL


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