Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 160536
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1136 PM CST MON DEC 15 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 330 PM CST MON DEC 15 2014

COUPLE OF CONSIDERATIONS FOR THE OVERNIGHT HOURS....LOW CONTINUES
TO TRACK ACROSS THE AREA THIS AFTERNOON. WEAK INSTABILITY STILL
EXPECTED TO BRUSH THE SOUTH THROUGH 23Z WITH RAIN INCREASING OVER
THE WEST AND NORTHWEST AS THE UPPER LEVEL SUPPORT SHIFTS NORTH.
MODELS CONTINUE TO SHOW CHANGEOVER TO BRIEF MIXTURE OF RAIN IP
PRIOR TO COLDER AIR MOVING ACROSS THE AREA AT HIGHER ELEVATIONS.
BUFR SOUNDINGS HAVE LOW LEVEL COLD AIR ADVECTION COMING IN
FASTER...WHICH RESULTS IN THE MIXTURE AND NOT A PURE RASN MIX TO
SNOW. AT PRESENT THE BEST FORCING AND HIGHER LIQUID AMOUNTS SHOULD
REMAIN NORTHWEST OF THE AREA INTO SOUTHERN MN...SO SNOWFALL
AMOUNTS AGAIN LOOK FAIRLY LIGHT OVER THE AREA. GIVEN A FEW HOURS
OF MIX...SNOWFALL AMOUNTS SHOULD REMAIN UNDER TO NEAR AN
INCH...EVEN ACROSS THE NORTHWEST. OVERNIGHT ICE INTRODUCTION IS
LOST WHICH MAY RESULT IN SOME VERY LIGHT FZDZ OR SMALL AMOUNT OF
FZRA OVER THE SOUTH. NOT EXPECTING ANY REAL ISSUES WITH RECENT
WARM TEMPERATURES AND LIKELIHOOD THAT ROAD SFC WILL REMAIN MILD
ENOUGH THROUGH THE NIGHT TO ALLOW ANY PRECIP TO MELT AND THEN WITH
INCREASING WIND...EVAPORATE PRIOR TO CAUSING ANY REAL PROBLEMS.
OVER THE FAR NORTH...WITH LIGHT ACCUMULATIONS OF SNOW THERE MAY BE
SOME MINOR ISSUES WITH SOME ICY SPOTS DUE TO MELTING AND
REFREEZING SNOW. THE OTHER CONCERN OVERNIGHT WILL BE INCREASING
WINDS. GRADIENT WINDS PICK UP BEHIND THE SYSTEM AND A GOOD SHARE
OF THE AREA NORTH OF US 30 AND WEST OF 65 LIKELY TO NEED AN
ADVISORY. THIS GO AROUND...GIVEN THE LIGHT AMOUNTS OF SNOW
EXPECTED AND EVEN WITH BRIEF VISIBILITY REDUCTIONS...HEADLINES FOR
WINTER WX NOT LIKELY TO BE NEEDED. COLDER AIR TO FILTER IN BY
MORNING WITH TEENS ACROSS THE NORTHWEST AND 20S OVER THE SOUTHEAST
IN THE WAKE OF THE LOW.

.LONG TERM /TUESDAY THROUGH MONDAY/...
ISSUED AT 330 PM CST MON DEC 15 2014

A RELATIVELY QUIET LONG TERM PERIOD IS IN STORE FOR THE THE AREA
WITH CLOUD COVER AND MIN TEMPERATURES THROUGH MIDWEEK BEING THE
BIGGEST CHALLENGES. CURRENT NEGATIVELY-TILTED UPPER LEVEL
TROUGH/CLOSED LOW WILL BE MOVING OVER LAKE MICHIGAN BY 12Z
TOMORROW MORNING AND ANY EARLY MORNING SNOW SHOULD HAVE EXITED THE
CWA BY THEN. WINDS WILL ALSO BE ON THE DECLINE AS THE ISALLOBARIC
GRADIENT WEAKENS BUT CANNOT RULE OUT A FEW POCKETS OF NEAR
ADVISORY WINDS IN THE NORTH AND EAST DURING THE MORNING. CAA WILL
CONTINUE ACROSS THE REGION THROUGHOUT THE DAY WITH HIGHS ONLY A
COUPLE OF DEGREES HIGHER THAN THE PREVIOUS NIGHT`S LOWS.

CURRENT STRATUS SHIELD ON THE 11-3.9U SATELLITE IMAGERY EXTENDS
ALL THE WAY BACK TO EASTERN ALBERTA WITH NORTH TO NORTHWESTERLY
LOW-LEVEL FLOW PERSISTING THROUGH LATE WEDNESDAY. THE
AFOREMENTIONED UPPER LEVEL TROUGH WILL INTERACT WITH A SECOND
SHORTWAVE DROPPING SOUTHEAST IN THE NORTHERN STREAM. THIS WILL
RESULT IN AN INVERTED 500MB WAVE WRAPPING SOUTHWARD ON THE
BACKSIDE OF THE LOW LATE TUESDAY AND INTO WEDNESDAY. WITH IOWA
REMAINING IN BROAD CYCLONIC FLOW DURING THIS TIME IN CONJUNCTION
WITH THE ABOVE INGREDIENTS...HAVE BOOSTED SKY COVER OVER MUCH OF
THE CWA ON TUESDAY AND OVER PORTIONS OF THE NORTH AND EAST ON
WEDNESDAY. NAM AND SREF BUFR SOUNDING TIME-HEIGHT CROSS SECTIONS
DO A GOOD JOB DEPICTING THIS STRATUS SHIELD ANCHORED JUST UNDER A
925MB INVERSION. HOWEVER...THERE IS STILL SOME UNCERTAINTY AS TO
HOW LONG THE STRATUS WILL LAST GIVEN A FEW HOLES ALREADY STARTING
TO SHOW UP IN THE CLOUD SHIELD IN MANITOBA AND THE BEST PV ANOMALY
STAYING JUST NORTH OF THE CWA ON WEDNESDAY.

WITH THE INCREASED CLOUD COVER...BUMPED UP LOWS OVER THE
NORTHEAST CWA FOR TUESDAY NIGHT. WEAK CAA WILL CONTINUE THROUGH
THURSDAY WITH TEMPS AT OR SLIGHTLY BELOW NORMAL. KINEMATIC FORCING
AHEAD OF A SHALLOW UPPER-LEVEL WAVE MAY KICK OFF SOME LIGHT SNOW
OVER THE SOUTHWEST PART OF THE CWA. TODAY`S MODEL SOLUTIONS HAVE
STRUGGLED WITH THE NATURE OF THIS SUBTLE WAVE WITH THE 12Z
GUIDANCE HAVING BACKED OFF ON QPF ONLY TO HAVE THE 18Z NAM COME IN
MORE ROBUST. WAA COMMENCES ON FRIDAY OUT AHEAD OF A DIGGING 300MB
TROUGH OVER THE FRONT RANGE WITH HIGHS RETURNING TO THE 30S
THROUGH THE WEEKEND. LATEST GFS/EC RUNS HAVE TAKEN THE SURFACE
REFLECTION OF THIS WAVE FURTHER SOUTH OF THE STATE AND HAVE
REMOVED POPS FROM THE SOUTH ON FRIDAY AS A RESULT.

&&

.AVIATION...16/06Z
ISSUED AT 1136 PM CST MON DEC 15 2014

NORTHWEST WINDS WILL REMAIN GUSTY OVERNIGHT WITH A FEW GUSTS OVER
35 KTS POSSIBLE THROUGH 12Z. RAIN HAS MOVED OVER EASTERN IOWA WITH
SOME WINTRY MIX OVER THE WESTERN PORTION OF THE STATE. MAINLY
NORTHERN SITES WILL HAVE SOME SNOW MIX THOUGH ANY VSBY REDUCTIONS
IN SNOW WILL BE BRIEF. LIFR CIGS ARE BEGINNING TO MOVE EAST.
EXPECT IFR THEN A TRANSITION TO MVFR LATER TONIGHT INTO TUESDAY.
NO CONFIDENCE WHEN THE LARGE STRATUS SHIELD WILL MOVE OUT OF THE
AREA THEREFORE KEPT MVFR STRATUS THROUGH THE PERIOD.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 AM CST TUESDAY FOR AUDUBON-BOONE-CALHOUN-
CARROLL-CERRO GORDO-CRAWFORD-EMMET-FRANKLIN-GREENE-HAMILTON-
HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-PALO ALTO-POCAHONTAS-SAC-STORY-
WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...REV
LONG TERM...SKOW
AVIATION...DONAVON



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