Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 241147
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
547 AM CST MON NOV 24 2014

.SHORT TERM /TODAY/...
ISSUED AT 347 AM CST MON NOV 24 2014

JUST ABOUT ALL FORECAST ELEMENTS WILL BE CONCERNS TODAY WITH EITHER
LOW CONFIDENCE OR ATYPICAL TRENDS. LONG WAVE TROUGH CONTINUES TO
EVOLVE OVER THE CENTRAL CONUS WITH POTENT SHORT WAVE DEEPENING
GREAT LAKES SURFACE LOW AS SHORT WAVE TRACKED FROM THE OH VALLEY
INTO THE ERN GREAT LAKES. WEAKER SHORT WAVE/PV ANOMALY IS ALSO
NOTED ALONG DAKOTAS/MN BORDER AND WILL CONTINUE TO AID BROAD LIFT
OVER THE UPPER MS VALLEY WITH FAIRLY IMPRESSIVE QG FORCING JUST TO
OUR NORTH AND EAST. THIS FEATURE APPEARS TO BE DRIVING OUR ERN IA
PRECIP AND ITS LIFT SHOULD EXIT OUR FORECAST AREA SHORTLY. HOWEVER
H85/H7 FORCING WITH CYCLONIC FLOW LINGERS INTO MN AND NERN
IA...AND EVEN MATURES A BIT INTO MIDDAY.

MUCH OF THIS FORCING AND MOISTURE IS 3KM AND UNDER WITH SOUNDINGS
SHOWING TEMPS EITHER SIDE OF -10C LEAVING ICE INTRODUCTION SOMEWHAT
IN QUESTION UNTIL MOISTURE DEEPENS LATE WHEN FORCING STARTS TO
WANE. ALTHOUGH FREEZING DRIZZLE IS POSSIBLE...HAVE LEFT FORECAST
ALL LIGHT SNOW WITH SOUNDINGS SUGGESTING ICE MORE TIMES THAN NOT.
IR SATELLITE TEMPS ALSO APPEAR COOL ENOUGH TO SUGGEST ICE
INTRODUCTION IN ALL BUT JUST A FEW VERY SMALL SLIGHTLY WARMER
PATCHES. HAVE ONLY TOKEN QPF AMOUNTS WITH SHALLOW MOISTURE SO
TYPICAL SNOW RATIOS WOULD POINT TOWARD A FEW TENTHS AT BEST
NORTHEAST HALF. STEEP LAPSE RATES BELOW 1KM SUGGEST SOME SNOW
SHOWERS ARE POSSIBLE WITH ISOLATED HIGHER AMOUNTS...BUT HI RES
MODELS DO NOT PICK UP ON ANY FAVORED AREAS SO WILL JUST BROAD
BRUSH THOSE AMOUNTS FOR NOW.

TEMPS WILL BE ANOTHER CONCERN. RAW MODEL TRENDS AND MOS SUGGEST
FALLING TEMPS EARLY...THEN FLATTENING OUT WITH ONLY A VERY MINOR
REBOUND BY AFTERNOON. HIGH TEMPS WILL LIKELY OCCUR WHEN VERIFICATION
STARTS AT 13Z. NO CHANGES TO WIND ADVISORY ALTHOUGH IT SEEMS QUITE
MARGINAL. ONLY ONE SITE REACHING CRITERIA AT THIS WRITING AND THAT
IS NOT IN THE HEADLINE. THERE IS LITTLE ISALLOBARIC COMPONENT NOTED.
IN FACT OBJECTIVE 09Z SURFACE ANALYSIS SHOWS NEUTRAL PRESSURE
CHANGES FROM KS INTO TWIN CITIES AREA WHICH WERE MORE WIDESPREAD
FALLS A FEW HOURS AGO DUE TO INFLUENCE OF DAKOTAS/MN SHORT WAVE ON
BACK SIDE OF TROUGH.  AFOREMENTIONED MIXING BELOW 1KM DOES NOT
APPEAR SUFFICIENT FOR CRITERIA LEVEL GUSTS AND BETTER MSLP GRADIENT
OVER US AT THE MOMENT LIFTS NE OUT OF AREA BY LATE MORNING. WILL
LEAVE HEADLINE UNCHANGED HOWEVER AS PUBLIC WILL STILL PERCEIVE BRISK
WINDS WITH CANCELLATION DELIVERING WRONG MESSAGE.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 347 AM CST MON NOV 24 2014

THE CLOUDS AND LIGHT SNOW DISCUSSED IN THE SHORT TERM SECTION
ABOVE WILL CLEAR OUT TO THE EAST/NORTHEAST TONIGHT...GIVING WAY TO
DRY AND COOL CONDITIONS LATE TONIGHT AS A WEAK SURFACE RIDGE
SLIDES ACROSS THE AREA. ON TUESDAY AS THE RIDGE MOVES OFF TO THE
EAST SKIES WILL CLEAR AND LIGHT SOUTH SOUTHWEST WINDS WILL
RETURN...BRINGING SOMEWHAT MILDER WEATHER WITH HIGHS RANGING IN
THE 30S OVER MOST OF THE AREA. RAISED HIGH TEMPERATURES A BIT FOR
TUESDAY ESPECIALLY WITH THE LACK OF SNOW COVER AND THE ANTICIPATED
SUNSHINE.

BY TUESDAY EVENING A COMPACT BUT ENERGETIC CLIPPER SYSTEM WILL BE
MOVING ACROSS THE DAKOTAS...CHARACTERIZED BY A SURFACE LOW
PRESSURE SYSTEM AND ATTENDANT TROUGH RACING QUICKLY
SOUTHEASTWARD. THE TRACK OF THE LOW HAS SHIFTED SOUTHWARD SINCE
LAST NIGHT...WITH VIRTUALLY ALL PROGNOSTIC GUIDANCE NOW TAKING IT
DIRECTLY ACROSS OUR FORECAST AREA. THE LOW WILL BE ACCOMPANIED BY
A SWATH OF SNOWFALL THAT WILL AFFECT THE AREA MAINLY LATE TUESDAY
NIGHT THROUGH WEDNESDAY MORNING...LIKELY PRODUCING LIGHT TO
MODERATE SNOW ACCUMULATIONS. FOR NOW NO HEADLINES ARE
ANTICIPATED...BUT IF THE LOW TRACK REMAINS NEAR ITS PRESENT
LOCATION THERE IS THE POTENTIAL FOR ADVISORY CRITERIA BEING MET AS
THE FORECAST IS FURTHER REFINED. THE GOOD NEWS IS THAT FORECAST
SOUNDINGS CONSISTENTLY SUPPORT ALL PRECIPITATION FALLING AS SNOW
WITH NO ICING POTENTIAL EVIDENT.

BEHIND THE MIDWEEK CLIPPER SYSTEM SURFACE HIGH PRESSURE WILL BUILD
ACROSS THE UPPER MIDWEST AND IOWA AROUND THANKSGIVING...RESULTING
IN COLDER WEATHER ESPECIALLY IF WE DO ESTABLISH SOME SNOW
COVER...BUT NO PRECIP POTENTIAL OTHER THAN PERHAPS A FEW FLURRIES.
BY THURSDAY NIGHT THE RIDGE WILL ALREADY BE MOVING QUICKLY OFF TO
THE EAST...REPLACED BY INCREASING SOUTHERLY FLOW FROM THURSDAY
NIGHT THROUGH FRIDAY. THIS INDICATES SOME WARMING...BUT IT MAY BE
TEMPERED DEPENDING ON THE DEPTH OF SNOW THAT DOES OR DOES NOT
REMAIN FROM THE EARLY WEDNESDAY SYSTEM. IT THEN APPEARS THAT
ANOTHER COOL FRONT WILL MOVE ACROSS THE AREA FRIDAY NIGHT WITH A
LARGER SURFACE HIGH PRESSURE AREA DOMINATING THIS WEEKEND.

&&

.AVIATION...24/12Z
ISSUED AT 546 AM CST MON NOV 24 2014

PERSISTENT SUB 2KFT MVFR CIGS ARE ANTICIPATED THROUGH MUCH OF THE
PERIOD OUTSIDE OF POSSIBLE IMPROVEMENT LATE. THERE MAY ALSO BE A
FEW PERIODS OF IFR CIGS OR VSBYS IN LIGHT SNOW NEAR KMCW/KALO...BUT
CONFIDENCE IN TIMING AND DURATION IS NOT GREAT ENOUGH FOR
INCLUSION AT THE MOMENT. NW WINDS WILL REMAIN BRISK WITH GUSTS
OFTEN APPROACHING 30KTS UNTIL DIMINISHING LATE.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM CST THIS EVENING FOR CALHOUN-CARROLL-
CERRO GORDO-EMMET-GREENE-HANCOCK-HUMBOLDT-KOSSUTH-PALO ALTO-
POCAHONTAS-SAC-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

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



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