Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 201120
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
620 AM CDT MON APR 20 2015

.SHORT TERM /TODAY/...
ISSUED AT 340 AM CDT MON APR 20 2015

EARLY MORNING PRECIPITATION ASSOCIATED WITH SURFACE LOW NEAR GREAT
LAKES REGION WILL LIFT NORTHEAST WITH LOW THROUGH MORNING HOURS.
NEXT MAIN CONCERN BECOMES LARGE UPPER LEVEL LOW PRESSURE SYSTEM
ACROSS NORTHERN MN WHICH WILL DROP SLOWLY SOUTHEAST THROUGH THE DAY.
THIS WILL PUSH NORTHWESTERLY FLOW ACROSS IOWA FOR THE DAY. SHORT
WAVE WRAPPING AROUND LOW MAY ALLOW FOR SCATTERED
SHOWERS...ESPECIALLY IN THE NORTHEAST DURING THE DAY. HAVE KEPT POPS
ACROSS THIS AREA...THOUGH HAVE PULLED FURTHER SOUTH WEST. HIGH RES
MODELS ARE HANDLING ONGOING PRECIPITATION WELL...AND INDICATE A
FURTHER SOUTH AND WEST EXTENT OF PRECIPITATION...AND MAY HAVE BEEN
TOO CONSERVATIVE. EXPECT ANY PRECIPITATION TO BE SCATTERED AND
LIGHT. WINDS WILL BE MAIN CONCERN FOR THE DAY. SOUNDINGS INDICATE
GOOD MIXING THROUGH THE AFTERNOON...WITH THE TOP OF THE MIXED LAYER
GENERALLY AROUND OR ABOVE 40KTS ACROSS THE CWA. WITH STRONG CAA
ASSOCIATED WITH LOW AND STEEP LAPSE RATES...FEEL MIXING WILL BE
REALIZED AND WILL ISSUE WIND ADVISORY FOR MUCH OF THE CWA THROUGH
THE DAY. OUTSIDE OF ADVISORY AREA WINDS WILL STILL BE STRONG AND
GUSTY AND ADVISORY MAY NEED TO BE EXTENDED IN THE AFTERNOON. HAVE
KEPT TEMPERATURES NEAR GOING WITH CAA...THOUGH MAY BE TOO WARM WITH
CLOUDS ACROSS MOST OF THE CWA THROUGH THE DAY.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 340 AM CDT MON APR 20 2015

THE MAIN STORY THIS WEEK WILL BE THE WINDY CONDITIONS THROUGH
TUESDAY AND THE COLD NIGHTS THROUGH THURSDAY MORNING. IN FACT
TEMPERATURES...WHILE DEPENDENT ON WINDS DIMINISHING OVERNIGHT AND
MAINLY CLEAR SKIES...WILL BE AT OR JUST BELOW FREEZING ACROSS THE
FAR WEST AND NORTH TONIGHT...ACROSS THE NORTHERN THIRD TUESDAY
NIGHT/WEDNESDAY MORNING AND AS FAR SOUTH AS INTERSTATE 80
WEDNESDAY NIGHT/THURSDAY MORNING. ADDITIONAL HEADLINES WILL
PROBABLY BE NEEDED FOR WIND ON TUESDAY AND POSSIBLY FOR FROST
ACROSS FAVORED LOCATIONS OVER THE NEXT COUPLE OF NIGHTS.

A LARGE AREA OF LOW PRESSURE WILL PARK ITSELF OVER THE GREAT LAKES
REGION AND SPIN FOR MUCH OF THIS WEEK. THE RESULT WILL BE A DEEP
NORTHWESTERLY FLOW OVER THE UPPER MIDWEST AND SOME VERY COLD AIR
BEING TRANSPORTED ACROSS THE AREA. A COUPLE OF SHORTWAVES WILL
LIKELY PUSH DOWN AROUND THE LOW AND ACROSS THE AREA AS WELL BUT AT
THIS POINT IT LOOKS LIKE THE MAIN AREAS TO PERHAPS BE IMPACTED BY
ANY PRECIP WOULD REMAIN NORTH AND EAST OF THE FORECAST AREA
THROUGH AT LEAST MID-WEEK. WITH OVERNIGHT LOWS BELOW FREEZING IN
PLACES...LOCATIONS OUTSIDE OF THE FORECAST AREA WILL LIKELY SEE
SNOW OR A RAIN/SNOW MIX. HOWEVER FOR CENTRAL IOWA WE SHOULD ESCAPE
PRECIP CHANCES THROUGH THURSDAY. SOUNDINGS FOR TUESDAY ARE QUITE
SIMILAR TO TODAY. ALTHOUGH WE WILL NOT MIX TO 650 MB TUESDAY...
MODELS EASILY MIX US TO 700 MB BUT WINDS ARE LOOKING A LITTLE
STRONGER THAN TODAY WITH 40 KTS IN THE MIXED LAYER AND 60 KTS JUST
ABOVE THE MIXED LAYER. THIS WILL LIKELY WARRANT ADDITIONAL
HEADLINES BUT WE WILL WAIT UNTIL TODAYS EVENT IS OVER AND WE GET
ANOTHER LOOK AT MODELS LATER TODAY AND THIS EVENING.

TEMPS WILL NOT BE AT THEIR COOLEST DURING THE DAY YET ON TUESDAY
BUT A COLD FRONT WILL PUSH THROUGH THE AREA AND HIGH PRESSURE WILL
SETTLE INTO THE AREA TUESDAY NIGHT AND WEDNESDAY AND THE COOLEST
TEMPS WILL OCCUR DURING THIS PERIOD...POSSIBLY LASTING INTO
FRIDAY.

THE FORECAST BECOMES MORE COMPLICATED GOING INTO NEXT WEEKEND AND
EARLY NEXT WEEK. ALL MODELS BUILD A RIDGE OVER THE ROCKIES KEEPING
THE REGION IN NORTHWEST FLOW BUT THE EURO DEVELOPS A LOW OVER THE
PLAINS PUSHING IT ACROSS THE PLAINS STATES FRIDAY NIGHT INTO
SATURDAY NIGHT WHILE THE GFS IS NOT NEAR AS ROBUST AND KEEPS A
SHORTWAVE MOVING ACROSS THE AREA. THIS WOULD GIVE A MUCH QUICKER
SHOT AT PRECIP TO THE AREA. THEN INTO MONDAY THE GFS HAS THE GREAT
LAKES LOW RETROGRADING WESTWARD INTO THE REGION DROPPING WEAK
SHORTWAVES INTO MAINLY EASTERN IOWA WHILE THE EURO DEVELOPS A MORE
SIGNIFICANT LOW ACROSS THE NORTHERN PLAINS BREAKING DOWN A RIDGE
OVER IOWA AND DROPPING A DEEPER WAVE INTO US BY LATE DAY MONDAY.
CONFIDENCE IS LOW AT THIS POINT SO I WENT WITH THE BLENDED MODEL
TRENDS BUT AS THE MODELS RESOLVE THINGS BETTER PRECIP CHANCES WILL
BECOME BETTER DEFINED.

&&

.AVIATION...20/12Z
ISSUED AT 614 AM CDT MON APR 20 2015

MVFR CEILINGS MAY AFFECT EASTERN SITES KALO/KOTM BRIEFLY FOR
BEGINNING OF PERIOD BEFORE CEILINGS LIFT TO LOW VFR THROUGH
PERIOD. SHRA WILL BE POSSIBLE AND SITES...ESPECIALLY KMCW AND KALO
NEAR 18Z AND HAVE INCLUDED VCSH MENTION ATTM. WINDS WILL BE FROM
THE NORTHWEST AND STRONG AND GUSTY AT SITES THROUGH THE DAY. GUSTS
TO 35 OR 40 KTS WILL BE POSSIBLE...ESPECIALLY IN THE AFTERNOON.
AFTER 00Z WINDS WILL DIMINISH AND SKIES WILL CLEAR.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM CDT THIS EVENING
FOR ADAIR-AUDUBON-BOONE-BUTLER-CALHOUN-CARROLL-CASS-CERRO GORDO-
CRAWFORD-DALLAS-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-
HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-MADISON-MARSHALL-PALO ALTO-
POCAHONTAS-POLK-SAC-STORY-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...AWB
LONG TERM...FAB
AVIATION...AWB



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