Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 031805
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1205 PM CST TUE MAR 3 2015

.UPDATE...
ISSUED AT 1204 PM CST TUE MAR 3 2015

CENTRAL/SERN IA ADVISORY HAS BEEN ALLOWED TO EXPIRE WITH NOTABLE
DECREASE IN RADAR DRIZZLE SIGNAL AND TEMPS WARMING JUST ABOVE
FREEZING. CONFIDENCE HAS DECREASED SOMEWHAT IN NRN ADVISORY...BUT
NOT TO THE POINT OF CANCELING JUST YET. BANDED SNOW
SHOWERS/SQUALLS HAVE DEVELOPED UPSTREAM INTO SD AND MN...BUT THERE
IS SOME QUESTION WHETHER THEY WILL ADVANCE THIS FAR SOUTH. MODEL
CROSS SECTIONS DO NOT PHASE STRONG MIXED LAYER WINDS...RH AND
STEEP LAPSE RATES INTO -12C OR LESS RANGE UNTIL LATE AFTERNOON AND
EVENING. WILL CERTAINLY RE-EVALUATE BY AFTERNOON PACKAGE.

THERE IS ALSO SOME CONCERN REGARDING A FLASH FREEZE WITH WET
SURFACES FROM DRIZZLE AND TEMPS FROM 18 AT MADISON SD TO 33 IN
SPENCER WITH FROPA. MAY ISSUE AN SPS IF DRYING DOES NOT OCCUR THIS
AFTERNOON.

&&

.SHORT TERM /TODAY/...
ISSUED AT 403 AM CST TUE MAR 3 2015

TWO PHASE SYSTEM TO AFFECT THE AREA TODAY. SURFACE LOW LIFTING
NORTHEAST INTO CENTRAL IOWA...AND PRECIPITATION WILL CONTINUE TO
LIFT NE THROUGH SOUTHERN/CENTRAL IOWA...LIFTING NORTH. FORCING WITH
THIS SYSTEM QUICKLY PUSHES EAST BY 15Z...AND PRECIPITATION CHANCES
WILL DIMINISH QUICKLY THEREAFTER. MODELS CONTINUE TO DEVELOP
PRECIPITATION ACROSS NORTHERN IOWA THROUGH THE MORNING
HOURS...THOUGH DO NOT HAVE HIGH CONFIDENCE WITH LACK OF FORCING AND
MOISTURE...AND HAVE TRENDED PRECIP DOWN ACROSS THE NORTH FOR THE
EARLY MORNING. HOWEVER...AS UPPER LEVEL LOW ACROSS CANADA PUSHES
EAST DROPPING FRONTAL BOUNDARY INTO IOWA...THIS WILL BRING THE BEST
CHANCES FOR PRECIPITATION ACROSS THE NORTH...WITH ONGOING
PRECIPITATION NEAR BOUNDARY IN DAKOTAS. HOWEVER...SYSTEM WILL BRING A
QUICK SHOT AND GIVEN LACK OF MOISTURE ACROSS THE AREA ATTM...HAVE
CONTINUED TO CUT BACK ON SNOWFALL TOTALS IN THE NORTH.

PRECIPITATION TYPE REMAINS CHALLENGING ACROSS SOUTHERN IOWA...WITH
ONGOING FREEZING RAIN AND MIXED PRECIPITATION ACROSS SOUTHERN CWA.
TEMPERATURES WILL CONTINUE TO WARM IN THE SOUTH AND WILL SEE A
TRANSITION BACK TO RAIN. WILL KEEP HEADLINE ACROSS THE SOUTH AS IS
FOR NOW WITH ROAD CONDITIONS INDICATING ICE GENERALLY ALONG I-80 AND
EAST OF I-35 WITHIN THE ADVISORY AREA. HOWEVER...MAY NEED TO CUT
BACK ON WESTERN EXTENT OF ADVISORY IF PRECIPITATION DOES NOT DEVELOP
TO THE NORTH. ACROSS THE NORTH PRECIPITATION WILL BE SNOW...WINDS
WILL INCREASE SIGNIFICANTLY BEHIND BOUNDARY AND WITH NEW SNOW
ACCUMULATIONS EXPECTED...WILL LIKELY SEE HAZARDOUS TRAVEL ACROSS THE
NORTH WITH LIMITED VISIBILITIES. THEREFORE WILL KEEP NORTHERN
PORTION OF HEADLINE AS IS...THOUGH WITH LOWER SNOWFALL TOTALS
EXPECTED IMPACTS FROM BLOWING SNOW MANY BE REDUCED.

EXPECT PRECIPITATION TO DIMINISH QUICKLY AFTER 18Z AS BOUNDARY
PUSHES IN WITH STRONG SUBSIDENCE. MAY HAVE HELD ONTO PRECIPITATION
TOO LONG INTO THE AFTERNOON...THOUGH LIGHT PRECIPITATION MAY LINGER.
AS BOUNDARY PUSHES THROUGH TEMPERATURES WILL DROP QUICKLY...AND HAVE
CUT BACK ON HIGHS TODAY...ESPECIALLY IN THE SOUTHEAST WITH SLIGHTLY
QUICKER PROGRESSION OF SYSTEM.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 403 AM CST TUE MAR 3 2015

LONGER TERM CONTINUES TO SEE BROAD NORTHWEST FLOW ACROSS THE EASTERN
CONUS ALTHOUGH LESS AMPLIFIED BY LATER IN THE FORECAST PERIOD AS
MAIN JET AXIS SHIFTS FARTHER NORTH.  FOR TONIGHT...COLD ARCTIC
AIRMASS WILL CONTINUE TO PUSH INTO THE STATE WITH COLD AIR RESERVOIR
DUMPING SOUTHWARD FROM CANADA.  WILL SEE ONE FINAL SHORTWAVE DROP
SOUTHWARD INTO THE MIDWEST LATE TONIGHT INTO WEDNESDAY MORNING WITH
ANOTHER ROUND OF LIFT OVERNIGHT INTO THURSDAY MORNING...ESPECIALLY IN
SOUTHERN IOWA. THIS WILL LIKELY PRODUCE SOME MID TO HIGH
CLOUDINESS OVERNIGHT...HOWEVER THE DRY AND COLD LOW LEVEL AIRMASS
WILL PREVENT THE THREAT OF PRECIPITATION AS THE WAVE PASSES.

THE THERMAL TROF WILL BE MOVING OVER THE STATE ON WEDNESDAY NIGHT
WITH ONE FINAL NIGHT OF BELOW ZERO READINGS FOR MUCH OF THE FORECAST
AREA.  THEREAFTER...WARM ADVECTION IS EXPECTED INTO FRIDAY BEFORE A
MINOR COOL DOWN INTO SATURDAY FOLLOWED CLOSELY BY WARMING INTO EARLY
NEXT WEEK.  IN GENERAL...AN UPWARD TREND TO MUCH MORE NORMAL
READINGS BY NEXT WEEK.  THERE WILL BE LITTLE THREAT FOR
PRECIPITATION AS MAIN STORM PATH IS EXPECTED TO BE NORTH OF THE
STATE.

&&

.AVIATION...03/18Z
ISSUED AT 1204 PM CST TUE MAR 3 2015

FREEZING DRIZZLE AND IFR POTENTIAL SEEMS TO BE ENDING BASED ON
RADAR TRENDS AND TEMPS WARMING ABOVE FREEZING. MAIN CONCERN WILL
BE POTENTIAL FOR REDUCED VSBYS IN SNOW SHOWERS/SQUALLS. AS NOTED
IN THE UPDATE SECTION...CONFIDENCE IN THIS OCCURRENCE IS
DECREASING SO HAVE KEPT IFR CONDITIONS GOING INTO THE EVENING
NORTH...BUT THIS IS DUE TO CIGS RATHER THAN VSBYS. IMPROVEMENT TO
VFR SHOULD OCCUR BY LATE EVENING WITH GRADUALLY DIMINISHING WINDS
AS WELL.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 9 PM CST THIS EVENING FOR BLACK
HAWK-BREMER-BUTLER-CERRO GORDO-EMMET-FRANKLIN-GRUNDY-HANCOCK-
HUMBOLDT-KOSSUTH-PALO ALTO-WINNEBAGO-WORTH-WRIGHT.

&&

$$

UPDATE...SMALL
SHORT TERM...AWB
LONG TERM...COGIL
AVIATION...SMALL


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