Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 141152
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
552 AM CST SUN FEB 14 2016

.SHORT TERM /TODAY/...
ISSUED AT 323 AM CST SUN FEB 14 2016

MAIN CONCERN IS ONGOING SYSTEM. FIRST ROUND OF SNOW CONTINUES TO
WEAKEN AS IT LIFTS TO THE NORTHEAST. ISENTROPICALLY FORCED BAND OVER
CENTRAL IOWA DROPPED 2-3 INCHES OF SNOW IN A NARROW CORRIDOR BETWEEN
00 AND 06Z. THOUGH LIGHT SNOW WILL CONTINUE AS THE WARM FRONT LIFTS
EAST...ATTENTION TURNS TO MAIN WAVE NOW OVER THE CENTRAL PLAINS.
TROUGH EXTENDS FROM CANADA SOUTH TO TEXAS WITH INCREASING QG FORCING
EXPECTED TO ARRIVE OVERNIGHT INTO SUNDAY MORNING. MOISTURE TRANSPORT
ACROSS KANSAS/NEBRASKA SOUTH TO TX WILL BE REALIZED AS THE WAVE GETS
INTO IOWA BY 12Z AND WARM FRONT SLOWLY LIFTS NORTHEAST OF A
DEVELOPING SFC LOW OVER SOUTHEAST SOUTH DAKOTA. SNOW WILL INCREASE
IN COVERAGE AND INTENSITY THROUGH 12Z...WITH ANOTHER INCH OR SO FROM
NORTH CENTRAL THROUGH NORTHWEST AREAS. FROM 12 TO 18Z A MORE
WIDESPREAD 1 TO 2 INCHES WILL FALL...LOCALIZED HEAVIER AMOUNTS MAY
OCCUR ALONG THE LEADING EDGE OF THE QG FORCING AND WARM FRONTAL LIFT
OVER THE EAST. 00Z GFS MUCAPE IS PROGGED TO REACH 100-200 J/KG OVER
OUR FAR EASTERN COUNTIES BY 12-15Z...WHICH MAY SIGNAL ISOLATED
THUNDER AT THAT TIME THERE...THOUGH CONFIDENCE NOT ALL THAT HIGH.
OVERALL...EXPECT STORM TOTALS TO RANGE FROM AROUND 2 TO 6 INCHES
WITH THE HIGHER READINGS MOST LIKELY WHERE THE INITIAL BANDING TOOK
PLACE LAST EVENING COMBINED WITH THE NEW ROUND OF SNOWFALL. WILL
MAINTAIN ADVISORY HEADLINES GIVEN THE MARGINALITY OF ANY TOTALS
ABOVE WARNING CRITERIA. AS THE TROUGH MOVES EAST TODAY...SFC
GRADIENT WINDS WILL RELAX SOMEWHAT...BUT STILL EXPECT WINDS OVER THE
EASTERN HALF TO RANGE FROM 15 TO 20 KTS CAUSING SOME BLOWING SNOW
DURING THE MORNING AND AFTERNOON HOURS. THIS WILL LEAD TO CONTINUED
SLICK ROADS AND TRAVEL CHALLENGES FOR ANY HOLIDAY TRAVELERS OVER THE
REGION LATER THIS AFTERNOON...AND CAUTION IS ADVISED. HIGHS WILL
REMAIN IN THE 20S OVER MOST OF THE REGION TO THE MID 30S IN THE
SOUTHWEST. HEADLINES MAY BE TRIMMED OVER THE WEST BY 18Z...BUT WILL
LEAVE THAT TO DAY CREW TO EVALUATE.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 323 AM CST SUN FEB 14 2016

EXPECT ANY LINGERING SNOWFALL IN THE EAST TO PUSH QUICKLY OUT OF
THE AREA FOR BEGINNING OF PERIOD. MODELS ARE BEGINNING TO INDICATE
A WEAK WAVE WILL DROP SOUTH INTO WESTERN IOWA AS TROUGH PUSHES
EAST SUNDAY NIGHT. HAVE THEREFORE INTRODUCED SLIGHT CHANCES FOR
SNOW IN THE WEST TONIGHT...BUT EXPECT ANY SNOW TO BE LIGHT GIVEN
SPEED OF SYSTEM.

ATTENTION WILL THEN TURN TO QUICK MOVING LOW PRESSURE SYSTEM WHICH
WILL DROP SOUTH INTO IOWA MONDAY NIGHT. SYSTEM WILL BE A QUICK HIT
OF PRECIPITATION...AND MODELS HAVE COME INTO GOOD ALIGNMENT WITH
TIMING AND PLACEMENT OF SYSTEM. MODELS ARE SLIGHTLY SLOWER WITH
SYSTEM ENTERING WESTERN IOWA AND HAVE SLOWED ONSET OF
PRECIPITATION. HOWEVER...TIMING STILL LOOKS ON TRACK FOR BULK OF
PRECIPITATION TO COME LATE MONDAY NIGHT. CONCERN WILL BE
PRECIPITATION TYPE AND AMOUNT OF PRECIPITATION. THERE ARE HINTS
THAT THERE COULD BE A PERIOD OF FREEZING RAIN BEFORE CHANGING TO
SNOW...WITH FREEZING RAIN AGAIN AS SYSTEM DEPARTS. HOWEVER...HAVE
NOT INCLUDED MENTION ATTM. ANALYSIS OF SOUNDINGS INDICATES ICE
INTRODUCTION EARLY WITH SYSTEM WHICH SHOULD KEEP PRECIPITATION
SNOW FOR ONSET. HOWEVER...A WARM LAYER NEAR THE SURFACE COULD
ALLOW FOR ENOUGH MELTING OF ICE FOR FREEZING RAIN...BUT ATTM...NOT
ENOUGH CONFIDENCE IN THIS TO BE WIDESPREAD. ACROSS THE SOUTH
TEMPERATURES WILL BE WARMER...BUT GENERALLY EXPECT PRECIPITATION
TO CHANGE TO RAIN OR RAIN/SNOW. CONCERN THEN BECOMES AS MOISTURE
DIMINISHES AS SYSTEM PULLS EAST AND ICE INTRODUCTION IS
LOST...THOUGH SOUNDINGS INDICATE LOW LEVEL MOISTURE REMAINING.
HOWEVER...FORCING IS WEAK ATTM AND THEREFORE HAVE KEPT
PRECIPITATION RAIN/SNOW...BUT PTYPE WILL NEED TO BE MONITORED. IN
ADDITION...FORCING RAMPS UP QUICKLY AFTER 06Z WITHIN SNOW...AND
COULD SEE GOOD SNOWFALL RATES. ATTM HAVE KEPT SNOWFALL TOTALS NEAR
GOING...WITH WARMER TEMPERATURES HELPING TO KEEP SNOW RATIOS LOWER
AND SPEED OF SYSTEM KEEPING SNOW TOTALS DOWN.

BEHIND SYSTEM NORTHWESTERLY FLOW WILL PERSIST THROUGH WEDNESDAY
WITH ANOTHER WAVE PUSHING SOUTH TUESDAY NIGHT. HAVE INTRODUCED POPS
ACROSS THE NORTH WITH THIS WAVE...BUT DO NOT HAVE HIGH CONFIDENCE
IN TIMING OR LOCATION AT THIS TEMPORAL LENGTH WITH WEAK WAVE...AND
HAVE KEPT POPS SLIGHT CHANCE ATTM. LARGE UPPER LEVEL RIDGE WILL
BUILD IN FOR THE END OF THE WEEK WITH TEMPERATURES EXPECTED TO
WARM SIGNIFICANTLY UNDER RIDGE. GOOD SOUTHERLY SURFACE FLOW AND
WAA WILL KEEP TEMPERATURES WELL ABOVE NORMAL FOR END OF PERIOD.
GUIDANCE CONTINUES TO BE WARM THROUGH THE WEEKEND AND HAVE
CONTINUED TO TREND THIS WAY. LOW WILL PUSH THROUGH RIDGE FOR END
OF THE WEEK...THOUGH MODELS HAVE PULLED THIS SYSTEM MUCH FURTHER
NORTH INTO NORTHERN PLAINS....THEREFORE KEEPING FORECAST DRY AND
WARM THROUGH END OF PERIOD.

&&

.AVIATION...14/12Z
ISSUED AT 552 AM CST SUN FEB 14 2016

BANDS OF SNOW AND IFR CIGS/MVFR TO IFR VSBY NOW MOVING ACROSS AREA
WITH UPPER LEVEL SYSTEM. DIFFICULT FCST TODAY DUE TO RAPID
VARIATIONS IN CLOUD DECKS/VSBY. OVERALL EXPECTING LOWER END MVFR
TO IFR AT TIMES WITH OCCASIONAL BREAKS TO VFR. HIRES MODELS AND
UPSTREAM CONDITIONS SUGGEST CIGS/VSBY REMAIN MVFR AFT 00Z AS
CLOUDS CONTINUE. WILL PROBABLY NEED SOME ADJUSTMENTS WITH LOWER
CONFIDENCE FORECAST TODAY. /REV

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR
APPANOOSE-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CERRO GORDO-
DALLAS-DAVIS-EMMET-FRANKLIN-GREENE-GRUNDY-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-JASPER-KOSSUTH-MAHASKA-MARION-MARSHALL-MONROE-
PALO ALTO-POCAHONTAS-POLK-POWESHIEK-SAC-STORY-TAMA-WAPELLO-
WARREN-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...REV
LONG TERM...AWB
AVIATION...REV


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