Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 020550
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1150 PM CST SUN MAR 1 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 350 PM CST SUN MAR 1 2015

LITTLE SENSIBLE WEATHER TONIGHT. ANY EFFECTS OF DAKOTAS/MN SHORT
WAVE WILL BE PAST IA TONIGHT WITH MOSTLY CLEAR SKIES ANTICIPATED.
ASSOCIATED COLD ADVECTION BEHIND ITS PASSAGE IS NOT SIGNIFICANT BUT
ANOTHER ARCTIC HIGH PRESSURE AREA WILL MOVE THROUGH IA OVERNIGHT.
THIS WILL STILL BE SUFFICIENT TO DROP TEMPS BACK INTO THE LOWER
TEENS TO SINGLE DIGITS AGAIN.

.LONG TERM /MONDAY THROUGH SUNDAY/...
ISSUED AT 350 PM CST SUN MAR 1 2015

PRIMARY FOCUS FOR THE LONG TERM PERIOD WILL BE ON SYSTEM MOVING
THROUGH THE REGION LATE MONDAY THROUGH TUESDAY. WARM AIR ADVECTION
COMMENCES BEHIND THE DEPARTING SURFACE HIGH ON MONDAY WITH A FEW
LIGHT SNOW SHOWERS POSSIBLE ACROSS NORTHWEST IOWA ALONG THE
LEADING EDGE OF THE THETA-E ADVECTION MONDAY AFTERNOON. PROFILES
RAPIDLY SATURATE BELOW 700 MB FROM SOUTHWEST TO NORTHEAST BETWEEN
00 AND 06Z. WITH SOUNDINGS NEARLY ISOTHERMAL BETWEEN 0 AND -3 C
AND SURFACE TEMPS INITIALLY BELOW FREEZING...EXPECT FREEZING
RAIN...MIXING IN AT TIMES WITH RAIN AND SNOW...ALONG AND SOUTH OF
INTERSTATE 80 THROUGH 12Z. THIS REGION OF FREEZING RAIN SHIFTS OFF
TO THE EAST CENTRAL CWA BETWEEN 12 AND 18Z AS THE PROFILES IN THE
SOUTH RISE ABOVE FREEZING AND THE PRECIP SWITCHES TO RAIN. TOTAL
ICE ACCUMULATIONS ARE EXPECTED TO BE LESS THAN A TENTH OF AN INCH.

MODEL DISCREPANCY ARISES DURING THE DAY ON TUESDAY AS THE SURFACE
CYCLONE EJECTS NORTHEASTWARD ACROSS THE STATE TUESDAY AFTERNOON.
THE NAM IS THE FURTHEST NORTH WHILE THE EC THE MORE SOUTHERN
SOLUTION WITH THE GFS IN THE MIDDLE...SO LEANED TOWARDS THE GFS
FOR THE THERMAL PROFILE FORECAST. THIS RESULTED IN LOWERING SNOW
RATIOS OVER THE NORTH WITH STORM TOTAL SNOWFALLS NOW ONLY EXPECTED
TO BE IN THE ONE TO THREE INCH RANGE. DGZ FORCING IS POTENT...BUT
NARROW AND SHORT LIVED OVER NORTHERN IOWA. WOULD NOT BE SURPRISED
TO SEE A FEW AREAS WITH OVER THREE INCHES OF SNOW...BUT GIVEN THE
RATHER UNCERTAIN LOCATION OF THIS FORCING...HAVE SHIFTED THE
FORECAST TOWARDS THE OVERALL TREND OF LESSER SNOWFALL. DRY SLOT
LOOKS TO PUNCH UP ACROSS THE CENTRAL AND SOUTHERN PORTIONS OF THE
CWA BETWEEN 12 AND 18Z...SO HAVE LOWERED POPS AND QPF IN THE SOUTH
AND WEST. THIS MAY HAVE TO BE FURTHER LOWERED IN UPCOMING SHIFTS.

WHILE SNOWFALL AMOUNTS OVER THE NORTH ARE NOT AS HIGH AS
PREVIOUSLY FORECAST...THE WIND AND BLOWING SNOW THREAT DURING THE
LATE MORNING AND AFTERNOON HOURS REMAINS QUITE HIGH. ARCTIC
BOUNDARY RACES SOUTHEASTWARD BEHIND THE DEPARTING LOW WITH WINDS
VEERING TO THE NORTHWEST AND INCREASING TO 25 TO 30 KTS WITH
HIGHER GUSTS. THESE WINDS LOOK TO SET IN BEHIND THE FALLING
SNOW...BUT GIVEN THE FRESH SNOWPACK ON TOP OF THE 4 TO 6 INCHES
OF SNOW THAT FELL THE PREVIOUS WEEK...CONFIDENCE IS INCREASING FOR
A GROUND BLIZZARD OVER THE NORTHERN CWA. THE PEAK IN WINDS WILL
BE BETWEEN 18Z AND 00Z WITH THE BEST PRESSURE GRADIENT OVER
NORTHERN IOWA. 0 TO 1 KM LAPSE RATES QUICKLY STEEPEN TO NEAR
ADIABATIC AT THIS SAME TIME WITH WEAK CONVECTIVE
INSTABILITY...THUS HAVE LEFT POPS IN THE HIGH CHANCE TO LOW
LIKELY POP FOR NORTHERN IOWA WITH THE EXPECTATION OF SOME SNOW
SHOWERS DEVELOPING IN THE CAA. IN COORDINATION WITH SURROUNDING
OFFICES HAVE NOT HOISTED ANY HEADLINES ATTM...WHICH WILL GIVE US
TIME TO FINE TUNE THE LOCATION OF HIGHEST THREAT.

BEYOND TUESDAY LOOKS RELATIVELY INACTIVE BUT WITH SOMEWHAT OF A
CHANGE IN TEMPERATURE REGIME. THE PATTERN LOOKS VERY FAMILIAR AT
ONSET WITH BROAD MEAN TROUGH MOVING THROUGH THE CENTRAL CONUS
RESULTING IN YET ANOTHER ITERATION OF ARCTIC HIGH PRESSURE. THIS
WILL LIKELY PRODUCE ANOTHER ROUND OF WIDESPREAD SINGLE DIGIT
ABOVE AND BELOW ZERO MINS WED NIGHT...EVEN SUB -10F NORTHEAST.
MODERATION WILL COMMENCE AFTER THIS POINT HOWEVER WITH HEIGHTS
BEGINNING TO RISE AS THE WESTERLIES RETREAT NORTHWARD. THIS WILL
EVENTUALLY BOOST TEMPERATURES BACK TO AROUND NORMAL INTO NEXT
WEEKEND. THE FORECAST IN THE EXTENDED REMAINS DRY WITH NO EVIDENCE
OF ANY SUBSTANTIAL FORCING OR ADEQUATE MOISTURE.

&&

.AVIATION...02/06Z
ISSUED AT 1150 PM CST SUN MAR 1 2015

FEW CHANGES TO PREVIOUS PACKAGE. CONDITIONS TO REMAIN VFR WITH MID
LEVEL WARM AIR ADVECTION BRINGING OVC070-110 TO THE REGION BY
15-16Z...THOUGH SCT-BKN200 WILL INCREASE ACROSS THE SOUTH FOR THE
REMAINDER OF THE NIGHT. WINDS GRAD BECOME MORE SSE AFT 15Z WITH
INCR WINDS TO 11-12KTS AFT 19Z WEST AND ELSEWHERE TOWARD 00Z.
MAIN SYSTEM TO BEGIN AFFECTING AREA TOWARD 03/06Z WITH LOWER CIGS
AND PSBL ONSET OF MIXED PRECIPITATION./REV

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...SMALL
LONG TERM...SKOW/SMALL
AVIATION...REV



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