000
FXUS63 KDMX 160432
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1132 PM CDT SAT MAR 15 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 342 PM CDT SAT MAR 15 2014

ANOTHER DIFFICULT FORECAST HEADING INTO TONIGHT WITH SNOW AMOUNTS
THE BIG QUESTION. PARENT LONG WAVE TROUGH MOVING THROUGH THE
ROCKIES HAS SPREAD SOME NRN STREAM WEIGHTED FORCING ASSOCIATED
WITH THE BAROCLINIC ZONE INTO SRN MN/NRN IA WHILE MOST SIGNIFICANT
SHORT WAVE AND PV ANOMALY IS PUSHING THROUGH TX. OUR LIFT IS
MAINLY DRIVEN BY THERMODYNAMICS AND FAIRLY DEEP FRONTOGENETICAL
RESPONSE...AND WITH LIMITED MOISTURE HAS BEEN PROBLEMATIC. OBS
OVER FAR SWRN MN AND EVEN INTO IA THIS AFTERNOON...CURRENTLY
AROUND CLARION FOR EXAMPLE...HAVE VARIED QUITE A BIT IN TIME AND
SPACE. ISOLATED 1-2 MILE VSBY SNOW AND LOWER CIGS SURROUNDED BY
8-10KFT CIGS AND NO PRECIP.

FORCING FROM TWO STREAMS PHASES TO SOME EXTENT LATER TONIGHT
TOWARD 06Z...HOWEVER IA CONTINUES TO BE MORE INFLUENCED BY
THERMODYNAMIC FORCING RATHER THAN MORE POTENT KINEMATICS WHICH
REMAIN TO OUR SOUTH. STATIC STABILITIES LOWER AROUND THIS TIME AS
WELL SO EXPECT TO SEE MORE WIDESPREAD SNOW WITH TIME TO THE SOUTH
AND SATURATION INCREASES...AND LIKELY A PERIOD OF MORE INTENSE
RATES. GENERALLY FOLLOWED A NON-GFS CONSENSUS WITH GFS QPF AMOUNTS
SEEMING TO BE TOO HIGH ON BACK SIDE OF THIS SYSTEM. DENDRITIC
GROWTH ZONE LIFT IS DECENT HOWEVER SO STILL EXPECT FAIRLY HIGH
RATES THROUGH THE TEENS POSSIBLY TO AROUND 20 TO 1 AT TIMES. EVEN
WITH MORE CONSERVATIVE QPF THESE RATIOS WILL STILL LIKELY RESULT
IN ONE TO TWO INCH ACCUMS FROM I80 SOUTH TO MO...AND LOCAL BANDING
PUSHING THREE INCHES. THERE MAY BE A LITTLE BIT OF MIX AS THE
PRECIP SPREADS NORTH TO SOUTH...BUT MOST SOUNDINGS SHOW THE
TRANSITION TO SNOW WILL BE FAIRLY QUICK.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 342 PM CDT SAT MAR 15 2014

MAIN FORECAST CONCERN WAS FOCUSED ON SYSTEM TUESDAY INTO
WEDNESDAY. THERE IS SOME DISAGREEMENT WITH THE TRACK LOCATION OF
THE UPPER LOW ACROSS THE REGION DURING THIS TIME AS THE
GFS/NAM/SREF ARE FURTHER NORTH THAN THE ECMWF/CANADIAN...LEANED
SLIGHTLY TOWARD THE NORTHERN TRACK ATTM.

SUNDAY AND MONDAY...CAA AND LOW STRATUS LOOK TO CONTINUE THROUGH
MUCH OF THE MORNING SUNDAY AND WILL HOLD TEMPS DOWN IN THE 20S
NORTH AND 30S SOUTH. SURFACE HIGH BUILDS INTO THE STATE BY THE
AFTERNOON AND BRINGS CLEARING SKIES INTO TOMORROW NIGHT. LOOKS TO
BE A COOL EVENING ACROSS THE FORECAST AREA SUNDAY NIGHT BEFORE
RETURN FLOW DEVELOPS EARLY MONDAY MORNING. HAVE NON-DIURNAL TEMP
TREND GOING PAST 06Z MONDAY TO REFLECT THE WAA DEVELOPING. GOOD
WAA AND DECENT MIXING PUTS TEMPS BACK INTO THE 50S ACROSS THE
WESTERN HALF OF THE FORECAST AREA. AS A RESULT...WARMED MAX TEMPS
SEVERAL DEGREES ON MONDAY.

TUESDAY THROUGH WEDNESDAY...DEEPLY STACK LOW PRESSURE SYSTEM
DEVELOPS OVER THE NORTHERN ROCKIES AND MOVES SOUTHEAST ACROSS THE
DAKOTAS AND INTO WESTERN IOWA BY TUESDAY AFTERNOON. THETA-E
ADVECTION AND ISENTROPIC LIFT DEVELOP LATE MONDAY NIGHT AND
CONTINUE INTO TUESDAY. THE DEEPER MOISTURE IS CONFINED TO
NORTHERN IOWA EARLY TUESDAY AND PRECIP TYPE LOOKS TO BE EITHER
RAIN OR FREEZING RAIN. THERE IS A PRETTY GOOD WARM LAYER ALOFT
THAT SHOULD COMPLETELY MELT ANY PRECIP FALLING THROUGH THIS LAYER
IN NORTHERN IOWA...BUT THE QUESTION REMAINS ON THE TIMING OF
SURFACE TEMPS RISING ABOVE FREEZING TUESDAY MORNING. KEPT MENTION
OF FREEZING RAIN FROM 06-12Z NORTH...THEN 12-18Z NORTHEAST ON
TUESDAY. BY TUESDAY NIGHT...STRONG CAA DEVELOPS AND WILL SWITCH
THE PRECIP TO ALL SNOW FROM NORTH TO SOUTH. WINDS ATOP THE MIXED
LAYER...PER MCW GFS BUFKIT SOUNDING...TOPS 50 KNOTS BY 09Z
WEDNESDAY AND SUGGESTS SNOW DURING THIS TIME. DECENT LIFT WITHIN
THE DENDRITIC LAYER ATTM AND INCREASED POPS AND WINDS OVER
NORTHERN IOWA TUESDAY NIGHT INTO WEDNESDAY. MAY NEED TO FURTHER
INCREASE POPS IF MODELS CONTINUE TO COME INTO BETTER AGREEMENT.
SNOW ACCUMS APPEAR LIGHT ATTM...BUT WITH THE WINDS AND FALLING
SNOW...MAY CAUSE SOME VISIBILITY ISSUES EARLY WEDNESDAY.

THURSDAY THROUGH SATURDAY...NOTHING SIGNIFICANT DURING THIS PERIOD
EXCEPT ONE WEAK SHORTWAVE TO BRING SNOW/RAIN CHANCES LATE THURSDAY
NIGHT INTO FRIDAY. OTHERWISE...WARMER TEMPERATURES THURSDAY THROUGH
SATURDAY.

&&

.AVIATION...16/06Z
ISSUED AT 1128 PM CDT SAT MAR 15 2014

BANDED SNOW CONTINUES TO DRIFT SOUTH ACROSS THE REGION TONIGHT AND
SHOULD EXIT THE I80 CORRIDOR AFT 08Z WITH IMPROVING CIGS/VSBY.
KOTM WILL CONTINUE TO SEE MVFR TO IFR CONDITIONS THROUGH 11Z WITH
IMPROVING CIGS/VSBY AFT 11Z. WINDS WILL REMAIN BRISK NE OVN WITH
GRADIENT RELAXING FROM NORTH TO SOUTH OVERNIGHT AND ACROSS THE
SOUTH AFT 14Z AS STORM DEPARTS OVER MID MS RIVER VALLEY. REMAINDER
OF DAY WILL BE QUIET AS HIGH PRESSURE BUILDS EAST ACROSS THE
REGION. EXPECTING WIND SHIFT LATE DAY TO SE AS HIGH RECEDES AND
TROUGH APPROACHES FROM WEST...MID TO HIGH CLOUDS ACROSS WEST AS
WELL.

&&

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

$$

SHORT TERM...SMALL
LONG TERM...PODRAZIK
AVIATION...REV