Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 200851
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
351 AM CDT SUN APR 20 2014

.SHORT TERM /TODAY/...
ISSUED AT 351 AM CDT SUN APR 20 2014

FRONTAL BOUNDARY STALLED UP ACROSS NORTHWEST IOWA WILL SLOWLY
TRANSITION SOUTHEAST THROUGHOUT THE DAY TODAY. MAIN CONCERN IS
WITH PRECIP ASSOCIATED WITH THE FRONT AND MAX TEMPERATURES.

UTILIZED A BLEND OF THE 20.03Z HOPWRF...20.05Z HRRR...AND 20.00Z
RUNS OF THE NMM/ARW-EAST AS THEY WERE IN GREAT AGREEMENT WITH SMALL
BATCH OF SHOWERS TO AFFECT NORTHERN IOWA THROUGH THE EARLY THIS
MORNING HOURS. THERE LOOKS TO BE A BRIEF BREAK LATE IN THE MORNING
INTO THE EARLY AFTERNOON BEFORE SHOWERS/STORMS DEVELOP ALONG THE
FRONT WITH DEEPER MOISTURE MOVING INTO THE STATE AND BETTER
INSTABILITY. STRONG MOISTURE TRANSPORT AND THETA-E ADVECTION WILL
CONTINUE PUSH SURFACE DEW POINTS INTO THE UPPER 40S/LOWER 50S
THROUGH THE DAY. SOUNDINGS DEPICTING ELEVATED LCL (AROUND 5000-6000
FEET) AND RAIN LOOKS TO HAVE TO FIGHT THROUGH A FAIRLY DEEP DRY
LAYER TO THE SURFACE THIS MORNING. THERE ARE A FEW ISOLATED SHOWERS
DEVELOPING ALONG THE 300-310K ISENTROPIC SURFACE WHERE ENOUGH LIFT
AND MOISTURE TRANSPORT PRESENT. BUT NOT ANTICIPATING THESE SHOWERS TO
PERSIST PAST 12Z AS THEY LOOK TO MOVE INTO MORE STABLE AIR FURTHER
EAST. AFTER THESE LITTLE SHOWERS MOVE THROUGH CENTRAL IOWA THIS
MORNING...NOT EXPECTING PRECIP UNTIL LATE THIS AFTERNOON AND CONFINED
POPS TO THE NORTH AND WEST UNTIL 21Z.

LATER INTO THE AFTERNOON...BETTER INSTABILITY BY 21Z SUNDAY ACROSS
WESTERN TO NORTHERN IOWA AND EXPECTING FRONT TO TRIGGER SCATTERED
SHOWERS/TSTMS OVER THIS AREA. PRECIPITABLE WATER VALUES AROUND 1.20"
THIS AFTERNOON AND WITH THE DEEPER MOISTURE MOVING INTO THE
STATE...COULD SEE A FEW ISOLATED HALF INCH AMOUNTS.

WITH THE WAA CONTINUING OVERNIGHT TONIGHT...TEMPERATURES REMAINED
SLIGHTLY WARMER THAN ANTICIPATED. THEREFORE...WAS CONFIDENT TO BUMP
MAX TEMPS UP A DEGREE OR TWO ACROSS THE FORECAST...WHICH WAS NEAR OR
SLIGHTLY WARMER THAN MOS.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 351 AM CDT SUN APR 20 2014

SYSTEM TRACKING MORE OR LESS AS EXPECTED TONIGHT...AS WEAKENED
INVERTED TROUGH WITH VERY WEAK SFC IMPULSE DRIFTING NORTHEAST INTO
WESTERN WI BY 12Z MONDAY. SO FAR...MOISTURE HAS BEEN LACKING BOTH AT
THE SFC AND ALOFT. SUBJECTIVE SFC ANALYSIS TONIGHT SHOWS SECONDARY
WARM FRONT FROM LOW OVER THE NE/KS BORDER SOUTHEAST ACROSS SOUTHEAST
KS TO NORTHERN AR. DEW POINTS POOLING IN THE 50-55F RANGE OVER THE
SOUTHERN PLAINS BUT SFC WINDS NOT HELPING MUCH TO TRANSPORT MOISTURE
NORTH. ALOFT AT H850...A THIN RIBBON OF 5C DEW POINTS HAS WORKED
NORTH TO MINNEAPOLIS BUT DEEPER MOISTURE STILL STUCK SOUTH IN THE
SOUTHERN PLAINS AND THIS SHOULD EXPAND INTO IOWA TONIGHT. H850
MOISTURE CHANNEL HAS BEEN HELD IN CHECK BY EXPANSIVE HIGH PRESSURE
ALOFT TO OUR EAST. BY TONIGHT THIS FEATURE WILL DRIFT EAST AND
ALLOW WEAK SFC SYSTEM SOUTHWEST OF US TO MOVE ACROSS THE REGION
AND TUG THE WEAK BOUNDARY SOUTHEAST THROUGH MONDAY AFTERNOON.
SHOWERS AND SCT THUNDER WILL INCREASE NORTH THIS EVENING AS THE
WEAK SFC LOW BEGINS TO MOVE NORTHEAST. AFTER 06Z TO 12Z THE ENTIRE
AREA DRIFTS SOUTHEAST BUT THE FAR SOUTHEAST SHOULD STILL BE MAINLY
DRY UNTIL 12Z. THROUGH THE DAY MONDAY THE SYSTEM WILL MOVE EAST OF
THE REGION WITH A SECONDARY COLD FRONT DROPPING INTO NORTHERN IA
BY 00Z TUE FOLLOWED BY CANADIAN HIGH PRESSURE FOR TUESDAY. LOWS
TONIGHT WILL REMAIN RATHER MILD WITH BOUNDARY TO THE NORTH AND
THICK CLOUD COVER. WITH THE MILD START TO THE DAY MONDAY...HIGHS
SHOULD REACH THE UPPER 60S TO NEAR 70. AS THE SECONDARY FRONT
DROPS SOUTH MONDAY NIGHT...COLDER AIR FILTERS INTO THE REGION
THROUGH 12Z TUES WITH LOWS IN THE 30S AND 40S. TUES LOOKS PLEASANT
WITH SEASONAL READINGS AS NORTHEAST FLOW KEEPS WARM AIR ADVECTION
WELL TO THE WEST. HIGHS RANGE FROM THE UPPER 50S NORTHEAST TO THE
MID 60S SOUTH. NEXT UPSTREAM WAVE OVER THE ROCKIES WILL SPREAD
SOME CLOUDS INTO WEST LATE IN THE DAY...AND SHOWERS ARRIVE BY 12Z
WED WEST. THROUGH WED...ENHANCED LIFT AS WARM FRONT AND THETAE
ADVECTION RETURN WILL KEEP TEMPS COOL...AND MAY STRUGGLE TO REACH
60 ACROSS THE NORTHEAST HALF OF THE FORECAST AREA AS SHOWERS WILL
OCCUR THERE AND ISO THUNDER DEVELOPS SOUTHWEST. MODELS CONTINUE TO
ADVERTISE VIGOROUS WAVE FOR WED/THUR WITH EXTENSIVE H500 LONGWAVE
TROUGH EXTENDING ALL THE WAY BACK TO DUTCH HARBOR AK ALONG THE
ALEUTIAN CHAIN. AS MENTIONED IN LAST NIGHTS AFD...WIND FIELDS
ALOFT STILL SOMEWHAT IMPRESSIVE BY WED/THU OVER THE PLAINS. SYSTEM
SHOULD GEN UP SHOWERS AS WARM AIR ADVECTION INCREASES WED WITH
POTENTIAL FOR ISO THUNDER. FOR THE MOST PART WE REMAIN IN THE COOL
SECTOR THROUGH WED AFTERNOON. AS WAVE BUCKLES AND CROSSES THE
REGION...CENTRAL/EASTERN AREAS BRIEFLY GET IN WARM SECTOR LATE WED
NIGHT INTO MIDDAY THUR. BEST CHANCE FOR ORGANIZED SVR WILL OCCUR
WED EVE OVER EASTERN NE AND WESTERN HALF OF IOWA ...WEAKENING
SLOWLY AS IT CROSSES THE REGION WED NIGHT AND REINTENSIFYING LATE
THU MORNING/EARLY AFTERNOON AS THE WARM SECTOR MOVES EAST INTO
EASTERN AND SOUTHEAST IOWA. POTENTIAL FOR EVENING AND LATE NIGHT
SVR WED NIGHT/EARLY MORNING THUR IS INCREASING WITH EURO SLOWING
THE SYSTEM DOWN. GFS APPEARS FASTER AT THIS POINT. WILL NEED TO
WATCH PROGRESSION OF WAVE FOR SEVERE POTENTIAL. THOUGH WINDS ALOFT
ARE NOT LINING UP VERY WELL FOR A SIGNIFICANT EVENT OVER OUR
AREA...ENOUGH OF A SIGNAL WITH SHEAR/CAPE TO BE WEARY OF OVERNIGHT
SUSTAINED SVR CONVECTION LATE WED NIGHT. TEMPS THURS WILL STILL BE
MILD BUT ON THE DOWNSWING LATE AS ANOTHER COOL FRONT DROPS SOUTH
INTO THE AREA BY FRIDAY MORNING. AIRMASS BEHIND THAT BOUNDARY
MODERATES A BIT AS IT ARRIVES FRIDAY...LEAVING MOST OF THE AREA IN
THE 50S TO LOWER 60S. LONG WAVE CONTINUES TO PUSH ENERGY EAST INTO
THE WESTERN STATES WHICH QUICKLY IS PROGGED TO ARRIVE IN THE
PLAINS ALREADY ON SATURDAY AND SUNDAY. NEXT WEEKEND IS BEGINNING
TO LOOK WET ONCE AGAIN. MEDIUM CONFIDENCE RIGHT NOW...WITH
EXTENSIVE H500 WAVE TRAIN HEADING OUR WAY.

&&

.AVIATION...20/06Z
ISSUED AT 1142 PM CDT SAT APR 19 2014

FRONTAL BOUNDARY WILL CONTINUE TO SLOWLY PUSH SE ACROSS CENTRAL
IOWA THROUGH THE PERIOD. SHRA AND TSRA ARE POSSIBLE NEAR
BOUNDARY...WITH WESTERN AND NORTHERN SITES KFOD/KMCW SEEING
PRECIPITATION FIRST BEFORE SHIFTING TO OTHER SITES BY 00Z...WITH
KOTM LAST. HAVE ONLY INCLUDED VCTS FOR NOW GIVEN UNCERTAINTIES IN
TIMING AND LOCATION. EXPECT CONDITIONS TO REMAIN VFR...THOUGH
COULD SEE MVFR OR LOWER CEILINGS AND VISIBILITIES AT TIMES WITH
SHRA.


&&

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

$$

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



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