Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 191735
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1235 PM CDT SAT APR 19 2014

.SHORT TERM /TODAY/...
ISSUED AT 333 AM CDT SAT APR 19 2014

MAIN FORECAST CONCERN TODAY WAS FOCUSED ON WINDS AND TEMPERATURES...
AND POPS LATE THIS AFTERNOON OVER NORTHWEST IOWA. MODELS HAVE
CONSISTENTLY PULLED BACK ON RAIN CHANCES PREVIOUS RUNS AND LEANED
TOWARD THE DRIER NAM/GFS FOR POPS TODAY. WRT TO TEMPS...LEANED
SLIGHTLY WARMER THAN THE SREF/NAM FOR MAX TEMPS.

ONGOING WAA WILL CONTINUE TO INCREASE THROUGH THE DAY AS THE
COMBINATION OF PRESSURE GRADIENT AND DEEP MIXING WILL LEAD TO A
WINDY DAY. WINDS REMAIN BELOW CRITERIA ATTM...BUT WOULD NOT BE
SURPRISED TO SEE SOME GUSTS TO 40 MPH THIS AFTERNOON AS MIXING TO
900MB TO 850MB SEEMS REASONABLE. WINDS ATOP THE MIX LAYER RANGE
AROUND 30-35 KNOTS. REGARDLESS...IT WILL WARM AND WINDY WITH HIGHS
OVER THE ENTIRE FORECAST AREA RISING WELL INTO THE 70S. TWEAK MAX
TEMPS UP A DEGREE OR TWO WITH WARM LOWS AND STRONG WAA.

FRONTAL BOUNDARY STALLS ACROSS FAR NORTHWEST IOWA AND MORE LIKELY IN
SOUTHEAST SOUTH DAKOTA THIS AFTERNOON. CONFIDENT ENOUGH TO PULL BACK
TIMING AND COVERAGE OF POPS FOR TODAY...AND HAVE LOW CONFIDENCE WE
WILL SEE ANY PRECIP IN THE STATE UNTIL LATE TONIGHT. BUFR SOUNDINGS
IN NORTHERN IOWA SHOW DEEP DRY LAYER FROM SURFACE TO 800MB AND
REMAIN STRONGLY CAPPED THROUGH THE AFTERNOON HOURS. PLUS THERE IS
VERY LITTLE ELEVATED OR SURFACE BASED INSTABILITY THROUGH 00Z
SUNDAY. EVEN THOUGH SHEAR PROFILES ARE ADEQUATE FOR
CONVECTION...THERE IS NO TRIGGER MECHANISM AVAILABLE UNTIL AFTER 00Z
SUNDAY.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 333 AM CDT SAT APR 19 2014

ACTIVE WEATHER PATTERN IN STORE FOR THE REGION THROUGH MUCH OF THE
PERIOD. FIRST CHALLENGE IS TIMING OF PRECIP AND COVERAGE WITH
APPROACHING PLAINS TROUGH.  UPPER LEVEL RIDGE TONIGHT CUTS ACROSS
ONTARIO SOUTHWEST THROUGH ILLINOIS SOUTH TO SOUTH TX. WEAK MOISTURE
ADV AT H850 BEGINNING TO CREEP NORTH ALONG THE RED RIVER VALLEY. AT
THE SFC...DEW POINTS TO 50F UP TO WICHITA FALLS WITH MID 40S ALONG
SOUTHERN PLAINS WARM FRONT TO WESTERN KS. MODELS DIFFER ON TIMING OF
PRECIP/COVERAGE AND FORCING/QPF AS WELL. INITIALLY IT LOOKS LIKE THE
MOISTURE WILL ARRIVE WITH LESS INSTABILITY...THEN GRADUALLY BECOME
MORE UNSTABLE SUNDAY. WITH THAT IN MIND...HAVE REDUCED TO ISO
THUNDER SAT NIGHT AND SCT THUNDER SUNDAY GRADUALLY GOING GENERAL
THUNDER FOR SUNDAY NIGHT. GEM/EURO ARE SLOWER AND HAVE LESS MOISTURE
INPUT/OUTPUT THAN GFS. TENDENCY HAS BEEN FOR GFS TO BE TOO FAST AND
THOUGH MOISTURE WILL SURELY GET HERE...HAVE SLOWED ARRIVAL AND
EASTWARD PROGRESSION WHILE KEEPING EXPECTED TROUGH ACROSS THE REGION
BY LATE SAT NIGHT/SUNDAY ACTIVE ACROSS THE NORTHWEST HALF OF THE
FORECAST AREA. THUS...QUITE A SPREAD OF CONDITIONS EXPECTED ON
EASTER SUNDAY WITH COOLER/WETTER WEATHER NORTH AND PARTLY SUNNY AND
MILDER WEATHER SOUTHEAST THROUGH MOST OF DAY AND EVENING. NORTHWEST
SHOULD SEE BEST LIFT NEARER THE UPPER LEVEL/SFC TROUGH AXIS WITH
THE ENTIRE TROUGH SLOWLY DRIFTING EAST SUNDAY NIGHT AND MONDAY
WHEN POP INCREASES FOR THE REMAINDER OF THE AREA. EXPECTED
RAINFALL FROM THE EURO/GEM THROUGH MON LOOKS GREATEST ACROSS THE
NORTHWEST...OVER AREAS WHICH SAW THE LEAST AMOUNT LAST WEEKEND
WHILE LESSER AMOUNTS EXPECTED SOUTHEAST WITH A GENERAL RANGE FROM
.25 TO .75 WITH LOCALLY HIGHER AMOUNTS. GFS APPEARS TO BE HAVING
SOME CONVECTIVE FEEDBACK ISSUES WITH POCKETS OF 1-2 INCH RAINS
NEAR A CLOSED SFC LOW AND LARGE STRIPE OF TOTALS OF 2-3 INCHES
WHICH DONT LOOK LIKELY...WHILE THE GEM/EURO SHOW MOSTLY A WEAKER
TROUGH ALIGNMENT SW/NE ORIENTATION. PREFER THE LATTER...WEAKER
FORCING SCENARIO. THE SYSTEM MAY LINGER INTO MONDAY AFTERNOON EAST
WITH SCT SHOWERS AND THUNDER PRIOR TO LIFTING OUT. RELATIVELY
QUIET WX RETURNS FOR TUESDAY WITH RIDGE OF HIGH PRESSURE ACROSS
THE REGION. DESPITE THE COOLER AIRMASS...H850 TEMPS WILL STILL
REACH 2C NORTHEAST TO 5-6C WEST/SOUTHWEST WHICH SHOULD SUPPORT
HIGHS NEAR 60 NORTHEAST AND IN THE MID 60S CENTRAL AND SOUTHWEST.
THE REMAINDER OF THE WEEK WILL RETURN TO ACTIVE WEATHER AS A
VIGOROUS UPPER LEVEL SYSTEM ENTERING THE PACNW MOVES EAST LATE
TUES NIGHT AND ENTERS THE PLAINS BY 00Z THURSDAY. AHEAD OF THE
SYSTEM...H500 RIDGING ALOFT WILL INCREASE THICKNESS/H850 TEMPS
WITH A ROUND OF WARM AIR ADVECTION CROSSING THE REGION BY WED
AFTERNOON WITH SHOWERS AND THUNDERSTORMS. DIFFICULT FORECAST FOR
TEMPS WED DUE TO POSSIBLE OVC/SCT THUNDER FOR MOST OF THE
AFTERNOON. HIGHS MAY RANGE FROM THE MID 50S TO MID 60S DEPENDING
ON THE COVERAGE. LITTLE CHANCE FOR SVR INITIALLY...BUT AS THE MAIN
WAVE ARRIVES WED NIGHT...STRENGTHENING WIND FIELDS FROM THE SFC
THROUGH H300 MAY BE ENOUGH TO KEEP CONVECTION GOING OVERNIGHT WITH
A POTENTIAL FOR SOME STRONG STORMS. AS THE SYSTEM LIFTS NORTHEAST
THURSDAY...IT OCCLUDES FURTHER AND FORCES THE BEST INSTABILITY
EAST INTO ILLINOIS BY 00Z FRIDAY...KEEPING THE BEST CHANCES FOR
ORGANIZED SVR WX MAINLY EAST OF THE REGION. ANY SLOWER EVOLUTION
AND DEPARTURE...HOWEVER...WOULD PLACE A BETTER CHANCE FOR STRONGER
STORMS BACK IN IOWA DURING THE DAY THURSDAY AND WILL NEED TO
MONITOR THIS WEEK ESPECIALLY WITH THE STRONG WIND FIELDS THROUGH
THE COLUMN. COOLER AIR REGIONWIDE AND LINGERING SHOWERS WILL
CONTINUE NORTH HALF WITH A BRISK WNW WIND THURSDAY NIGHT AND
FRIDAY RESULTING IN HIGHS BACK IN THE 50S OVER MOST OF THE AREA.
UNCERTAINTY REMAINS INTO THE WEEKEND AS THE MODELS DIVERGE ON
SOLUTIONS. WHILE THE GFS SHOWS MOISTURE RETURN LATE IN THE
WEEKEND...THE EURO IS SPINNING UP ANOTHER LOW SATURDAY OVER THE
PLAINS AHEAD OF THE MAIN SYSTEM WITH WARM AIR ADVECTION THUNDER BY
00Z SUNDAY OVER OUR AREA. FOR NOW...WILL LEAN TOWARD A DRIER
SOLUTION ON SATURDAY UNTIL SOME CONFIRMATION OF TRENDS IS
APPARENT. SEEMS MORE REASONABLE THAT SOME SEPARATION WILL OCCUR
BETWEEN FRIDAYS LINGERING OCCLUDED LOW AND THE NEXT UPSTREAM WAVE.

&&

.AVIATION...19/18Z
ISSUED AT 1230 PM CDT SAT APR 19 2014

KEPT VFR CONDITIONS FOR TAF FORECAST PERIOD. MAY NEED TO
REEVALUATE AND LOWER CEILINGS FOR KMCW...KFOD...AND KALO AS
BOUNDARY APPROACHES FROM THE NORTHWEST AROUND SUNRISE SUNDAY
MORNING. CONFIDENCE THIS FAR OUT NOT HIGH ENOUGH TO MENTION
THUNDER FOR ANY TAF SITES...BUT THAT TREND WILL NEED TO BE
MONITORED AS WELL.

STRONG WINDS THROUGH 01Z SUNDAY FROM THE SOUTH. BOUNDARY
APPROACHING FROM NORTHWEST WILL BRING PRECIPITATION CHANCES TO
THE AREA SUNDAY MORNING INTO THE AFTERNOON HOURS. WINDS WILL LOWER
SIGNIFICANTLY SUNDAY INTO MONDAY.


&&

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

$$

SHORT TERM...PODRAZIK
LONG TERM...REV
AVIATION...KOTENBERG



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