098
FXUS63 KDMX 061747
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1247 PM CDT MON APR 6 2026
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- HIGH CONFIDENCE IN AN ACCUMULATING, NARROW SNOWBAND TONIGHT
INTO TUESDAY MORNING, PRIMARILY OVER SOUTHWEST INTO PARTS OF
SOUTH CENTRAL IOWA. LIGHT SNOW AND RAIN THEN DRIFTS NORTH
THROUGH TUESDAY, BUT ANY NEW ACCUMULATIONS ARE MINIMAL FARTHER
NORTH.
- WINDY WEDNESDAY WITH SHOWERS AND A FEW STORMS ALONG A COLD
FRONT LATE IN THE DAY INTO THURSDAY. NO APPARENT WIDESPREAD
SEVERE RISK.
- SIGNAL REMAINS FOR A WET PATTERN AND THREAT OF HEAVY RAINFALL,
THOUGH TRENDS ARE DELAYING THIS UNTIL LATER IN THE WEEKEND
INTO EARLY THE FOLLOWING WEEK.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 330 AM CDT MON APR 6 2026
GOES-EAST UPPER LEVEL WATER VAPOR IMAGERY SHOWS A LONGWAVE TROUGH
OVER THE EASTERN HALF OF THE CONUS WHILE RIDGING IS OVER THE
WESTERN CONUS. AT THE SURFACE, A COLD FRONT HAS SETTLED
SOUTHWARD THROUGH MUCH OF THE STATE WITH LOW LEVEL COLD AIR
ADVECTION ONGOING. THIS NORTHERLY FLOW IS ALLOWING AREAS OF LOW
LEVEL STRATUS CLOUDS TO DROP SOUTHWARD OUT OF MINNESOTA INTO
NORTHERN IOWA PER NIGHTTIME MICROPHYSICS RGB. THERE ARE
ADDITIONAL CLOUDS IN THE MID-LEVELS, WHICH ARE STREAMING FROM
SOUTH DAKOTA AND PARTS OF NEBRASKA INTO WESTERN IOWA. LIGHT
RADAR RETURNS ARE NOT REACHING THE GROUND PER SURFACE
OBSERVATIONS WITH CLOUD BASES GENERALLY ABOVE 9000 FEET AT THIS
TIME. TODAY, BREEZY WINDS AVERAGING 10 TO AROUND 15 MPH WILL
PREVAIL UNDER A PARTLY TO MOSTLY CLOUDY SKY WITH A SURFACE HIGH
PRESSURE TRACKING INTO THE WESTERN GREAT LAKES WHILE THE SURFACE
COLD FRONT SETTLES INTO KANSAS AND MISSOURI. THERE WILL BE AN
ATTEMPT TO PRODUCE LIGHT RAIN OR SNOW OVER PARTS OF THE WESTERN
HALF OF THE STATE AS WEAK LOW LEVEL THETA-E ADVECTION BEGINS.
HOWEVER, THIS PRECIPITATION WILL BE FIGHTING AGAINST LOW LEVEL
DRY AIR BEING FUNNELED IN FROM THE HIGH PASSING TO THE
NORTHEAST. WITH EXPECTATIONS THAT THE DRY AIR WILL BE
DETRIMENTAL TO THE PRECIPITATION, HAVE TRIMMED AND LOWERED POPS
FROM INITIAL NATIONAL BLEND OF MODELS (NBM) GUIDANCE.
AS WE HEAD INTO TONIGHT, THE LOW LEVEL THETA-E ADVECTION WILL
INTENSIFY AS A STRENGTHENING FRONTOGENETICAL (FGEN) BAND IN THE 850-
700MB LAYER SETS UP A PRECIPITATION AXIS OVER SOUTHWEST INTO SOUTH
CENTRAL IOWA INTO NORTHEASTERN MISSOURI. THE HIGH TO THE NORTH WILL
TIGHTENING THE NORTHERN EDGE OF THE PRECIPITATION SHIELD AS THE DRY
AIR EATS AWAY AT SATURATION IN THE LOW LEVELS WITH THE CURRENT
FORECAST ATTEMPTING TO REFLECT THIS GRADIENT. WHILE
DETERMINISTIC MODELS VARY GREATLY ON THE PLACEMENT OF THIS BAND
OF PRECIPITATION, WHICH IS OFTEN THE CASE, AIGFS AND AIFS BOTH
HAVE SIMILAR PLACEMENT OF THE QPF AXIS. WHILE THE AI SOLUTIONS
DO NOT HANDLE THE AMOUNTS WELL, THEY HAVE SHOWN SKILL IN THE
LOCATION OF THE BAND. THEREFORE, HAVE OPTED FOR THE WPC QPF,
WHICH HAS SIMILAR PLACEMENT TO THE AI SOLUTIONS, BUT HAS
MAGNITUDE TOWARDS SIX TENTHS. FORECAST SOUNDINGS POINT TO NEAR
SURFACE TEMPERATURES JUST ABOVE FREEZING, BUT AS WET BULBING
OCCURS EARLY THIS EVENING, A TRANSITION TO ALL SNOW IS EXPECTED
ACROSS ALL OF SOUTHERN IOWA. VARYING DEGREES OF LIFT ARE SHOWN
GENERALLY ABOVE 2KM WITH MODERATE TO STRONG LIFT IN THE
TRADITIONAL DENDRITIC GROWTH ZONE (DGZ), THOUGH THE DEPTH IS NOT
REMARKABLE. BELOW 2KM, SUBSIDENCE AND NORTHEASTERLY FLOW IS
SHOWN SO NOT SURE HOW MUCH THE LESSER KNOWN DGZ WILL PLAY A ROLE
IN SNOW RATIOS, WHICH SHOULD BE MAINLY BELOW 10:1. LOOKING AT
STRAIGHT MODEL OUTPUT SNOWFALL IS QUITE CONCERNING WITH A STREAK
OF 6"+ SHOWN IN SOUTHWEST TO SOUTH CENTRAL IOWA WITH CSQ COBB
OUTPUT TABLES SIMILAR. THE CHALLENGE WILL BE THE SNOW
ACCUMULATION ON THE GROUND AS 4" SOIL TEMPERATURES ARE IN THE
MIDDLE TO UPPER 40S. SNOW RATES HAVE PROVEN TO PLAY A CRUCIAL
ROLE IN OVERCOMING THESE WARM GROUND TEMPERATURES WITH RATES OF
AROUND 0.75"/HR BEING SUFFICIENT TO START ACCUMULATION. WITH THE
STRONG FORCING, THERE IS POTENTIAL FOR HIGHER RATES WITH THE
LATEST SREF AND HREF SHOWING A 20-30% OF 1"/HR RATES OVERNIGHT
WITH MEAN RATES OF HALF TO THREE-QUARTERS OF AN INCH EXPECTED.
THIS BRINGS THE SNOW ACCUMULATION AXIS OF 2 TO 3 INCHES FROM
AROUND THE OMAHA METRO TO ATLANTIC, CRESTON, AND LAMONI. AT
THIS TIME, NOT PLANNING A WINTER WEATHER ADVISORY GIVEN AMOUNTS
GENERALLY UNDER 3 INCHES AND THE TIME WHEN MUCH OF THE SNOW WILL
FALL. HOWEVER, THE WET, SLICK SNOW IS LIKELY TO IMPACT THE
TUESDAY MORNING COMMUTE IN SOUTHWEST AND SOUTH CENTRAL IOWA SO
WILL BE MONITORING OBSERVATIONAL AND MODEL TRENDS. WHILE
TEMPERATURES OVERNIGHT WILL BE BELOW FREEZING, NOT PLANNING ANY
FREEZE HEADLINES OVER SOUTHERN IOWA AS CONDITIONS WERE SIMILAR
JUST YESTERDAY/SUNDAY MORNING.
THE SNOW OVER SOUTHERN IOWA WILL BEGIN TO LIFT NORTHEASTWARD THROUGH
THE DAY TUESDAY AS THE THETA-E ADVECTION PUSHES IN A SIMILAR
DIRECTION. AS TEMPERATURES WARM, THE INITIAL SNOW AT A GIVEN
LOCATION WILL MIX WITH AND CHANGE TO RAIN. WITH THE FGEN WEAKENING
BY TUESDAY MORNING, PRECIPITATION WILL BE LIGHTER THAN TONIGHT AND
ANY NEW SNOW ACCUMULATIONS AFTER DAYBREAK TUESDAY WILL BE NEAR IF
NOT UNDER AN INCH OVER SOUTHERN INTO CENTRAL IOWA. THE
PRECIPITATION SHOULD WANE INTO TUESDAY NIGHT WITH A BRIEF DRY
PERIOD.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
ISSUED AT 330 AM CDT MON APR 6 2026
A SHORTWAVE TROUGH CROSSING THE SOUTHERN CANADIAN PRAIRIES WILL HAVE
AN ASSOCIATED SURFACE LOW AHEAD OF IT WITH A SOUTHWESTWARD TRAILING
COLD FRONT, WHICH WILL REACH IOWA LATE WEDNESDAY. AHEAD OF THIS
FRONT, BREEZY WINDS FROM THE SOUTH AND SOUTHWEST WILL PREVAIL
AT 20 TO 30 MPH WITH GUSTS OF 30 TO 40 MPH. FIRE WEATHER
CONCERNS SHOULD BE MINIMIZED AS MINIMUM RELATIVE HUMIDITY VALUES
STAY ABOVE 40%. AS THE FRONT MOVES THROUGH WEDNESDAY NIGHT INTO
THURSDAY, SCATTERED SHOWERS AND A FEW STORMS ARE EXPECTED ALONG
THIS BOUNDARY. WIDESPREAD SEVERE WEATHER PROSPECTS CONTINUE TO
LOOK LOW IN THIS PERIOD DUE TO WEAK INSTABILITY DESPITE
OTHERWISE FAVORABLE LOW LEVEL KINEMATICS AND DEEP SHEAR.
PRECIPITABLE WATER VALUES AND WARM CLOUD DEPTHS LOOK SEASONAL SO
NOT LOOKING AT EXCEPTIONAL RAINFALL, BUT AMOUNTS UP TO 1 TO 2
INCHES WILL BE POSSIBLE WITH THIS FRONT.
THE FRONT SHOULD SLIP SOUTH OF IOWA THURSDAY NIGHT OR FRIDAY, THOUGH
HOW FAR VARIES IN THE MODELS AND THIS IMPACTS THE POSITION OF A
SURFACE HIGH ON FRIDAY. THESE SURFACE FEATURES ALONG WITH THE
MID-LEVEL RIDGE OVER THE EASTERN US, WHICH CONTINUES TO TREND
SLIGHTLY WESTWARD DELAYING THE OFF-OF-CALIFORNIA SHORTWAVE
TROUGH, ARE EVOLVING THE HEAVY RAINFALL THREAT LATER INTO THE
WEEKEND AND EARLY NEXT WEEK. THIS IS REFLECTED IN LOWER NBM
POPS THAT HAVE TRENDED DOWN ON FRIDAY. HOWEVER, THE PERSISTENT
SIGNAL FOR AN ACTIVE, WET PATTERN REMAINS AS THE CALIFORNIA
TROUGH EVENTUALLY MOVES THROUGH THE DESERT SOUTHWEST AND LIFTS
NORTHEASTWARD TOWARDS THE STATE WITH THE GFS AND ECMWF BOTH
NEGATIVELY TILTING IT EARLY NEXT WEEK. WILL BE MONITORING HEAVY
RAINFALL THREAT WITH QPF VALUES TICKING UP BY ANOTHER 1 TO 3
INCHES FROM SATURDAY NIGHT THROUGH EARLY NEXT WEEK. MORE DETAILS
ON THE IMPACT OF THIS POTENTIAL RAINFALL IN THE HYDRO
DISCUSSION BELOW. FINALLY, A WINDOW FOR SEVERE WEATHER MAY STILL
DEVELOP OVER THE WEEKEND WITH NSSL GEFS SHOWING 10 TO 15%
PROBABILITIES AND COLORADO STATE UNIVERSITY'S MACHINE LEARNING
RANDOM FOREST OUTLOOK SHOWING 15 TO 30% ON SUNDAY.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1231 PM CDT MON APR 6 2026
MVFR CLOUDS OVER NORTHEASTERN IOWA ARE SLOWLY ERODING EARLY THIS
AFTERNOON, AND WILL GIVE WAY TO VFR CONDITIONS THROUGH THE NEXT
FEW HOURS. WINDS HAVE BEEN BREEZY OUT OF THE NORTH NORTHWEST,
WITH GUSTS AROUND 20 TO 25 KTS. THE HIGHER GUSTS SHOULD DIMINISH
SOME LATER THIS AFTERNOON, BUT REMAIN LIGHT TO BREEZY INTO THE
EVENING. MID-LEVEL CLOUDS AND LIGHT RAIN WILL DRIFT OVER THE
STATE THROUGH THE AFTERNOON, ALTHOUGH IMPACTS ARE EXPECTED TO BE
MINIMAL. LATER TONIGHT AND INTO TUESDAY MORNING, A BAND OF SNOW
WILL DEVELOP ACROSS SOUTHEASTERN INTO SOUTH CENTRAL IOWA.
EXPECTATION IS FOR THIS TO MOSTLY STAY SOUTH AND WEST OF KDSM
AND KOTM, BUT A SLIGHT SHIFT COULD LEAD TO SOME IMPACTS AT
EITHER SITE. THEREFORE, HAVE INCLUDED SOME PROB30S FOR LIGHT
SNOW FOR BOTH SITES. LOW CEILINGS ALSO LIFT UP INTO THE AREA
THORUGH TUESDAY MORNING, LEADING TO MVFR TO IFR CONDITIONS.
HYDROLOGY
ISSUED AT 330 AM CDT MON APR 6 2026
MANY RIVERS ARE CRESTING OR WILL CREST OVER THE NEXT 24 HOURS OR SO
WITH ABOUT 15 FORECAST POINTS REACHING ACTION STAGE. THE CEDAR RIVER
AT CEDAR FALLS HAS REACHED MINOR FLOOD STAGE AND WE ARE ALSO
MONITORING THE IOWA RIVER NEAR TAMA THAT IS EXPECTED TO CREST NEAR
FLOOD STAGE TUESDAY MORNING.
THE PRECIPITATION TODAY INTO TONIGHT, INCLUDING THE SNOW BAND,
WILL LARGELY FALL OVER AREAS THAT HAVE NOT SEEN THE HIGHER
RAINFALL THAT OCCURRED LAST WEEK. NASA SPORT GFS FORCED 0-10CM
AND 0-40CM SOIL MOISTURE PERCENTILES ARE FORECAST TO RECOVER TO
BETWEEN THE 30TH AND 70TH PERCENTILES BY LATE THIS WEEK. WHILE
RIVER FORECAST ARE ONLY ACCOUNTING FOR 24 HOURS OF
PRECIPITATION, BOTH THE OFFICIAL FORECAST AND THE 120 HOUR
CONTINGENCY FORECAST SHOW ALL CURRENT ACTION OR MINOR FLOOD
STAGE FORECAST POINTS FALLING BELOW ACTION STAGE BY LATE THIS
WEEK, THOUGH THEY ARE UNLIKELY TO RETURN TO THEIR BASE FLOWS OF
EARLY LAST WEEK.
SOME RAINFALL UP TO 1 TO 2 INCHES WILL FALL WITH A COLD FRONT
WEDNESDAY INTO THURSDAY, WHICH MAY TAKE AWAY SOME SOIL CAPACITY AS
THE ACTIVE, WET PATTERN SETS UP LATE THIS WEEKEND INTO EARLY NEXT
WEEK. A FEW ADDITIONAL INCHES MAY BE POSSIBLE OVER PORTIONS OF THE
STATE, BUT UNCERTAINTY ON AMOUNTS AND PLACEMENT WITHIN ANY GIVEN
BASIN AT THIS TIME RANGE REMAINS HIGH. THE GFS AND NBM FORCED
NATIONAL WATER MODEL HIGH MAGNITUDE FLOW ANNUAL EXCEEDANCE
PROBABILITIES ARE GENERALLY 50% ON LARGER STREAMS. THIS POINTS
TO RENEWED RIVER RISES THAT ARE GENERALLY WITHIN BANK, WITH
THIS ESPECIALLY SHOWN OVER SOUTHERN INTO EASTERN IOWA. THE
EXPERIMENTAL FLOOD HAZARD OUTLOOK FROM LATE SUNDAY CONTINUES TO
HIGHLIGHT MUCH OF IOWA FOR LIMITED POTENTIAL FLOODING IMPACTS
WITH THE EXPERIMENTAL HYDROLOGIC ENSEMBLE FORECASTING SERVICE
(HEFS) AT THE 30% CHANCE OF EXCEEDANCE WITH STAGES SIMILAR TO
CURRENT, BUT AT THE 10% CHANCE OF EXCEEDANCE WITH SEVERAL MORE
POINTS REACHING MINOR STAGE AND A FEW TO MODERATE STAGE. TRENDS
IN THE HEAVY RAINFALL SIGNAL WILL NEED TO BE MONITORED THIS
WEEK.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...ANSORGE
LONG TERM...ANSORGE
AVIATION...DODSON
HYDROLOGY...ANSORGE
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