066
FXUS63 KDMX 031754
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1254 PM CDT FRI APR 3 2026
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- TWO ROUNDS OF SEVERE STORMS POSSIBLE TODAY. 1) LARGE HAIL THE
MAIN HAZARD AS STORMS LIFT FROM WESTERN IOWA THIS MORNING INTO
NORTHEASTERN IOWA EARLY THIS AFTERNOON. 2) STORMS FORM THIS AFTERNOON
AHEAD OF A COLD FRONT WITH HAIL, TORNADOES, AND STRONG WIND
POTENTIAL.
- LOCALLY HEAVY RAINFALL COULD LEAD TO ISOLATED FLASH FLOODING
WITH THIS RISK HIGHEST IN URBAN AREAS.
- COOLER, BLUSTERY ON SATURDAY. A BIT MILDER, LESS WIND ON SUNDAY.
- INCREASES CHANCES FOR RAINFALL AND STORMS MID INTO LATE NEXT
WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 345 AM CDT FRI APR 3 2026
EARLY MORNING GOES-EAST UPPER LEVEL WATER VAPOR IMAGERY SHOWS A
CYCLONIC SPIN OVER THE NORTHERN ROCKIES WHILE THE SYSTEM
RESPONSIBLE FOR OUR STORMY THURSDAY WEATHER HAS LIFTED OVER LAKE
SUPERIOR AND VICINITY. WHILE THIS FLUSHED OUT THE MOISTURE IN
THE ATMOSPHERE WITH NOW MUCH LOWER DEWPOINTS AND PRECIPITABLE
WATER (PWATS) VALUES, THIS WILL CHANGE QUICKLY TODAY AS SURFACE
LOW PRESSURE OVER WESTERN KANSAS LIFTS TO NEAR ST. JOSEPH, MO BY
MID-AFTERNON TO NORTHEASTERN IOWA LATE THIS EVENING. AHEAD OF
THIS SURFACE LOW, WHICH WILL BE RELATIVELY STEADY STATE IN ITS
PRESSURE AROUND 1000MB THROUGH ITS TRACK, MOISTURE TRANSPORT AND
RECOVERY WILL BE IMPRESSIVE AHEAD OF IT. THIS IS DUE TO STRONG
LOW LEVEL WARM AIR ADVECTION (WAA) AIDED BY A 40 TO 45 KNOT LOW
LEVEL JET THIS MORNING THAT WEAKENS INTO THIS AFTERNOON. AS THIS
WAA OCCURS, INSTABILITY WILL BE BUILDING ABOVE AN ELEVATED WARM
LAYER WITH MUCAPE VALUES UP TO AROUND 1000 J/KG POSSIBLE WITH
MID-LEVEL LAPSE RATES AROUND 7 C/KM. EFFECTIVE SHEAR OF 40 KNOTS
OR HIGHER IS FORECAST WITH MUCH OF THIS DRIVEN BY SPEED SHEAR
WITHIN THE CAPE LAYER. WITH A RATHER STRAIGHT HODOGRAPH, LARGE
HAIL WILL BE THE MAIN CONCERN AS STORMS DEVELOP OVER WESTERN
IOWA IN THE WAA WING BY 9 OR 10 AM THIS MORNING AND LIFT
NORTHEASTWARD INTO NORTH CENTRAL AND NORTHEASTERN IOWA BY EARLY
THIS AFTERNOON.
ATTENTION THEN TURNS TO THE AFTERNOON STORM POTENTIAL. A WARM FRONT
WILL BE LIFTING NORTHWARD INTO SOUTHERN IOWA WITH A TEMPERATURE
BIFURCATION FROM NORTHWESTERN IOWA WHERE TEMPERATURES WILL STRUGGLE
TO REACH 40 DEGREES TO SOUTHEASTERN IOWA WHERE HIGHS WILL PEAK IN
THE 70S. DEWPOINTS IN THE WARM SECTOR ARE FORECAST WELL INTO THE 50S
AND EVEN LOW 60S. FORECAST SOUNDINGS SHOW THE INVERSION PERSISTING
MUCH OF THE DAY IN THE WARM SECTOR WITH HREF CLOUD COVER SHOWING
SCATTERED POCKETS OF INSOLATION. THIS ALONG WITH THE WAA REGIME WILL
BE WORKING TO WEAKEN THE INHIBITION/CAPPING, BUT IT SEEMS STORMS
DEVELOPMENT, AT LEAST SURFACE BASED, WILL HAVE TO WAIT UNTIL THE
SURFACE COLD FRONT REACHES ANY GIVEN LOCATION IN CENTRAL AND SOUTH
CENTRAL IOWA THIS AFTERNOON. SURFACE INSTABILITY JUST AHEAD OF THE
FRONT WILL GROW TO BETWEEN 1500 TO 2000 J/KG WITH EFFECTIVE INFLOW
LAYER SHEAR OF 30 KNOTS AND MODEST LOW AND MID-LEVEL LAPSE RATES OF
6 C/KM. CLOUD BASES/LCLS WILL BE LOW AND THE SURFACE LOW WILL
CONTRIBUTE BACKED SURFACE FLOW WITH HODOGRAPHS HAVING AN OMINOUS
CURVATURE ON FIRST GLANCE WITH IMPRESSIVE 0-500M AND 0-1KM STORM
RELATIVE HELICITY VALUES OF AROUND 200 M2/S2. HOWEVER, THE HODOGRAPH
IS MORE MESSY IN THE 1-3 KM LAYER AND THIS MAY HAVE A NEGATIVE
EFFECT ON TORNADO POTENTIAL. BEYOND THE TORNADO POTENTIAL, LARGE
HAIL WILL BE A CONCERN, ESPECIALLY WITH ANY DISCRETE, ISOLATED
CELLS. WIND THREAT ALSO REMAINS, BUT MAY BE DIMINISHED SOME BY THE
LOW LEVEL (SURFACE TO 1.5KM) SATURATION SHOWN IN THE SOUNDINGS
RESULTING IN DOWNDRAFT CAPE VALUES UNDER 600 J/KG.
SO, WHERE DOES THE UNCERTAINTY LIE IN THIS AFTERNOON'S FORECAST? IN
NO PARTICULAR ORDER...1) THE AMOUNT OF INSOLATION/SUNSHINE. LESS
SUNSHINE MAY RESULT IN STORMS BEING ELEVATED (FAVOR HAIL/WIND RISK)
VERSUS SURFACE BASED (HIGHER TORNADO RISK ALONG WITH HAIL AND WIND).
HOWEVER, EVEN AN HOUR OF SUNSHINE HAS PROVEN TO BE MORE THAN ENOUGH
WITH EARLY/LATE SEASON SEVERE WEATHER SETUPS FOR TORNADO POTENTIAL.
STORM COVERAGE MAY BE LIMITED, AT LEAST INITIALLY, THOUGH THE FRONT
SHOULD BE SUFFICIENT FOR SLAB LIFTING TO GET STORMS GOING,
ESPECIALLY INTO EASTERN IOWA AS THE STORMS CONGEAL INTO MORE OF A
LINE. 2) THE MESSY HODOGRAPH, ESPECIALLY THE AFOREMENTIONED 1-3KM
LAYER. WHILE THIS IS SHOWN IN MULTIPLE MODEL FORECAST SOUNDINGS, IF
THE HODOGRAPH ENDS UP BEING LESS MESSY AND 'SMOOTHER', THIS MAY LEND
TO A HIGHER TORNADO POTENTIAL, WHICH IS SOMETHING WE AND SPC WILL BE
WATCHING FOR IF PARAMETERS ALIGN 'JUST WRONG'. 3) THE TRACK OF THE
SURFACE LOW, WHICH WILL DICTATE THE AREA OF HIGHEST SEVERE WEATHER
CONCERN. THERE IS GENERALLY GOOD AGREEMENT IN MODEL PLACEMENT
THROUGH EARLY AFTERNOON, BUT SPREAD GROWS INTO THIS EVENING.
ON THE RAINFALL AND POTENTIAL FLASH FLOODING FRONT, MANY AREAS OVER
THE LAST 24 HOURS HAVE RECEIVED THREE QUARTERS OF AN INCH ACROSS
CENTRAL IOWA WITH NARROW BANDS OF 1.5 TO 2 INCHES, PER RADAR
ESTIMATES. NASA SPORT RELATIVE SOIL MOISTURE (RSM) IN THE 0-10CM
LAYER (IMPORTANT FOR RAPID ONSET RESPONSES) SHOW ABOVE THE 80TH
PERCENTILE ROUGHLY ALONG AND NORTH OF HIGHWAY 20 ACROSS MUCH OF IOWA
WITH AN AREA IN NORTHEASTERN IOWA ABOVE THE 95TH PERCENTILE. HEAVY
RAINFALL PARAMETERS ARE NOTEWORTHY FOR EARLY SEASON WITH FORECAST
PRECIPITABLE WATER VALUES NEAR OR ABOVE THE DVN RAOB CLIMATOLOGICAL
MAX, WHICH IS AROUND 1.2 INCHES. WARM CLOUD DEPTHS ARE SEASONALLY
HIGH AROUND 3000M. WHILE THE 850-300MB FLOW WILL BE FAST, IT WILL BE
THE POTENTIAL FOR TWO ROUNDS OF STORMS THAT FLASH FLOODING COULD
BECOME A CONCERN. EARLIER CANADIAN MODEL RUNS AND MPAS MEMBERS AND
6Z HRRR WERE PEGGING NORTHEASTERN IOWA WITH 2-3.5 INCHES OF RAINFALL
BY FRIDAY EVENING, WHICH LINED UP UNFORTUNATELY WELL WITH THE MORE
SATURATED SOIL. IN COORDINATION WITH WPC, A SLIGHT RISK WAS
INTRODUCED OVER PARTS OF OUR EASTERN FORECAST AREA, INCLUDING
WATERLOO/CEDAR FALLS AND MARSHALLTOWN, INTO PARTS OF NORTHEASTERN
AND EAST CENTRAL IOWA. THIS SLIGHT RISK LINES UP WITH THE NORTHERN
EXTENT OF THE LATE THURSDAY UPDATE FROM THE NATIONAL WATER CENTER IN
THEIR FLOOD HAZARD OUTLOOK. LOOKING AT THE LATEST CANADIAN RUNS, IT
HAS SHIFTED ITS HEAVIEST RAINFALL INTO SOUTH CENTRAL IOWA WITH 2-3
INCHES SO WILL NEED TO MONITOR TRENDS IN RAINFALL LOCATION SINCE IT
MAY BE SHIFTING. THE HIGHEST FLASH FLOOD RISK WILL LIKELY BE IN
URBAN AREAS.
AS THE LOW LIFTS INTO WISCONSIN OVERNIGHT AND THE COLD FRONT MOVES
THROUGH THE STATE, THIS WILL END THE RISK OF SEVERE STORMS AND HEAVY
RAINFALL FROM WEST TO EAST THIS AFTERNOON INTO THIS EVENING.
LONG TERM /SATURDAY THROUGH THURSDAY/
ISSUED AT 345 AM CDT FRI APR 3 2026
MOISTURE WILL TRY TO WRAP BACK INTO IOWA AS THE SURFACE LOW MOVES
AWAY FROM IOWA WITH SPOTTY LIGHT RAIN OR SNOW SHOWERS. GUSTY WINDS
FROM THE NORTHWEST WILL PREVAIL AND INCREASE THROUGH THE DAYTIME
SATURDAY WITH SUSTAINED WINDS PEAKING AT 20 TO NEAR 30 MPH AND GUSTS
IN EXCESS OF 35 OR 40 MPH. HIGHS WILL RANGE FROM THE LOW 40S OVER
NORTHERN IOWA TO THE LOW 50S OVER SOUTHERN IOWA, WHICH WILL BE ABOUT
5 TO 10 DEGREES BELOW NORMAL FOR EARLY APRIL. HIGH PRESSURE WILL
TRANSIT THE REGION ON SUNDAY BRINGING LIGHTER WINDS. ON MONDAY,
MODEST LOW LEVEL THERMAL LIFT AND COINCIDENT QG CONVERGENCE MAY
ALLOW FOR AN AREA OF LIGHT PRECIPITATION INTO PARTS OF WESTERN IOWA.
STRONGER WAA IS FORECAST ON TUESDAY, WHICH WILL BRING IN WARMER AIR
BY WEDNESDAY AHEAD OF A FRONT. BY LATE NEXT WEEK, THE PATTERN LOOKS
MORE ACTIVE AGAIN AS THE FRONT SLOWLY MOVES THROUGH THE STATE. WHILE
THERE ARE VERY LOW SEVERE PROBABILITIES IN THE AI/ML, WILL ALSO NEED
TO WATCH HEAVY RAINFALL WITH DETERMINISTIC, ENSEMBLE, AND AI
SOLUTIONS SHOWING 1-3 INCHES IN VARYING PORTIONS OF IOWA.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1254 PM CDT FRI APR 3 2026
AREAS OF THUNDERSTORMS CONTINUE TO LIFT ACROSS IOWA INTO THE
AFTERNOON, IMPACTING KDSM AND ESPECIALLY AT KALO OVER THE NEXT
FEW HOURS, WITH PERIODS OF RAIN SHOWERS OTHERWISE OVER THE
NORTHERN TERMINALS. THE EXPECTATION REMAINS FOR ADDITIONAL
SHOWERS AND THUNDERSTORMS TO DEVELOP AHEAD OF A COLD FRONT THAT
WILL TRACK EASTWARD ACROSS IOWA THROUGH THE EVENING. KEPT
THUNDERSTORM MENTIONS AT MOST OF THE TERMINALS DURING THIS
TIMEFRAME IN PROB30 GROUPS AS EXACT TIMING AND COVERAGE REMAIN
ON THE LOWER END OF CONFIDENCE AT THIS TIME. TRENDS WILL
CONTINUE TO BE MONITORED, WITH AMENDMENTS MADE AS NEEDED.
CEILINGS ARE EXPECTED TO REMAIN LOW, WITH LARGELY IFR AND EVEN
MVFR AS PERIODS OF LOWER VISIBILITIES ARE ALSO EXPECTED AT TIMES
FROM EITHER HEAVY RAINFALL OR PATCHY FOG COVERAGE. WINDS OUT OF
THE NORTHEAST WILL GRADUALLY SHIFT NORTHWESTERLY TONIGHT INTO
SATURDAY MORNING BEHIND THE DEPARTING FRONT AND INCREASING.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...ANSORGE
LONG TERM...ANSORGE
AVIATION...BURY
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