199
FXUS63 KDMX 212330
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
630 PM CDT FRI AUG 21 2026
...UPDATED FOR THE 00Z AVIATION DISCUSSION...
KEY MESSAGES
- MARGINAL (LEVEL 1 OF 5) RISK FOR SEVERE WEATHER ACROSS
SOUTHERN IOWA. DAMAGING WINDS AND LARGE HAIL ARE THE PRIMARY
THREATS.
- FAIRLY CONSISTENT HIGHS THROUGH MIDWEEK NEXT WEEK, RANGING
FROM THE 70S TO LOW 80S ACROSS IOWA.
- DRY THROUGH THE WEEKEND, PRECIPITATION CHANCES RETURN SUNDAY
NIGHT INTO MONDAY AND AT TIMES NEXT WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 230 PM CDT FRI AUG 21 2026
A COLD FRONT IS CURRENTLY MAKING ITS WAY ACROSS IOWA THIS AFTERNOON
AND EVENING. IN FRONT OF IT, A FIELD OF DIURNAL CUMULUS HAS FORMED.
THERE ARE LOW EXPECTATIONS WITH THIS CUMULUS FIELD AS FAR AS
PRECIPITATION CHANCES GO TODAY. AS FAR AS THE ENVIRONMENT ACROSS
IOWA GOES, MLCAPE VALUES ARE IN THE NEIGHBORHOOD 2500J/KG ACROSS
CENTRAL AND EASTERN IOWA WITH LITTLE IN THE WAY OF CIN. SHEAR IN
NORTHWEST IOWA IS DECENT - AROUND 30 KTS - AND GUIDANCE SUGGESTS
WEAK FORCING IS AVAILABLE IN THE NORTHWESTERN PORTION OF THE AREA.
THAT SAID, DRY AIR HAS BEEN PUSHING ITS WAY INTO THE STATE THROUGH
THE DAY AND THERE IS VERY LITTLE IN THE WAY OF MOISTURE RETURN WHICH
LIMITS THE POTENTIAL FOR CONVECTION. SIMILARLY, ACROSS SOUTHERN IOWA
WHICH HAS BEEN OUTLINED BY A MARGINAL (LEVEL 1 OF 5) RISK FOR SEVERE
WEATHER TODAY, CAPE (AROUND 2500J/KG) AND SHEAR (35-40KTS) WOULD
INDICATE SOME AMOUNT OF SEVERE WEATHER POTENTIAL, BUT WITH DRY AIR
PUSHING IN AND VERY LITTLE IN THE WAY OF FORCING, THE THREAT FOR
SEVERE WEATHER LOOKS HIGHLY CONDITIONAL. SHOULD THE BOUNDARY PROVIDE
ENOUGH FORCING FOR AN UPDRAFT TO ORGANIZE, THERE'S STILL POTENTIAL
FOR IT TO PRODUCE LARGE HAIL AND DAMAGING WINDS.
OTHERWISE, OVERNIGHT PRECIPITATION CHANCES DIMINISH EVEN FURTHER AS
THE AFOREMENTIONED DRY AIR CONTINUES TO BE ADVECTED IN FROM THE
NORTH. THIS DRY AIR IS BEING ADVECTED BY A HIGH PRESSURE SYSTEM,
WHICH WILL SINK INTO THE AREA ON SATURDAY. THIS HIGH PRESSURE
INDICATES FAIR WEATHER AND CLEAR SKIES FOR THE WEEKEND. CONTINUED
NORTHWESTERLY FLOW MEANS TEMPERATURES WILL REMAIN JUST BELOW NORMAL.
KEEPING WITH THIS TREND, SKIES WILL REMAIN CLEAR SATURDAY NIGHT AND
THROUGH PART OF SUNDAY BEFORE MOISTURE BUILDS BACK INTO WESTERN
IOWA.
LONG TERM /SATURDAY THROUGH FRIDAY/
ISSUED AT 230 PM CDT FRI AUG 21 2026
IOWA REMAINS SEATED BETWEEN A RIDGE CENTERED OVER THE FOUR CORNERS
REGION AND A TROUGH OVER THE GREAT LAKES. IF EITHER OF THESE SYSTEMS
SHIFT, THAT WILL CHANGE HOW FAR EAST OR WEST MOISTURE GETS BACK INTO
THE AREA BY SUNDAY NIGHT, WHICH IS WHEN THE NEXT SHORTWAVE LOOKS TO
MOVE THROUGH, POTENTIALLY BRINGING MORE PRECIPITATION CHANCES INTO
SUNDAY MORNING. AT THE MOMENT, HOWEVER, DETERMINISTIC GUIDANCE IS
STILL STRUGGLING WITH THE TIMING OF THIS SYSTEM. WITH THIS COMES
SOME DEGREE OF DISAGREEMENT WITH PLACEMENT, ALL OF WHICH WILL BE
BETTER ASSESSED IN THE COMING DAYS. THIS UPPER LEVEL PATTERN LOOKS
TO REMAIN RATHER STAGNANT, WITH THE POTENTIAL FOR ADDITIONAL
SHORTWAVES TO MOVE THROUGH THE REGION NEXT WEEK.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 628 PM CDT FRI AUG 21 2026
SKIES ARE CLEAR FOR THE MOST PART ACROSS THE STATE EXCEPT FOR SOME
LINGERING SMOKE ALOFT. THIS MAY CONTINUE INTO TOMORROW BUT IS NOT
EXPECTED TO BE IMPACTFUL. SOME PATCHY FOG DEVELOPMENT REMAINS
POSSIBLE TONIGHT, BUT GIVEN THE EXTRA BREEZE BEHIND THE FRONT AND
DRY AIR ADVECTION, SEEMS UNLIKELY AT THIS POINT. VFR CUMULUS MAY
DEVELOP AT OUR SOUTHERN TERMINALS TOMORROW AFTERNOON BUT CONFIDENCE
IS TOO LOW FOR INCLUSION AT THIS TIME.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...67
LONG TERM...67
AVIATION...DE BRUIN
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