643
FXUS63 KDMX 230345
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1045 PM CDT SAT AUG 22 2026
...UPDATED FOR THE 06Z AVIATION DISCUSSION...
KEY MESSAGES
- GENERALLY QUIET WEATHER FOR THE UPCOMING WEEK, WITH DAILY
HIGH TEMPERATURES IN THE UPPER 70S TO MID-80S.
- DECENT RAIN CHANCES (AROUND 50%) LATE SUNDAY NIGHT AND
MONDAY, OTHERWISE ONLY LOW AND SPOTTY CHANCES FOR MOST OF THE
WEEK.
- EARLY SIGNS OF A SOMEWHAT MORE ACTIVE WEATHER PATTERN NEXT
WEEKEND, WITH A RETURN OF MORE PERSISTENT RAIN CHANCES BUT ANY
DETAILS STILL UNCLEAR AT THIS RANGE.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 1237 PM CDT SAT AUG 22 2026
AN OMEGA BLOCKING PATTERN IS ATTEMPTING TO SET UP ACROSS NORTH
AMERICA, BUT IS NOT FULLY ENTRENCHED. AT 500 MB A LARGE RIDGE IS
ENTRENCHED ACROSS THE SOUTHERN HIGH PLAINS AND OVER TOWARD THE
FOUR CORNERS REGION, BRINGING NEAR-RECORD WARMTH TO PARTS OF
THAT AREA, AND EXTENDING FAR NORTHWARD INTO CENTRAL CANADA.
MEANWHILE, TWO TROUGHS ARE PRESENT WITH THE WESTERN ONE JUST
COMING ASHORE OVER THE U.S. PACIFIC NORTHWEST, WHILE DOWNSTREAM,
ANOTHER TROUGH IS DIGGING FROM HUDSON BAY DOWN ACROSS ONTARIO
AND INTO THE U.S. GREAT LAKES REGION. IOWA CURRENTLY LIES
BENEATH THE BRISK NORTHWESTERLY STEERING FLOW BETWEEN THE RIDGE
AND THE EASTERN TROUGH. AT THE SURFACE, A LARGE HIGH PRESSURE
AREA IS SPILLING DOWN FROM THE CANADIAN PLAINS INTO THE
MIDWEST, HERALDING RELATIVELY QUIET AND COMFORTABLE WEATHER FOR
IOWA THIS WEEKEND. HIGH TEMPERATURES WILL RANGE IN THE UPPER 70S
TO LOWER 80S BOTH TODAY AND SUNDAY, WITH DEWPOINTS GENERALLY IN
THE 50S AND 60S. THIS WILL MAKE FOR A GLORIOUS WEEKEND FOR MOST
LATE SUMMER OUTDOOR ACTIVITIES. TONIGHT INTO EARLY SUNDAY, AS
THE RIDGE SETTLES ACROSS IOWA AND WINDS TO LIGHT TO CALM BENEATH
VIRTUALLY CLEAR SKIES, WE SHOULD RADIATE NICELY WITH
TEMPERATURES FALLING INTO THE 50S IN MUCH OF THE STATE. SOME
GUIDANCE OUTPUTS LIGHT FOG AROUND SUNRISE SUNDAY, HOWEVER, MOST
DOES NOT AND GIVEN RELATIVELY DRY SOILS AND MORE ORGANIZED WINDS
RIGHT OFF THE DECK, AS WELL AS THE SPARSITY OF WISPY FOG THAT
OCCURRED THIS MORNING, DO NOT BELIEVE PROBABILITY OR IMPACTS ARE
SUFFICIENT TO JUSTIFY ADDING IT TO THE FORECAST FOR SUNDAY
MORNING.
DURING THE DAY ON SUNDAY, THE PACIFIC NORTHWEST 500 MB TROUGH
WILL BEGIN TO MOVE EAST NORTHEASTWARD AROUND THE PERIPHERY OF
THE HIGH PLAINS RIDGE, WHICH WILL BEGIN TO FLATTEN THE NORTHWARD
PART OF THE RIDGE AND ALLOW A SUBTLE SHORTWAVE IMPULSE TO
OVERTOP IT AHEAD OF THE MAIN TROUGH. THIS SHORTWAVE WILL MOVE
OVER OR NEAR IOWA ON SUNDAY NIGHT INTO MONDAY AND BRING A RETURN
OF RAIN CHANCES TO OUR FORECAST AREA. INITIALLY, THERE WILL BE
SUBSTANTIAL DRY AIR TO OVERCOME PER FORECAST SOUNDINGS, SO WHILE
A FEW MODEL SOLUTIONS ATTEMPT TO BRING ISOLATED SHOWERS INTO
OUR WESTERN AND SOUTHWESTERN COUNTIES LATE IN THE DAY SUNDAY,
HAVE HELD POPS OUT UNTIL LATER SUNDAY NIGHT WHEN SATURATION MAY
ACHIEVE SUFFICIENT DEPTH TO SUPPORT RAIN CHANCES. THESE CHANCES
WILL THEN CONTINUE DURING THE DAY MONDAY BEFORE FADING OUT AS
THE SHORTWAVE MOVES AWAY TO THE EAST. INSTABILITY WILL BE VERY
LIMITED WITH THIS SYSTEM SO WHILE SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE FORECAST, SEVERE WEATHER IS NOT CURRENTLY
ANTICIPATED.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
ISSUED AT 1237 PM CDT SAT AUG 22 2026
BY MONDAY NIGHT THE EASTERN 500 MB TROUGH WILL HAVE SHIFTED
OVER QUEBEC, WHILE THE WESTERN ONE CROSSES FROM SASKATCHEWAN
INTO MANITOBA, THEN SUBSEQUENTLY SHIFTS EAST SOUTHEASTWARD INTO
THE LAKE SUPERIOR REGION BY WEDNESDAY. IN IOWA THIS WILL BE
CONCURRENT WITH A VERY LIGHT SURFACE PRESSURE/FLOW PATTERN,
RESULTING IN NEBULOUS LOW RAIN CHANCES AT TIMES FROM MONDAY
NIGHT INTO WEDNESDAY. AS THE 500 MB TROUGH MOVES OVER LAKE
SUPERIOR, IT WILL HELP PUSH A LARGE SURFACE HIGH PRESSURE AREA
DOWN THE NORTHERN HIGH PLAINS AND MIDWEST DURING THIS TIME,
LATER BRINGING RELATIVELY COMFORTABLE AND DRY WEATHER FROM
AROUND WEDNESDAY NIGHT THROUGH FRIDAY. THE ONSET OF THE
INFLUENCE OF THIS SURFACE RIDGE WILL TAKE THE FORM OF A MODEST
TROUGH, PUSHING THROUGH AHEAD OF THE MAIN MID-LEVEL SHORTWAVE
SOMETIME AROUND TUESDAY NIGHT. DIFFERENCES IN TIMING AND THE
SHARPNESS OF THE TROUGH LEAD TO A HIGH VARIABILITY IN MODEL
SOLUTIONS, HOWEVER, THERE DOES APPEAR TO BE SOME POTENTIAL FOR
GOOD DESTABILIZATION ON TUESDAY AFTERNOON/EVENING AND ALSO
POTENTIAL FOR MODERATE DEEP-LAYER (0-6 KM) SHEAR OF PERHAPS
30-35 KT OR SO. AGAIN, THERE IS SIGNIFICANT VARIABILITY IN
THESE SOLUTIONS AND MUCH WILL DEPEND ON DIURNAL TIMING, BUT IT
IS POSSIBLE IF THE TROUGH HAS ENOUGH LOW-LEVEL CONVERGENCE AND
COMES THROUGH DURING PEAK DIURNAL HEATING TIME, THERE MAY BE A
NARROW WINDOW OF OPPORTUNITY FOR PULSE STORMS WITH A SEVERE
WEATHER THREAT LATE TUESDAY. A MORE LIKELY SCENARIO, HOWEVER,
IS THAT THE TROUGH COMES THROUGH OVERNIGHT WITH MUCH LESS
INSTABILITY AND/OR WEAKER SHEAR, OR THAT THE TROUGH IS TOO WEAK
AND LOW-LEVEL CONVERGENCE IS NOT SUFFICIENT TO SUPPORT STRONGER
UPDRAFTS, OR BOTH. BY NEXT WEEKEND, THE 500 MB PATTERN SHOULD
BEGIN TO SHIFT JUST A BIT, WITH THE RIDGE FLATTENING AND
SHIFTING A BIT TOWARD THE SOUTHWESTERN U.S., WHILE A MORE ZONAL
FLOW PATTERN SETS UP ACROSS THE NORTHERN CONUS AND IOWA. THIS
WOULD FAVOR A SOMEWHAT MORE ACTIVE WEATHER REGIME IN OUR
REGION, WITH PERSISTENT RAIN CHANCES LIKELY RETURNING. OF
COURSE THAT IS STILL A WEEK-PLUS OUT, BUT SOMETHING TO KEEP AN
EYE ON IN THE COMING DAYS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1045 PM CDT SAT AUG 22 2026
VFR CONDITIONS ARE EXPECTED ACROSS THE TERMINALS THROUGH THE
PERIOD. WHILE A LOW CHANCE REMAINS FOR FOG THIS MORNING, IT
SHOULD REMAIN QUITE ISOLATED AND TRANSIENT IN NATURE. CONFIDENCE
IS NOT HIGH ENOUGH TO INCLUDE AT ANY PARTICULAR SITE BUT WILL
AMEND AS NEEDED GIVEN TRENDS. CLOUD COVER WILL INCREASE
THROUGHOUT THE DAY, ESPECIALLY LATE IN THE PERIOD AS SHOWERS
MOVE INTO WESTERN IOWA. ANY SHOWERS WITH THIS INCOMING SYSTEM
ARE NOT EXPECTED TO IMPACT KFOD/KDSM UNTIL AFTER THE END OF THE
FORECAST PERIOD.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...LEE
LONG TERM...LEE
AVIATION...BURY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page