361
FXUS63 KDMX 080613
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
113 AM CDT FRI MAY 8 2026
KEY MESSAGES
- 20% CHANCE OF LIGHT SHOWERS THIS MORNING OVER SOUTHERN IOWA,
WITH A FEW SPRINKLES POSSIBLE INTO PORTIONS OF CENTRAL IOWA.
VERY LOW (10%) CHANCE OF LIGHT SHOWERS IN THE NORTHERN HALF OF
IOWA LATE THIS AFTERNOON AND EVENING.
- SEVERAL CHANCES FOR SHOWERS AND/OR THUNDERSTORMS FROM
SATURDAY NIGHT INTO NEXT WEEK. THERE CONTINUES TO BE NO
APPARENT SIGNAL FOR SIGNIFICANT OR WIDESPREAD SEVERE WEATHER
OR HEAVY RAINFALL WITH ANY STORM CHANCES.
SHORT TERM /THROUGH SATURDAY/
ISSUED AT 112 AM CDT FRI MAY 8 2026
A LARGE 500 MB GYRE IS CENTERED OVER HUDSON BAY, WITH BROAD
CYCLONIC FLOW EXTENDING FAR TO THE SOUTH, OVER IOWA AND MOST OF
THE CENTRAL U.S. A SHORTWAVE TROUGH IS ROUNDING THE BASE OF THIS
FLOW AND CURRENTLY GENERATING THICKENING CLOUDS OVER NEBRASKA
AND FAR SOUTHWESTERN IOWA. MEANWHILE, A LARGE SURFACE HIGH
PRESSURE AREA REMAINS DRAPED ACROSS THE GREAT LAKES AND
EXTENDING OVER IOWA, BUT IS STEADILY MOVING AWAY TO THE EAST. AS
IT RETREATS THIS MORNING AND THE SHORTWAVE ALOFT APPROACHES FROM
THE WEST, CLOUDS WILL SPREAD OVER OUR FORECAST AREA AND
PARTICULARLY OUR SOUTHERN COUNTIES WHERE THE INFLUENCE OF DRY
AIR ENTRAINMENT OUT OF THE SURFACE HIGH WILL BE SOMEWHAT LESS.
FORECAST SOUNDINGS SHOW A GOOD SATURATED LAYER ABOVE THE NEAR-
SURFACE DRY LAYER, WITH A FEW HOURS OF MODEST FORCING ASSOCIATED
WITH WEAK THETA-E ADVECTION ON THE LEADING FLANK OF THE
SHORTWAVE. THIS MAY BE ENOUGH TO GENERATE SOME SPRINKLES OR
LIGHT SHOWERS ACROSS SOUTHERN IOWA AND HAVE INCLUDED 10-20% POPS
TO ACCOUNT FOR THIS, BUT WITH LITTLE TO NO ACCUMULATION OR
IMPACT AND ANY SUCH LIGHT SHOWERS MOVING AWAY BY THE AFTERNOON.
A WEAK SURFACE TROUGH WILL ALSO MOVE THROUGH OUR AREA LATE TODAY
INTO TONIGHT, PUSHED THROUGH BY THE PASSING SHORTWAVE ALOFT, AND
MANY CAM SOLUTIONS GENERATE SMALL SHOWERS OR THUNDERSTORMS
ACROSS ABOUT THE NORTHERN HALF OF IOWA AS THE TROUGH PASSES
THROUGH. HOWEVER, FORECAST SOUNDINGS SHOW A MUCH DRIER COLUMN IN
THAT TIME AND AREA, WITH MINIMAL OPPORTUNITY FOR SATURATION OR
INSTABILITY. THIS WOULD SUPPORT PERHAPS A FEW HIGH-BASED
(AROUND 8-10 KFT) SHOWERS BUT WITH ANY ASSOCIATED LIGHT RAIN
EVAPORATING BEFORE IT REACHES THE SURFACE. WHILE BRIEF RAIN IS
THUS POSSIBLE, THE EXPECTED COVERAGE AND THE PROBABILITY OF
MEASURABLE ACCUMULATION ARE LOW ENOUGH THAT ONLY 10% CHANCES ARE
CARRIED IN THE FORECAST. IT SHOULD BE NOTED THAT WITH THE DEEP
DRY LAYER EXTENDING UP FROM THE SURFACE TO THE CLOUD BASE, IF
ANY SUCH SHOWERS DO MANAGE TO FORM THEN GUSTY WINDS MAY BE
POSSIBLE AS THEY PASS THROUGH.
MORE SUBTLE IMPULSES WILL ROUND THE BASE OF THE CYCLONIC 500 MB
FLOW ON SATURDAY. THE FIRST WILL PASS MAINLY TO OUR
NORTHEAST SATURDAY MORNING, AND MAY GENERATE LIGHT RAIN OVER
MINNESOTA AND WISCONSIN BUT SHOULD REMAIN NORTHEAST OF OUR
FORECAST AREA. THE SECOND WILL ROUND OVER THE HIGH PLAINS LATE
IN THE DAY AND APPROACH IOWA AROUND SATURDAY EVENING, EVEN AS A
LARGE SURFACE HIGH PRESSURE AREA BUILDS INTO THE REGION FROM THE
NORTHWEST. AS A RESULT, FORCING FOR SHOWER/THUNDERSTORM
DEVELOPMENT WILL INCREASE OVER SOUTHERN IOWA LATE SATURDAY BUT
ONCE AGAIN UNDERCUT BY DRY AIR ENTRAINMENT FROM NORTHWESTERLY
BREEZES OUT OF THE HIGH PRESSURE AREA. LOW (20-30%) RAIN CHANCES
ARE CARRIED IN OUR FAR SOUTH, BUT THE FORECAST REMAINS DRY FOR
THE BULK OF OUR AREA.
ASIDE FROM THE SPORADIC LIGHT RAIN CHANCES DESCRIBED ABOVE, THE
RAPIDLY ALTERNATING SERIES OF SURFACE HIGH PRESSURE AREAS AND
TROUGHS WILL SUPPORT CONTINUED SLOW AIRMASS MODIFICATION HEADING
INTO THE WEEKEND, WITH HIGH TEMPERATURES INCREASING A FEW
DEGREES TODAY AND AGAIN SATURDAY, WHEN READINGS WILL PEAK IN THE
MID TO UPPER 70S ACROSS OUR CENTRAL AND SOUTHERN COUNTIES IN THE
AFTERNOON, AND COULD EVEN REACH 80 DEGREES NEAR THE MISSOURI
BORDER.
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
ISSUED AT 145 PM CDT THU MAY 7 2026
BROAD CYCLONIC FLOW WILL CONTINUE OVER THE REGION THIS WEEKEND INTO
EARLY NEXT WEEK AS THE CLOSED, UPPER LOW GYRE CONTINUES OVER
HUDSON BAY AND EVENTUALLY MOVES AWAY FROM IT. THIS WILL KEEP
TEMPERATURES AROUND SEASONAL LEVELS IF NOT GENERALLY ABOVE
NORMAL. IN ADDITION, THERE WILL BE SHOWER AND/OR STORM CHANCES
IN AT LEAST SOME PORTION OF IOWA EVERY 36 TO 48 HOURS STARTING
SATURDAY NIGHT THROUGH ABOUT THE MIDDLE OF NEXT WEEK. AS
INDICATED BY THE PREVIOUS DISCUSSION, THE NEXT SHORTWAVE TROUGH
IS STAYING THE COURSE THIS MODEL CYCLE BEING MORE FOCUSED OVER
MISSOURI SATURDAY NIGHT. COMPARED TO THIS TIME YESTERDAY, QG
CONVERGENCE AND THETA-E ADVECTION IS NOW MAXIMIZED SOUTH OF
IOWA, THOUGH MAY STILL SEE A FEW SHOWERS SNEAK INTO FAR SOUTHERN
IOWA WITH THOSE CHANCES UP TO AROUND 30% - ABOUT 30 TO 40%
LOWER THAN THIS TIME YESTERDAY. THE NEXT CHANCE FOR SHOWERS AND
STORMS ARRIVES LATE MONDAY INTO TUESDAY MORNING. KINEMATICS ARE
IMPRESSIVE WITH A STRONG LOW LEVEL JET, BUT INSTABILITY IS
MARGINAL OWING TO THE NIGHTTIME PASSAGE OF THE SYSTEM POINTING
TO PERHAPS STRONG TO A FEW SEVERE STORMS. THIS IS IN LINE AND
CONTINUES TO BE SUPPORTED BY THE GFS/EC FORCED ML/AI SEVERE
PROBABILITY TOOLS WITH NO WIDESPREAD SEVERE WEATHER THREAT
APPARENT. WEDNESDAY AND BEYOND, PATTERN AGREEMENT DETERIORATES
LEADING TO LOWER CONFIDENCE IN ADDITIONAL STORM CHANCES.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1054 PM CDT THU MAY 7 2026
FEW CHANGES FROM PREVIOUS. VFR CONDITIONS ONGOING AND EXPECTED
TO CONTINUE THROUGH THE TAF PERIOD. LIGHT AND VARIABLE WINDS ARE
EXPECTED OVERNIGHT BUT WILL SETTLE OUT OF THE WEST AND INCREASE
INTO FRIDAY AFTERNOON, THE STRONGEST WINDS IN THE NORTH. CLOUDS
WILL INCREASE AGAIN THROUGH THE OVERNIGHT INTO EARLY FRIDAY
MORNING ESPECIALLY OVER SOUTHERN IOWA WITH SOME LOW CHANCES FOR
LIGHT RAIN NEAR KOTM DURING THE MORNING HOURS, AND SPRINKLES
INTO PORTIONS OF CENTRAL IOWA WHICH MAY REACH KDSM. CONFIDENCE
IN IMPACTS REMAINS LESS THAN 30% SO CONTINUED WITH NO EXPLICIT
MENTIONS, THOUGH SHOULD SPRINKLES/AN ISOLATED SHOWER OCCUR NEAR
A TERMINAL, IMPACTS WOULD REMAIN MINIMAL.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...LEE
LONG TERM...ANSORGE
AVIATION...05
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