817
FXUS63 KDMX 071139
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
539 AM CST WED JAN 7 2026
...UPDATED FOR THE 12Z AVIATION DISCUSSION...
KEY MESSAGES
- AREAS OF DENSE FOG EAST AND NORTHEAST THIS MORNING.
- NEAR RECORD HIGH TEMPERATURES TODAY FOR PARTS OF CENTRAL AND
SOUTHERN IOWA. COOLER NORTH WITH PASSING MID-LEVEL CLOUDS.
- WIDESPREAD RAIN ARRIVING ON THURSDAY WITH A TRANSITION TO SNOW
LATE IN THE DAY AND NIGHT OVER THE NORTHWEST/NORTH CENTRAL.
- ANOTHER SYSTEM ARRIVES FRIDAY INTO EARLY SATURDAY WITH SOME
LIGHT SNOW POSSIBLE.
DISCUSSION
ISSUED AT 410 AM CST WED JAN 7 2026
FOG HAS ONCE AGAIN DEVELOPED ACROSS PARTS OF THE AREA THIS MORNING
AND IS MAINLY CONFINED TO EAST OF INTERSTATE 35. A STEEPENING AND
LOWERING LOW LEVEL INVERSION IS OCCURRING DUE TO WARM ADVECTION JUST
ABOVE THE SURFACE. WHILE THIS IS ENHANCING THE MOISTURE TRAPPING
BELOW THE INVERSION, THIS LOWERING INVERSION IS ALSO LIMITING THE
DEPTH OF THE FOG LAYER WHICH HAS BEEN EVIDENT ON WEBCAMS AND ON
SATELLITE IMAGERY. WHAT DOES THIS MEAN? IT MEANS THAT MUCH OF THE
AREA SHOULD HAVE SUNSHINE TODAY WITH THE FOG ERODING MUCH QUICKER
THAN THE PAST SEVERAL DAYS AND IT IS ONE OF THE FEW TIMES THIS TIME
OF YEAR THAT MODELS GUIDANCE IS TOO SLOW CLEARING THE STRATUS OUT.
THE SURFACE WARM FRONT WILL LIFT INTO THE STATE WITH THE SOUTHEAST
HALF OF THE AREA MAKING A RUN FOR RECORD HIGH TEMPERATURES TODAY
THAT ARE IN THE UPPER 50S TO LOW 60S. MID TO HIGH LEVEL CLOUDINESS
PASSING OVER THE NORTH/NORTHEAST HALF MAY LIMIT HIGH TEMPERATURES IN
THAT PART OF THE STATE BUT STILL HAVE MID TO UPPER 40S THERE.
THE FORECAST FOCUS FOR THIS CYCLE IS THE ACTIVE WEATHER THURSDAY
THROUGH SATURDAY AS SEVERAL SYSTEMS PASS THROUGH THE AREA. THE FIRST
STRONG SHORT WAVE AND ASSOCIATED SURFACE LOW PRESSURE ARRIVE ON
THURSDAY. TREMENDOUS LOW AND MID LEVEL MOISTURE TRANSPORT FROM THE
GULF REGION WILL LIFT NORTH AHEAD OF THIS SYSTEM AND FOCUS INTO
IOWA. PWAT VALUES OVER THE SOUTHEAST HALF OF IOWA ARE EXPECTED TO
EXCEED ONE INCH, WHICH IS AT THE 99TH PERCENTILE FOR EARLY TO MID
JANUARY. PERIODS OF ELEVATED INSTABILITY ALSO PASS ACROSS SOUTHEAST
IOWA AS THERE WILL BE TIMES WITH FAVORABLE MOIST ADIABATIC LAPSE
RATES FOR CONVECTIVE INSTABILITY. EFFICIENT RAINFALL RATES ARE
EXPECTED. THERE IS FROST IN THE GROUND INCLUDING AROUND 7 INCHES
HERE AT THE OFFICE. HOWEVER, WITH A WARM DAY TODAY AND OVERNIGHT, IT
WON'T TAKE LONG TO DRIVE THAT FROST OUT OF THE GROUND TO ALLOW FOR
WATER PENETRATION. WHILE SOME PONDING IS LIKELY, NOT ANTICIPATING
ANY HYDROLOGICAL ISSUES WITH THIS RAINFALL. THE AREA OF LOW PRESSURE
WILL LIFT ACROSS SOUTHEAST IOWA THURSDAY AFTERNOON LEADING TO COLD
ADVECTION IN THE NORTHWEST QUAD OF THE SYSTEM, INCLUDING
NORTHWEST/NORTH CENTRAL IOWA WHICH WILL LEAD TO AN EVENTUAL
TRANSITION TO SNOW OVER PARTS OF IOWA. AMOUNTS WILL DEPEND ON TIMING
OF THE TRANSITION AND THUS THE TIME PERIOD OF SNOW. SOUNDING
PROFILES SHOW DEEP SATURATION THROUGH THE 0C TO -3C LAYER DURING
THIS TRANSITION TO SNOW ALONG WITH STRONG VERTICAL ASCENT WITHIN
THIS LAYER. THIS SETUP IS VERY FAVORABLE FOR THE LARGE AND WET
AGGREGATE SNOWFLAKES THAT ARE STICKY AND HEAVY. THIS SCENARIO LEADS
TO QUICK SLIPPERY CONDITIONS ON ROADWAYS WITH AN IMMEDIATE FORMATION
OF SLUSH THAT IS EVENTUALLY BECOMES A VERY SLICK SNOW/SLUSH
COMBINATION. TREE DAMAGE AND SUBSEQUENT POWER OUTAGES CAN ALSO OCCUR
WHEN THIS TYPE OF SNOW FLAKE MORPHOLOGY BEGINS TO ACCUMULATE OVER 3-
4 INCHES AS IT ADDS SIGNIFICANT WEIGHT TO TREE BRANCHES. WILL
CONTINUE TO MONITOR THIS AS A CORRIDOR MAY OCCUR ESPECIALLY JUST
WEST/NORTHWEST OF THE RAIN/SNOW TRANSITION LINE THURSDAY NIGHT.
NOTE, AT THIS POINT, THE RAIN TO SNOW TRANSITION IN THE GRIDS MAY BE
A BIT DELAYED THAN REALITY, ESPECIALLY INTO NORTHWEST IOWA. ALSO,
SUBSTANTIALLY INCREASED POPS OVER THE NBM AND NEAR CONSSHORT, WHICH
INTRODUCES 100 POPS.
THAT SYSTEM WILL LIFT OUT LATE THURSDAY NIGHT AND WILL BE QUICKLY
FOLLOWED BY THE NEXT SYSTEM. AS EXPECTED AND NOTED IN PREVIOUS
FORECAST DISCUSSIONS, THE DETERMINISTIC MODELS ARE BOUNCING AROUND
WITH HOW THIS TIMEFRAME WAS GOING TO EVOLVE. THE MOST SIGNIFICANT
DEVELOPMENT IS THE THURSDAY SYSTEM DRAG THE GULF MOISTURE WITH IT
AND DRAGGING DRIER AIR SOUTH INTO THE NORTHERN PLAINS WITH AN
OVERALL SYSTEM TRACK FRIDAY AND INTO SATURDAY BEING A BIT FURTHER
SOUTH. SNOW IS STILL EXPECTED ACROSS PARTS OF IOWA. THIS SYSTEM
STILL OFF THE PACIFIC COAST OF WASHINGTON, A BETTER UPPER AIR
SAMPLING AND THUS BETTER MODEL HANDLING OF THE SYSTEM WILL IMPROVE
OVER THE NEXT 24 HRS. THE CANADIAN UPPER LOW IS BEING BETTER SAMPLED
NOW AND IS HAVING SOME IMPACT ON THIS SHIFT SOUTHWARD AS IT ARRIVES
AS A CLOSED LOW INTO THE NORTHERN PLAINS LATE FRIDAY AND FRIDAY
NIGHT. COLDER AIR WILL THEN FOLLOW FOR THE WEEKEND THOUGH WARM
ADVECTION IS ALREADY UNDERWAY ON SUNDAY.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 534 AM CST WED JAN 7 2026
AREAS OF SHALLOW DENSE FOG ARE STILL ONGOING AT KALO/KOTM AND
JUST EAST OF KMCW/KDSM. CONDITIONS HAVE BEEN IMPROVING ON THE
WESTERN EDGE OF THE FOG AND TRANSLATING EASTWARD WHICH SUGGESTS
GUIDANCE IS TOO SLOW CLEARING THE FOG OUT THIS MORNING.
THEREFORE, SPED UP TIMING AT ALL SITES AND REMOVED FROM
KDSM/KMCW ALL TOGETHER. ONCE THE FOG DOES DISSIPATE, VFR
CONDITIONS ARE EXPECTED THROUGH THE PERIOD WILL THE WIND
BECOMING MORE SOUTHERLY. PERHAPS A PERIOD OF SUSTAINED 12KTS
WITH A FEW GUSTS AT KDSM/KOTM THIS AFTERNOON BEFORE DIMINISHING
AGAIN THIS EVENING.
DMX WATCHES/WARNINGS/ADVISORIES
DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR IAZ017-
026>028-037>039-049-050-061-062-074-075-086-097.
DISCUSSION...DONAVON
AVIATION...DONAVON
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