982
FXUS63 KDMX 061011
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
411 AM CST THU NOV 6 2025
KEY MESSAGES
- WARMER AND BREEZY TODAY. ELEVATED FIRE WEATHER CONCERNS
POSSIBLE NORTHEAST.
- SCATTERED LIGHT RAIN POSSIBLE SOUTHEAST THIS EVENING.
- WEEKEND SYSTEM BRINGING THE POTENTIAL FOR BOTH RAIN AND SNOW
TO CENTRAL IOWA, FOLLOWED BY MUCH COOLER TEMPERATURES ON
SUNDAY.
DISCUSSION
ISSUED AT 408 AM CST THU NOV 6 2025
>>> WINDS AND FIRE WEATHER CONCERNS TODAY, RAIN TONIGHT <<<
ANOTHER WAVE MOVING INTO THE AREA TODAY WILL BRING WARM SOUTHERLY
WINDS AS PRESSURE GRADIENTS TIGHTEN AHEAD OF THE COINCIDENT SURFACE
LOW. WHILE WARM AIR ADVECTION AND HEIGHT FALLS TYPICALLY DON'T
PROMOTE MIXING OF WINDS ALOFT, THE TIGHT SURFACE PRESSURE GRADIENT
WILL STILL WORK TO MIX OUT THE BOUNDARY LAYER TODAY, HELPING IT TAP
INTO A 30 TO 40 KT LOW LEVEL JET ALOFT. SHOULD WE ATTAIN ENOUGH
MIXING TO TAP INTO THESE STRONGER WINDS, WIND GUSTS 30 TO 35 MPH
WILL BE POSSIBLE, ESPECIALLY IN NORTHERN IOWA NEAREST TO THE SURFACE
LOW. DRY AIR WILL ALSO BE IN PLACE OVERHEAD, WHICH WILL BOTH HELP
PROMOTE MORE MIXING AND DROP DEWPOINTS NEAR THE SURFACE. THIS IS
ESPECIALLY TRUE IN EAST CENTRAL IOWA, WHERE WARM TEMPERATURES AND
DRY CONDITIONS COULD CAUSE RELATIVE HUMIDITIES TO DROP INTO THE 25
TO 30% RANGE. THIS, IN COMBINATION WITH BREEZY WINDS, WOULD SUGGEST
SOME ELEVATED FIRE WEATHER CONCERNS IN THE NORTH AND NORTHEAST
TODAY, ESPECIALLY AS FUELS DRY OUT. FORTUNATELY, HIGHER DEWPOINT AIR
WILL ADVECT IN THROUGH THE AFTERNOON, HELPING TO NEGATE THE DRY
CONDITIONS. BY THE AFTERNOON, A TROUGH MOVING THROUGH THE AREA WILL
COMBINE WITH INCREASING MOISTURE TO PRODUCE SOME SCATTERED RAIN IN
THE SOUTHEASTERN PORTIONS OF THE AREA TONIGHT INTO FRIDAY MORNING.
WHILE THERE WILL BE QUITE A BIT OF DRY AIR TO OVERCOME, TWO HEALTHY
MOISTURE STREAMS SHOULD BE ABLE TO SQUEAK OUT AT LEAST SOME LIGHT
RAIN, ALTHOUGH BETTER CHANCES WILL BE FARTHER EAST AND OUTSIDE
OUR FORECAST AREA.
>>> RAIN AND SNOW POTENTIAL SATURDAY <<<
THE SYSTEM MOVING THROUGH ON SATURDAY REMAINS ON TRACK TO BRING
PRECIPITATION BACK TO THE AREA. AN EMBEDDED SHORTWAVE WILL DROP
SOUTHEASTWARD THROUGH BROAD UPPER TROUGHING, PASSING THROUGH IOWA ON
SATURDAY. A SURFACE LOW PRESSURE WILL FORM IN RESPONSE TO THIS
SHORTWAVE. THIS SURFACE LOW WILL PASS ACROSS NORTHERN MISSOURI JUST
SOUTH OF THE IA/MO BORDER. A PATH LIKE THIS PUTS IOWA ON THE COLD
SIDE OF THE LOW IN THE DEFORMATION ZONE, BRINGING A CHILLY
PRECIPITATION TO CENTRAL IOWA. CONFIDENCE IS RELATIVELY HIGH IN AT
LEAST THIS PART OF THE EVENT, AS MOST OF GUIDANCE AGREES THAT THE
LOW WILL TRACK SOMEWHERE AROUND THE IA/MO BORDER, BARRING A FEW
OUTLIERS WITH A MORE NORTHERLY TRACK (SOME OF WHICH BEING
EXPERIMENTAL MODELS). AS A RESULT, CHANCES FOR PRECIPITATION ON
SATURDAY ARE IN THE 65 TO 75% RANGE FOR MUCH NORTHERN AND CENTRAL
IOWA, WITH SLIGHTLY LOWER CHANCES (40 TO 50%) FOR SOUTHERN IOWA.
WHERE THE FORECAST GETS TRICKY IS IN DETERMINING THE PRECIPITATION
TYPE THAT WILL OCCUR, SPECIFICALLY SNOW OR RAIN. THIS PART OF THE
EQUATION IS HEAVILY DEPENDENT ON HOW COLD TEMPERATURES CAN GET
BEFORE THE WAVE ARRIVES ON SATURDAY, AND THEN THE AMOUNT OF COLD AIR
AVAILABLE TO BE PULLED DOWN BY THE SYSTEM ITSELF AS IT PASSES
OVERHEAD. IF YOU'VE BEEN FOLLOWING ALONG WITH PREVIOUS DISCUSSIONS,
WE'VE TALKED ABOUT THE DIFFERENCE BETWEEN THE DETERMINISTIC GFS
(COLDER, SNOWIER) AND ECMWF (WARMER, LESS SNOW), WHICH HAD DIFFERING
TIMINGS FOR THE REINFORCING COLD AIR BEHIND THE SATURDAY SYSTEM.
HOWEVER, OVER THE LAST 24 HOURS, THIS REINFORCING WAVE HAS BEEN
SLOWING DOWN IN THE GFS AND TRENDING CLOSER TO THE ECMWF, NOW ONLY
SEPARATED BY AN HOUR OR TWO. AS A RESULT, TIMING AND PROGRESSION OF
BOTH TEMPERATURES/WETBULBS AT THE SURFACE AND TEMPERATURES ALOFT ARE
FAIRLY SIMILAR BETWEEN THE TWO MODELS. HOWEVER, THE RESULTANT
SNOWFALL FROM EACH 00Z MODEL IS SIGNIFICANTLY DIFFERENT, WITH THE
ECMWF STRUGGLING TO PRODUCE EVEN AN INCH OF SNOW, FALLING AS MOSTLY
RAIN. THE GFS FALLS AS MOSTLY SNOW, PRODUCING 1 TO 3 INCH SNOW
AMOUNTS OVER NORTH CENTRAL IOWA. THE DIFFERENCE? LIKELY ONLY A FEW
DEGREES IN THE LOWEST LEVELS AND HOW THE INDIVIDUAL MODELS HANDLE
THE SURFACE WARM LAYER. SEE, THE GFS IS PRODUCING SNOW PRIOR TO THE
ARRIVAL OF THE SUB-FREEZING TEMPERATURES, WITH SOUNDINGS
SHOWING A SHALLOW 1K FT LAYER ABOVE THE SURFACE THAT IS ABOVE
FREEZING. THE STRONG LIFT IN THE GFS IS ALLOWING SNOW TO FALL
THROUGH THIS LAYER, COOLING IT DYNAMICALLY. THE ECMWF HAS A
SIMILAR SHALLOW WARM LAYER PRESENT WHILE PRECIPITATION IS
FALLING, BUT IT'S SURFACE TEMPERATURES ARE ABOUT 2 DEGREES
WARMER AND LAYER SLIGHTLY DEEPER, CAUSING IT TO MELT THE SNOW
AND FALL AS RAIN. THEREFORE, WHILE MODELS ARE COMING INTO BETTER
AGREEMENT, TEMPERATURES AND RATES WILL BE VERY IMPORTANT TO
MONITOR IN THE COMING DAYS.
OUTSIDE OF THE DETERMINISTIC SPACE, ENSEMBLE PROBABILITIES FOR
MEASURABLE SNOWFALL HAVE CHANGED SLIGHTLY SINCE THIS TIME YESTERDAY.
THE LREF GRAND ENSEMBLE (COMBINATION OF GEFS, EPS, AND GEPS) NOW
SHOWS A 60 TO 70% CHANCE OF MEASURABLE SNOW FOR AREAS NORTH OF
HIGHWAY 30, WITH PROBABILITIES TAPERING OFF STEADILY SOUTH OF THERE.
THE NBM IS LESS CONVINCED, WITH PROBABILITIES FOR MEASURABLE SNOW
ONLY AROUND 40 TO 50% ALONG AND NORTH OF HIGHWAY 30. REGARDLESS, THE
GREATEST PROBABILITY FOR SNOWFALL AMONG THE ENSEMBLE GUIDANCE IS
ACROSS NORTHERN IOWA, WHICH MAKES SENSE PHYSICALLY AS THIS IS WHERE
SURFACE TEMPERATURES ARE MOST LIKLEY TO REACH FREEZING. WE ARE
APPROACHING THE HIGH RESOLUTION WINDOW NOW, WHICH SHOULD GIVE US
MORE DETAILS ON HOW THIS SYSTEM WILL EVOLVE THROUGH SATURDAY.
TEMPERATURES INEVITABLY COOL OFF BEHIND THE PRECIPITATION ON
SATURDAY, WITH LOWS OVERNIGHT SATURDAY INTO SUNDAY MORNING DROPPING
INTO THE UPPER TEENS TO MID 20S THEN HIGHS ONLY REACHING THE LOW TO
MID 30S ON SUNDAY. AS ELUDED TO IN THE DAY TIME DISCUSSION, THIS MAY
LEAD TO RE-FREEZING OF RAIN OR WET SNOW THAT IS OVERTOPPED BY MUCH
COOLER AIR SATURDAY NIGHT, WHICH COULD MAKE TRAVEL HAZARDOUS.
FORTUNATELY, COLD CONDITIONS ONLY LAST THROUGH SUNDAY WITH
TEMPERATURES STEADILY WARMING INTO NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1034 PM CST WED NOV 5 2025
VFR CONDITIONS ARE EXPECTED ACROSS THE TERMINALS THROUGH THE
PERIOD. CLOUDS WILL INCREASE THROUGH THE DAY, ESPECIALLY BY
21-00Z AS A SYSTEM PASSES ACROSS THE REGION. MID-LEVEL CLOUDS
WILL BECOME COMMON, WITH RAIN SHOWERS POSSIBLE (AROUND 40%) AT
KOTM AFTER 00Z WHERE THE PROB30 MENTION WAS USED. WINDS WILL
INCREASE OUT OF THE SOUTH, WITH GUSTS REACHING UP TO 20-25+
KNOTS LATE MORNING THROUGH THE AFTERNOON, BEFORE TURNING LIGHT
AS WINDS SHIFT WESTERLY NEAR 06Z.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...DODSON
AVIATION...BURY
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