349
FXUS63 KDMX 011711
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1111 AM CST SAT MAR 1 2025
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- NOTABLY COOLER TODAY WITH HIGHS ONLY IN THE 30S, BUT THEN
WARMING AGAIN WITH HIGHS IN THE 50S MONDAY AND TUESDAY.
- SEVERAL CHANCES FOR PRECIPITATION IN THE COMING WEEK; HIGHEST
CHANCES (NEAR 100%) AND POTENTIAL AMOUNTS/IMPACTS FROM TUESDAY
INTO WEDNESDAY.
- COOLER AGAIN IN THE LATTER HALF OF THE WEEK, WITH HIGHS IN THE
30S AND 40S EACH DAY FROM WEDNESDAY THROUGH FRIDAY.
DISCUSSION
ISSUED AT 205 AM CST SAT MAR 1 2025
IT IS DRY AND MOSTLY CLEAR ACROSS IOWA EARLY THIS MORNING, BUT
NOTABLY COOLER THAN THE LAST SEVERAL DAYS AND WITH BLUSTERY
NORTHWEST WINDS OF GENERALLY 10 TO 20 MPH AND GUSTY. A LARGE
SURFACE HIGH PRESSURE AREA IS SINKING FROM SOUTHERN CANADA INTO
THE NORTH DAKOTA/MINNESOTA BORDER AREA, HOWEVER, AND WILL SLIDE
DOWN THE UPPER MISSISSIPPI RIVER VALLEY BY THIS EVENING. THE
RESULT WILL BE A CONTINUATION OF MOSTLY CLEAR SKIES AND COOLER
TEMPERATURES, BUT WITH STEADILY DECREASING WINDS THROUGH THE DAY
BECOMING NEARLY CALM AFTER SUNSET TONIGHT. WITH THE CENTER OF
THE HIGH ROUGHLY OVER NORTHEASTERN IOWA AT THAT TIME THIS WOULD
NORMALLY FAVOR EFFICIENT RADIATIONAL COOLING, HOWEVER, THERE ARE
TWO MITIGATING FACTORS. FIRST IS THAT ALL SNOW COVER IS LONG
GONE. SECOND IS THAT THE HIGH WILL THEN BE MOVING FAIRLY QUICKLY
OFF TO THE EAST OVERNIGHT, SUCH THAT BUT SUNRISE SUNDAY OUR
ENTIRE FORECAST AREA SHOULD SEE A RETURN OF SOUTHERLY BREEZES
AROUND 5-10 MPH. THIS SCENARIO SHOULD RESULT IN RAPIDLY FALLING
TEMPERATURES AFTER SUNSET, MAINLY IN THE NORTH AND EAST, THEN
SLOWING OR EVEN STEADYING LATER IN THE NIGHT. HAVE MAINTAINED A
TEMPERATURE FORECAST CLOSE TO THE PREVIOUS ISSUANCE, WITH
OVERNIGHT LOWS MOSTLY IN THE 15-20 DEGREE RANGE ONLY A FEW
DEGREES BELOW NORMALS FOR THE DATE. TEMPERATURES WILL THEN WARM
NICELY DURING THE DAY SUNDAY AS SOUTH SOUTHEASTERLY SURFACE FLOW
PICKS UP A BIT, PUSHING HIGHS INTO THE 45-55 DEGREE RANGE AND
MAKING FOR A FAIRLY PLEASANT AFTERNOON.
A MORE ACTIVE WEATHER PATTERN IS ON TAP FOR THE COMING WEEK,
WITH SEVERAL STORM SYSTEMS MOVING THROUGH THE CENTRAL U.S. THE
FIRST WILL COME IN THE FORM OF A COMPACT BUT ENERGETIC WAVE
TRAVELING FROM NEW MEXICO INTO OKLAHOMA ON SUNDAY, THEN FADING
OUT SUNDAY NIGHT AND MONDAY AS IT MOVES INTO THE SOUTHEASTERN
U.S. AS THIS SYSTEM MOVES BY WELL TO OUR SOUTH, UP HERE ON THE
NORTHERN FRINGES THERE WILL BE A GOOD PUSH OF WARM AIR ADVECTION
ALOFT GENERATING CLOUDS AND SOME PRECIPITATION CHANCES, HOWEVER,
THE FORCING FOR ASCENT IS WEAK AND FORECAST SOUNDINGS INDICATE
LOW-LEVEL DRY AIR INITIALLY, SO THOSE CHANCES ARE LIMITED TO
ONLY ABOUT 20% LATE SUNDAY NIGHT INTO MONDAY MORNING. SOUNDINGS
AND FORECAST TEMPERATURES SUPPORT LIGHT RAIN AS THE
PRECIPITATION TYPE IF ANY OCCURS, BUT EVEN IF IT DOES ANY
ACCUMULATIONS WOULD BE SCANT.
THE SECOND (AND STRONGEST OF THE WEEK) STORM SYSTEM WILL EMERGE
FROM THE ROCKIES AS A LARGE, DEEPENING CYCLONE OVER THE HIGH
PLAINS ON MONDAY NIGHT AND BY TUESDAY MORNING SHOULD BE CENTERED
SOMEWHERE AROUND WESTERN KANSAS. HOWEVER, EVEN BY THAT TIME
THERE IS SIGNIFICANT LATITUDINAL VARIATION BETWEEN DIFFERENT
MODEL RUNS, AND THIS TRACK VARIABILITY CONTINUES THEREAFTER AS
THE CYCLONE CONTINUES TO DEEPEN AND MOVES THROUGH THE MIDWEST ON
TUESDAY AND WEDNESDAY. GIVEN THE LARGE AND DYNAMIC NATURE OF
THE SYSTEM AND THE OPEN GULF STREAMING IN MOISTURE AHEAD OF IT,
THERE IS HIGH CONFIDENCE IN PRECIPITATION (NEAR 100% CHANCE)
ACROSS IOWA DURING THIS TIME, ESPECIALLY FROM TUESDAY AFTERNOON
THROUGH TUESDAY NIGHT, BUT LOWER CONFIDENCE IN PRECIPITATION
TYPES. CONCEPTUAL MODELS SUPPORT A LIKELIHOOD OF TWO ROUNDS OF
PRECIPITATION, THE FIRST COMING IN THE FORM OF SHOWERS AND
THUNDERSTORMS IN A LONG LINE PRECEDING AND TRAILING SOUTHWARD
FROM THE CYCLONE, AND THE SECOND COMING IN THE FORM OF
WIDESPREAD STRATIFORM PRECIPITATION AROUND THE NORTHERN AND
WESTERN FLANK ON THE BACKSIDE OF THE LOW. CERTAINLY ALL
PRECIPITATION IN THE FIRST ROUND WILL COME IN THE FORM OF
RAIN/THUNDERSTORMS, BUT IT IS DIFFICULT TO TELL HOW MUCH OF OUR
SERVICE AREA THESE WILL EFFECT. THE HIGHEST CHANCES WOULD BE IN
OUR SOUTHEASTERN COUNTIES CLOSER TO THE LOW TRACK, WITH
DIMINISHING CHANCES FURTHER NORTHWEST. HOWEVER, THE SECOND ROUND
OF PRECIPITATION COULD COME IN THE FORM OF RAIN CHANGING TO
SNOW, DEPENDING ON THE TIMING OF THE PRECIPITATION COUPLED WITH
COLD AIR ADVECTION BEHIND THE SYSTEM, AS FORECAST WEDNESDAY
MORNING LOW TEMPERATURES CURRENTLY RANGE FROM THE MID 20S
NORTHWEST TO THE MID 30S SOUTHEAST. THESE DETAILS WILL BE WORKED
OUT OVER THE COMING DAYS, AS THE 500 MB TROUGH THAT IS THE
GENESIS OF THE EVENT WILL NOT EVEN COME ASHORE OVER THE PACIFIC
U.S. COAST UNTIL LATE SUNDAY.
THE THIRD AND FINAL STORM SYSTEM NEXT WEEK WILL CROSS THE
ROCKIES AROUND THURSDAY OR THURSDAY NIGHT BUT MAY BE BROADER AND
MORE STRETCHED IN NATURE. THIS BRINGS A RETURN OF LOWER 30-40%
POPS ACROSS MUCH OF OUR AREA THURSDAY NIGHT AND FRIDAY, BUT
AGAIN VARIATIONS IN TEMPERATURE PROFILES LEAVE PRECIPITATION
TYPE A QUESTION MARK AT THIS RANGE.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1109 AM CST SAT MAR 1 2025
VFR CONDITIONS REMAIN IN THE FORECAST THROUGH THE PERIOD. THE
WIND WILL CONTINUE TO DIMINISH THROUGH THE AFTERNOON THEN BECOME
LIGHT AND VARIABLE AT TIMES TONIGHT. THE WIND WILL BECOME
SOUTH/SOUTHEAST BY MID SUNDAY MORNING. SCT CUMULUS WITH BASES
AROUND 3 KFT OVER SOUTHEAST IOWA IS ERODING AND NOT EXPECTED TO
IMPACT KOTM. OTHERWISE MID TO HIGH LEVEL CLOUDS THROUGH TONIGHT.
A FEW CLOUDS WITH BASES AROUND 5 KFT ARE POSSIBLE BY SUNDAY
MORNING.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...LEE
AVIATION...DONAVON
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