521
FXUS63 KDMX 051744
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1144 AM CST THU MAR 5 2026
...UPDATED FOR THE 18Z AVIATION DISCUSSION...
KEY MESSAGES
- PATCHY FOG AND A FEW LIGHT SHOWERS THIS MORNING, WITH DENSE
FOG POSSIBLE MAINLY FAR SOUTH AND SOUTHEAST.
- THUNDERSTORMS WILL CROSS IOWA FROM WEST SOUTHWEST TO EAST
NORTHEAST LATE TONIGHT INTO FRIDAY MORNING. A FEW STRONG TO
SEVERE STORMS WILL BE POSSIBLE, WITH LARGE HAIL THE PRIMARY
THREAT.
- STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE FROM LATE FRIDAY
AFTERNOON INTO EARLY FRIDAY NIGHT. UNCERTAINTY REMAINS IN THE
EVOLUTION OF THE INCOMING SYSTEM, WHICH WILL IMPACT THE
POTENTIAL SEVERITY AND TYPES OF HAZARDS. WATCH CLOSELY FOR
FORECAST UPDATES TODAY AND FRIDAY!
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 158 PM CST WED MAR 4 2026
SKIES REMAIN OVERCAST IN IOWA EARLY THIS MORNING WITH A WEAK
SURFACE HIGH PRESSURE RIDGE DRAPED ACROSS THE REGION. A FEW
SHOWERS HAVE MOVED INTO SOUTHERN IOWA AND PATCHY FOG IS BEING
OBSERVED AROUND THE AREA. THE FOG IS GENERALLY NOT DENSE, EXCEPT
IN FAR SOUTHERN AND SOUTHEASTERN IOWA WHERE ADVISORIES REMAIN
IN EFFECT THROUGH AROUND SUNRISE. AS THE SURFACE RIDGE GRADUALLY
MOVES AWAY TODAY WINDS WILL COME AROUND TO SOUTHEAST AND ANY
LINGERING SPRINKLES OR SHOWERS WILL EXIT LATER THIS MORNING,
YIELDING TO A MILD DAY AS TEMPERATURES CLIMB INTO THE 50S TO
LOWER 60S. IT REMAINS TO BE SEEN HOW MUCH CLEARING WILL OCCUR,
BUT WITH MODEST LOW-LEVEL MIXING THIS AFTERNOON AND THE WANING
INFLUENCE OF THE DEPARTING RIDGE, WE SHOULD SEE AT LEAST SOME
BREAKS IN THE CLOUDS.
A DEEP 500 MB TROUGH WILL SLOWLY CROSS THE ROCKIES TODAY INTO
TONIGHT, AND BY FRIDAY MORNING IT WILL EXTEND FROM THE FOUR
CORNERS REGION UP INTO THE NORTHERN HIGH PLAINS. DURING THE DAY
FRIDAY A LARGE VORTICITY ELEMENT WILL EJECT NORTHEASTWARD OUT OF
THE PARENT TROUGH, REACHING WESTERN KANSAS AND NEBRASKA BY
FRIDAY EVENING. AT THE SURFACE, A LOW PRESSURE TROUGH WILL FORM
ALONG THE LEE OF THE ROCKIES TODAY IN RESPONSE TO THE
APPROACHING 500 MB SYSTEM, AND BY FRIDAY THIS TROUGH WILL SHIFT
EASTWARD AND EXTEND FROM SOMEWHERE AROUND SOUTHWESTERN KANSAS UP
INTO EASTERN NEBRASKA AND WESTERN IOWA BY LATE IN THE DAY. THIS
IS A CLASSIC SYNOPTIC SETUP FOR CONVECTIVE POTENTIAL ACROSS OUR
REGION. INITIALLY, ON THURSDAY NIGHT, AS THE AFOREMENTIONED
SURFACE TROUGH BEGINS TO OOZE EASTWARD, A NOCTURNAL LOW-LEVEL
JET WILL SPREAD INTO IOWA. 850 MB WINDS OF 50-60 KT WILL
PROMOTE INCREASING MOISTURE AND ISENTROPIC LIFT, TRIGGERING
THUNDERSTORMS THAT WILL SPREAD OVER MUCH OF OUR FORECAST AREA
MAINLY AFTER MIDNIGHT INTO FRIDAY MORNING. FORECAST SOUNDINGS
INDICATE STRONG SHEAR PROFILES BUT ALSO AN EML THAT WILL
PROHIBIT ANY SURFACE-BASED CONVECTION OVERNIGHT AND LIMIT THE
MAGNITUDE OF SHEAR UPDRAFTS WILL BE ABLE TO TAP INTO. EVEN SO,
ALL INDICATIONS ARE THAT 700-500 MB LAPSE RATES WILL INITIALLY
BE QUITE STEEP, AND EVEN MODEST SHEAR MAGNITUDES ARE ENOUGH TO
JUSTIFY A RISK OF LARGE HAIL. THIS WILL BE MAXIMIZED DURING THE
FIRST COUPLE HOURS OF STORMS REACHING A GIVEN AREA, AS
THEREAFTER THE MID-LEVEL LAPSE RATES WILL DIMINISH AS THE COLUMN
SATURATES.
THE CONVECTIVE AND SEVERE WEATHER FORECAST FOR FRIDAY IS MORE
COMPLEX. AS THE 500 MB VORTICITY MAXIMUM AND CONCORDANT SURFACE
TROUGH APPROACH, DEEP-LAYER SHEAR WILL INCREASE THROUGH THE DAY
AND BY FRIDAY EVENING 0-6 KM BULK SHEAR VALUES WILL RANGE FROM
AROUND 40-50 KT IN OUR SOUTHEAST TO NEAR 60 KT IN OUR NORTHWEST.
FORECAST SOUNDINGS INDICATE LARGE CURVED HODOGRAPHS AND WHILE
THERE IS A RELATIVE LACK OF LOW-LEVEL BACKING TO MAXIMIZE NEAR-
SURFACE SHEAR, ANY RIGHT-MOVING STORMS WOULD QUICKLY REALIZE
LARGE HELICITY VALUES. THE BIGGEST FLY IN THE OINTMENT HERE WILL
BE THE DEGREE OF DESTABILIZATION THAT CAN OCCUR DURING THE DAY.
WHILE THERE WILL BE A LULL IN CONVECTION AFTER THE DEPARTING
STORMS FRIDAY MORNING, HIGH-RES MODELS VARY CONSIDERABLY ON THE
AMOUNT OF LINGERING SHOWER DEVELOPMENT THAT WILL OCCUR DURING
THE DAY, AS WELL AS HOW PERSISTENT THE ASSOCIATED STRATUS DECK
WILL BE. IF WE REMAIN OVERCAST THEN INSTABILITY WILL BE SOMEWHAT
LIMITED AND THE THREAT OF SURFACE-BASED CONVECTION LOWER, BUT
EVEN LOW CAPE VALUES IN THE PRESENCE OF STRONG DEEP-LAYER SHEAR
AND ROBUST DYNAMIC LIFT WOULD SUPPORT A THREAT OF STRONG
UPDRAFTS AND AT LEAST SOME HAIL. HOWEVER, IF ANY CLEARING CAN
OCCUR AT ALL, THEN INSTABILITY IN SUCH AREAS WOULD INCREASE
RAPIDLY FRIDAY AFTERNOON/EVENING, ENHANCING THE THREAT OF HAIL
AND STRONG WINDS. IN ADDITION, IF ANY SUCH STORMS ARE ABLE TO
ROOT TO THE SURFACE, AND PARTICULARLY IF DEVIANT MOTIONS OR
SMALL-SCALE BACKING OF THE WINDS ALLOW FOR SIGNIFICANTLY
ENHANCED VORTICITY INGESTION, THEN A TORNADO THREAT COULD BE
REALIZED. THE SPC OUTLOOKS REMAIN UNCHANGED THIS MORNING AND
COVER THIS POSSIBILITY WELL. WE WILL BE UPDATING THE FORECAST
FOR SEVERE WEATHER POTENTIAL CONTINUOUSLY OVER THE NEXT COUPLE
DAYS IN ANTICIPATION OF THIS EVENT.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 254 PM CST WED MAR 4 2026
THE SYSTEM QUICKLY DEPARTS WITH HIGH PRESSURE SETTLING ACROSS THE
AREA THROUGH THE WEEKEND. TEMPERATURES WILL BE MILD ON
SATURDAY, THEN WARMING FURTHER ON SUNDAY WITH INCREASING
SOUTHERLY FLOW INTO THE AREA. WARM AIR ADVECTION CONTINUES INTO
EARLY NEXT WEEK WITH 60S TO NEAR 70 BY MONDAY. THE NEXT WEEK
LOOKS TO REMAIN ACTIVE WITH SEVERAL WAVES MOVING ACROSS THE
CENTRAL US. THE NEXT CHANCE FOR PRECIPITATION IMPACTS ACROSS
IOWA LOOKS TO ARRIVE ON TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1144 AM CST THU MAR 5 2026
LINGERING PATCHY FOG WILL CONTINUE TO SLOWLY LIFT OVER THE NEXT
HOUR OR SO BEFORE IMPROVING AT ALL SITES, THOUGH LOW STRATUS IS
EXPECTED TO REMAIN THROUGH THE REST OF THE DAY, LEADING TO
CONTINUED MVFR CEILINGS ACROSS THE TERMINALS. CLOUDS ARE
EXPECTED TO LOWER FURTHER AFTER 06Z FROM SOUTHWEST TO NORTHEAST
AS SCATTERED SHOWERS AND THUNDERSTORMS SPREAD ACROSS THE STATE
INTO FRIDAY MORNING. UNCERTAINTY REMAINS ON THE EXACT TIMING AND
COVERAGE OF STORMS OVER ANY PARTICULAR TERMINAL, SO HAVE
CONTINUED USE OF PROB30 GROUPS AT THIS ISSUANCE AND WILL
CONTINUE TO REFINE OVER THE LATER FORECAST PACKAGES. LOW
VISIBILITIES AS WELL AS LOW CEILINGS ARE EXPECTED TO RESULT IN
WIDESPREAD IFR AND EVEN PERIODS OF LIFR CONDITIONS FRIDAY.
DMX WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...LEE
LONG TERM...HAGENHOFF
AVIATION...BURY
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