460
FXUS63 KDVN 291956
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
256 PM CDT SAT MAR 29 2025
KEY MESSAGES
- THE SEVERE RISK ON SUNDAY HAS SHIFTED SLIGHTLY EAST. WHILE THE
LEVEL 1 AND 2 OUT OF 5 RISKS REMAIN, THE SEVERE RISK AREA
LOOKS TO BE ALONG AND EAST OF THE MISSISSIPPI RIVER. THE
PRIMARY RISKS ARE DAMAGING WINDS AND HAIL.
- THE ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH NEXT WEEK
WITH ADDITIONAL SYSTEMS MOVING THROUGH THE MIDWEST.
- TEMPERATURES WILL RISK ABOVE NORMAL AHEAD OF APPROACHING
SYSTEM AND THEN FALL BELOW NORMAL BEHIND EACH SYSTEM.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 254 PM CDT SAT MAR 29 2025
THROUGH THE LATE AFTERNOON AND EARLY EVENING SOME ISOLATED SHOWERS
OR SPRINKLES ARE POSSIBLE. A LARGE MAJORITY OF THE AREA WILL REMAIN
DRY. THE COLD FRONT WILL CONTINUE TO SAG SOUTH BEFORE STALLING
BETWEEN HIGHWAYS 20 AND 30.
BY LATE EVENING AND CONTINUING OVERNIGHT THE FIRST UPPER LEVEL
IMPULSE MOVES INTO THE AREA. THIS IMPULSE COMBINED WITH 25-30 KNOT
LLJ SHOULD BE ENOUGH TO INDUCE ISOLATED TO SCATTERED (20-40%)
SHOWERS AND SOME THUNDERSTORMS WITH THE BETTER COVERAGE WEST OF THE
MISSISSIPPI. GIVEN THE FREEZING LEVELS ALOFT, THE STRONGER SHOWERS
AND THUNDERSTORMS WOULD BE CAPABLE OF PRODUCING COPIOUS AMOUNTS OF
VERY SMALL HAIL. WHILE THE OVERALL PROBABILITY IS NO GREATER THAN 15
PERCENT, A ROGUE THUNDERSTORM COULD PRODUCE SOME HAIL UP TO 1 INCH.
AT SUNRISE SUNDAY A SECONDARY UPPER LEVEL DISTURBANCE SHOULD PUSH A
BAND OF RAIN WITH EMBEDDED THUNDERSTORMS THROUGH THE AREA. THIS
SECONDARY UPPER LEVEL DISTURBANCE LOOKS TO BE THE RESULT OF A
NOCTURNAL CONVECTIVE COMPLEX THAT DEVELOPS IN THE PLAINS AND RACES
NORTHEAST ACROSS MISSOURI. ONCE THIS DISTURBANCE PASSES THROUGH THE
AREA, DOWNWARD MOTION IN THE ATMOSPHERE BEHIND IT COULD SUPPRESS ANY
NEW CONVECTION WEST OF THE MISSISSIPPI DURING THE AFTERNOON.
THE BOUNDARIES PUT OUT BY THE SECOND DISTURBANCE AND STRENGTH OF THE
DOWNWARD MOTION BEHIND IT WILL BE THE KEY AS TO WHERE THE DIURNAL
SEVERE STORMS DEVELOP ON SUNDAY.
DATA FROM THE VERY HIGH RESOLUTION MODELS ARE GENERALLY POINTING TO
AREAS EAST OF THE MISSISSIPPI FOR SEVERE STORMS SUNDAY AFTERNOON,
WHICH, IS A TAD FURTHER EAST THAT WHAT WAS SUGGESTED YESTERDAY. ONE
OR TWO SOLUTIONS ARE SUGGESTING ALONG/EAST OF THE ILLINOIS RIVER
WITH CONVECTION SUPPRESSED ACROSS EASTERN IOWA AND WEST CENTRAL
ILLINOIS.
MESO-BETA AND GAMMA SCALES WILL BE KEY PLAYERS FOR STORM
DEVELOPMENT SUNDAY AFTERNOON. TAKING INTO ACCOUNT MODEL ERRORS,
AN EDUCATED GUESS WOULD PUT THE INITIATION POINT FOR THE DIURNAL
SEVERE STORMS BETWEEN THE MISSISSIPPI AND ILLINOIS RIVERS
SHORTLY AFTER MID- DAY SUNDAY. STORMS WOULD THEN QUICKLY GROW
UPSCALE INTO A BROKEN LINE AND MOVE EAST.
IF THIS SCENARIO IS CORRECT, THE OVERALL WINDOW FOR SEVERE STORMS IN
OUR EASTERN HALF WOULD BE FAIRLY NARROW AT 4 TO 5 HOURS.
SUNDAY NIGHT COLD AIR WILL GET RAPIDLY PULLED INTO THE AREA BEHIND
THE DEPARTING STORM. SHOWERS WILL CONTINUE DURING THE EVENING WITH
THE RAIN CHANGING OVER TO ALL SNOW BEFORE ENDING AFTER MIDNIGHT.
DUE TO THE WARMTH THE GROUND AND ROADS HAVE ABSORBED, ANY SNOW WILL
MELT ON CONTACT WITH ONLY A LIGHT DUSTING ON ELEVATED SURFACES.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 254 PM CDT SAT MAR 29 2025
MONDAY/MONDAY NIGHT
ASSESSMENT...HIGH CONFIDENCE ON COOLER BUT DRY CONDITIONS
THE MODEL CONSENSUS HAS A CANADIAN HIGH MOVING THROUGH THE MIDWEST
WITH COOLER THAN NORMAL TEMPERATURES FOR EARLY APRIL. ATTENTION THEN
TURNS TO THE NEXT SYSTEM.
TUESDAY THROUGH WEDNESDAY NIGHT
ASSESSMENT...HIGH CONFIDENCE ON ANOTHER STORM SYSTEM
THE OVERALL FLOW PATTERN REMAINS VERY CONDUCIVE FOR STRONG
EXTRATROPICAL STORM SYSTEMS AND THE GLOBAL MODELS HAVE BEEN
ADVERTISING A MID-WEEK SYSTEM FOR THE PAST SEVEN DAYS.
WHILE THERE ARE TIMING AND TRACK DIFFERENCES BETWEEN THE INDIVIDUAL
MODELS, THERE IS LOOSE AGREEMENT THAT TUESDAY NIGHT INTO WEDNESDAY
MORNING IS PRIME TIME FOR RAIN. THE PROBABILITIES FOR RAIN ARE; 20-
40% TUESDAY AFTERNOON, 80-90% TUESDAY NIGHT, 50-80% WEDNESDAY AND
20% WEDNESDAY EVENING.
THIS TIMING IS SLIGHTLY FASTER THAN PREVIOUS RUNS AND MAY OR MAY NOT
BE AN ANOMALY. IF THE FASTER TIMING PROVES TO BE CORRECT, THEN WHILE
STORMS WILL BE SEEN, THE STRENGTH OF THOSE STORMS WOULD BE IN
QUESTION.
SPC ALREADY HAS THE AREA HIGHLIGHTED IN A SLIGHT RISK OF SEVERE
STORMS ON WEDNESDAY BASED ON THE LARGE SCALE SYNOPTIC FEATURES.
WHILE THE SYNOPTIC SCALE FEATURES PRIME THE AREA, IT WILL BE THE
MESOSCALE (20-200 KM) FEATURES THAT WILL DICTATE THE WHEN AND WHERE
ANY SEVERE STORMS DEVELOP. THE CURRENT FASTER MOVEMENT OF THE LARGE
SCALE SYSTEM SUGGESTS THE HIGHER PROBABILITY OF STORMS BEING TUESDAY
NIGHT INTO WEDNESDAY MORNING WHICH, IF CORRECT, WOULD REMOVE THE
DIURNAL HEATING ASPECT USUALLY NEEDED TO GENERATE SEVERE STORMS.
HOWEVER, SOME OF THE LARGER SCALE FEATURES THAT CAN BE RESOLVED THIS
FAR OUT DO SUPPORT THE POTENTIAL FOR SEVERE STORMS.
REGARDLESS, TUESDAY NIGHT INTO WEDNESDAY WILL NEED TO BE WATCHED
CAREFULLY FOR THE OVERALL SEVERE RISK.
THURSDAY THROUGH SATURDAY
ASSESSMENT...MEDIUM CONFIDENCE ON RAIN CHANCES
THE GLOBAL MODELS HAVE A WEAK SYSTEM BRUSHING ACROSS THE SOUTHERN
HALF OF THE AREA. MOISTURE AVAILABILITY IS IN QUESTION REGARDING THE
CHANCES FOR RAIN BUT THE MODEL CONSENSUS HAS A 20 PERCENT CHANCE
THURSDAY/THURSDAY NIGHT.
THE GLOBAL MODELS HAVE WEAK BUT BETTER ESTABLISHED SYSTEM PROGGED TO
MOVE THROUGH THE MIDWEST LATE FRIDAY AFTERNOON INTO FRIDAY NIGHT.
THERE ARE MINOR TIMING DIFFERENCES BUT FRIDAY NIGHT HAS THE BETTER
CHANCES FOR RAIN, CURRENTLY AT 20-40 PERCENT. RAIN THAT DEVELOPS
FRIDAY NIGHT WILL LINGER INTO SATURDAY MORNING BEFORE ENDING.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1243 PM CDT SAT MAR 29 2025
FRONTAL BOUNDARY INTO EASTERN IOWA WILL STALL AND REMAIN NEARLY
STATIONARY UNTIL ABOUT 12Z/30 WHEN IT WILL BEGIN MOVING EAST.
WIND ALOFT INCREASE OVERNIGHT WHICH WILL BRING 20-40% COVERAGE
OF SHRA WITH A 10% RISK OF A TSRA. GIVEN THE LOW RISK, TSRA WAS
NOT INCLUDED IN THE 18Z TAFS. THERE IS A MARGINAL LLWS RISK IN
SOUTHEAST IOWA INTO WESTERN ILLINOIS WIDESPREAD MVFR WITH
POCKETS OF IFR TO DEVELOP BY 12Z/30 ACROSS EASTERN IOWA AND
NORTHERN ILLINOIS. AFTER 14Z/30 NEW SHRA/TSRA WILL DEVELOP WITH
BETTER COVERAGE ALONG/EAST OF THE MISSISSIPPI RIVER.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...08
LONG TERM...08
AVIATION...08
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