518
FXUS63 KLOT 292343
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
643 PM CDT SAT MAR 29 2025
KEY MESSAGES
- A COLD FRONT WILL STALL NEAR LAKE MICHIGAN AND THE WISCONSIN
STATE LINE, LEADING TO A TIGHT GRADIENT IN OVERNIGHT LOW
TEMPERATURES (LOW 40S NORTH OF THE FRONT, 60S ELSEWHERE).
- THERE IS A THREAT FOR SEVERE WEATHER AREAWIDE ON SUNDAY
ESPECIALLY BETWEEN 2 AND 6 PM CDT THAT INCLUDES ALL HAZARDS
(DAMAGING WINDS, DAMAGING HAIL, TORNADOES).
- A PERIOD OF BELOW AVERAGE TEMPERATURES IS EXPECTED MONDAY AND
TUESDAY BEFORE ANOTHER STORM SYSTEM (WITH A THREAT FOR SEVERE
WEATHER) ARRIVES ON WEDNESDAY.
DISCUSSION
ISSUED AT 306 PM CDT SAT MAR 29 2025
THROUGH SUNDAY NIGHT:
SHOWERS ASSOCIATED WITH A WAVE MOVING ACROSS INDIANA THIS
AFTERNOON AND EARLY EVENING WILL GRADUALLY END ACROSS THE
SOUTHEAST HALF OF THE CWA. MEANWHILE, AN AREA OF WEAK ISENTROPIC
ASCENT WILL BRING SCATTERED SHOWERS ACROSS THE FAR NORTHWEST
CWA THROUGH THIS EVENING. OTHERWISE, BROAD DIFFLUENCE ALOFT OVER
MODEST LOW-LEVEL MOISTURE WILL SUPPORT AT LEAST WIDELY
SCATTERED SHOWERS AT ANY TIME OVER THE AREA THROUGH SUNRISE
SUNDAY.
THE BACK-DOOR COLD FRONT, LIKELY ENHANCED BY A LAKE BREEZE, IS
DRIFTING SOUTHWESTWARD OVER FAR NORTHEAST ILLINOIS THIS
AFTERNOON, WITH A 30 DEGREE TEMP GRADIENT OBSERVED ACROSS THE
BOUNDARY. HAVE CONTINUED TO FAVOR GUIDANCE DEPICTING A MORE
AGGRESSIVE INWARD PUSH OF THE FRONT, AND EVEN THAT GUIDANCE HAS
BEEN RUNNING AN HOUR OR TWO TOO SLOW. THE FRONT WILL BEGIN
CONTRACTING THIS EVENING IN RESPONSE TO THE BROADER LOW-LEVEL
FLOW AHEAD OF SUNDAY'S SYSTEM. SO WE SHOULD SEE THE BOUNDARY
STALL SOMEWHERE ALONG THE I-88 CORRIDOR AND INTO THE SOUTH SIDE
OF CHICAGO LATER THIS EVENING BEFORE SLOWLY RETREATING NORTH AS
A WARM FRONT TOWARD SUNRISE. THIS WILL ULTIMATELY RESULT IN AN
UNSEASONABLY MILD NIGHT WITH LOWS AROUND 60 SOUTH OF THE
BOUNDARY, WHEREAS TEMPS SETTLE IN THE 40S NORTH OF THE BOUNDARY.
ADDITIONALLY, HAVE DELAYED THE DEVELOPMENT OF FOG BEHIND THE
FRONT TO AFTER SUNSET, BUT STILL EXPECT TO SEE PATCHY FOG INLAND
AND POSSIBLY DENSE FOG OVER THE LAKE AND ALONG THE SHORE.
AN INITIAL AREA OF STEEPENING MID-LEVEL LAPSE RATES OVER A
SMALL 40- 50 KNOT LLJ SHOULD FORCE A POCKET OF ELEVATED STORMS
ACROSS AT LEAST SOME OF THE NORTHWEST HALF OF THE CWA SUNDAY
MORNING, WITH A CHANCE OF LOCALLY GUSTY WINDS AND SMALL HAIL.
A SIGNIFICANT CHANGE IN FORECAST GUIDANCE TODAY HAS BEEN TOWARD
AN OVERALL STRONGER SURFACE LOW AND MID-LEVEL WAVE ON SUNDAY
OWING TO CONVECTIVE ENHANCEMENT OF AN MCS OVER OKLAHOMA AND
KANSAS LATE THIS EVENING AND OVERNIGHT. THIS WILL POTENTIALLY
RESULT IN A DEEPENING SURFACE LOW OVER NORTHWEST ILLINOIS DURING
THE DAY, WHICH HAS NOTABLE IMPLICATIONS ON THUNDERSTORM MODE
AND EVOLUTION OVER NORTHERN ILLINOIS DURING THE AFTERNOON.
THE DYNAMIC SET-UP OF A SLIGHTLY NEGATIVELY TROUGH AND LEFT-
EXIT OF A POTENT UPPER-LEVEL JET STREAK WILL SUPPORT PLENTY OF
FORCING OVER THE AREA, SO THE POTENTIAL FOR SEVERE CONVECTION
WILL DEPEND ON 1) RECOVERY OF THE THERMODYNAMIC ENVIRONMENT
BEHIND ANY MORNING CONVECTION AND 2) THE ABUNDANCE OF LINGERING
LOW-LEVEL CLOUD COVER TRAPPED UNDER AN EML LATE MORNING INTO THE
AFTERNOON. SUNDAY WILL REQUIRE CLOSE MESOANALYSIS OF LOW-LEVEL
THERMODYNAMIC TRENDS, BUT IF ANY DETRIMENTAL EFFECTS OF THE TWO
SCENARIOS LISTED ABOVE ARE MINIMIZED, SEVERE THUNDERSTORMS ARE
LIKELY ACROSS MUCH OF THE FORECAST AREA DURING THE AFTERNOON.
THE FAVORED STORM MODE IS A STRONGLY FORCED LINE WITH EMBEDDED
SUPERCELL STRUCTURES. DAMAGING WINDS WILL BE THE PRIMARY THREAT,
THOUGH THE PRESENCE OF ANY SUPERCELLS AS WELL AS ANY NORTHWEST
ARCING LINE OF CONVECTION INTERACTING WITH MOISTURE POOLING NEAR
THE RETREATING WARM FRONT WILL POSE A LOCALIZED TORNADO THREAT.
FALLING TEMPS BEHIND THE STORMS/COLD FRONT WILL RESULT IN A
POTENTIAL CHANGEOVER OF PRECIP TO WET SNOW WITH LITTLE TO NO
ACCUMULATION FOR A FEW HOURS IN THE TRAILING DEFORMATION AXIS
LATE SUNDAY NIGHT.
KLUBER
MONDAY THROUGH SATURDAY:
IN THE WAKE OF THE LOW PRESSURE SYSTEM RESPONSIBLE FOR STORMY
WEATHER ON SUNDAY, UPPER-LEVEL TROUGHING WITH AN ASSOCIATED LOW-
LEVEL COLD POOL WILL MEANDER THROUGH THE GREAT LAKES LEADING TO
A PERIOD OF BELOW AVERAGE TEMPERATURES. TEMPERATURES ON MONDAY
WILL STRUGGLE TO CLIMB OUT OF THE 40S (UPPER 30S LAKESIDE),
WHICH WILL FEEL EVEN COLDER GIVEN THE EXPECTATION FOR BRISK
NORTHERLY WINDS AND OVERCAST SKIES. A FAVORABLY LONG FETCH DOWN
THE SPINE OF LAKE MICHIGAN MAY ALLOW FOR A FEW FLURRIES INTO
NORTHWESTERN INDIANA AS WELL, IN SPITE OF OTHERWISE MARGINAL
THERMODYNAMICS. A SURFACE HIGH IS THEN POISED TO SLIDE THROUGH
THE REGION MONDAY NIGHT, SETTING THE STAGE FOR CLEARING, LIGHT
WINDS, AND OTHERWISE IDEAL CONDITIONS FOR SURFACE
DECOUPLING/AGGRESSIVE RADIATIONAL COOLING. LOWS SHOULD HAVE NO
ISSUE FALLING INTO THE UPPER 20S AREAWIDE. IN ALL, MONDAY/MONDAY
NIGHT LOOK CHILLY.
ATTENTION THEN TURNS TOWARD THE NEXT STORM SYSTEM WHICH IS
EXPECTED TO BARREL THROUGH THE CENTRAL UNITED STATES TUESDAY
THROUGH THURSDAY. GENERALLY SPEAKING, INCREASING LOW-LEVEL WARM
AIR ADVECTION AHEAD OF THE APPROACHING UPPER-LEVEL TROUGH AND
SURFACE LOW ON TUESDAY SHOULD PROVIDE A BOOST OF TEMPERATURES
TOWARD THE UPPER 40S TO LOWER 50S, FOLLOWED BY HIGHS IN THE
UPPER 60S TO LOWER 70S ON WEDNESDAY. ENSEMBLE MODEL GUIDANCE
FAVORS THE SURFACE LOW LIFTING EAST-NORTHEASTWARD TOWARD THE
UPPER GREAT LAKES IN THE TUESDAY NIGHT THROUGH WEDNESDAY
TIMEFRAME, WHICH WILL PRESENT ANOTHER PERIOD OF STRONG
SOUTHWESTERLY WINDS AS WELL AS SHOWERS AND THUNDERSTORMS TO OUR
REGION. CONCEPTUALLY, THE PATTERN CERTAINLY LOOKS SUPPORTIVE OF
SEVERE WEATHER ACROSS A WIDE SWATH OF THE CENTRAL/EASTERN US
(AND INDEED, THE STORM PREDICTION CENTER ALREADY HAS OUR ENTIRE
AREA IN AN EQUIVALENT LEVEL 2/5 THREAT LEVEL FOR SEVERE WEATHER
FOR WEDNESDAY). WE'LL BE ABLE TO ASSESS THE DETAILS AS WE GET
CLOSER.
THURSDAY ONWARD, ENSEMBLE MODEL GUIDANCE EXHIBITS FAIR
CONSISTENCY IN DEPICTING PERSISTENT SOUTHWESTERLY LOW-LEVEL FLOW
ACROSS THE CENTRAL US IN RESPONSE TO DEEP TROUGHING BECOMING
ESTABLISHED ACROSS THE DESERT SOUTHWEST. SUCH A PATTERN MAY
PROVIDE CONTINUED OPPORTUNITIES FOR RAIN IN OUR GENERAL REGION,
THOUGH ALL WILL HINGE ON THE EVENTUAL EVOLUTION OF THE WESTERN
TROUGH AND LOCATION OF A REMNANT LOW-LEVEL BAROCLINIC ZONE. FOR
NOW, NBM-DELIVERED SEASONABLE TEMPERATURES AND CONTINUED
CHANCES FOR RAIN SEEMED FAIR.
BORCHARDT
AVIATION /00Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 643 PM CDT SAT MAR 29 2025
AVIATION WEATHER CONCERNS ARE:
- CIGS LOWERING TO IFR TONIGHT WITH PERIODS OF SHOWERS AND
DRIZZLE.
- WIND SPEED/DIRECTION TRENDS WITH A STALLING FRONT TONIGHT.
LOW CONFIDENCE ON WINDS, ESPECIALLY TIMING THE RETURN OF GUSTY
SOUTH/SOUTHWEST WINDS SUNDAY MORNING.
- SEVERAL CHANCES FOR SHOWERS AND STORMS SUNDAY. ONE EARLY-MID
MORNING, ANOTHER MID-LATE MORNING, AND A FINAL AROUND MID
AFTERNOON.
A BACKDOOR COLD FRONT HAS SLIPPED INTO THE REGION THIS EVENING,
AND CURRENTLY STRETCHES FROM NEAR A RFD TO DPA TO DOWNTOWN
CHICAGO LINE. THE FRONT'S FORWARD PROGRESS HAS SLOWED RECENTLY,
LEADING TO LOWER CONFIDENCE ON TIMING INTO MDW, AND HAVE PUSHED
THIS BACK A SMIDGE. THE FRONT MAY NOT MAKE IT TO GYY, AND HAVE
CONTINUED WITH SOUTHERLY WINDS THERE, BUT WILL CLOSELY MONITOR
OBSERVATIONS.
PERIODS OF SHOWERS AND DRIZZLE ARE EXPECTED TONIGHT,
PARTICULARLY ACROSS THE CHICAGO-AREA TERMINALS. THE DEEPEST
MOISTURE AND STEADIEST ASCENT LOOKS TO ARRIVE LATE THIS EVENING
INTO THE OVERNIGHT HOURS, AND HAVE FOCUSED TEMPO GROUPS FOR
LOWER VSBYS DURING THIS PERIOD AT ORD/MDW AS A RESULT. IFR CIGS
ARE EXPECTED TO SLOWLY OOZE INLAND OFF THE LAKE TONIGHT.
ON SUNDAY MORNING, THE AFOREMENTIONED FRONT WILL BEGIN TO LIFT
BACK NORTHWARDS. TIMING THE RETURN OF GUSTY SOUTH/SOUTHWESTERLY
WINDS REMAINS UNCERTAIN, AND ALTERATIONS TO THIS TIMING CAN BE
EXPECTED.
THERE ARE THREE MAIN WINDOWS WHERE HEAVIER SHOWERS/STORMS WILL
BE POSSIBLE ON SUNDAY. THE FIRST IS DURING THE PRE-DAWN INTO
EARLY MORNING HOURS. THIS REMAINS LOWER CONFIDENCE, AND TOO LOW
TO WARRANT THE ADDITION OF PROB30S. THE SECOND WINDOW WILL BE
MID-LATE MORNING. MAINTAINED THE INHERITED PROB30S FOR THIS
PERIOD, AND WILL REFINE THIS TIMEFRAME AS CONVECTION DEVELOPS
ACROSS OKLAHOMA AND KANSAS LATE THIS EVENING. THE FINAL WINDOW
WILL BE TIED TO A COLD FRONT DURING THE MID AFTERNOON. DIDN'T
SEE ENOUGH OF A REASON TO MAKE CHANGES TO THE INHERITED TEMPO
GROUPS FOR THIS LAST PERIOD OF STORMS. THESE MID AFTERNOON
STORMS MAY BE STRONG TO SEVERE.
ONCE CONVECTION CLEARS THE REGION SUNDAY EVENING, BREEZY WEST-
SOUTHWESTERLY WINDS WILL CONTINUE, ALONG WITH MVFR CIGS.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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