815
FXUS63 KLOT 292006
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
306 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 BECOMEING
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-LEVLE BAROCLINIC ZONE. FOR
NOW, NBM-DELIVERED SEASONABLE TEMPERATURES AND CONTINUED CHANCES
FOR RAIN SEEMED FAIR.
BORCHARDT
AVIATION /18Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 1247 PM CDT SAT MAR 29 2025
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- GUSTY SOUTHWESTERLY WINDS THROUGH THIS AFTERNOON
- POTENTIAL NORTHEAST WIND SHIFT AT ORD/MDW AROUND 00Z
- PERIOD OF IFR CONDITIONS OVERNIGHT REGIONWIDE
- 30% CHANCE OF TSRA DEVELOPING LATE SUNDAY AM, WITH BETTER
POTENTIAL IN THE AFTERNOON.
WINDS REMAIN OUT OF THE SOUTHWEST THIS AFTERNOON WITH GUSTS
AROUND 20 KNOTS. THERE IS A SMALL PATCH OF MOISTURE IN CENTRAL
ILLINOIS THAT IS MOVING NORTHWARD AND IS EXPECTED TO BRING
ANOTHER PERIOD OF -SHRA AT AREA TERMINALS LATER THIS AFTERNOON.
A COLD FRONT IS SLOWLY MOVING DOWN WISCONSIN, SWITCHING WIND
DIRECTIONS AROUND TO THE NORTHEAST WITH MVFR CIGS ALONG WITH IT.
WHILE ITS PROGRESSION HAS SLOWED DOWN OVER THE LAST COUPLE
HOURS, IT STILL REMAINS AHEAD OF MODEL GUIDANCE. THERE IS LOW
CONFIDENCE ON THE EXACT TIMING OF THE WINDS SWITCHING TO THE
NORTHEAST AT ORD AND MDW BUT THE EXPECTATION IS FOR IT TO ARRIVE
AROUND 00Z (+/- AN HOUR DEPENDING ON IF IT SPEEDS UP/SLOWS
DOWN).
BEHIND THIS FRONTAL ARRIVAL, CIGS ARE EXPECTED TO GRADUALLY
COME DOWN TO IFR LEVELS OVERNIGHT FOR ALL REGIONAL TERMINALS.
THERE IS A CHANCE FOR SOME LOWER VIS FROM MIST, OR MAYBE EVEN
SOME LIGHT RAIN, BUT THERE IS LOW CONFIDENCE IN VIS REDUCTIONS.
A LOW PRESSURE SYSTEM IS EXPECTED TO MOVE FROM THE CENTRAL
PLAINS AND NORTHEASTWARD THROUGH NORTHERN ILLINOIS TOMORROW.
SHOWERY ACTIVITY IS EXPECTED LATE MORNING THROUGH THE AFTERNOON.
THERE ARE TWO WINDOWS BEING MONITORED FOR THE THREAT OF THUNDER.
THE FIRST BEING IN THE LATE MORNING AS THE LOW ARRIVES. CHICAGO
TERMINALS WERE KEPT IN A PROB30 FOR THIS WINDOW WITH A TEMPO
BEING ADDED TO RFD AS MODELS ARE SHOWING BETTER CHANCES FOR
THUNDER TO THE NORTH AND WEST, THOUGH IT IS ENTIRELY POSSIBLE
THAT LATER TAF ISSUANCES OPT TO SWITCH TO A TEMPO. THERE IS
HIGHER CONFIDENCE FOR STRONG GUSTY WINDS AND THUNDERSTORMS IN
THE AFTERNOON ALLOWING FOR THE ADDITION OF TEMPOS IN THE ORD/MDW
TAF. DEPENDING ON THE COVERAGE OF STORMS IN THE MORNING, THE
OPPORTUNITY EXISTS FOR STORMS IN THE AFTERNOON TO BECOME STRONG
TO SEVERE.
DK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR
WILMETTE HARBOR IL TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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