795
FXUS63 KLOT 300559
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1259 AM CDT SUN MAR 30 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.
UPDATE
ISSUED AT 901 PM CDT SAT MAR 29 2025
GENERALLY THE PREVAILING FORECAST REMAINS ON TRACK, BUT THERE
ARE A FEW TRENDS ABOUT SUNDAY'S THUNDERSTORM THREAT THAT ARE
WORTH DISCUSSING.
FIRST OFF, THE COLD FRONT THAT HAS BEEN WORKING ITS WAY
SOUTHWARD ACROSS NORTHEAST IL HAS STALLED ALONG A LINE FROM
ROCKFORD TO O'HARE TO CHICAGO. AREAS NORTH OF THE FRONT HAVE
SEEN NOTABLE TEMPERATURE DROPS WITH READINGS CURRENTLY IN THE
40S TO MID-50S WHILE THOSE TO THE SOUTH OF THE BOUNDARY REMAIN
IN THE LOW TO MID-60S. WHILE THE FRONT MAY STILL WOBBLE
SOUTHWARD A BIT OVER COOK COUNTY, IT SHOULD REMAIN GENERALLY
ALONG A ROCKFORD TO GARY LINE OVERNIGHT RESULTING IN A
SEASONABLE NIGHT FOR THOSE NORTH OF THE FRONT AND A MILD SUMMER-
LIKE NIGHT FOR THOSE TO THE SOUTH.
IN TERMS OF PRECIPITATION, POCKETS OF LIGHT SHOWERS AND DRIZZLE
HAVE CONTINUED TO FESTER ACROSS NORTHWEST IN AND FAR NORTHERN
IL DUE TO THE MODEST WARM ADVECTION OVERHEAD. GIVEN THAT THE
WARM ADVECTION WILL REMAIN IN PLACE TONIGHT ALONG WITH THE
MOISTURE RICH ATMOSPHERE, THE DRIZZLE/LIGHT SHOWERS ARE EXPECTED
TO PERSIST OFF AND ON THROUGH THE NIGHT. FURTHERMORE, THE
CONTINUED ADVECTION OF 50-60 DEGREE DEW POINTS OVER THE COLD
LAKE MICHIGAN WATERS HAS ALLOWED FOR SOME FOG TO DEVELOP OVER
THE OPEN WATERS. WITH WINDS NORTH OF THE FRONT OUT OF THE EAST-
NORTHEAST, IT IS LIKELY THAT THE FOG SHOULD OOZE INLAND THROUGH
THE NIGHT RESULTING IN SHARPLY REDUCED VISIBILITY (LOCALLY UNDER
2 MILES) FOR AREAS NEAR THE LAKE.
LOOKING AHEAD TO SUNDAY, THE POTENTIAL FOR A COUPLE ROUNDS OF
THUNDERSTORMS REMAINS WITH THE AFTERNOON ROUND BRINGING A
THREAT FOR SEVERE WEATHER. THUNDERSTORMS HAVE STARTED TO DEVELOP
ALONG A COLD FRONT STRETCHING FROM SOUTHERN NE/IA SOUTHWARD
INTO WEST-CENTRAL OK ASSOCIATED WITH A DEEPENING UPPER TROUGH
IN THE FOUR CORNERS AND THE SURFACE LOW OVER WESTERN IA. WHILE
THE THUNDERSTORMS DEVELOPING IN EASTERN KS ARE FORECAST TO
WEAKEN AS THEY RUN INTO A CAPPED ATMOSPHERE OVER WESTERN MO, THE
STORMS IN OK ARE FORECAST TO GROW INTO AN ORGANIZED CLUSTER.
THE AFOREMENTIONED CAP IS EXPECTED TO WEAKEN TONIGHT AS THE
TROUGH PIVOTS EAST AND COOLS THE MID-LEVELS WHICH SHOULD ALLOW
THE STORM CLUSTER TAKE ADVANTAGE OF THE 7.5-8.0 C/KM LAPSE RATES
IN MO AND REMAIN TOGETHER AS IT TRAVERSES INTO IL SUNDAY
MORNING. HOWEVER, THE MODEST MID-LEVEL FLOW SHOULD ALLOW THE
CLUSTER TO BECOME MORE OUTFLOW DOMINANT WITH TIME AND WEAKEN TO
SUB-SEVERE LIMITS BEFORE IT ENTERS IL. REGARDLESS, CONFIDENCE IS
GROWING THAT THIS STORM CLUSTER WILL SURVIVE AND MOVE INTO THE
WESTERN PARTS OF OUR CWA (ALONG I-39) AROUND 9-10 AM CDT AND
THEN TRACK ACROSS AT LEAST THE NORTHERN HALF OF THE AREA THROUGH
12-1 PM CDT. WHILE ANY SEVERE WEATHER WITH THIS MORNING ROUND
OF STORMS CONTINUES TO LOOK LOW, SOME LOCALLY GUSTY WINDS AND
SMALL HAIL MAY OCCUR WITH THE STORMS.
SHOULD THIS EXPECTATION REMAIN AS THE UPSTREAM ENVIRONMENT AND
RECENT FORECAST GUIDANCE TRENDS SUGGEST, IT WILL LIKELY USE UP
SOME OF THE INSTABILITY NEEDED FOR THE AFTERNOON STORMS ACROSS
PORTIONS OF NORTHERN IL. MEANING THAT THE THREAT FOR SEVERE
WEATHER MAY FOCUS FURTHER SOUTH WHERE A LESSER COVERAGE OF
MORNING SHOWERS IS EXPECTED AND THUS WHERE MORE DESTABILIZATION
CAN OCCUR. OBVIOUSLY THERE REMAINS A FAIR AMOUNT OF UNCERTAINTY
WITH THE DEGREE OF DESTABILIZATION AND HOW FAR SOUTH THE SEVERE
THREAT WILL GET PUSHED IF THINGS EVOLVE THIS WAY, BUT IT SEEMS
THAT AREAS ALONG AND SOUTH OF I-80 WILL HAVE THE GREATEST
POTENTIAL FOR SEVERE WEATHER. THAT SAID, EVERYONE IN NORTHERN IL
AND NORTHWEST IN (INCLUDING THOSE NORTH OF I-80) SHOULD REMAIN
WEATHER AWARE AND BE PREPARED FOR DAMAGING WINDS, HAIL, AND
TORNADOES SUNDAY AFTERNOON.
YACK
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 /06Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 1255 AM CDT SUN MAR 30 2025
KEY AVIATION MESSAGES:
- IFR/LIFR CIGS AND VSBYS PERSIST NORTH OF A STALLED FRONT
EARLY THIS MORNING IN STEADY DZ.
- LOW CONFIDENCE IN WIND TRENDS OVERNIGHT WITH THE FRONT
EXPECTED TO VERY GRADUALLY RETREAT BACK NORTH THROUGH THE
OVERNIGHT HOURS.
- MULTIPLE CHANCES FOR SHOWERS AND STORMS TODAY. ONE EARLY IN
THE MORNING TOWARD RFD, ANOTHER MID-LATE MORNING AREAWIDE, AND
A FINAL ROUND IN THE AFTERNOON.
A STALLED FRONT IS CURRENTLY DRAPED ALONG A LINE FROM ROCKFORD
TO NAPERVILLE TO WHITING, IN EARLY THIS MORNING. AREAS OF
DRIZZLE HAVE DEVELOPED AMIDST WARM AIR ADVECTION ATOP THE
BOUNDARY, WHICH HAS IN TURN LED TO CIGS DROPPING TO LOW-END IFR
TO AT TIMES LIFR ALONG WITH VSBYS DOWN TO IFR (LOWEST IN AREAS
FURTHEST NORTH OF THE BOUNDARY). EXPECT THESE CONDITIONS TO
CONTINUE FOR MUCH OF THE OVERNIGHT HOURS, THOUGH A VERY GRADUAL
IMPROVEMENT MAY BEGIN PRIOR TO DAYBREAK IF THE BOUNDARY LIFTS
NORTH A BIT FASTER THAN CURRENTLY INDICATED IN THE TAFS.
THERE REMAIN CHANCES FOR MULTIPLE ROUNDS OF SHOWERS AND STORMS
TODAY. THE FIRST WILL BE MAINLY TOWARD RFD WHERE THUNDERSTORMS
CURRENTLY OVER CENTRAL IA WILL DRIFT NORTHEAST TOWARD NORTHWEST
ILLINOIS. IT APPEARS THIS ACTIVITY MAY JUST MISS RFD TO THE
NORTH BUT GIVEN IT WILL BE QUITE CLOSE, OPTED TO ADD A PROB30
FOR TSRA THROUGH FROM 11-13Z. FURTHER UPSTREAM THUNDERSTORMS
CURRENTLY OVER OKLAHOMA ARE PROGGED TO LIFT NORTHEAST TOWARD THE
AREA TOWARD MID MORNING. THIS WILL BRING ADDITIONAL CHANCES FOR
ISOLATED TO WIDELY SCATTERED THUNDERSTORMS AREAWIDE IF IT HOLDS
TOGETHER, THOUGH CONFIDENCE IN COVERAGE REMAINS ON THE LOWER
SIDE.
THE AFTERNOON SEVERE WEATHER POTENTIAL REMAINS CONDITIONAL AND
WILL ULTIMATELY DEPEND ON THE MORNING STORMS. MORE
ROBUST/GREATER COVERAGE OF STORMS IN THE MORNING COULD SHIFT THE
BETTER POTENTIAL FOR AFTERNOON STORMS SOUTH OF I-80. HOWEVER,
LESS COVERAGE COULD LEAD TO STRONG TO SEVERE THUNDERSTORMS
LIFTING AS FAR NORTH AS THE CHICAGO AREA TERMINALS DURING THE
AFTERNOON. OPTED TO NOT MAKE ANY MAJOR CHANGES TO BOTH OF THESE
TIME PERIODS FOR NOW.
ONCE AFTERNOON STORMS SHIFT OFF TO THE SOUTHEAST BY THIS
EVENING, LIGHT WRAP AROUND PRECIPITATION MAY DRIFT INTO NORTHERN
ILLINOIS AFTER 0Z IN THE FORM OF LIGHT SNOW AND DRIZZLE.
QUESTIONS REMAIN AS TO WHETHER THERE WILL BE SUFFICIENT
SATURATION THIS FAR SOUTH SO OPTED TO HOLD OFF ON A FORMAL
MENTION IN THE TAFS WITH THIS UPDATE.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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