284
FXUS63 KLOT 100522
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1222 AM CDT SAT MAY 10 2025
KEY MESSAGES
- SHARPLY DROPPING TEMPERATURES ARE EXPECTED SATURDAY AFTERNOON
AND EVENING BEHIND A BACKDOOR COLD FRONT (SIMILAR TO THIS
PAST WEDNESDAY).
- TEMPERATURES WILL REBOUND TO ABOVE AVERAGE SUNDAY AND CONTINUE
THROUGH NEXT WEEK. HIGHS MAY APPROACH 90 BY THURSDAY FOR SOME
AREAS, AND SHORELINE LOCATIONS WILL REMAIN COOLER THAN AREAS
INLAND.
- CHANCES FOR SHOWERS AND STORMS WILL RETURN NEXT WEEK, THOUGH
MANY HOURS WILL ALSO BE DRY.
DISCUSSION
ISSUED AT 208 PM CDT FRI MAY 9 2025
THROUGH SATURDAY NIGHT:
AN APPROACHING SURFACE RIDGE CONTINUES TO SUPPORT A BEAUTIFUL
SPRING DAY WITH MOSTLY SUNNY SKIES, LOW HUMIDITY LEVELS,
RELATIVELY LIGHT WINDS, AND TEMPERATURES IN THE LOW TO MID 60S.
OF COURSE, SHORELINE LOCATIONS ARE SOME 15 TO 20 DEGREES COLDER
AS IS TYPICALLY THE CASE THIS TIME OF YEAR. WITH THE RIDGE
PASSING SOUTHWARD AND OVER OUR HEADS TONIGHT, THE EXPECTATION IS
FOR A CONTINUATION OF TRANQUIL CONDITIONS WITH CLEAR SKIES,
LIGHT WINDS, AND OVERNIGHT LOWS IN THE 40S. (WARMER
TEMPERATURES THIS AFTERNOON COMPARED TO YESTERDAY AFTERNOON WILL
ACT AS A HIGHER "STARTING POINT" FOR RADIATIONAL COOLING
TONIGHT, CURTAILING THE THREAT FOR FROST).
BY TOMORROW, ANTICYCLONIC FLOW ALONG THE NORTHERN SIDE OF THE
SURFACE RIDGE (BY THEN) TO OUR SOUTH WILL OPEN THE DOOR FOR A
LAKE-ENHANCED COLD FRONT TO RACE INTO NORTHEASTERN ILLINOIS AND
NORTHEASTERN INDIANA BY LATE MORNING AND SURGE
WEST/SOUTHWESTWARD ACROSS THE REST OF OUR AREA DURING THE
AFTERNOON. AS A RESULT, A WARM SPRING DAY WILL BE CUT SHORT BY
TUMBLING TEMPERATURES FROM LATE MORNING TO EARLY AFTERNOON.
TEMPERATURES WILL BE POISED TO DROP SOME 10 TO 15 DEGREES WITHIN
90 MINUTES OR SO BEHIND THE FRONT, WHICH WILL FEEL EVEN
CHILLIER GIVEN BLUSTERY EAST TO NORTHEASTERLY WINDS GUSTING 25
TO 30 MPH (3-HR PRESSURE RISES ON THE ORDER OF 3-4MB; NOT TOO
SHABBY FOR THIS TIME OF YEAR). IF OUT AND ABOUT TOMORROW
(PARTICULARLY IN NORTHEASTERN IL AND NORTHWESTERN IN), KEEP A
SWEATSHIRT OR JACKET HANDY! TOMORROW NIGHT DOES LOOK CHILLY AS
WELL WITH OVERNIGHT LOWS IN THE UPPER 30S NEAR WISCONSIN TO
LOWER 40S ELSEWHERE. SUPPOSE THERE COULD BE SOME PATCHY FROST
WHERE TEMPERATURES ARE COLDEST, THOUGH IT DOESN'T LOOK LIKE A
REPEAT OF LAST NIGHT (A CONTINUED EAST TO NORTHEASTERLY BREEZE
SHOULD WORK AGAINST TEMPERATURES AT GRASS LEVEL FALLING BELOW
FREEZING).
WITH UPPER-LEVEL RIDGING BUILDING INTO THE GREAT LAKES NORTH OF
A CUT-OFF LOW PRESSURE SYSTEM MEANDERING ALONG THE GULF COAST,
THE BRIEF COOLDOWN SATURDAY WILL BE SHORT-LIVED SETTING THE
TABLE FOR A SPECTACULAR MOTHER'S DAY. COMPLETELY SUNNY SKIES IN
TANDEM WITH LITTLE TO NO ADVECTION (THANKS TO FLOW AT OR BELOW
20KT THROUGH THE ENTIRE DEPTH OF THE TROPOSPHERE) WILL
EFFECTIVELY "BAKE" TEMPERATURES BACK INTO THE MID TO UPPER 70S.
THE EXCEPTION WILL BE ALONG THE LAKE MICHGIAN SHORELINE, WHERE
EASTERLY WINDS OF 5 TO 10 MPH WILL LEAD TO A LAKE SHADOW
EFFECTIVELY KEEPING TEMPERATURES IN THE UPPER 50S (LAKESIDE) TO
MID 60S (NEAR I-294).
MONDAY INTO TUESDAY, A PACIFIC TROUGH WILL DIVE INTO THE
NORTHWESTERN UNITED STATES AND ENCOURAGE THE AFOREMENTIONED CUT-
OFF LOW PRESSURE SYSTEM ALONG THE GULF COAST TO LIFT EAST-
NORTHEASTWARD TOWARD THE OHIO RIVER VALLEY. THE SPEED AT WHICH
THIS HAPPENS REMAINS SOMEWHAT VAST WITHIN ENSEMBLE MODEL
GUIDANCE. NEVERTHELESS, THE TREND SHOULD BE A GRADUAL INCREASE
IN HUMIDITY LEVELS EARLY NEXT WEEK WITH CORRESPONDING INCREASES
IN CHANCES FOR SHOWERS AND THUNDERSTORMS. AT THIS POINT,
TUESDAY CONTINUES TO BE THE FAVORED DAY FOR THE HIGHEST COVERAGE
OF SUCH ACTIVITY, WARRANTING 30 TO 50% POPS AND "SCATTERED"
COVERAGE WORDING. UNINSPIRING LAPSE RATES AROUND 6 K/KM AND A
DEARTH OF FLOW WITHIN THE CONVECTIVE LAYER POINT TOWARD
QUINTESSENTIAL SLOW-GROWING SPRINGTIME "POP-UP" THUNDERSTORMS
WITH THE MAIN HAZARDS OF OCCASIONAL LIGHTNING STRIKES AND
DOWNPOURS. HIGHS BOTH DAYS WILL BE WELL ABOVE AVERAGE AND IN THE
UPPER 70S TO LOWER 80S, SAVE FOR SHORELINE LOCATIONS (WHERE
EAST TO SOUTHEASTERLY FLOW WILL CONTINUE TO SERVE AS AN
EFFICIENT COOL DRAFT TO ABOUT I-294). OVERNIGHT LOWS WILL ALSO
BE UNSEASONABLY WARM AND IN THE LOWER 60S.
WEDNESDAY INTO EARLY THURSDAY, UPPER-LEVEL HEIGHT RISES AHEAD
OF THE PACIFIC TROUGH MOVING INTO THE SOUTHWESTERN UNITED STATES
WILL EFFECTIVELY SQUASH THE UPPER-LEVEL LOW WHILE LIFTING
INTO THE GREAT LAKES. AS A RESULT, DO THINK WEDNESDAY AND AT
LEAST THE FIRST HALF OF THURSDAY SHOULD BE LARGELY DRY.
INCREASING HUMIDITY LEVELS, AN INCREASINGLY SOUTHERLY COMPONENT
TO THE WIND, AND WARM OVERNIGHT LOW TEMPERATURES WILL SET THE
STAGE FOR THE WARMEST AIR THUS FAR THIS SPRING TO SURGE INTO THE
REGION. HIGHS ON WEDNESDAY WILL BE POISED TO CLIMB INTO THE LOW
TO MID 80S, FOLLOWED BY PERHAPS UPPER 80S TO NEAR 90 ON
THURSDAY. THE INFLUENCE OF THE LAKE ON TEMPERATURES MAY BE MORE
MUTED BY THURSDAY OWING TO THE STRONGER SOUTHERLY WINDS.
THURSDAY EVENING INTO FRIDAY, THE UPPER-LEVEL TROUGH WILL
FINALLY EJECT INTO THE MIDWEST. CONSIDERING WARM TEMPERATURES,
BUILDING HUMIDITY LEVELS, THE EASTWARD-ADVECTION OF AM EML
PLUME, AND INCREASING DEEP-LAYER FLOW AHEAD OF THE TROUGH, THE
THURSDAY TO FRIDAY TIMEFRAME WILL NEED TO BE WATCHED FOR SEVERE
WEATHER SOMEWHERE WITHIN THE BROAD MIDWEST TO GREAT LAKES
REGION. INDEED, AI/ML GUIDANCE ALREADY HIGHLIGHTS A BROAD REGION
ACROSS THE CENTRAL US AS HAVING A THREAT FOR SEVERE WEATHER
TOWARD THE END OF NEXT WEEK. WE'LL GET INTO MORE DETAILS AS WE
GET CLOSER AND CAN ACCORDINGLY ASSESS WHETHER OR NOT A THREAT
WILL MATERIALIZE LOCALLY. HOWEVER, CAN'T RESIST MENTIONING THAT
THE USUAL ISSUES WITH CAPPING AT THE BASE OF THE EML AS WELL AS
THE TIMING OF THE FORCING ALREADY LOOK TO BE PLAYERS THAT MAY
GOVERN WHETHER OR NOT WE SEE STORMS.
TAKING A STEP BACK, ENSEMBLE MODEL GUIDANCE FAVORS A
PATTERN CHARACTERIZED BY WESTERN-US TROUGHING PREVAILING THROUGH
THE LAST FEW WEEKS OF THE MONTH. SUCH A PATTERN WOULD TYPICALLY
FAVOR NEAR TO ABOVE AVERAGE TEMPERATURES AND REGULAR
OPPORTUNITIES FOR SHOWERS AND STORMS IN THE GREAT LAKES. SO, THE
ONGOING PERIOD OF DRY WEATHER (HOWEVER COMFORTABLE
TEMPERATURE-WISE) DOES HAVE AN END IN SIGHT.
BORCHARDT
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1220 AM CDT SAT MAY 10 2025
KEY MESSAGES:
- GUSTY NORTHEAST WIND SHIFT BEHIND BACKDOOR FRONT EXPECTED LATE
MORNING BETWEEN ~15-17Z.
LIGHT AND VARIABLE WINDS WILL SETTLE INTO A PREVAILING
SOUTHWESTERLY DIRECTION TOWARD DAYBREAK AND GRADUALLY VEER
NORTHWEST AHEAD OF AN APPROACHING BACKDOOR COLD FRONT. THE FRONT
IS EXPECTED TO MOVE ACROSS THE AREA BETWEEN ~15-17Z. EXPECT
SOME FINE TUNING TO THE TIMING OF THE GUSTY NORTHEAST WIND SHIFT
AS THE FRONT GETS CLOSER. WIND GUSTS IN THE MID-20 KT RANGE
WILL CONTINUE THROUGH THE AFTERNOON AND EARLY EVENING HOURS,
THEN GRADUALLY EASE OVERNIGHT.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 AM CDT
SUNDAY FOR THE IL AND IN NEARSHORE WATERS.
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