618
FXUS63 KLOT 211125
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
525 AM CST FRI FEB 21 2025
KEY MESSAGES
- TEMPERATURES WILL MODERATE TO CLOSER TO NORMAL ON SATURDAY AND
THEN ABOVE NORMAL SUNDAY THROUGH TUESDAY.
- POTENTIAL (20-30%) FOR RAIN/SHOWERS MONDAY NIGHT, WITH BETTER
CHANCES (40-50%) FOR PRECIP WEDNESDAY AND WEDNESDAY NIGHT.
DISCUSSION
ISSUED AT 147 AM CST FRI FEB 21 2025
THROUGH SATURDAY:
AN EXPANSIVE 1041 HPA HIGH CENTERED OVER MISSOURI WILL DRIFT
EASTWARD TO THE MID-ATLANTIC STATES THROUGH SATURDAY AS STRONG
NORTHWEST FLOW ALOFT REMAINS MOSTLY ANCHORED OVER THE AREA. A
VIGOROUS WAVE SHIFTING SOUTHEAST ACROSS LAKE SUPERIOR THIS
EVENING AND ANOTHER WAVE TRACKING ESE FROM KANSAS TONIGHT MAY
BRUSH THE AREA WITH SOME HIGH CLOUDS TO THE NORTH AND SOUTH,
RESPECTIVELY. BUT WITH AN ANTECEDENT VERY DRY AIRMASS (PWATS
UNDER 0.2"), CLEAR CONDITIONS ARE EXPECTED THROUGH AT LEAST
TONIGHT. TEMPS WILL CONTINUE TO MODERATE TODAY, WITH LOW/NO-
SNOWPACK AREAS NEARING OR REACHING THE FREEZING MARK THIS
AFTERNOON.
EXPECT MORE MID TO UPPER-LEVEL CLOUD COVER ON SATURDAY AS AN
UNORGANIZED WAVE MOVES SOUTHEASTWARD ACROSS WISCONSIN, THOUGH
TEMPS SHOULD STILL RISE TOWARD THE MID 30S AMID SOUTHWEST WINDS
GUSTING OVER 20MPH.
KLUBER
SATURDAY NIGHT THROUGH THURSDAY:
AN ACTIVE JET STREAM WILL DEVELOP DURING THE LONG TERM WHICH
WILL GUIDE A HANDFUL OF FAST-MOVING DISTURBANCES ACROSS THE
UPPER MIDWEST AND GREAT LAKES REGIONS. NOTABLY MILDER
CONDITIONS, AT LEAST THROUGH THE MIDDLE OF NEXT WEEK, SUGGEST
P-TYPES WILL BE MAINLY RAIN, AND LOW-LEVEL DRY AIR WILL ALSO
PLAY A ROLE IN LIMITING PRECIP CHANCES UNTIL MONDAY NIGHT.
THE FIRST PERTURBATIONS IN THIS WAVE TRAIN WILL ARRIVE ON SUNDAY
INTO SUNDAY EVENING. AT THIS TIME, ESSENTIALLY ALL GUIDANCE
(ASIDE FROM JUST A FEW ENSEMBLE MEMBERS) BRING THESE FEATURE
THROUGH OUR REGION WITHOUT PRECIPITATION, WITH SATURATION
RELEGATED GENERALLY ABOVE 700 MB. INTENSIFYING WARM ADVECTION
ASSOCIATED WITH STRENGTHENING 925-850 MB WESTERLY WINDS IS
SLATED TO PUSH 850 MB TEMPERATURES INTO THE +0 TO +4 C RANGE
THROUGH THE AFTERNOON. WHILE SOME DEGREE OF MID AND HIGH-LEVEL
CLOUD COVER WILL REDUCE INSOLATION, BREEZY SOUTHWESTERLY WINDS
AT THE SURFACE SHOULD HELP PUSH HIGHS INTO THE 40S AT LEAST
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. WITH DEWPOINTS
GENERALLY IN THE UPPER 20S AND LOWER 30S, A LINGERING MODEST
SNOWPACK (OR WHAT'S LEFT OF IT) ACROSS OUR NORTHERN LOCALES MAY
LOCALLY HOLD HIGHS IN THE UPPER 30S.
A MORE ROBUST SHORTWAVE IS THEN SET TO ARRIVE MONDAY NIGHT INTO
TUESDAY. WHILE NOTABLE DIFFERENCES IN THE ORIENTATION, SPEED,
AND INTENSITY OF THIS FEATURE EXIST ACROSS THE MODEL SUITE, A
DECENT SIGNAL EXISTS FOR AT LEAST SPOTTY PRECIPITATION WITHIN
THE INITIAL WARM ADVECTION WING. ASCENT PROFILES ARE IMPRESSIVE,
WITH VERTICAL VELOCITIES NEAR 15-25 UBAR/SEC FOR A BRIEF TIME
(OFF THE GFS). ADDITIONALLY, FAIRLY COLD TEMPERATURES ALOFT (-25
TO -30 C AT 500 MB) WILL SUPPORT A PLUME OF STEEPENED 700-500
MB LAPSE RATES NEARING 7-7.5 C/KM AHEAD OF THE MAIN VORT MAX.
WITH ROBUST ATTENDANT FORCING FOR ASCENT, EXPANDED SOME LOW-END
CHANCE POPS ACROSS THE NORTHERN 2/3RDS OF THE FORECAST AREA
MONDAY EVENING. IF TRENDS CONTINUE, POPS WILL NEED TO BE BOOSTED
GOING FORWARD AS WELL. THANKFULLY, THERMAL PROFILES LOOK WARM
ENOUGH TO KEEP THINGS AS ALL RAIN.
ANOTHER VIGOROUS SHORTWAVE AND ATTENDANT SURFACE REFLECTION IS
FORECAST TO ARRIVE DURING THE WEDNESDAY-WEDNESDAY NIGHT TIME
FRAME. THE SPREAD IN MODEL GUIDANCE BY THIS TIME IS PRETTY
SUBSTANTIAL THOUGH, AND RUN-TO-RUN CONSISTENCY LEAVES A LOT TO
BE DESIRED. THE SIGNAL FOR PRECIP IN THE REGION IS PRETTY HIGH
HOWEVER, SO SAW NO REASON TO MAKE ANY CHANGES TO THE NBM-
DELIVERED HIGH-END CHANCE POPS DURING THIS PERIOD. DEPENDING ON
THE SURFACE LOW'S TRACK, THERMAL PROFILES COULD FLIP A BIT
TOWARDS SNOW GIVEN THE DYNAMICS INVOLVED, ALTHOUGH A TRACK TO
OUR NORTHWEST REMAINS WITHIN THE ENSEMBLE ENVELOPE WHICH WOULD
BE A DECIDEDLY WARMER SCENARIO. BEYOND THURSDAY, AN ACTIVE
PATTERN LOOKS SET TO CONTINUE WITH A TREND (AT LEAST BRIEFLY)
BACK TOWARDS BELOW NORMAL TEMPERATURES.
CARLAW
AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 525 AM CST FRI FEB 21 2025
THERE ARE NO SIGNIFICANT AVIATION WEATHER CONCERNS. LIGHT SW/WSW
WINDS WILL INCREASE TO AROUND 10 KNOTS LATER THIS MORNING AND
AFTERNOON, PERHAPS WITH A FEW GUSTS INTO THE UPPER TEENS. WHILE
SOME VERY SPOTTY CU WITH BASES AROUND 020-025 MAY DEVELOP THIS
AFTERNOON, VFR CONDITIONS ARE EXPECTED TO PREVAIL. WINDS WILL
INCREASE LATE SATURDAY MORNING, WITH GUSTS INTO THE 20-25 KNOT
RANGE EXPECTED INTO THE AFTERNOON.
CARLAW
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page