486
FXUS63 KLOT 192100
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
300 PM CST WED FEB 19 2025
KEY MESSAGES
- VERY COLD OVERNIGHT AND MORNING CONDITIONS WILL PERSIST
THROUGH FRIDAY.
- INTERMITTENT FLURRIES AND POTENTIALLY PERIODS OF LIGHT SNOW
ARE EXPECTED THIS EVENING INTO THURSDAY MORNING, WHICH MAY
CAUSE SLIPPERY TRAVEL FROM LOCALIZED MINOR ACCUMULATIONS.
- LIGHT LAKE EFFECT SNOW SHOWERS WILL CLIP NORTHEAST PORTER
COUNTY AT TIMES THROUGH THURSDAY, WITH THE BEST CHANCE (40%)
OF LIGHT ACCUMULATIONS AND SLIPPERY TRAVEL TONIGHT.
- A MILDER PATTERN IS EXPECTED NEXT WEEK WITH TEMPERATURES
POTENTIALLY 10 TO EVEN 15 DEGREES ABOVE NORMAL.
DISCUSSION
ISSUED AT 300 PM CST WED FEB 19 2025
THROUGH THURSDAY NIGHT:
WE'RE FREE OF ANY COLD WEATHER ADVISORIES FOR THE FIRST TIME IN
A FEW DAYS, BUT IT WILL STILL BE QUITE COLD, ESPECIALLY FOR THIS
TIME OF YEAR. MID-UPPER LEVEL LOW PRESSURE OVER NORTH CENTRAL
IOWA THIS AFTERNOON WILL PIVOT EAST-SOUTHEASTWARD, TO NEAR LAKE
ERIE BY EARLY THURSDAY MORNING. LARGER SCALE MID-LEVEL HEIGHT
FALLS AND ASSORTED TROUGHS AND IMPULSES ASSOCIATED WITH THE 500
MB LOW WILL PRODUCE MODEST ASCENT TONIGHT. INITIALLY DRY LOW-
LEVELS ARE EXPECTED TO BECOME MORE SATURATED WITH TIME THIS
EVENING, WHICH WILL RESULT IN A DEEP LAYER OF 80%+ RH. DESPITE
THE DRY ARCTIC AIR MASS IN PLACE, CONCERN REMAINS FOR VERY SMALL
SNOWFLAKES ("ARCTIC DUST"), WHICH WOULD BE CAPABLE OF CAUSING
LOCALIZED SLIPPERY TRAVEL CONDITIONS AND REDUCED VISIBILITY.
BASED ON THE MID-LATE AFTERNOON LOCATION OF 2-6 MILE VISIBILITY
IN FLURRIES/LIGHT SNOW ACROSS CENTRAL AND SOUTHEAST IOWA, WE
SLOWED DOWN THE ONSET OF INTERMITTENT FLURRIES AND 20-30%
MEASURABLE SNOW CHANCES UNTIL THE EARLY TO MID EVENING HOURS.
SUFFICIENT LOW-LEVEL SATURATION IS A BIT MORE QUESTIONABLE
NEAR/WEST OF I-39 IN NORTH CENTRAL AND NORTHWEST ILLINOIS, SO
KEPT POPS JUST BELOW 15% IN THOSE AREAS. GIVEN THE LIGHT
EXPECTED RATES AND OVERALL LIMITED MOISTURE, IT DOESN'T APPEAR
THERE WILL BE WIDESPREAD DUSTINGS/COATINGS OF SNOW. HOWEVER, IF
AND WHERE SNOW CAN COAT THE GROUND, THE VERY COLD TEMPS WILL
MAKE ROAD TREATMENTS LESS EFFECTIVE. WITH THIS AFTERNOON'S
FORECAST ISSUANCE, WE HELD ONTO A CHANCE OF FLURRIES IN
NORTHEAST ILLINOIS AND PARTS OF NORTHWEST INDIANA THROUGH MID
MORNING ON THURSDAY (PER MODEL FORECAST SOUNDINGS).
LAKE EFFECT SNOW PARAMETERS BECOME MAXIMIZED MAINLY EAST OF THE
AREA WHERE A DOMINANT BUT TRANSIENT LAKE EFFECT BAND IS
EXPECTED TO IMPACT PORTIONS OF SOUTHWEST LOWER MICHIGAN AND
NORTHWEST INDIANA. HAVE MAINTAINED A 30-40% CHANCE OF LAKE
EFFECT SNOW ACROSS NORTHEAST PORTER COUNTY THROUGH THURSDAY
MORNING TO ACCOUNT FOR LIGHT MEASURABLE SNOW OCCURRING AT TIMES
LEADING TO SLICK TRAVEL. IT DOES APPEAR THAT THE MORE DOMINANT
BAND WILL REMAIN SAFELY EAST OF PORTER COUNTY THOUGH.
LINGERING CLOUD COVER AND FLURRIES "LEAKING" FROM THE STRATUS
WILL SERVE TO LIMIT OUR OVERNIGHT COOLING, WITH FORECAST LOWS IN
THE SINGLE DIGITS ABOVE ZERO FOR MOST OF THE AREA, WITH THE
EXCEPTION OF NEAR/WEST OF THE FOX VALLEY, WHERE CLOUDS SHOULD
SCATTER OUT A BIT EARLIER. THERE MAY BE ENOUGH WIND PAIRED WITH
TEMPS A FEW DEGREES BELOW ZERO FOR LOCALIZED MINIMUM WIND
CHILL READINGS APPROACHING 20 BELOW ZERO FOR AN HOUR OR TWO
TOWARD AND AFTER SUNRISE. GIVEN THE LIMITED EXPECTED COVERAGE
OF NEAR COLD WEATHER ADVISORY CRITERIA WIND CHILLS AND WIND
CHILLS NOT AS COLD AS EXPECTED DUE TO CLOUDS ON TUESDAY NIGHT,
OPTED TO HOLD OFF ON A NEW ADVISORY ISSUANCE.
THURSDAY WILL STILL BE WELL BELOW NORMAL, BUT BETTER THAN THE
PAST FEW DAYS, AS SOME SPOTS COULD POTENTIALLY REACH THE MID
20S, ESPECIALLY IN/NEAR CHICAGO. THE RIDGE AXIS OF STRONG
SURFACE HIGH PRESSURE CENTERED TO OUR SOUTHWEST WILL EXTEND FAR
ENOUGH EAST FOR LIGHTER WINDS AND MORE FAVORABLE RADIATIONAL
COOLING (AMIDST CLEAR SKIES) THURSDAY NIGHT. THIS WILL SET THE
STAGE FOR ONE LAST NIGHT OF LOWS NEAR TO A BIT BELOW ZERO,
COLDEST NEAR/WEST OF THE FOX VALLEY AGAIN. WIND CHILLS WILL ONLY
BE A BIT BELOW THE AIR TEMPS DUE TO THE LIGHTER WINDS.
CASTRO
FRIDAY THROUGH WEDNESDAY:
A SURFACE HIGH IS EXPECTED TO GRADUALLY DRIFT EAST OF THE
SOUTHERN PLAINS AND THROUGH THE OHIO RIVER VALLEY FROM FRIDAY
THROUGH SUNDAY. COLD TEMPERATURES IN THE TEENS AND 20S WILL
REMAIN ON FRIDAY. BUT AS THE HIGH DRIFTS TO THE SOUTHEAST, WINDS
WILL TURN TO THE SOUTHWEST HELPING TO RAISE TEMPERATURES ON
SATURDAY INTO THE 20S AND POTENTIALLY LOW 30S. AS THE
TEMPERATURES CONTINUE TO RISE THROUGH THE WEEKEND, RIVERS WILL
NEED TO BE MONITORED FOR THE POTENTIAL FOR ICE JAM-RELATED
LOCALIZED FLOODING DUE TO RIVER ICE MELT AND ICE JAM BREAKS UPS.
THE UPPER LEVEL PATTERN BECOMES SLIGHTLY MORE ACTIVE OVER THE
WEEKEND AND INTO NEXT WEEK. A QUICK SHORTWAVE WILL DROP OUT OF
CANADA AND HEAD TOWARD THE GREAT LAKES SATURDAY INTO SUNDAY. IT
CAN BE MONITORED IN THE COMING DAYS, BUT FOR NOW MODELS ARE
SUGGESTING IT SHOULD REMAIN FAR ENOUGH TO THE NORTHEAST FOR ANY
FORMAL MENTION OF PRECIP IN THE FORECAST.
A MUCH MORE PRONOUNCED UPPER LEVEL TROUGH IS EXPECTED TO DROP
DOWN LATE MONDAY AND INTO TUESDAY MORNING. AN UPPER LEVEL JET
STREAK IS PROJECTED TO REACH NEAR 120 KNOTS WITH THE LEFT EXIT
REGION RIGHT OVER CHICAGO TO PROVIDE ADDITIONAL SYNOPTIC LIFT.
THERE WILL BE DECENT WARM AIR ADVECTION OUT AHEAD OF THE WAVE
ALONG WITH SUFFICIENT MOISTURE AND STEEPER MID LEVEL LAPSE
RATES. IT IS HARD TO HAVE A LOT CONFIDENCE ON EXACT TIMING AND
DETAILS FOR THE RAIN GIVEN ITS STILL FIVE DAYS AWAY. BUT IF
MODELS CONTINUE TO TREND THIS WAY, ITS POSSIBLE THAT THE SLIGHT
CHANCE (15 TO 25 PERCENT) POPS THAT THE BLEND OF MODELS PROVIDED
MAY NEED TO BE INCREASED DOWN THE ROAD.
IF THAT WAS NOT AN ACTIVE PATTERN ENOUGH, MODELS ARE SUGGESTING
YET ANOTHER WAVE WILL PASS THROUGH THE AREA FOR ADDITIONAL
CHANCES FOR RAIN WEDNESDAY INTO THURSDAY NEXT WEEK. AND WHILE
THE PATTERN LOOKS ACTIVE NEXT WEEK, THERE IS INCREASING
CONFIDENCE THAT ANY OF THE PRECIPITATION ASSOCIATED WITH ANY
SYSTEM WOULD BE RAIN DUE TO THE FORECASTED WARMER TEMPERATURES.
AS SOUTHWESTERLY WINDS DEVELOP ON SUNDAY (AND REMAIN FOR MUCH OF
THE WEEK), WARM AIR ADVECTION WILL HELP A MORE MILD AIRMASS
MOVE OVER THE REGION.
TEMPERATURES NEXT WEEK COULD EASILY MOVE INTO THE MID TO EVEN
UPPER 40S (WHICH WOULD BE 10 DEGREES ABOVE NORMAL FOR THAT TIME
OF YEAR). THERE IS SOME DOUBT REGARDING HOW "WARM" (RELATIVELY
SPEAKING) TEMPERATURES COULD GET GIVEN THE AMOUNT OF SNOWPACK
THAT REMAINS AROUND THE REGION AS WELL AS POTENTIAL CLOUD COVER.
HOWEVER, THE EURO ENSEMBLE (THE MEAN OF MANY MODELS) AS WELL AS
THE NUMERICAL BLEND OF MODELS ARE SHOWING THE SOUTHERN PART OF
THE FORECAST AREA (NEAR AND AROUND FORD COUNTY) THAT COULD TOUCH
THE LOW 50S! WHILE THE EXACT MAGNITUDE IS STILL TO BE
DETERMINED, IT LOOKS LIKE A STRETCH OF MILDER ABOVE NORMAL
TEMPERATURES CAN BE EXPECTED NEXT WEEK.
DK
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 1131 AM CST WED FEB 19 2025
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- POTENTIAL FOR FLURRIES AT AREA TERMINALS OVERNIGHT.
- 30 PERCENT CHANCE FOR MVFR VIS/CIGS TO DEVELOP FROM ANY
SNOW/FLURRIES THAT OCCUR.
MOSTLY VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD WITH
NORTHWEST WINDS AROUND 10 KNOTS. THERE IS AN UPPER LEVEL WAVE
PASSING OVERNIGHT THROUGH TONIGHT. WHILE FORCING IS NOT TERRIBLY
STRONG, WITH TEMPERATURES AS COLD AS THEY ARE, IT WOULD NOT BE
SURPRISING FOR SOME FLURRIES OR EVEN A BRIEF PERIOD OF STEADIER
SNOW OCCURRED. THE MAIN UPDATE TO THE TAF WAS WITH RESPECT TO
TIMING. BASED ON THE CURRENT POSITION OF THE WAVE AND MODELS
SUGGESTING A SLOWER MOVEMENT TO IT, TIMING FOR FLURRIES WAS
PUSHED OUT SLIGHTLY. LASTLY, AS EVIDENT FROM CURRENT SURFACE OBS
IN CENTRAL IOWA, IF A SNOW SHOWER WERE TO MATERIALIZE OVER A
TERMINAL, MVFR VIS AND POTENTIALLY CIGS WOULD BE EXPECTED.
HOWEVER, THE CURRENTLY PROBABILITY OF IT OCCURRING REMAINS AT
AROUND 30 PERCENT. ANY ACCUMULATIONS FROM SNOW SHOULD ONLY BE A
DUSTING.
DK
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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