137
FXUS63 KLOT 211927
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
127 PM CST FRI FEB 21 2025
KEY MESSAGES
- MILDER, ABOVE NORMAL TEMPERATURES ARE EXPECTED SUNDAY THROUGH
TUESDAY
- CHANCES FOR RAIN/SHOWERS MONDAY NIGHT (20-30%) AND WEDNESDAY
INTO WEDNESDAY NIGHT (40-60%)
DISCUSSION
ISSUED AT 126 PM CST FRI FEB 21 2025
THROUGH SATURDAY NIGHT:
A LARGE 1040 MB HIGH CENTERED OVER THE MID-MISSISSIPPI VALLEY
WILL GRADUALLY SHIFT EASTWARD TOWARDS THE MID-ATLANTIC INTO
SATURDAY NIGHT. THE EASTWARD EXIT OF THIS SURFACE HIGH WILL
CONTINUE TO SET THE STAGE FOR A WARMING TREND THROUGH THE
WEEKEND AS SOUTHWESTERLY LOW-LEVEL FLOW PERSISTS. DRY AND
PRIMARILY CLEAR SKIES ARE EXPECTED THROUGH TONIGHT. WHILE THIS
WILL AID IN TEMPERATURES REMAINING ON THE COLD SIDE AGAIN
TONIGHT, READINGS WILL NOT BE AS COLD AS THE LAST FEW NIGHTS.
OVERNIGHT LOWS ARE SLATED TO GENERALLY RANGE FROM THE UPPER
SINGLE DIGITS ABOVE ZERO IN NORTHWEST IL TO THE LOW TO MID TEENS
ELSEWHERE.
BREEZY SOUTHWEST WINDS WILL DEVELOP DURING THE DAY ON SATURDAY
(AFTERNOON GUSTS UP TO 25 MPH) AS THE SURFACE GRADIENT
STRENGTHENS ALONG THE NORTHERN PERIPHERY OF THE EXITING SURFACE
HIGH. THESE WINDS WILL HELP FOSTER WARMER DAYTIME TEMPERATURES
UNDER MOSTLY SUNNY SKIES. READINGS LOOK TO TOP THE FREEZING MARK
IN MOST LOCATIONS FOR THE FIRST TIME IN ABOUT A WEEK. QUIET
WEATHER CONTINUES SATURDAY NIGHT, ALBEIT WITH THE PRESENCE OF A
FEW MORE MID AND HIGH LEVEL CLOUDS.
KJB
SUNDAY THROUGH FRIDAY:
SOUTHWESTERLY SURFACE WINDS WILL PREVAIL THROUGH MUCH OF THE EARLY
PART OF NEXT WEEK. THESE WINDS WILL HELP TRANSPORT A MILDER AIR
MASS NORTHWARD. WHILE THERE IS STILL SOME UNCERTAINTY REGARDING
CLOUD COVER AND SNOW PACK AND THEIR IMPACT ON THE EXACT HIGH
TEMPERATURES, IT LOOKS LIKE MILDER, ABOVE NORMAL TEMPERATURES
ARE IN STORE. AFTERNOON TEMPERATURES ARE EXPECTED TO TOP OUT IN
THE 40S, WITH SOME POTENTIAL FOR REACHING INTO THE 50S FOR
AREAS SOUTH OF I-80.
A LOW PRESSURE SYSTEM WILL PASS FROM WEST TO EAST THROUGH CANADA
SUNDAY INTO MONDAY, DEEPENING AS IT TRAVERSES ONTARIO. AS THE
SURFACE TROUGH EXTENDS FAR ENOUGH SOUTH, IT COULD BRING
PRECIPITATION TO SOUTHERN WISCONSIN. FOR NOW, MODELS HAVE
CONSISTENTLY KEPT THIS SYSTEM TO THE NORTH OF THE STATELINE.
WHILE CHANCE FOR PRECIP IN THE FAR NORTHERN COUNTIES IS NON-
ZERO, MODELS KEEP ENOUGH LOW-LEVEL DRY AIR AROUND TO PREVENT IT
FROM BEING ADDED TO THE FORECAST.
IN THE WAKE OF THAT SYSTEM, THE UPPER-LEVEL PATTERN WILL BECOME
PREDOMINANTLY NORTHWESTERLY WITH THE POTENTIAL FOR A NUMBER OF
SUCCESSIVE PERTURBATIONS TO PASS THROUGH DURING THE WEEK. THE
FIRST BEING ON MONDAY NIGHT AND INTO TUESDAY MORNING. AS A SHORT
WAVE TROUGH MOVES SOUTHEAST OUT OF MANITOBA, THE UPPER-LEVEL
JET WILL STRENGTHEN AS IT APPROACHES THE GREAT LAKES SUPPORTING
VERTICAL ASCENT. WITH MODEL SOUNDS SHOWING FAIRLY STEEPENED
LAPSE RATES AND LOW-LEVEL WARM AIR ADVECTION ASSOCIATED WITH A
SURGE OF MID-LEVEL MOISTURE, THERE LOOKS LIKE A DECENT CHANCE
FOR RAIN ACROSS MUCH OF THE FORECAST AREA MONDAY NIGHT AND
POTENTIALLY LINGERING INTO THE TUESDAY MORNING COMMUTE AS IT
EXITS TO THE EAST.
ANOTHER STRONG SHORTWAVE IS PROJECTED TO MOVE ACROSS THE NORTHERN
PLAINS/CANADA WEDNESDAY AND INTO WEDNESDAY NIGHT. MODELS HAVE
CONSISTENTLY SHOWN THIS SYSTEM TO BE SLIGHTLY STRONGER/DEEPER;
HOWEVER, THEY HAVE STRUGGLED WITH THE PLACEMENT AND TIMING OF THE
TROUGH. THE SYSTEM WILL START OUT AS RAIN ON WEDNESDAY WITH ILLINOIS
BEING FIRMLY WITHIN THE WARM SECTOR. HOWEVER, AS THE SURFACE
LOW MOVES TO THE EAST IN THE EVENING/OVERNIGHT, WINDS WILL
SWITCH OVER TO THE NORTHWEST. WITH BETTER COLD AIR ADVECTION,
THERE IS A CHANCE FOR PRECIP TO CHANGE OVER TO A RAIN SNOW MIX,
IF NOT ALL SNOW, OVERNIGHT INTO THURSDAY MORNING. THERE IS STILL
UNCERTAINTY ON WHETHER OR NOT IT WILL IMPACT THE THURSDAY
MORNING COMMUTE GIVEN THE LOWER CONFIDENCE AT THIS TIME RANGE.
BEYOND THURSDAY, THERE MAY BE A BREAK ON FRIDAY, BUT AN ACTIVE
UPPER-LEVEL PATTERN LOOKS TO CONTINUE WITH ADDITIONAL PRECIP
CHANCES IN THE LONG RANGE WITH A TREND (AT LEAST BRIEFLY) BACK
TOWARDS BELOW NORMAL TEMPERATURES.
DK
AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 1121 AM CST FRI FEB 21 2025
THERE ARE NO SIGNIFICANT AVIATION WEATHER CONCERNS FOR THE 18Z
TAF PERIOD.
WSW WINDS WILL CONTINUE MOVING AT NEAR OR JUST UNDER 10 KT FOR
THE REMAINDER OF TODAY. SW WINDS WILL GUST TO AROUND 20 TO 25
KT DURING THE DAY ON SATURDAY. EXPECT VFR CONDITIONS THROUGH THE
PERIOD.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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