067
FXUS63 KDVN 230300
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
900 PM CST SUN DEC 22 2024
KEY MESSAGES
- THE RISK OF FREEZING DRIZZLE TONIGHT INTO MONDAY MORNING HAS
GONE DOWN. THE RISK NOW LOOKS TO BE A 20-30 PERCENT CHANCE
NORTH OF AN INDEPENDENCE, IA TO NORTH OF STERLING, IL LINE.
- WARMER TEMPERATURES ALONG WITH SEVERAL CHANCES FOR RAIN WILL
FINISH OUT 2024 WITH VERY LITTLE SUNSHINE.
UPDATE
ISSUED AT 852 PM CST SUN DEC 22 2024
LOOKING AT 00Z GUIDANCE COMING IN, AND BOTH THE NAM AND NAMNEST
CONTINUE TO SUPPORT A LOWER END FREEZING DRIZZLE IN OUR NORTHERN
AND / EASTERN CWA. HOWEVER, BOTH OF THESE MODELS HAVE ONCE AGAIN
INCORRECTLY INITIALIZED AND MAINTAIN A OVERLY AGGRESSIVE SNOW
DEPTH OVER OUR ENTIRE NORTHEAST 1/2 OF THE CWA THROUGH THE NEXT
COUPLE DAYS, AND THAT'S ALREADY WRONG. OUR CURRENT SNOW DEPTH
GENERALLY RUNS 1+" FROM NEAR DUBUQUE TO FREEPORT, WITH MUCH LESS
TO THE SOUTH AND SOUTHWEST. WITH TEMPERATURES ALREADY RUNNING
3+ DEGREES HIGHER ON 2M TEMPERATURES THAN BOTH MODELS, THAT
INCORRECT SNOW DEPTH SEEMS TO BE PLAYING A FACTOR.
THE HRRR HAS LESS SNOW DEPTH THIS FAR SOUTH, AND NOT TOO
SURPRISINGLY, HAS LITTLE TO NO ICE. THUS, OUR FORECAST WITH
LOWER END CHANCES (15-25%) FOR LIGHT ICING WILL REMAIN UNTIL WE
SEE SHORT TERM TRENDS TAKE PLACE LATE TONIGHT.
THE INCOMING LOW CLOUDS ARE MAKING THE WAY NORTHEAST AS
EXPECTED, BUT REMAIN WELL SOUTHWEST OF THE CWA, IN SOUTHEASTERN
KANSAS AS OF 845 PM. THEY ARE LIFTING NORTHEAST AT 40KTS, SO WE
DO EXPECT AN INCREASE IN LOWER CLOUDS TOWARDS MORNING.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 237 PM CST SUN DEC 22 2024
QUIET CONDITIONS WILL BE SEEN THROUGH MIDNIGHT AS A STORM SYSTEM
APPROACHES THE AREA.
AFTER MIDNIGHT AND THROUGH MONDAY MORNING, THE CLIPPER SYSTEM WILL
QUICKLY MOVE THROUGH THE AREA. THE TREND FROM THE MODELS 24 HOURS
AGO HAS BEEN TO MOVE THE TRACK OF THE STORM FURTHER NORTH. THE
FURTHER NORTH TRACK NOW RAISES QUESTIONS REGARDING ANY IMPACTFUL
WEATHER LATE TONIGHT INTO THE MONDAY MORNING COMMUTE.
THE BETTER FORCING IS STILL FROM MINNESOTA INTO WISCONSIN. FORECAST
PROFILES OF THE ATMOSPHERE CONTINUE TO SUGGEST THE POTENTIAL FOR
DRIZZLE AND/OR FREEZING DRIZZLE FOR ROUGHLY A 6 HOUR TIME FRAME FROM
ABOUT 3 AM TO 9 AM MONDAY MORNING. THE FURTHER NORTH TRACK OF THE
LOW CENTER NOW WOULD CONFINE ANY FREEZING DRIZZLE TO THE DEEPER SNOW
FIELD ACROSS THE AREA; ROUGHLY INDEPENDENCE, IA TO NORTH OF A
STERLING, IL LINE. COMPARED TO YESTERDAY, THE OVERALL RISK FOR
FREEZING DRIZZLE HAS GONE DOWN AND NOW LOOKS TO BE AT A 20-30
PERCENT CHANCE.
THE SOUTHERLY WINDS PUSHING WARM AIR AND MOISTURE INTO THE AREA AT
LOWER LEVELS COMBINED WITH CLOUD COVER DOES HAVE THE POTENTIAL (15-
20 PERCENT) FOR KEEPING ANY PRECIPITATION IN A LIQUID FORM LATE
TONIGHT INTO MONDAY MORNING.
CLEARING SKIES FROM WEST TO EAST BY LATE MONDAY MORNING AND THROUGH
THE AFTERNOON AND CONTINUED SOUTHERLY WINDS WILL HELP BOOST
TEMPERATURES ABOVE NORMAL.
LONG TERM /MONDAY NIGHT THROUGH SUNDAY/
ISSUED AT 237 PM CST SUN DEC 22 2024
MONDAY NIGHT/TUESDAY
ASSESSMENT...HIGH CONFIDENCE ON DRY CONDITIONS
DRY CONDITIONS WITH NEAR SEASONABLE TEMPERATURES WILL BE SEEN AS
HIGH PRESSURE QUICKLY MOVES THROUGH THE MIDWEST. ATTENTION THEN
TURNS TO THE REMAINDER OF THE WEEK.
TUESDAY NIGHT THROUGH SUNDAY
ASSESSMENT...HIGH CONFIDENCE ON WARMER THAN NORMAL TEMPERATURES.
SEVERAL CHANCES FOR RAIN WITH LITTLE SUNSHINE EXPECTED.
THE SECOND HALF OF THE WEEK AND INTO THE WEEKEND WILL RESULT IN VERY
LITTLE IF ANY SUNSHINE BEING SEEN. THE LACK OF SUNSHINE CAN BE
TRACED TO AN INVERSION ALOFT HELPING TO TRAP MOISTURE IN THE FORM OF
CLOUDS ACROSS THE MIDWEST AS EACH SYSTEM MOVES THROUGH THE MIDWEST.
IT WILL NOT RAIN CONTINUOUSLY THE ENTIRE TIME PERIOD. THERE WILL BE
PERIODS OF 6-12 HOURS WHERE DRY CONDITIONS WILL BE SEEN.
THERE ARE DIFFERENCES BETWEEN THE GLOBAL MODELS IN TIMING. HOWEVER,
THERE IS LOOSE AGREEMENT OF AT LEAST TWO AND POSSIBLY THREE SYSTEMS
MOVING THROUGH THE MIDWEST.
THE MODELS AGREE THAT MONDAY NIGHT AND TUESDAY WILL BE DRY ACROSS
THE AREA.
THE MODELS DIVERGE SLIGHTLY BUT STILL HAVE FAIRLY GOOD AGREEMENT
THAT THE FIRST ROUND OF RAIN WILL OCCUR TUESDAY NIGHT INTO WEDNESDAY
FOR AREAS ALONG AND EAST OF THE MISSISSIPPI. THE MODEL CONSENSUS
DURING THIS TIME FRAME HAS A 20 TO 40 PERCENT CHANCE OF RAIN.
THE INDIVIDUAL MODELS BEGIN TO DIVERGE AFTER WEDNESDAY BUT THE
OVERALL TREND OF THE DETERMINISTIC AND ENSEMBLE MEMBERS INDICATE
WEDNESDAY NIGHT AND THURSDAY LOOKS TO BE DRY.
THE NEXT TIME FRAME THAT LOOKS FAVORABLE FOR RAIN IS THURSDAY NIGHT
THROUGH FRIDAY NIGHT AS ANOTHER STORM SYSTEM MOVES THROUGH THE AREA.
GIVEN THE SLIGHT DIFFERENCES IN TIMING AND TRACK, THE MODEL
CONSENSUS HAS A 35-50 PERCENT CHANCE OF RAIN.
SATURDAY INTO SUNDAY HAS THE HIGHEST UNCERTAINTY REGARDING RAIN
CHANCES. TWO SCENARIOS ARE IN PLAY; 1) A SECOND STORM SYSTEM WILL
ARRIVE RIGHT ON THE HEELS OF THE LATE WEEK SYSTEM OR 2) A SEPARATE
UPPER LEVEL DISTURBANCE TRAVELING WELL BEHIND THE FIRST SYSTEM MOVES
IN FROM THE PLAINS.
REGARDLESS OF WHICH SCENARIO IS CORRECT, THE MODELS AGREE THAT
MOISTURE WILL BE TRAPPED BELOW AN INVERSION ALOFT WHICH WILL KEEP
CLOUDS ACROSS THE AREA. WITH A LAYER OF SATURATED MOISTURE ALREADY
IN PLACE, THERE WILL BE A RISK OF RAIN WHEN LIFT ACTS UPON IT. RIGHT
NOW THE MODEL CONSENSUS HAS A 30-40 PERCENT CHANCE OF RAIN SATURDAY
AND SATURDAY NIGHT THAT DECREASES TO A 20 PERCENT CHANCE OF RAIN FOR
SUNDAY.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 532 PM CST SUN DEC 22 2024
VFR CONDITIONS ARE EXPECTED THROUGH EARLY MONDAY MORNING, AS
SOUTH WINDS AT THE SURFACE AND ALOFT CONTINUE TO DRAWN IN MILDER
AIR AND EVENTUALLY MOISTURE. THE ONSET OF LOW CLOUDS, WITH BASES
OF 2500 TO 3500 FT ARE EXPECTED TO ARRIVE LATE TONIGHT, WITH
SOME POSSIBLE DRIZZLE OR FREEZING DRIZZLE IN NORTHWEST ILLINOIS
AND FAR NORTHEAST IOWA. THESE CLOUDS ARE CURRENTLY IN OKLAHOMA,
AND WILL NEED TO TRAVEL AND EXPAND FROM A LONG WAYS AWAY, BUT
THIS SHOULD SPREAD INTO EASTERN IOWA AND ILLINOIS AROUND THE 09Z
TO 12Z TIME FRAME. A FAST MOVING CLIPPER SYSTEM MOVING NORTH OF
OUR AREA WILL SWITCH WINDS TO WEST MONDAY MORNING, AND IN COLD
ADVECTION THROUGH THE DAY, MVFR CIGS MAY LINGER IN NORTHEAST
IOWA ALL DAY.
LOW LEVEL WIND SHEAR IS EXPECTED OVERNIGHT, WITH STRONG SOUTH
WINDS OF 40 TO 45 KTS ABOUT 1400-1600 FT ABOVE THE GROUND. THIS
LLWS SHOULD END AROUND 12Z, AS THE LOW PRESSURE SYSTEM SHIFTS
EAST INTO WISCONSIN.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
UPDATE...ERVIN
SHORT TERM...08
LONG TERM...08
AVIATION...ERVIN
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