337
FXUS63 KDVN 201733
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1133 AM CST WED NOV 20 2024
KEY MESSAGES
- SCATTERED RAIN AND SNOW SHOWERS MOVING INTO TODAY AND TONIGHT, MORE
SNOW THAN RAIN BY LATE AFTERNOON WITH SOME GUSTY WIND SQUALL
POTENTIAL. WINDY TODAY TOO.
- ANOTHER WINDY DAY ON THURSDAY, WITH A WINTER SYSTEM OCCURRING
ALONG AND EAST OF THE LOCAL AREA.
- COOLER TEMPERATURES WILL CONTINUE UNTIL A BRIEF WARM UP OCCURS
BY SUNDAY, THEN COOLER AGAIN INTO EARLY NEXT WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 305 AM CST WED NOV 20 2024
TODAY...WILL WALK OUT SPRINKLES AND LIGHT RAIN OUT OF THE SOUTHEAST
BY 12Z WITH PASSING VORT, WHILE WATER VAPOR IMAGERY(WV)WAS
INDICATING THE LARGE CLOSED UPPER LOW CENTER SPIRALING ACRS THE
NORTHEASTERN PLAINS. ROUNDING 135+ KT UPPER JET STREAK WILL CONTORT
THE UPPER LOW INTO THE SOUTHWESTERN GRT LKS THROUGH THU MORNING.
FIRST VORT SPOKE RIPPLING THRU THIS FEATURE'S WESTERN FLOW FLANK
WILL SWEEP ACRS THE AREA FROM LATE MORNING INTO THE AFTERNOON, THEN
A MUCH MORE SUBSTANTIAL LOBE WILL WHIRL DOWN ACRS THE AREA TONIGHT
IN THE UPPER LOW'S MIGRATION PROCESS. THE FIRST ONE WILL UTILIZE
FCST SOUNDING INDICATED DEVELOPING STEEP LOW TO MID LEVEL(AND VERY
STEEP LLVL) LAPSE RATES AND MOISTURE DRAGGED DOWN FROM THE NORTHWEST
TO PRODUCE SCTRD RAIN AND SNOW SHOWERS MOVING INTO THE AREA FROM THE
NORTHWEST FROM LATE MORNING AND INTO THE AFTERNOON. MOST OF TODAY'S
ACTIVITY WILL OCCUR ALONG AND NORTH OF THE I-80 CORRIDOR. CONVECTIVE
PROFILES SUGGEST TOP-DOWN AND ENOUGH DYNAMICAL COOLING FOR THE RAIN
AND SNOW TO TURN TO MORE SNOW BY LATE AFTERNOON AND EARLY EVENING. A
FEW SWATHS OF A TENTH OR TWO OF SNOW ACCUM IS POSSIBLE, BUT MAINLY
ON ELEVATED SFCS DURING THE DAY WITH INSOLATION AND MILD GROUND
TEMPS MELTING SNOW ON GROUND CONTACT. AMBIENT WINDS IN TIGHTENING
CYCLONIC LLVL PRESSSURE GRADIENT AS THE CYCLONE COMPLEX ROLLS TOWARD
THE SOUTHWESTERN GRT LKS WILL MAKE FOR A WINDY DAY, BUT SHOULD BE
UNDER ADVISORY LEVELS AT 15 TO 25 MPH WITH GUSTS UP TO 35 MPH
ESPECIALLY ACRS THE SOUTHWESTERN HALF OF THE DVN CWA.
WITH THE UNSTABLE PROFILES, SEVERAL SNOW SQUALL PARAMETERS ARE
SPIKING WIT THIS AFTERNOON'S SHOWERS, ESPECIALLY SHALLOW BUOYANCY
AND THTA-E GRADIENTS. INVERTED-V SOUNDINGS AND VERTICAL MIX PROFILES
MID AFTERNOON INTO EARLY EVENING SUPPORT THE MORE ROBUST SNOW
SHOWERS MIXING DOWN WIND GUSTS OF 40 TO 45 MPH, AND CAMS SUGGEST
QUICK PASSING VISIBILITY RESTRICTIONS RANGING FROM 1.5 SM TO A HALF
MILE AT LEAST. AS MENTIONED BEFORE ON PREVIOUS SHIFTS, THE ONE THING
THAT MAY SAVE US FROM MORE IMPACTFUL TRUE SNOW SQUALL EFFECTS WILL
BE A LACK OF FLASH FREEZE ON PAVEMENT WITH ONGOING RADIATING UPWARD
MILD SOIL TEMPS. HIGH TEMPS TODAY NOT MUCH MORE THAN WHAT'S OUT
THERE RIGHT NOW BEING HELD UP BY THE PASSING CLOUD DECK. BUT 30S
LURK UPSTREAM IN THE CLEARING ACRS CENTRAL/WESTERN IA.
TONIGHT...WITH THE ABOVE MENTIONED MAIN VORT SPOKE/SHORT WAVE TROF
PROPAGATING DOWN ACRS THE AREA, SEE THE SCTRD SNOW SHOWER ACTIVITY
INCREASING AGAIN FROM THE NORTH/NORTHWEST AND SPREADING DOWN ACRS
MUCH OF THE DVN CWA INTO THE OVERNIGHT, BEFORE WANING AND SHIFTING
OFF TO THE SOUTHEAST BEFORE DAWN. GREATLY REDUCED PASSING
VISIBILITY, ENHANCED WIND GUSTS AND SOME LIGHT SNOW ACCUMS SHOULD
CONTINUE THROUGH THE NIGHT AS WELL, AND BEING AT NIGHT AND TEMPS
FALLING INTO THE LOWER 30S BY MIDNIGHT, MAY HAVE TO WATCH FOR SOME
LIGHT SNOW ACCUMS AND LOCALIZED SLICK SPOTS ON ELEVATED RAMPS AND
BRIDGES. OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S WITH ONGOING
GUSTY WEST-NORTHWEST SFC WINDS.
LONG TERM /THURSDAY THROUGH TUESDAY/
ISSUED AT 305 AM CST WED NOV 20 2024
THURSDAY...ENSEMBLES ARE STILL HANDLING THE UPPER CYCLONE BY MOVING
IT OUT OF THE WESTERN GRT LKS TO THE EAST-SOUTHEAST TOWARD THE
EASTERN OH RVR VALLEY. THERE STILL APPEARS TO BE ANOTHER VORT LOBE
SPIRALING SOUTHWARD ON IT'S WESTERN FLANK DOWN THE WESTERN GRT LKS
PRODUCING A SWATH OF PRECIP, ESPECIALLY ALONG AND EAST OF THE LOCAL
CWA. MODELS VARY ON WET ACCUMULATING SNOW, AND THEN A SWITCH OVER TO
A RAIN-SNOW MIX, THEN POSSIBLY BACK TO ALL WET SNOW DURING THE DAY
AND INTO THE EVENING. THERE MAY BE SEVERAL INCHES OF SNOW ACCUM'S
ACRS SOUTHEASTERN WI INTO THE CHICAGOLAND/NORTHEASTERN IL. WE MAY
HAVE TO WATCH FOR LIGHTER PRECIP SCRAPING THE FAR EASTERN FCST AREA
DURING THE DAY WITH PRECIP PTYPE ISSUES. MORE OF A WIDESPREAD
WEATHER IMPACT FOR US WILL BE PROBABLY ADVISORY LEVEL NORTHWEST
WINDS DURING THE DAY AS ANOTHER ROUND OF CYCLONIC TIGHT PRESSURE
GRADIENT OVERTAKES THE REGION AS A DEEP SFC LOW DROPS SOUTH DOWN LK
MI. EARLY LOOKS SUGGEST GUSTS OF 45-50+ MPH BY MIDDAY , WITH THE
STRONGEST WINDS ACRS NW IL. THE EXTENT OF COOL ADVECTION MAY KEEP
MUCH OF THE AREA IN THE 30S TO LOWER 40S FOR MUCH OF THE DAY.
FRIDAY THROUGH SUNDAY...WEAK UPPER RIDGING TO FLATTENED WESTERLY
STEERING FLOW FOR MOST OF THIS PERIOD IN THE WAKE OF THE CYCLONE.
MAINLY DRY AND NEAR SEASONABLE TEMPS THRU SAT, THEN SOME TEMP
MODERATION INTO SUNDAY ABOVE NORMAL BACK INTO THE 50S. EARLY NEXT
WEEK. THE NEXT PRECIP MAKING IMPULSE MAY IMPACT THE REGION LATE
SUNDAY INTO MONDAY LOOKING AT ENSEMBLE WAVE PROGRESSION IN THIS
FLOW, BUT TOUGH TO DEFINE THAT FAR OUT.
MONDAY AND TUESDAY...LONGER RANGE PROSPECTS SUGGEST A COOL
PUSH/FRONT TO MAKE IT'S WAY THROUGH THE AREA SUNDAY NIGHT INTO
MONDAY MAKING FOR AN EARLY WEEK CHILL DOWN. BUT LITTLE SIGNS OF ANY
ORGANIZED PRECIP AT THIS POINT THROUGH AT LEAST TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1124 AM CST WED NOV 20 2024
VFR CONDITIONS WILL BECOME MVFR TO IFR THROUGH THE NEXT FEW
HOURS, AS A SYSTEM PASSING THROUGH THE REGION BRINGS SCATTERED
RAIN/SNOW SHOWERS. MAIN PRECIPITATION TYPE WILL BE SNOW, MAINLY
IMPACTING CID, DBQ, AND MLI. THESE SNOW SHOWERS WILL BRING
PERIODS OF REDUCED CIGS, BUT THE MAIN THREAT WILL BE THE
REDUCTIONS IN VIS EXPECTED. CURRENTLY, WE ARE HIGHLIGHTING 2 SM,
BUT IT IS POSSIBLE THAT WE SEE LOWER VIS. IF OBSERVATIONAL
TRENDS SUPPORT THAT, WE WILL AMEND THE NECESSARY SITES. THESE
SHOWERS WILL BE OFF AND ON THROUGH THE AFTERNOON AND EVENING,
WANING AWAY FROM WEST TO EAST AROUND 06Z TONIGHT. CIGS WILL
REMAIN BETWEEN 2000-3500 THROUGH THE NIGHT AS WELL. THE WINDS
WILL ALSO BE A THREAT THROUGH THE DAY, AS WE ARE SEEING WESTERLY
WINDS GUSTING UPWARDS TO 35 KTS OR MORE AT TIMES. SOME LOCALLY
HIGHER GUSTS CAN BE SEEN IN THESE SHOWERS. THROUGH THE NIGHT,
THE WINDS WILL REMAIN RELATIVELY GUSTY, BUT WE ARE EXPECTING
THEM TO PICK UP QUITE A BIT AGAIN TOMORROW, WITH NORTHWEST GUSTS
UPWARDS TO 40 KTS IN AREAS AS WE APPROACH 18Z TOMORROW.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...NONE.
MO...NONE.
SHORT TERM...12
LONG TERM...12
AVIATION...GUNKEL
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