904
FXUS63 KDVN 181121
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
521 AM CST MON NOV 18 2024
KEY MESSAGES
- A STRONG STORM SYSTEM WILL AFFECT THE AREA TODAY THROUGH
TUESDAY AM LEADING WET AND WINDY CONDITIONS WITH POSSIBLE
STRONG TO SEVERE STORMS THIS EVENING.
- SNOW SHOWERS OR A RAIN/SNOW MIX THE MIDDLE OF THIS WEEK.
- WINDY DAYS WILL BE PLENTIFUL THIS WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 308 AM CST MON NOV 18 2024
AN UPPER LEVEL LOW IS EXPECTED TO MOVE NORTHEAST INTO THE AREA
DURING THE DAY AND INTO THE EVENING, SWINGING NEGATIVELY TILTED
AS IT MOVES OVER OUR AREA. WARM FRONTAL CONVECTION IS EXPECTED
TO AFFECT THE AREA FIRST. THE MAIN SURFACE LOW WILL MOVE ACROSS
EASTERN NE AS THE WARM SECTOR PULLS INTO OUR AREA IN THE
EVENING. A TIGHT SURFACE PRESSURE GRADIENT IS EXPECTED, WITH THE
STRONGEST WINDS BEING IN THE LATE AFTERNOON AND INTO THE
EVENING. THIS WILL RESULT IN WINDS GUSTING TO NEAR 40 MPH.
OVERALL, A COUPLE OF THINGS ARE DIFFERENT WITH THE STORM SYSTEM
TODAY INTO TONIGHT THAN 24 HOURS AGO. FIRST, THE LOW CONTINUES
TO BE FURTHER WEST AS IT PULLS NORTH INTO THE AREA. SECOND,
OVERALL TREND IN SURFACE BASED CAPE IS LOWER. SO WHAT DOES THIS
MEAN TO THE OVERALL IMPACTS? FIRST THE FURTHER WEST TRACK OF THE
LOW HAS SHIFTED THE TRACK OF THE HEAVIER QPF WEST AS WELL.
LOOKING AT THE PROBABILITY OF EXCEEDING 1 INCH OF QPF IN 24
HOURS, THE HIGHER PROBABILITIES ARE NOW FURTHER WEST AS WELL.
THESE DROP OFF SHARPLY AT THE MISSISSIPPI. LOOKING AT THOSE SAME
PROBS BUT FOR 0.5 INCH OF QPF, THEY DO THE SAME THING,
SUGGESTING THAT AREAS EAST OF THE MISSISSIPPI RIVER MAY ACTUALLY
BE OVERFORECAST FOR RAINFALL TOTALS. THAT SAID, THE EXPECTED
CONVECTION WITH THE CLEAR SLOT TONIGHT WILL LIKELY GIVE AREAS
EAST OF THE MISSISSIPPI RIVER THE AMOUNT OF QPF PREDICTED.
SECOND, THE DECREASE IN SBCAPE. AS IS USUALLY THE CASE WITH HSLC
TORNADOES, SMALL CHANGES IN THE THERMAL ENVIRONMENT CAN MEAN
GAME ON OR GAME OFF FOR THEM. LATEST RUNS SUGGEST THAT CAPE
WOULD SUGGEST THEY ARE OFF THE TABLE AND THAT WE WOULD SEE MORE
OF A WIND THREAT. IN FACT, THE HRRR HAS SOME IMPLICIT WIND GUSTS
OF 50KTS ASSOCIATED WITH CONVECTION. AS SUCH, WILL BE
HIGHLIGHTING A SEVERE THREAT LOCALLY IN PRODUCTS. AS FAR AS
TORNADOES GO, THE CSU MACHINE LEARNING PROBS CONTINUE TO SHOWER
THE 2% TOR RISK TO I80 AND EVEN NORTH TO THE WI STATE LINE. ANY
SMALL CHANGE IN SBCAPE AND THIS THREAT WOULD BE BACK ON. THIS
WILL REQUIRE INTENSE MESOANALYSIS LATER AS WE START TO SEE
CONVECTION THIS EVENING.
AS FAR AS WINDS GO, WE ARE ON THE BORDERLINE FOR NEEDING A WIND
ADVISORY, ESPECIALLY POST FRONTAL AS LAPSE RATES STEEPEN. THE
CAMS SHOW THIS SECOND PUSH OF NEAR WIND ADVISORY WINDS. NOT
CONFIDENT IN THIS YET, SO WILL HOLD OFF ON ADVISORY AT THIS
TIME.
LONG TERM /TUESDAY THROUGH SUNDAY/
ISSUED AT 308 AM CST MON NOV 18 2024
THIS WEEK WILL BE THE WEEK OF WIND WITH CHANCES FOR RAIN AND
SNOW MIDWEEK. IF THERE ARE ANY LEAVES LEFT ON YOUR TREES THEY
WILL LIKELY NOT BE THERE AFTER THIS WEEK, AND THEY MAY EVEN BE
ADVECTED OUT OF YOUR YARD! WE SEE WAVES OR UPPER LOWS MOVING
THROUGH THE AREA ALMOST EVERY 12 HOURS THROUGH THE REST OF THE
WEEK. WHILE MOST OF THESE WILL BE DRY OR HAVE LITTLE QPF
ASSOCIATED WITH THEM, THEY WILL ALL HAVE WIND. IF WE DON'T END
UP ISSUING A WIND ADVISORY TODAY, WE PROBABLY WILL BE THE END OF
THE WEEK.
LATER THIS WEEKEND, GUIDANCE REMAINS ALL OVER THE PLACE WITH THE
MOMENTUM FIELDS RESULTING IN A LOW CONFIDENCE FORECAST. IF YOU
WANT PRECIP THIS WEEKEND, USE THE GFS. IF YOU WANT A DRY
WEEKEND, USE THE ECMWF. THE ENSEMBLE SYSTEMS AREN'T MUCH BETTER
WITH MEANS FOR QPF SHOWING THE SAME THING AS THEIR DETERMINISTIC
MODELS.
WEDNESDAY INTO THURSDAY, A SERIES OF CLIPPERS IN QUICK
SUCCESSION ARE EXPECTED TO PULL THROUGH THE AREA. VERY LITTLE
QPF IS ASSOCIATED WITH THIS SYSTEM, LEADING TO LOW POP CHANCES.
THAT SAID, PTYPES WILL BE AN ISSUE IF PRECIP WERE TO FORM. IF
PRECIP IS FORMED BY LARGESCALE ASCENT THEN SNOW WOULD BE
FAVORED, IF PRECIP IS FORMED BY CONVECTIVE PROCESSES, GUIDANCE
HAS STEEP LLVL LAPSE RATES AND INSTABILITY, WE COULD SEE SOME
GRAUPEL/RAIN. TEMPERATURES DURING THE DAY ARE WELL ABOVE
FREEZING. SO NOT CLEAR ON PTYPE YET, THAT SAID, DO THINK IF WE
GET SNOW, WE SEE LITTLE TO NO IMPACTS.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 520 AM CST MON NOV 18 2024
IMPACTFUL WEATHER TO AVIATION EXPECTED THROUGH THE PERIOD AS
CIG/VSBYS BECOME IFR AND EVEN LIFR TODAY WITH A STORM SYSTEM
MOVING THROUGH THE AREA. WINDS WILL ALSO BE AN ISSUE WITH GUSTS
UP TO 35 KTS LATER IN THE PERIOD. CIGS MAY IMPROVE BRIEFLY WHEN
RAIN ENDS THIS AFTERNOON, BUT SHOULD BE SHORT LIVED AS MORE RAIN
AND WIND SHIFT SHOULD OCCUR WITH A FRONT PASSAGE THIS EVENING
AND OVERNIGHT.
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE.
IL...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR ILZ001-002-
007-009.
MO...NONE.
SHORT TERM...GIBBS
LONG TERM...GIBBS
AVIATION...GIBBS
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