704  
FXUS63 KDVN 231100  
AFDDVN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE QUAD CITIES IA IL  
500 AM CST SAT JAN 23 2021  
   
..12Z AVIATION UPDATE
 
 
   
SYNOPSIS
 
 
ISSUED AT 341 AM CST SAT JAN 23 2021  
 
A QUIET, BUT VERY COLD NIGHT WAS UNFOLDING ACROSS EASTERN IOWA,  
NORTHWEST ILLINOIS AND NORTHEAST MISSOURI, AND WAS BROUGHT TO US BY  
HIGH PRESSURE, ABUNDANT CLEAR SKIES AND LIGHT TO CALM WINDS.  
TEMPERATURES AS OF 2 AM WERE MOSTLY IN THE SINGLE DIGITS CWA WIDE,  
BUT SOME SPOTS WITH MORE ABUNDANT, FRESH SNOW COVER FOUND THEMSELVES  
BELOW ZERO. SO FAR, THE COLD SPOT HAS BEEN MXO, WHICH HAS BEEN  
SITTING AROUND FOUR BELOW ZERO FOR THE PAST FEW HOURS.  
 
NOT FAR AWAY TO THE WEST, NIGHTTIME GOES-16 RGB WAS SHOWING  
INCREASING CLOUD COVER OVER EASTERN NEBRASKA, FAR SOUTHWEST IOWA AND  
NORTHWEST MISSOURI IN RESPONSE TO INCREASING MOISTURE AND WAA ACROSS  
THE PLAINS. OVERTIME, THIS WILL WORK ITS WAY EAST, AND WILL IMPACT  
OUR AREA THROUGH THE SHORT TERM PERIOD.  
 

 
   
SHORT TERM
 
(TODAY THROUGH SUNDAY)  
ISSUED AT 341 AM CST SAT JAN 23 2021  
 
KEY MESSAGES:  
 
1) SNOW DEVELOPS BY LATE AFTERNOON AND CONTINUES THROUGH TONIGHT, 1-  
3 INCHES MAINLY NORTH OF HWY 30 EXPECTED.  
 
2) LIGHT SNOW/FREEZING DRIZZLE CHANCES PERSIST THROUGH SUNDAY  
MORNING, MAINLY DRY FOR THE REMAINDER OF THE DAY WITH CLOUDY SKIES.  
 
OTHER THAN GRADUALLY INCREASING CLOUDS, MOST OF THE AREA WILL SEE A  
QUIET DAY ON THE WEATHER FRONT AS THE SURFACE HIGH SLOW EXITS THE  
AREA TO THE EAST. THIS HIGH WILL TAKE THE COLD AIR MASS WITH IT,  
ALLOWING FOR SOUTHERLY FLOW ALOFT TO ADVECT SLIGHTLY WARMER  
TEMPERATURES BACK INTO THE AREA. HIGHS SHOULD RANGE FROM NEAR 20  
ALONG THE HWY 20 CORRIDOR, TO LOW 30S ALONG AND SOUTH OF HWY 34.  
 
EARLY THIS AFTERNOON, OUR FIRST SHOT AT SOME PRECIPITATION SHOULD  
BEGIN TO MAKE ITS WAY INTO OUR NORTHWEST CWA AS INCREASING LOW-LEVEL  
WINDS BEGIN MOVING INTO THE AREA. GFS/NAM IN GOOD AGREEMENT OF 30-40  
KT LLJ IN PLACE OVER CENTRAL IOWA BY MID-AFTERNOON, WHICH PUTS MUCH  
OF NORTHEAST IOWA/SOUTHERN MINNESOTA IN A GOOD SPOT FOR SOME  
INCREASED LIFT/FRONTOGENESIS. MOISTURE WITH THIS INITIAL SURGE OF  
WINDS WILL BE MORE LACKING IN OUR AREA VS. AREAS TO OUR NORTHWEST AS  
WE ARE CLOSER TO THE SURFACE HIGH, WHICH SHOULD HELP KEEP THE  
HEAVIEST SNOWFALL WELL OUT OF THE AREA. FOR OUR CWA, EXPECT A  
DUSTING TO A FEW TENTHS NORTH OF A WATERLOO TO DUBUQUE LINE.  
 
MORE MOISTURE AND LIFT WILL ARRIVE ACROSS THE AREA LATER THIS  
EVENING AND TONIGHT AS SOUTHERLY FLOW AHEAD OF A DEVELOPING SURFACE  
LOW IN KANSAS INCREASES. FAVORABLE TEMPERATURES AND PLENTY OF ICE  
FROM SEEDER CLOUDS ALOFT WILL ALLOW THE BULK OF PRECIPITATION TO BE  
ALL SNOW FOR THE NIGHT, BUT AMOUNTS WILL BE LIMITED THANKS TO A  
RELATIVELY SHALLOW AND NOT FULLY SATURATED DGZ. HOWEVER, DECREASING  
CLOUD ICE LATE IN THE NIGHT COULD RESULT IN MORE OF A THREAT OF  
FREEZING RAIN/DRIZZLE, BUT CONFIDENCE REMAINS LOW ON THIS BEING  
WIDESPREAD.  
 
SNOWFALL TOTALS WILL BE HIGHEST NORTH OF THE HWY 30 CORRIDOR, WHERE  
1-3 INCHES IS EXPECTED THROUGH 6 AM SUNDAY. AMOUNTS WILL AROUND 1  
INCH OR LESS TO THE SOUTH. DUE TO THE LOW EXPECTED TOTALS, KEPT WITH  
THE THEME OF NO WINTER WEATHER ADVISORY WITH THIS FORECAST PACKAGE.  
 
EXPECT A LULL IN WIDESPREAD PRECIPITATION SUNDAY, AS HIGH PRESSURE  
ACROSS THE UPPER MISSISSIPPI VALLEY ATTEMPTS TO BUILD INTO THE AREA.  
DESPITE THE HIGH, CLOUDS WILL BE PLENTIFUL AS THE LOW-LEVELS REMAIN  
SATURATED. THIS WILL HELP KEEP TEMPERATURES THROUGH THE DAY IN THE  
UPPER 20S TO LOW 30S, WITH THE HIGHER END OF VALUES FAVORED OVER  
SOUTHEAST IOWA, WEST CENTRAL ILLINOIS AND NORTHEAST MISSOURI.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 341 AM CST SAT JAN 23 2021  
 
KEY MESSAGES:  
1) INCREASING CONFIDENCE ON A STRONG WINTER STORM IMPACTING THE  
REGION MONDAY INTO TUESDAY.  
2) ACTIVE PATTERN TO PERSIST THROUGH THE END OF JANUARY.  
 
SUNDAY NIGHT  
 
LINGERING WEAK WARM ADVECTION SHOULD FOSTER POTENTIAL FOR  
EXCEEDINGLY LIGHT PRECIPITATION ACROSS AREAS NEAR TO SOUTH  
OF I-80. FORECAST SOUNDINGS SUGGEST POTENTIAL FOR LOSS OF  
IN-CLOUD ICE, AND THEREFORE COULD BE FREEZING DRIZZLE ALONG  
WITH SOME FLURRIES OR VERY LIGHT SNOW POSSIBLY. WILL HAVE TO  
KEEP AN EYE ON ANY LIGHT GLAZING POTENTIAL AND IMPACTS TO  
TRAVEL INTO THE MONDAY AM COMMUTE.  
 
MONDAY-TUESDAY  
 
CONFIDENCE IS INCREASING ON A STRONG WINTER STORM IMPACTING  
THE REGION WITH POTENTIAL SIGNIFICANT TRAVEL IMPACTS DUE  
TO HEAVY SNOW AND ALSO A WINTRY MIX POSSIBLE SOUTH. STILL  
UNCERTAINTY IN THE EXACT TRACK, LOCATION OF THE HEAVIEST  
PRECIPITATION AND AMOUNTS, BUT IF YOU ARE PLANNING ANY TRAVEL  
DURING THIS TIME YOUR STRONGLY ENCOURAGED TO KEEP UPDATED ON  
THE FORECAST AND PERHAPS EVEN CONSIDER DELAYING OR ADJUSTING  
TRAVEL PLANS.  
 
ATTENTION IS FOCUSED ON A SHORTWAVE EJECTING FROM THE GREAT BASIN.  
STRONG UPPER LEVEL JET DIVERGENCE WILL AID CYCLOGENESIS IN THE  
SOUTHERN PLAINS /OKLAHOMA/ LIFTING NORTHEAST INTO THE OHIO VALLEY.  
NAM APPEARS TO BE AN OUTLIER IN QUICKLY DEAMPLIFYING THE  
SHORTWAVE AND DISCOUNTED IN FAVOR OF BLEND OF GFS/ECMWF WITH  
INPUTS FROM UKMET. GENERAL CONSENSUS OF THIS DETERMINISTIC BLEND  
AND GFS/ECMWF ENSEMBLE MEANS FAVOR A MORE NORTHERLY TRACK OF THE  
SURFACE LOW, ALBEIT STILL PASSING SOUTH OF OUR AREA. A BIT OF A  
SLOWING TREND IN THE SYSTEM HAS ALSO BEEN OBSERVED IN THE  
GUIDANCE. PRECIPITATION IS LIKELY TO OVERSPREAD MUCH OF THE AREA  
AS MONDAY PROGRESSES FROM SOUTH TO NORTH, AND LINGERS TUESDAY  
ALBEIT WEAKER. STILL SOME TIME FOR THE FINER DETAILS TO GET IRONED  
OUT, BUT STRENGTH OF SYSTEM AND ANOMALOUSLY GULF MOISTURE FEED  
PER NAEFS 3-4 STANDARD DEVIATIONS ON PWATS SUPPORT THE POTENTIAL  
FOR A MODERATE TO HEAVY PRECIPITATION EVENT, WHICH WOULD LIKELY OFFER  
SIGNIFICANT TRAVEL IMPACTS.  
 
TIMING  
 
THE PRECIPITATION IS LIKELY TO OVERSPREAD THE AREA FROM SOUTH  
TO NORTH ON MONDAY AIDED BY UPPER LEVEL DIFFLUENCE AND  
WAA/ISENTROPIC ASCENT WITHIN INCREASING GULF MOISTURE TAP INTO  
SYSTEM. PEAK WOULD APPEAR TO BE MONDAY AFTERNOON/NIGHT BEFORE  
SLOWLY DECREASING BUT LINGERING TUESDAY IN A SLOWLY WANING  
DEFORMATION AXIS. MONDAY PM COMMUTE WOULD APPEAR TO HAVE GREATEST  
IMPACTS, BUT LIKELY STILL AN IMPACT FOR THE TUESDAY AM COMMUTE AS WELL.  
 
PRECIPITATION  
 
THE INCREASING WAA/ISENTROPIC ASCENT WILL LIKELY DRIVE AN ELEVATED  
WARM NOSE AT OR ABOVE 0C, WHICH COULD LEAD TO A WINTRY MIX  
POTENTIAL INTO PORTIONS OF THE AREA MAINLY SOUTH OF I-80 ON MONDAY.  
OTHERWISE, PREDOMINANTLY SNOW IS FAVORED OF WHICH COULD BE HEAVY  
AT TIMES GIVEN THE STRENGTH OF FORCING AND WELL ABOVE NORMAL MOISTURE.  
IT APPEARS THAT SEVERAL INCHES OF SNOW ARE LIKELY, WITH INCREASING  
POTENTIAL FOR A BAND OF 6 INCHES OR MORE OF ACCUMULATION. STILL  
UNCERTAINTY THOUGH ON PLACEMENT OF THIS BAND. THE SNOW IS LIKELY TO  
BE PRIMARILY A WETTER/HEAVIER TYPE SNOW EARLY IN THE EVENT, BUT  
BY LATE MONDAY NIGHT AND TUESDAY A TRANSITION TO A HIGHER SLRS AND A  
FLUFFIER SNOW IS ANTICIPATED AS COLD ADVECTION INCREASES. SOME ICE  
ACCUMULATION IS ALSO POSSIBLE SOUTH OF I-80, AND THIS APPEARS TO BE  
LIGHT AT THIS TIME.  
 
WINDS  
 
NAEFS CONTINUES TO SUGGEST AN ANOMALOUSLY NORTHEAST JET COMPONENT  
DEVELOPING WITH THIS SYSTEM, AS IT TRACKS TO OUR SOUTH. THUS,  
HAVE BUMPED UP WINDS ESPECIALLY GUSTS BY MONDAY NIGHT THROUGH  
TUESDAY WITH GUIDANCE INDICATING SOME POTENTIAL FOR 25-30+ MPH  
GUSTS FROM E/NE. THIS COULD LEAD TO SOME BLOWING/DRIFTING POTENTIAL  
BY MONDAY NIGHT THROUGH TUESDAY WITH A TRANSITION TO A FLUFFIER SNOW.  
 
MIDWEEK AND BEYOND  
 
WHILE A FAIR AMOUNT OF UNCERTAINTY EXISTS WITH THE NEXT SYSTEM,  
THERE IS SEEMINGLY A GENERAL CONSENSUS SIGNAL FOR A WEAKER  
SHORTWAVE AROUND THE WEDNESDAY TIMEFRAME. NBM POPS APPEARED TOO LOW  
AS SEEMINGLY IT HAS STRUGGLED WITH LIGHTER QPF EVENTS OF LATE, AND  
THUS HAVE COLLABORATED WITH NEIGHBORS TO BUMP UP INTO CHANCE POPS  
FOR MAINLY SNOW. MAIN MESSAGE WITH THIS SYSTEM IS MUCH LOWER IMPACT  
POTENTIAL WITH IT.  
 
THE ACTIVE SOUTHWEST FLOW PATTERN LOOKS TO LINGER INTO NEXT WEEKEND,  
AND WOULD OFFER SOME POTENTIAL FOR ANOTHER SYSTEM HEADING DEEPER INTO  
NEXT WEEKEND. TEMPERATURES ALSO LOOK TO REBOUND, WITH THE EXTENT OF  
ANY WARMUP PREDICATED ON EXTENT OF SNOW COVER.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 459 AM CST SAT JAN 23 2021  
 
DEPARTING HIGH PRESSURE WILL KEEP VFR CONDITIONS IN PLACE ACROSS THE  
AREA THROUGH MUCH OF THE DAYTIME TODAY. CALM WINDS AND CLEAR  
SKIES WILL GIVE WAY TO INCREASING CLOUDS AND INCREASING SOUTHEAST  
WINDS BY MIDDAY. BY LATE AFTERNOON, THERE IS POTENTIAL FOR BAND OF  
MAINLY VFR SNOW TO IMPACT CID/DBQ. HOWEVER, PLENTIFUL DRY AIR IN  
PLACE MAY LIMIT THIS, SO HAVE CHOSEN TO MAINTAIN THE PROB30 GROUP  
FOR THIS TAF. HIGHER CONFIDENCE OF A WIDESPREAD SNOW ARRIVING  
TONIGHT FOR ALL TERMINALS, WITH CONDITIONS DETERIORATING TO MVFR  
WITH SPOTTY IFR POSSIBLE.  
 

 
   
DVN WATCHES/WARNINGS/ADVISORIES
 
 
IA...NONE.  
IL...NONE.  
MO...NONE.  

 
 

 
 
SYNOPSIS...SPECK  
SHORT TERM...SPECK  
LONG TERM...MCCLURE  
AVIATION...SPECK  
 
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