000 
fxus63 kdvn 160228 
afddvn 


Area forecast discussion 
National Weather Service Quad Cities Iowa Illinois 
828 PM CST Tue Jan 15 2019 


Update... 
issued at 828 PM CST Tue Jan 15 2019 


Surface temperatures have remained steady or have even risen a 
few degrees over the past several hours, with widespread 
readings a few degrees above freezing at 8 PM in the low level 
warm advection southwesterly flow over the forecast area. The 
next cold front and influx of cooler, drier air was just to the 
northwest, roughly from Decorah to Fort Dodge, advancing steadily 
southeastward. 


With winds already shifting to more westerly, little if any 
drizzle occurring and no reported issues with Road conditions, 
will cancel the Winter Weather Advisory for areas north of I-80. 
Will keep the advisory going across the south for now as cannot 
totally rule out at least patchy drizzle with temps near freezing 
to create slick spots on untreated roads later tonight. 


&& 


Synopsis... 
issued at 238 PM CST Tue Jan 15 2019 


Broad high pressure was centered over the southern Mississippi River 
valley at 19z, with temperatures across the region in the upper 20s 
to lower 30s. Aloft, low-level warm air advection was contributing to patchy -fzdz 
development in low clouds underneath a strong inversion, which was 
creating some travel difficulties across the County Warning Area. To the north, a 
frontal boundary extended from northern Minnesota to southeastern ND, and 
was quickly moving south. 


&& 


Short term...(this evening through wednesday) 
issued at 238 PM CST Tue Jan 15 2019 


The main challenge of the short term period is the threat of -fzdz 
heading into tonight. 


Patchy areas of -fzdz will continue to be a problem across the 
region through the afternoon as the warm air advection remains in place. Ice isn't 
apparent on the top of the clouds from the GOES-16 cloud phase 
distinction rgb, so expecting this precipitation to primarily remain 
-fzdz through the evening. As the aforementioned front approaches 
the region tonight, additional lift will translate to areas of -fzdz 
through Wednesday morning. 


As a result, have continued the Winter Weather Advisory 
for the entire County Warning Area. Counties along and north if I-80 are covered 
through midnight, with counties south of I-80 through 6 am 
Wednesday. With surface temperatures falling below freezing, any 
untreated surfaces will quickly become slippery, which could create 
problems for the evening and Wednesday morning commutes. 


Short-lived quiet weather follows behind the front Wednesday 
morning. Unfortunately, confidence on clouds breaking remains low as 
model soundings show the low-level inversion remaining strongly in 
place. 


Long term...(wednesday night through tuesday) 
issued at 238 PM CST Tue Jan 15 2019 


The weather pattern will be turning much more active due to a major 
pattern change in the flow aloft. Refer to the climate section for 
more information about the pattern change. 


With the weather pattern turning much more active over the next 
seven days, the potential for winter weather headlines will also be 
increasing. 


Wednesday night/Thursday 
assessment...medium to high confidence 


The first of many systems will move through the Midwest bringing a 
mix of snow and some freezing rain to the area. The area most at 
risk for accumulating snow and freezing rain looks to be along/south 
of I-80. Winter weather headlines will likely be needed for this 
system. North of I-80, precipitation will be in the form of light 
snow. 


As for accumulations, a dusting of accumulation should occur in the 
I-80 corridor. South of the I-80 corridor accumulations of an inch or 
less are expected with the highest amounts south of an Ottumwa, Iowa 
to Galesburg, Illinois line. North of I-80 accumulations should range from 
a trace to a dusting at best. 


Thursday night/Friday morning 
assessment...high confidence 


Quiet and dry conditions are expected across the area as high 
pressure quickly moves through the Midwest. Attention then turns to 
the weekend storm system. 


Friday night on... 


Friday afternoon through Saturday 
assessment...high confidence on a winter storm. Medium confidence 
on timing and low to medium confidence on amounts. 


The next storm system will affect the Midwest for the start the 
weekend. There are still some timing and track differences with the 
storm system. However, it appears that snow will begin moving into 
the area by sunset Friday and will continue through Saturday before 
ending around sunset on Saturday. 


Given the timing and track differences snowfall amounts have yet to 
firm up. However, the snow will be of the dry fluffy kind so it will 
not take much moisture to produce accumulating snow. Additionally, 
the dry fluffy snow will easily drift if not blow with the 
increasing winds. 


Headlines for this storm system will likely be needed. 


Saturday night through Tuesday 
assessment...high confidence on much colder than normal 
temperatures and that headlines will be needed for the cold. Low 
to medium confidence on the timing/impact of additional storm systems. 


Very cold conditions will be seen Saturday night through Monday. 
Headlines for the cold temperatures will likely be needed Saturday 
night into Sunday morning and again Sunday night into Monday morning. 


On top of the very cold weather, a weak storm system will move 
through the area Sunday night into Monday producing some light snow 
followed by another storm system Monday night into Tuesday. 


Right now the model consensus has slight chance pops for areas 
along/north of I-80 Sunday night into Monday. 


For Monday night into Tuesday, the model consensus has slight chance 
to chance pops Monday night that increase to likely/categorical pops 
on Tuesday. 


The Monday night/Tuesday storm system bears watching as the 
potential exists for another widespread accumulating snow event. 


&& 


Aviation...(for the 00z tafs through 00z Wednesday evening) 
issued at 528 PM CST Tue Jan 15 2019 


Widespread IFR conditions with low ceilings, fog and patchy light 
drizzle and freezing drizzle will impact the terminals this 
evening. A weak front dropping south through the region will end 
the threat of drizzle and shift winds from southwest to north 
overnight. The low clouds are likely to linger behind the front 
through Wednesday morning, and possibly through the afternoon. The 
latest forecast has taken a more pessimistic approach, keeping 
the low clouds in place through the day, resulting in MVFR 
conditions. 




&& 


Climate... 
issued at 238 PM CST Tue Jan 15 2019 


Week 2...January 23 through 29th 


A major pattern change will occur starting around January 20th with 
a high probability of it continuing into early February. The climate 
prediction center has a 70 percent probability of below normal 
temperatures through the end of the month. 


The cfs model has the Arctic oscillation trending sharply negative 
through the end of month. There is a high probability of an Arctic 
outbreak, potentially significant, occurring toward the end of 
January. 


&& 


Dvn watches/warnings/advisories... 
Iowa...Winter Weather Advisory until 6 am CST Wednesday for Des Moines- 
Henry Iowa-Jefferson-Keokuk-Lee-Louisa-Van Buren-Washington. 


Illinois...Winter Weather Advisory until 6 am CST Wednesday for Bureau- 
Hancock-Henderson-Henry IL-McDonough-Mercer-Putnam-Warren. 


MO...Winter Weather Advisory until 6 am CST Wednesday for Clark- 
Scotland. 


&& 


$$ 


Update...sheets 



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