Official Winter Storm Thread for 12/21 - 12/26

jsb

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Seems like they may be starting to back off the potential of this storm as time goes on for a majority of Iowa. Sounds like the trump card will be what the temps do.

Yeah, but the bad news for me, is that it will be at it's worst now on Christmas Day when I am scheduled to fly to London. I can't afford to have too many delays in that plan because I have to be there by Sunday morning and due to time differences I pretty much must leave Des Moines on Friday and make my connection in Chicago.
 

garn91

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The next round of updates from the NWS including forecasts, Area Forecast Discussions, possible watches/warnings and Hazardous Weather Outlooks should be coming out within the next hour, normally by 3:30 at the latest, all though in situations like this, the DSM NWS normally drags their feet and is the last NWS office in the state (Omaha for SW & WC Iowa, Sioux Falls for NW Iowa, Lacrosse for NE Iowa and the Quad Cities for eastern & SE Iowa) to issue their updates.
 

chuckd4735

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I heard we are supposed to get more than we got last week. For the central Iowa area

Well since Central Iowa didn't get much snow last week, yes. Now if you meant the last storm, from what I am seeing/hearing, I doubt this one will be worse, but still could be bad. Looks like temps are a little unknown as of right now and will be the determining factor.
 
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alarson

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I heard we are supposed to get more than we got last week. For the central Iowa area

from what i'm reading (weather experts correct me if i'm wrong) more total precipitation, but a lot of it might come in the form of water, so actual snowfall may be less.
 

garn91

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Here's the NWS DSM Area Forecast Discussion:

NOW ON TO THE BIG STORM SYSTEM...WHICH REMAINS MORE OR LESS ON TRACK
RELATIVE TO THINKING OF PREVIOUS FORECAST SHIFTS. THE OVERALL TIMING
AND LONG DURATION/HIGH QPF NATURE OF THE EVENT HAVE NOT
CHANGED...HOWEVER THE MODELS ARE GENERALLY COMING INTO BETTER
AGREEMENT ON CURVING THE CYCLONE LEFTWARD...MOVING NORTH OR NORTH
NORTHWEST FROM MISSOURI INTO IOWA...AS IT IS BECOMING STACKED AND
OCCLUDED ON WEDNESDAY NIGHT/THURSDAY. IN THIS SITUATION...FORECAST
SOUNDINGS ARE UNANIMOUS IN BRINGING MOST OF THE PRECIP IN OUR
SOUTHEASTERN AREAS FROM WEDNESDAY THROUGH THURSDAY IN THE FORM OF
RAIN...WITH MOSTLY SNOW IN THE NORTHWEST AND A MIX IN BETWEEN.
EVENTUALLY THE PRECIP WILL CHANGE OVER TO SNOW FROM NORTHWEST TO
SOUTHEAST AS THE SYSTEM BEGINS TO MOVE AWAY...HOWEVER THE TIMING OF
THIS CHANGE IS STILL VERY UNCERTAIN AND WILL HAVE SIGNIFICANT
EFFECTS ON FORECAST SNOWFALL TOTALS ACROSS MUCH OF THE
AREA...ESPECIALLY CENTRAL PORTIONS FROM AROUND ATLANTIC...TO DES
MOINES...TO WATERLOO. WE ARE ISSUING A WINTER STORM WATCH FOR AREAS
ROUGHLY ALONG AND NORTHWEST OF THAT LINE WHICH IS WHERE WE EXPECT
SNOW AND/OR FREEZING RAIN/SLEET ON WEDNESDAY. WARNING CRITERIA
ACCUMULATIONS ARE MOST LIKELY FURTHER NORTHWEST WITHIN THE WATCH
AREA...WHILE IN THE DES MOINES METRO AND AREAS TO THE SOUTHWEST TO
NORTHEAST ACCUMULATIONS OF WINTER PRECIP ON WEDNESDAY MAY NOT REACH
WARNING CRITERIA. HOWEVER...THERE IS ENOUGH UNCERTAINTY IN THIS
SCENARIO TO WARRANT A MARGIN OF ERROR...AND EVEN IN THE WARMER
SOLUTIONS OF THE 12Z GFS AND ECMWF WHERE THE PRECIP AT DSM FALLS AS
RAIN FROM AROUND MIDDAY WEDNESDAY THROUGH MOST OR ALL OF
THURSDAY...THERE ARE STILL INDICATIONS OF A BRIEF PERIOD OF
SLEET/FREEZING RAIN ON WEDNESDAY MORNING AS THE PRECIP MOVES IN FROM
THE SOUTH AND BEFORE WAA BECOMES STRONG ENOUGH TO PUSH THE PROFILES
ABOVE FREEZING. WITH THE POSSIBILITY OF THIS FREEZING PRECIP COMING
DURING THE WEDNESDAY MORNING COMMUTE HOURS...AS WELL AS THE
AFOREMENTIONED UNCERTAINTY BUFFER...FEEL IT IS WISE TO INCLUDE THOSE
AREAS IN THE WATCH AT THIS TIME. WE ARE ALSO ISSUING AN ESF TO
ACCOUNT FOR POTENTIAL FLOODING IN OUR SOUTHERN AND SOUTHEASTERN
COUNTIES WHERE SIGNIFICANT RAINFALL TOTALS ARE POSSIBLE ON TOP OF
SNOWPACK. HYDROLOGICAL CONCERNS ARE POTENTIALLY SIGNFICIANT IN SOME
OF THESE AREAS. THE STORM SYSTEM WILL BE MOVING AWAY LATE IN THE
WEEK WITH PRECIP TAPERING OFF FRIDAY NIGHT OR SATURDAY. THEREAFTER A
QUIETER WEATHER PATTERN APPEARS IN STORE FOR THE LATTER HALF OF THE
WEEKEND AND EARLY NEXT WEEK.

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY AFTERNOON
FOR ADAIR-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-
CASS-CERRO GORDO-CRAWFORD-DALLAS-EMMET-FRANKLIN-GREENE-GRUNDY-
GUTHRIE-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-MARSHALL-PALO
ALTO-POCAHONTAS-POLK-SAC-STORY-TAMA-WEBSTER-WINNEBAGO-WORTH-WRIGHT.
 

chuckd4735

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
259 PM CST MON DEC 21 2009

...SIGNIFICANT RAINFALL AND SNOW MELT POSSIBLE WEDNESDAY AND THURSDAY...

AN UNSEASONABLY STRONG SURGE OF MOISTURE IS EXPECTED INTO THE
STATE ON WEDNESDAY AND THURSDAY. THIS IS FORECAST TO PUSH
TEMPERATURES ABOVE FREEZING BY WEDNESDAY AFTERNOON...PRIMARILY
ALONG AND SOUTH OF INTERSTATE 80. THEREFORE...RAIN IS THE PRIMARY
PRECIPITATION TYPE EXPECTED ACROSS THE SOUTHERN THIRD TO HALF OF
CENTRAL IOWA WEDNESDAY AFTERNOON INTO THURSDAY. BETWEEN THREE-
QUARTERS AND AN INCH AND A HALF OF RAIN IS FORECAST DURING THIS
TIME. IN ADDITION...THE SNOW ON THE GROUND CONTAINS AROUND AN INCH
TO INCH AND A HALF OF WATER. THE COMBINATION OF THE RAINFALL AND
SNOW MELT WILL LEAD TO LARGE AMOUNTS OF RUNOFF.

TEMPERATURES WILL BE THE BIG FACTOR IN THE EFFICIENCY OF THE
RUNOFF FROM SNOW MELT. SHOULD READING STAY JUST ABOVE
FREEZING...SNOW MELT WILL NOT BE AS QUICK AND RUNOFF WILL BE
MUTED. HOWEVER...SHOULD TEMPERATURES REACH 40 OR HIGHER...THEN
SNOW MELT WILL BE MUCH FASTER WITH A BIGGER RESPONSE IN RUNOFF.

AREA STREAMS AND RIVERS ACROSS THE SOUTHERN HALF OF IOWA WILL
LIKELY EXPERIENCE LARGE RISES DUE TO THE COMBINATION OF RAINFALL
AND SNOW MELT BY THURSDAY AND RIVER FLOODING MAY BECOME
PROBLEMATIC. BASINS WHICH APPEAR MOST LIKELY TO BE AFFECTED
INCLUDE THE CHARITON...LOWER DES MOINES...SOUTH SKUNK...CEDAR
CREEK...AND THE THOMPSON RIVERS ACROSS THE SOUTHERN HALF OF
CENTRAL IOWA.
 

wxman1

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Anyone else think that the latest NAM run is taking the freezing line crazy far north?
 

garn91

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Anyone else think that the latest NAM run is taking the freezing line crazy far north?

I don't know how to read the models or anything like that, but with the existing snow cover that we have, I just find it hard to believe that it's going to warm up all that much. The warmest it's been since the blizzard a couple of weeks ago has been what 33 or 34? Guess i'm just not convinced that a big time warm up is on the heels with the this storm.

Edit: yes I know 33 or 34 is above freezing. My point is that areas of Kansas that are in the Blizzard watch are forecasted to stay well below freezing, but here, the temp is going to jump even with a already decent snow pack?
 
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wxman1

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Sounds like good news. Care to elaborate?

It just seems to me like that particular model is keeping the freezing line up around the Iowa Minnesota border longer than any other model. It has it up there most of the day Wednesday and Thursday with a good deal of precip during that time period. This would in theory fall in the form of sleet I have a feeling. It's too hard to tell what will happen at this point.
 

chuckd4735

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I don't know how to read the models or anything like that, but with the existing snow cover that we have, I just find it hard to believe that it's going to warm up all that much. The warmest it's been since the blizzard a couple of weeks ago has been what 33 or 34? Guess i'm just not convinced that a big time warm up is on the heels with the this storm.

???
1997-10-25-14.jpg
 

CyinCo

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Anyone hearing anything about freezing rain tomorrow (tuesday) as well? Weather.com is saying wintery mix throughout the day. Doesn't sound significant but for those of us trying to avoid the storm by driving on Tuesday may STILL have to deal with some nasty weather. Ugh!!!! I can't wait for the Holidays to be done.
 

Iastfan112

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It just seems to me like that particular model is keeping the freezing line up around the Iowa Minnesota border longer than any other model. It has it up there most of the day Wednesday and Thursday with a good deal of precip during that time period. This would in theory fall in the form of sleet I have a feeling. It's too hard to tell what will happen at this point.

It was mentioned as an outlier in the 3 am DMX weather discussion. Just looking at the tracks I'll stick with the map I posted earlier, keep in mind that it'll be a situation where just a small difference in location will make a huge difference, one sounding, the Bufkit Cobb shows Des Moines getting 4 inches of snow but Carroll just to the northwest getting over 20 inches. That shows you how big of deal being off ever so slightly on where the low pressure tracks and how warm temperatures get influence the final precip types and totals from a storm.
 
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d4nim4l

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I don't know how to read the models or anything like that, but with the existing snow cover that we have, I just find it hard to believe that it's going to warm up all that much. The warmest it's been since the blizzard a couple of weeks ago has been what 33 or 34? Guess i'm just not convinced that a big time warm up is on the heels with the this storm.

Edit: yes I know 33 or 34 is above freezing. My point is that areas of Kansas that are in the Blizzard watch are forecasted to stay well below freezing, but here, the temp is going to jump even with a already decent snow pack?

What areas of Kansas are in the blizzard watch?

If it's far western Kansas then it is entirely possible that they're on the cold end of the jet stream while we are on the warm end.