WINTER STORM WATCH/RISK

Mar 27, 06:42 AM

The final figures are in on snowfall and eastern Iowa was the “big” winner using the term loosely. A pocket of heavy snow fell in Linn, Cedar, and Johnson counties with up to 7” reported in the Cedar Rapids area. Temperatures were just warm enough in most of Illinois except the far northwest that much of the precip fell as rain or sleet. Officially, the Quad Cities managed 3.2”. That was a tough one. So it goes…

Snow cover Sunday afternoon

10:40PM CALL OFF THE DOGS, THE STORM TANKED
The GFS has arrived and boy did it let me down. The 18Z run had 1” of precip. between midnight and 6am and the new run (6hrs. later) has .07” That is the difference between 8-9” of snow and less than an inch. I throw in the towel and respectfully ask for you forgiveness. I busted and it is crushing because I put everything I had into this forecast. As the saying goes, (and it really sounds trite), it wasn’t meant to be.
Folks, this really blows. I know every other forecaster ate this one but it sure doesn’t make me feel any better. Thanks for checking out my site and putting your faith in me. All I can say is nobody tried harder and that is the one thing you will always get from me, straight up, honest forecasts with 100% effort. Good night to you all and now it’s time to clean up my mess.
Ride the wind,
T. Swails

UPDATE 9:40PM
The new WRF has come in and it has bust all over it. Without seeing the new GFS which is going to be down within the hour, I can’t throw the towel in just yet but I don’t like the trends and I am warming up my arm. Currently snow is piling up just to the northwest of the Quad Cities. 4” has fallen in Cedar Rapids, while 3” accumulations have been measured in Lowden and Dubuque and it is still snowing. Later tonight I suspect another band will develop just to the southeast but unless that backs into the region snowfall projections will need to be cut back. Freezing rain has also popped up in spots but that is not likely to last long. Anyway, I will be getting the GFS around 10:30 and I will make a final call on where this event is going. What a dog this has turned into. More to come.

UPDATE 8:33PM
Well, the reason I have not been on lately is because not much is going on and I am trying to regroup as the storm does the same thing in s/eastern Illinois. What we expect to happen is the formation of a deformation band over the region by midnight. This makes me nervous because you have to put a lot of faith in a model and to be honest, this break we are in has not been well depicted by the models. Be that as it may, I now have my trust in this band that was predicted to form by the GFS 6 hours ago. So, I am playing the old waiting game and hoping like heck I do not get drilled by a major model flip flop. Only time will tell and the new GFS won’t clear until 10:35pm

With that in mind I am adding a satellite image of the system and you can see the moisture on the east side of the storm that is expected to be thrust our way. In a nutshell, this whole forecast will bust if this comes up short! Obviously, I’m sitting on pins and needles as a snow bust is my worst nightmare. When the new data hits or if something fresh pops up, I will be back….

UPDATE 6:49PM
Hey weatherheads, I am back from media business and I just got a fresh diet dew and it tasted mighty fine! Depending where you are, you are probably wondering what is going on with the storm. Well, first and foremost we are in a bit of a precip lull right now as a spoke of energy rotated through and took the first volley of rain, sleet, and snow with it.
Now, the primary deformation snow band is developing and that will arrive in here later this evening. Any mixed precip will quickly flip to snow and then we get into the real nuts and bolts of this system. As you know, the winds are really cranking and that depicts the dropping pressures that are associated with the deepening storm. As it matures tonight, the deformation band will spring to life and that will be when our snow accumulations will occur. Right now midnight to 6am seems to be prime time. Based on my earlier reasoning, snowfall rates of 1-2” per hour may materialize. It looked on the GFS that from the Quad Cities east the snow intensity would be greatest. This is where the potential for 8” snow totals exists.

Again, the situation is fluid and a little twist or turn can mean significant adjustments. Right now I just have to do what you are doing, which is wait and see how the puzzle comes together. More on that soon

MAJOR UPDATE 5:25PM………………………….
The new 18Z GFS which is my model of choice, is painting a very significant snowstorm picture as of 5:15pm. If its depiction is correct, and it is just a model with its flaws and quirks just like all of us, we are looking at a storm which happens this late in the year maybe once every 20 years. Heavy wet snow has the potential to accumulate more than 8” in some spots and we have already seen winds gusting 40-50 mph. I want to stress, I am not an alarmist and I am not 100% sure where the heaviest snow band will set up, but I am seeing big-time potential from the GFS. If you are reading this, you probably dig weather and understand how complex these situations are. In fact, most forecasters won’t touch what I said with a ten foot pole. However, I think it is prudent to put it out there that a special storm may be in the making. I have a forecast to freshen up and some media issues to deal with and I will be right back. Do stay tuned.

MAJOR UPDATE 4:58PM………………………….

STAND BY FOR A MAJOR UPDATE ON THE LATEST STORM TRENDS. IT LOOKS LIKE WE ARE IN FOR A RIPPER!!!!!!

UPDATE 4:32PM
Just saw this report of a 54mph gust in good old GOOD HOPE. That tells me we have a special storm on our hands. That really gets my attention…
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
327 PM CDT SAT MAR 28 2009

..TIME… …EVENT… …CITY LOCATION… …LAT.LON…
..DATE… ….MAG…. ..COUNTY LOCATION..ST.. …SOURCE…. ..REMARKS..

0321 PM NON-TSTM WND GST NE GOOD HOPE 40.56N 90.67W
03/28/2009 M54 MPH MCDONOUGH IL TRAINED SPOTTER

UPDATE 4:15

Here is an 850 Millibar chart from the 18Z WRF showing the freezing line aloft. (a threshold necessary to have in place for snow at the surface. This is at 7pm and anything west of that green line should be experiencing snow. Upper air soundings also were showing boundary layer temps initialized a bit warm at 12Z so this may be quite a bit far west meaning the transition could take place earlier. The bottom line here is that all snow should be falling from the Mississippi west by 7pm and within a couple hours of that off to the east. After 5 or 6 conditions should go downhill pretty fast as evaporative cooling kicks in.
Moderate sleet continues here at the home office and I am waiting for the new GFS due in about 20 minutes from now.

UPDATE 3:29PM
.SYNOPSIS…
AT 3 PM CDT…A DEEP LOW PRESSURE SYSTEM WAS LOCATED OVER SW MISSOURI WITH HEIGHT AND PRESSURE CHANGE FIELDS SUPPORTING
SYSTEM TO MOVE NE INTO NORTH CENTRAL INDIANA EARLY SUNDAY MORNING. LARGE HEAVY DEFORMATION ZONE MOVING INTO FORECAST AREA AND TRENDS SUPPORT SIGNIFICANT PRECIPITATION NEXT 8 TO 12 HOURS BEFORE ENDING FROM WEST TO EAST. SURFACE OBSERVATIONS SHOW A MIXTURE OF SLEET AND SNOW NORTHWEST 1/3 AND RAIN AND SLEET SE 2/3 SUGGESTING 18Z RAOB SOUNDINGS FINDING OF 12Z NAM-WRF AND GFS RUNS TOO MILD BY A DEGREE OR 2 IN LOWEST 0-1 KM OF BOUNDARY LAYER. AS A RESULT, I WILL ADJUST THE THERMAL FIELDS AND MAKE MY FORECAST ON CONCEPTUAL FORCING FROM THE GFS/-WRF MODELS ALONG WITH MY PERSONAL OBSERVATIONS OF RADAR, SATELLITE, AND TEMPERATURE. THIS SUPPORTS KEEPING CURRENT WARNINGS AND ADVISORIES IN PLACE WITH VERY MINOR CHANGES.

PRECIPITATION TO CHANGE OVER TO ALL SNOW NEXT 2 TO 4 HOURS WEST OF
MISSISSIPPI RIVER AND EAST OF RIVER BY LATE EVENING AS DEEPENING
SURFACE LOW MOVES NORTHEAST PULLING IN COLDER AIR ALLOWING FOR
SIGNIFICANT EVAPORATIVE COOLING TO CONTINUE. JUST RECEIVED A REPORT
PAST 5 MINUTES FROM FORT MADISON IOWA NOW REPORTING HEAVY WET SNOW
ATTM WITH BIG FLAKES SUPPORTING DECENT SNOW ACCUMULATIONS AFTER DARK.

ALSO RAIN CHANGING TO SNOW IN KEOSAUQUA IOWA. THUS…KEEPING 4 TO 8
INCH ACCUMULATIONS ALL AREAS. SOME THUNDER-SNOW POSSIBLE ON EDGE OF DEFORMATION AND THIS MAY ALLOW FOR LOCALIZED HIGHER AMOUNTS ALONG AND EAST OF MISSISSIPPI RIVER. NE TO NORTH WINDS OF 20 TO 35+ MPH WITH LOCALLY HIGHER SPEEDS MAY COMBINE WITH HEAVY WET SNOW TO PRODUCE NEAR WHITEOUT CONDITIONS LATER THIS EVENING AND OVERNIGHT. MINIMUMS HAVE BEEN UPPED A DEGREE OR TWO WITH SLOWER PASSAGE OF SFC LOW.
..NICHOLS..

UPDATE 2:50PM

Sleet is banging on the window and the wind is howling a gale from the northeast. Mother nature is in a fowl mood and the fun is just beginning. There is much to ponder until the new runs hit the computer begining around 3:30. I will have much to say once I feel informed enough too stick my out so put that on your weather agenda.

I did want to show you a satellite image of the storm from over 20,000 miles in space. I’ts very easy to see both the warm and cold sectors of the storm. What we will experience is the deformation band associated with the cold sector. I have highlighted this in the satellite pic. That is where our sleet and snow found and the enhancement with its blue colors shows the cold cloud tops of a mature cyclone. I would not be at all shocked to see and hear thunder and lightning over the next few hours as the maximum lift and instability arrives. Another way to tell how strong the storm is is by observing the dry slot on the image. Right behind the low you can see there is little cloud cover and no enhancement. That is dry air pulling into the center of the storm. Overall, this is a classic looking winter storm.

OK, now I am going to scrape up a couple new graphics and await the new runs. From here on out time will be tight so I may just plunk the images that are self explanatory without text. Hope you understand. By the way, I just want to say thanks for coming to the sight. My new one will be up soon and it will have radar, satellites, temperatures, and much more. It will make your time here even richer. Be sure to keep that in mind. What I have here is just the tip of the Terry Swails weather experience!
By the way, nice snowflakes are now falling at the home office in Port Byron. I’m liking that…. See you soon.

UPDATE 12:58PM
Just looked at the RUC (a short term high resolution model) and it is really disturbing. It has the storm deepening so much that it is wrapping that warm air aloft all the way back to Iowa City and up to Dubuque even through 7 this evening. That is going to mean the switch to snow will be even later. It also makes me very concerned that with the mixture of rain and sleet so prolonged we may not reach our predicted snow levels.

This is a really ugly twist and the forecast has now gotten extremely complicated. One of the things I have said all along about these big spring storms is that they are very fickle and subject to surprises such as this. For 4 days none of the models had this complication and had been very consistent keeping 850 temps. cold enough for just a short period of rain or mix before the switch to snow. So much for consistency.

Now my dilemma is what to do with the forecast. The dynamics are so powerful that we will eventually cool the full column and snow will result. We will also get a period where it will likely snow pretty darn good. The big question is…for just how long? Warning level snows will not be achieved if we can’t sustain the strong lift for at least 5 or 6 hours. I am quite concerned about that. My gut feeling is to cut back on snow totals but there is enough doubt that I will hold off a couple more hours or until something happens that puts me over the edge. Stay tuned on this major issue….

UPDATE 11:37AM
OK, here is the scoop and there are some new factors that will make this a really tricky forecast. Here we go. As I noted earlier this morning, the closed low is really creeping along and so is precip. My 7:30am blog reflected this and the NWS has pushed the start of the warnings back 3 hours to 4:00pm. Obviously, we have several more hours to go before we get into a mess.

Speaking of a mess, the new 12Z runs show a narrow wedge of warm air aloft that will not kick out of the s/east half of the region until mid evening (this includes the Quad Cities.) What this means is that rain, sleet or even some freezing rain my develop for several hours until the column can cool enough to change this over to snow. That is significant because it will chop snow totals down at least a couple inches in those spots where the changeover is slower.

On top of that, we see the tight circulation of the storm forcing heavier precip totals further west into eastern Iowa. This is the area where the warm layer will exist the shortest so the change over to snow will happen first. For this reason the winter storm warning will be extended further west and it appears the counties from the Quad Cities north and west may very well end up with the highest snow totals which still should reach into the 3-7” range.

Because of the complexity of this new development, I will need to do some more analysis and fine tuning. That means some new graphics and tweaks and an update of the fresh forecast. I will be back asap with those.

Thanks…T. Swails

UPDATE 10:59AM
Hey out there, I have the new model runs to share and I will have a full report on in just a few minutes time right here. Thanks for coming to the site…

UPDATE 7:34AM
Good morning everybody. I hope your night’s sleep was longer than mine! As you can see from the above graphic all of the area is under some sort of winter weather advisory or warning. For many of us, a winter storm warning is in effect from 1:00pm today until 10:00am Sunday. What this all boils down to is that winter weather will arrive in all areas by late afternoon or early this evening. The system’s arrival has slowed some meaning we will get through most of the day without many issues. However, conditions will go downhill rapidly as we approach Saturday evening. In all locations, snowfall of 3-7” is likely by Sunday morning.

This graphic will give you an idea how to plan your day and the storms arrival

By the way, is that pancakes I smell? If so, send some my way! Anyway, as things get cooking weatherwise later today and tonight I will be active on this blog with regular reports and insights. For that reason I am going back for a couple hours of shut eye. I have a long day ahead and a challenging forecast. See you in a bit. T. Swails

UPDATE 10:58PM

OK everybody, the 0z GFS is in and like the WRF earlier, strength, track, etc. are all very close to the previous runs. The one exception, the precip totals which again are down about 1/4” from 18Z run (6 hrs. before) This may be due to convection in the lower Mississippi Valley or it just might be the model correcting itself. On thing is for sure, there is great consistency between both U.S. models and that still leaves most of us with 4-7” snow potential. (a few spots might rack up 8”) One minor detail is that the storm is just a bit slower and that will keep us pretty much problem free until mid-afternoon or later.

UPDATE 10:17PM
I did a quick fact check and I found that this year the QCA has officially measured 43” of snow. The majority of that fell in a 6 week period from December 1st to January 15th. To date, the 43” is 9” above normal. What is interesting is that we have had no measurable snow since the 21st of February. If for some reason this storm misses us completely (If that happens you will never see or hear from me again) that would be the second earliest date of our last measurable snowfall. So, with my whole future riding on this storm, I await the verdict of the new GFS which will be in in about 30 minutes. Until then, ride low and fast.

UPDATE 9:30PM
OK guys and gals, I have not forgotten about you. The new model runs are running like a red dog and that means I will have some fresh thoughts on where we stand soon. So far I have seen the WRF and it is nearly identical on track, strength, timing, and extent of the precip shield. It does come in about 1/4” lighter on precip totals which would mean 2 or 3” less snow. I was far more concerned about the other parameters holding and it may be that later runs push totals back up. Those types of fluctuations are common in back to back runs.

Now we wait for the GFS which will not clear for an hour. This is the model I put most of my faith in and this will be an important piece of the puzzle in terms of what our storm ends up doing. I’m nervous as all get out. I personally love snow so it would be nice if it would come in big for me. It’s been years since the Quad Cities has had an official 8” snowfall. If we don’t get it this time around it will likely be at least 9 months before our next chance.

I will be back with some facts on this years biggest snowfalls in a few. See you all then

UPDATE 6:58PM
Hey all you hard core weather heads. The new storm briefing is up. You can get your fix there. Secondly, I am in for a short lunch break before I get back in gear for the late evening runs. These will be very important. If they hold, the chances of getting missed are slim and none. I will be back with more so keep your engine running.

UPDATE 4:57PM
The new 18Z GFS and WRF models are in. If they are to be believed, about 1 inch of moisture is slated to fall southeast of a line from Burlington to the Quad Cities and on towards Clinton and Sterling. Much of that will be snow and that means warning criteria if these parameters are met again in our evening runs. Even the eastern 1/4 of Iowa will get good accumulations so the bottom line here is that the storm is still on track. I have some media obligations to sneak in and will be back with some graphics and a video briefing by 6:30. Peace out!

UPDATE 4:28PM
New data is flowing. I will be out with a the latest trends soon and will have an updated video briefing out early this evening. More on that as the time table is ironed out. My guess is around 6pm. Lots to do and see. Later gators.

UPDATE 1:45PM
Just a quick shout out to those interested that I am having a special briefing on the upcoming storm around 2pm. You can catch the full video on the home page of Terryswails.com when it’s convenient for you. Thank you very much

UPDATE 12:20PM FRIDAY
AS I INDICATED WAS LIKELY IN SEVERAL PREVIOUS BLOGS-(MOST RECENTLY AT 11:11AM), THE NATIONAL WEATHER SERVICE HAS ISSUED A WINTER STORM WATCH FOR MUCH OF THE AREA. IT IS VERY LIKELY THAT THIS WILL BE UPGRADED TO A WARNING IF FURTHER RUNS CONFIRM THE LATEST TRENDS. STAY TUNED

UPDATE 11:11am

UPDATE 11:11am

The fresh GFS is down and it is impressive. As I mentioned earlier this was an important run and it has come in deeper and wetter. I have to believe the fine folks at NWS will be issuing some sort of watch or perhaps a warning. I will be showing two graphics and the first one is the total liquid precip. Note the 1” line runs from Rockford back to west of the Quad Cities and then into southeast Iowa. Everything from there east is progged for 1” liquid Equivalent. The 1.25” line runs nearly to the Quad Cities. If that verifies and it is all snow, that will be a hefty dump.

On my next graphic I show the surface low and its position Saturday evening. That is a very sweet position for snow, especially if you could see the 850 low just off to our east. I really have to say this gets me fired up. The next runs will be out later this afternoon and I hope they look like this. If this does hold, I think this has a great chance of being the biggest snow of the whole winter! Stay tuned this afternoon as I will dig up some numbers on that and will continue to monitor progress.

Time for a quick bite to eat and a massive diet dew. I’m gonna need some energy for the long haul ahead. Stay with me weather buddies…

UPDATE 9:51am FRIDAY

Just got a look at the new WRF 12Z run. Nothing too shocking to report. It may be slightly east than 6hrs. earlier but it’s normal for it to wobble a bit. That eastward trend is important if it continues as it would shift the heavy snow band eastward as well. That would cut down on snow totals in eastern Iowa. I will be anxious to see the new GFS run but that will not begin until 10:30. It will be a significant indicator now that we are getting closer to lift-off. More when I see it…..

UPDATE 6:30am FRIDAY

I just analyzed the new 6Z data and we have a consensus amonst the models! Both the U.S. and European models have converged on a track that looks bullish for snow in our area. As a forecaster this is what you are looking for,especially when you are within 36 hours of the event. Hopefully this will continue with subsequent runs from now til we wrap things up.

The screaming message here is that our storm should track in such a way that we get into the snow late morning Saturday and keep it going for about 12 hours. While the snow will be very wet and slushy, it will likely accumulate at least 6” in parts of our area. The heavy nature of the snow should limit blowing and drifting but we may get some late Saturday and Saturday evening as temps. cool and the winds peak near 30mph.

Here is some graphical data for you to enjoy. Remember I will have regular updates here throughout the day. I will also have a video briefing on the site later this afternoon…approximately 1 to 2pm.

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