Wind Chills Looking Just As Bad As a Few Weeks Ago (Dropping to Near -20 Tonight)……..New Snowfall Information For Late Friday Night-Saturday Morning & Summary of Last Two Winter SystemsJanuary 31st, 2013 at 10:29 pm by Chad Evans under Chad's WLFI Weather Blog
UPDATE AS OF 12:45 A.M.
It is 6.4 degrees at WLFI & just took a wind gust of 31 mph, dropping wind chill to -17. Autumn’s weather station as Pine Village reads 5.4 degrees with a recent gust to 27 mph. Her wind chill also dropped to -17. Mary Anne’s weather station in Remington reads 5.2 degrees with wind gust of 22 mph, dropping her wind chill down to -16. At Grissom Air Reserve Base, with 9 degrees, wind just gusted to 33 mph, dropping wind chill to -14.
Be careful out there!
With temperatures already falling into the single digits with winds gusting to 32 mph, Wind Chill Advisory criteria will likely be met tonight. Levels will likely reach those of the brutal numbers several weeks ago. With lows of -1 to 4 & breezy conditions with gusts to 25 mph tomorrow morning, dangerous winds chill of -20 are likely.
Treat it as a Wind Chill Advisory & be careful out there! You’ll get frostbite in 30 minutes with the kind of wind chills we will have late tonight-early tomorrow morning.
Fast-moving clipper will bring about 5 hours of decent snow late Friday night-Saturday morning.
Looking at latest data, looks like a 1-3″ snow late Friday night-Saturday morning. Changed it from 1-2″ to 1-3″ due to another high-ratio event of 20:1.
I DO think there will be a NARROW 3-5″ band……………BUT NOT HERE………..thinking that will set up south & southeast of the viewing area.
SUMMARY OF SUNDAY ICE & CONCLUDING THOUGHTS………….
In last ice event, too much dry air was recycled in after days of Arctic high over Ontario bled in very dry air. By the time the first freezing rain showers/sleet/snow arrived, a chunk of that dry, dry air remained over the Ohio Valley & was pushed in via southeast breezes. The deeper moisture did arrive by evening with steady rain. As the rain dropped through 35-degree air with 21-degree dew point, it did drop to 31 over the area for a bit with freezing rain. However, it then quickly rebounded. Glaze ice amounts ended up generally under 0.10″ & any morning snow/sleet amounts were minimal.
Arctic highs are snow/rain eaters. This happens frequently here. Even if the surface high as moved well to the east, unless there is a good south wind, southeast wind will tend to recycle that air back into our region. This eats up parts of next precipitation event. Also, slightly downsloping off Appalachians may play slight role in drying out an already dry airmass to our southeast.
SUMMARY OF LAST SNOWFALL EVENT & CONCLUDING THOUGHTS…………
Last snow event looked like a pretty decent one several days out from an analog standpoint & model data standpoint. Statistically-speaking the probability of it being a 3-6″ was very high in a look at 5 similar cases over the past 20 years. One, with no measurable snow in the month probablity was high of a decent snow based on the fact that only 5 Januarys since 1887 in West Lafayette have had a trace or less with only a few others at under 1″. Secondly, the forcing & dynamics properties were similar to a storm in late January 2004 that dropped a surprise 3-7″ snow on the area after only 1-3″ was forecasted. The snow ratios were so high with it that 6.7″ of snow fell at Indiana State with only 0.30″ of melted precipitation.
Model data began to diverge tremendously into a performance nothing short of horrendous. NAM & Futurecast continued to show nothing, most foreign models had a decent snow.
Ended up being a hybrid of the models with most areas seeing around 1″. Some locations in the far north & far east saw 2-4″. The least amount of snow occurred in our southern counties with 0.6″ at Crawfordsville & Covington with a pocket around Remington & Wolcott with a trace to 0.5″.
WHAT I DID RIGHT:
1. Frontagenic forcing was excellent for great snowfall production. We were able to have an 18:1 to 20:1 snow ratio. So snowflake production was very efficient.
2. Storm merger did happen & was in the correct spot in the Lower Ohio Valley.
3. Snowfall did blossom out seemingly no where with the upper forcing, frontagenic forcing/banding & development of Lower Ohio Valley surface low.
4. Low-level jet did development & widespread precipitation with convection elements formed on its nose.
5. Used usual statistical analysis & did case-by-case analysis of each system matching this one in several ways with all dynamical aspects of the system considered. I then drew a forecasting conclusion from that.
6. Explained how much uncertainty there was in the forecast & that it would probably be an awful forecast no matter what given extreme dicotamy between data.
7. Used a strong analog approach, which has aided tremendously in all of my snowfall forecasts.
8. Feel good that I did painstaking work on this one & tried to let everyone know how uncertain it was. This was the hardest system I have every dealt with.
9. Dropped totals to 1-2″ for most of the area by 10:30 p.m. the night before it started with 3-5″ in the far north & far east, which was the most accurate forecast I had for the event. Explained we would have to rely on now-casting & that the forecast may be a last minute decision, so stay tuned. Feel good about how I did handle that, despite the forecast’s diffculties.
10. Learned that analog is usually a way too go as I did learn once again that there are issues to be worked out with U.S. numerical models. I am glad NOAA is getting the massive brand-new, state-of-the-art supercomputer installations for models in August 2013. I also know that METS RELY TOO MUCH ON MODELS, but in this case, maybe I did not totally rely on them enough.
11. I threw out the models that had nothing for us.
WHAT I DID WRONG………..
1. Low-level jet veered too far to the east & this threw my off. All the moisture & heavier precipitation blossomed in Tennessee & western Kentucky, rather than southern Illinois & Missouri, like I thought it would.
2. What I did not see was low-level jet veering so far east. WHY did it veer so far east? It appears the major winter drought in the Plains played a major factor. Major droughts deflect the low-level jet by putting the temperature & moisture gradient or dryline east. This tend to shift & push LLJ eastward, which is largely responsible for the nocturnal development of widespread precipitation. The baroclinic zone was too far east.
3. Afformentioned low-level jet shift cut our moisture DRASTICALLY. Our snow was 100% DRIVEN by upper dynamics & frontagenic forcing in 850-700 mb layer. With such impressive forcing, it took hardly ANY MOISTURE AT ALL, really, to make the snow. Foreign models painted up to 0.25″ liquid for area with 18:1 to 20:1 ratio. Only 0.06″ of liquid occurred at WLFI with the 1.0″ of snowfall. At Kokomo, the 2.5″ snowfall melted to 0.11″.
4. Snowfall duration was much shorter than I thought. It was pretty much a 3-hour event. I figured it would be a 6 to 7 hour event.
5. My data was so consistent & agreed so much, I had a 4-6″ graphic several days out, followed by a 3-6″ graphic. I put a 4-6″ & 3-6″ graphic too early. For snow like that, I should’ve waited a day, even if my numbers were on my side. I did not like having to trim numbers over & over. That goes against what I believe as a met.
6. I need to watch that LLJ in these situations & where the LLJ zone exists based on a tendency for it to shift east at times with that major Plains drought.
Overall, this boiled down to WATER, WATER, WATER………………or a lack thereof & the direction of transport of that water.