WKU Meteorology

Recent model runs are predicting better snowfall totals than previously expected for south central Kentucky with tonight’s impending winter storm. Read the rest of this entry »

The belief over the past week is that the major storm that will move through the Mid-South early next week would be a significant snow-maker for everyone in Kentucky.  But recent model outputs express a mixed-bag of precipitation for south central Kentucky with warmer temperatures in place than previously thought. Read the rest of this entry »

Storm totals were from 5-7 inches across our region. This was slightly less than my going forecast of about 8 inches with the potential for locally more perhaps even over a foot. This was due to a dry slot which formed along the Kentucky/Tenn line late in the overnight  as a result another period of snow across western Kentucky which was producing moderate snowfall tracked just north of our region this would have produced another 2-4 inches of snow ( locally more) and the forecast would have verified.  As for the historical aspect of the storm we’ll see if the official measurement is 6 inches right now I would doubt it only getting 5.5 where i am.

looking ahead the rest of the weekend will be cold with highs only in the 20’s and single digits for lows. There will be a chance of light snow on Tuesday with another system late next week.  enjoy the snow.

MG

snow ratios- using the avg mesonet qpf of .15 and snowfall reports of 2-3 inches earlier and looking at the composition of the snow a 15:1 ratio seems reasonable with temps in the 20’s.

banding- snow had become banded in nature with dry slots heading heading our way getting filled back in again moderate snow should continue through 1 am with rates of .5 to 1 inch per hour. It is very possible as the low moves east the bands stay right over the bowling green area and then as the low moves northeast pinwheel back around again along the snow from the second part making it a steadier area tomorrow morning. Right now no major dry slot is expected.

modeling- the gfs had to many deep thunderstorms in the first 6 hrs ,while the nam’s frist 6 hrs were a fairly accurate view of things. I will use a blend of the nam and ruc models for this forecast. The ruc is the rapid update which updates every hour and is ncep’s model page.

forecast- thse models call for an addtional .5  qpf give or take a little overnight and Saturday morning which could be another 7.5  inches of fresh snow. so with that being said will raise totals to 7-14 inches for the Bowling Green which would make this the biggest snow in over 20 years. One point unlike with the 6-10 where I leaned toward the higher end this forecast will lean toward the lower end of the range (7-14).

Enjoy the snow!!

MG

- WKU has cancelled classes through Saturday due to weather.

Right now light snow has spread into south central Kentucky. Moderate snowfall with bursts of hvy snow is moving across western Tennessee into our region and should arrive around 5 pm. A dry slot is working across Mississippi/Alabama is of concern however i think this more aimed at the somerset area than us. the nam and the gfs still have there differences mainly with the front wave tonight which is moisture streaming north ahead of the low radar imagery and the ruc have me leaning in the direction of the 18z nam for this first wave. Banding could also develop causing wide ranges in areas seeing light and heavy snow this evening and still leads to wide range in forecasted totals. The second part to this storm is the upper air feature which is still back over the Southern plains this will provide the snow from early Saturday morning till Saturday night the models finally have a good handle on just where snow will be enhanced Saturday morning which appears to be the southern half of Kentucky, this should be a more general moderate snow.  Overall the models are coming close to about .7 qpf  which may be bumped up a bit by slightly higher than 10:1 snow ratios.  For now will forecast 6-10 inches of snow for Bowling Green with the potential for this to closer to 12 if we get some more bursts of heavier snow when the qpf is expected a bit lighter this evening. The nws in Louisville provided  a more technical discussion of this.  I’m quite surprised that my thinking on this storm has had me close to the nws with each update so I will leave with an independent thought thinking that we may end up on the higher end of the totals.

Temperatures now are in the mid 20’s across the region which means when the  snow starts it will stick to most everything. If you’re looking at the radar puzzled this morning it’s because of virga, precipitation that shows up on radar but evaporates before it reaches the surface this happens in the wintertime with cold and dry airmasses when humidity levels are below 75%,right now the humidity is a touch under 60%. looking at the radar the dark green shading area across western Tennessee is moving toward Bowling Green and that is fairly intense precipitation which would raise those humidty values quickly. The yellow is where snow could potentially fall at an inch per hour. Right now some light snow by 2 pm appears to be a safe bet based on the radar with moderate snow by late afternoon even with the roads well treated the evening commute will be hazardous.

nws radar

As for storm totals I’m still sticking to the 5-9 as the gfs came in dryer keeping the mositure in thunderstorms to our south. the nam came in much wetter bringing a direct line of deep mositure into the region. From here on the meteorlogy will be looking at radar trends and observations. I also still can’t rule out a sleet pelet or two thrown in. My personal thinking is the gfs may be suffering to much from convective feedback while the 12z nam runs are often slightly to wet with systems than other runs.

Don’t worry it’s still coming.  For those of you wanting to leave school or even WKU early for the snow will be disappointed as all of the model data now does not start the snow till mid or late afternoon, however the new RUC as of 1 am starts the precip around 1 pm. The good news out of that is the snow will be falling and with colder temperatures allows for the possibility of higher ratios say 12:1 with temperatures in the 20’s.

Snow should overspread the region late Friday afternoon and become hvy at times Friday night before tapering off Saturday. The main question continues to be exactly how the precipitation is distributed throughout the storm for the region the NAM and UKMET models are very similar keeping some the deeper moisture to our south while the GFS the 00z GFS Ensemble mean, NOGAPS and Canadian allow for more of the deeper moisture to move into the region at the height of the storm. looking at the Nam it was a little odd with a precip min spot in Western Kentucky still hitting Missouri and eastern Kentucky hard.

Overall i can’t go much different than the 5-9 inches the nws put out Thursday pm with the moister models now bringing 8 or so and the dryer models bringing 5.  However the 00z gfs has over a foot of snow about 30 miles south of BWG and only a couple of inches in E-town so any shifts in the track will affect this forecast.

MG

Recent model trends of both the GFS (6z and 12z) and NAM 12z suggest that a band of 8-12″ of snow is increasingly likely for some portion of the Mid-South Friday into Saturday. Read the rest of this entry »

qpf= amount of water that will fall

I have looked at the US 00z models which come in during the evening so this analysis includes the 00z Nam and gfs, Wednesday’s 12z Canadian, euro and several other overseas and less known models and there 12z runs. Normally as it gets closer to crunch time the models begin to arrive at a common solution however the 00z nam and gfs are far apart on qpf totals. The track of the low on the modeling is in a tight cluster from south Texas to the Florida panhandle and off the east coast and the 540 line on the modeling has been projected on the other side of the Tennessee line consistently for several days now all of which suggests snow will fall.

Let’s go over the meteorological set-up and questions I have with this storm.

A cold front will move through Wednesday night stretching from Texas to eastern New England by late Thursday. At the same time low Pressure will be forming over South Texas as cold arctic air moves into the region. So after temperatures in the upper 30’s to low 40’s for the middle of week they will fall off into the mid 20’s by the time moisture begins moving northeast. This low pressure will send moisture northward ahead of it into the Tennessee and lower Ohio valley Friday and early Saturday this moisture will be lifted along the front during the Friday to produce snowfall here. There are significant QPF differences in the modeling, more so than earlier today. The first one is how quick to bring in the precipitation Friday the nam holds it off while the gfs brings it in early Friday, both of these projections fit the typical biases of both models and both will likely need to correct with regards to this difference.  Further south across the deep south  thunderstorms will form ahead of the low these thunderstorms may act to take moisture destined for snowfall over South Central Kentucky, models may overdo this such as Wednesday’s 12z gfs or miss it, this variable is still a uncertainty and may lead to more changes in expected qpf. The third uncertainty I  see with this system is what the wrap around band will contain late Friday night into Saturday this is when I think snow ratios have the potential to rise a bit. I do see  a minor  feature in the upper levels at the 500 mb level early Saturday on the models which may serve to enhance this back period of snow but right now the qpf ranges from a few hundredths to .1 from this, but I could see this going higher as the models get a better sense of any potential shortwave that could enhance the back edge.  

Model Solutions

The 00z GFS was the most aggressive with regards to qpf with the 12z Canadian and 12z Japanese models fairly close to this solution yielding about an inch liquid from the storm from Friday morning into Saturday. The ECMWF qpf forecasts are not public but the track of the low on this model   is similar to the 00z GFS however several NWS offices have referenced the ECMWF being quite a bit lighter in terms of total qpf. The 00z NAM was quite a bit lighter with the 00z run and skipped Bowling Green with a half an inch of qpf west across paducah and east toward Pikeville future runs will determine if it is hinting at something in terms of precipitation patterns with the storm or a minor one run glitch, the 18z nam had .5 qpf with the new 00z run around .3.  The UKMET model was slightly moister would likely be around .4 or .5 at the completion of the storm and is similar to Wednesday afternoon runs of the GFS ensembles.

Forecast

Taking the model spread literally would result in a forecast of 3-10 inches using 10:1 ratios these ratios can  shift either way

A: sleet mixes in which is possible as the 540 is close this would potentially lower the ratio a bit

B: temperatures in the 10’s and 20’s Friday night can raise these ratios leading to dryer fluffier snow, the clipper earlier this month at Lexington brought 30:1 ratios with temps in the 20’s however with this being a southern storm with more moisture they will much closer to the traditional 10:1 but still do have the potential to go over 10:1 since the surface temp will be well under 32.

My thoughts are to tighten that spread of totals up a bit given we still have another set of runs to adjust the forecast. For now the forecast is for 4-8 inches of snow this is slightly up from the 3-7 inches I issued for the stormtoppers earlier tonight primary based on the 00z gfs bringing close to an inch of liquid which couldn’t be ignored but this forecast also indicates the gfs is overdone with the qpf. Like with the stormtoppers forecast I would tend to lean more to the lower end of the totals for now.

Detailed  timeline

- Wal mart and Kroger will be mobbed On Thursday with all of you getting bread and milk

- snow overspreads the region Friday morning with temps in the 20’s throughout the storm.

-  snow may become moderate to heavy at times Friday afternoon making for one of the worst evening commutes due to weather in a long time as roads will become snowcovered in many areas. If schools don’t close expect your kids to eat a 9 am lunch and to be home by noon based on this forecast. I could even see businesses and maybe even WKU closing early on Friday if the GFS solution is correct, but at the same time the NAM solution would yield an advisory level event with much less impact.

- Wind will increase Late Friday into Saturday and snow tapers off. Very cold weather will last into Sunday.

- storm total 4-8 inches

Another discussion will be posted around noon Thursday.  Just a note as I’m finishing this write-up the snowfall projection map which takes into account ratios on the 00z gfs has 14 inches in Bowling Green. However the 12z model runs will continue to adjust snow totals and remember as you may jump for joy after reading that, the 00z nam has just 4 in Bowling Green.

MG

The NWS has issued a winter storm watch for the region. Periods of snow are likely from Friday morning into early Saturday with still a large spread in model data. Right now it appears between 3 and 7 inches will fall and with temperatures below freezing travel problems are likely. This has the chance of being the first 6 inch snowfall in over 20 years for Bowling Green however much uncertainty still exists and I will have another update after the 00z runs late tonight.

MG