WKU Meteorology

– 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. Continue reading →

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

a quick post to start the spring term. Right now the modeling suggests a winter storm will impact the region starting Thursday night and lasting into Saturday. An arctic front will move through the region Thursday with low pressure tracking along this front bringing a lot of mositure north potentially over 1 inch of liquid. All types of precipitation and amounts are still on the table however most of the models suggest mainly snow. Right now there is a decent chance for over 4 inches of snow but any change in the track of the low makes this subject to change. Check back later in the week for more.

MG

I will be unable to post updates from wed-mon so i have posted a seven day forecast.  The one change in forecasting strategy I have made is to go a few degrees higher than the raw gfs which was to cool over the weekend. With the start of classes on the 25th there will be more students along with Dr.Goodrich who will volunteer or take course credit and become authors on the blog.

For some climatic perspective on this week upcoming it has been very dry this month and this weekend’s rain and the forecasted rain should catch the region back close to normal.  Looking at February a negative epo, ao and nao are projectedthis would indicate another blast of fairly chilly weather is on the way for Feb 1-10 with an active storm track.

seven day forecast Continue reading →

1. Friday will see a weak cold front pass through with some low clouds and patchy drizzle this will be followed by some sun later with highs in the mid 50’s.

2. The main action arrives as low pressure rides up the east coast Saturday night through Sunday which looks to bring rain and more overcast skies to the region however any shift in the track could alter the forecast from a passing shower or two to a washout lows will be in the mid to upper 30’s with highs in the low to mid 40’s. winds will also switch from southerly ahead of the low to northeast in behind it making Sunday a very raw day across the region.

Continue reading →

Yesterday thanks to a surge of warm air advection Bowling Green the temperature at Bowling Green finally went above freezing this month not counting the first few hours of the New Year. Temperatures for the month are about 14*F below normal as of Tuesday. Here is the climate report so far for the month a very cold first half of Janurary.

How does this compare to other stretches of cold

this from the nws in Louisville

“Bowling Green ended up with 9 days in a row below freezing from January 2 through the 10th.  The record is 11 days set January 22 – February 1, 1948.  This was Bowling Green’s longest stretch below freezing since December 16-25, 1989, and the 3rd longest on record”.

so close to the record!!

– we have one more system passing to our south early Sunday before a week long thaw of above normal temperatures sets in. Right now the upper levels on the modeling are just to warm for snow, no way getting around that. However there is still a threat of enough low level cold below freezing at the surface Sunday morning for light freezing rain. I’ll have one more update later this week on this threat.

– by the way the thaw does not mean that winter’s over and at least the start of February appears to be another cold stretch compared to average.