January 18-19th Accumulating Snow Threat

[Bgoney]

Pretty much the same for me . Going with a dusting to 2” for counties bordering the river and north of those 1-3” range

[tron777]

6Z GFS is even coming back down to earth with 0.22" of QPF at CVG.

[tron777]

The latest thinking from the boys:

A complex scenario develops Thursday with several weak features
leading to snow chances. An initial mid level shortwave tracks
across the area with isentropic lift leading to the development
of light snow Thursday morning. This development looks to be
initially across the northwest and then work southeast across
the area. Late in the afternoon snow ahead of a southern
shortwave and weak surface wave may bring an increased threat
for snow across the southern counties. With these features being
weak we are seeing expected differences in placement and timing
and ultimately QPF. Looking at ensembles - the 100 member super
ensemble suggests only a 40 to 50 percent chance of a half inch
across the north by evening. Adjusting for a SLR of about 15:1,
expect snowfall to be an inch or less with the highest totals
across the north by evening. Temperatures will be milder with
highs from the upper 20s north to the lower and mid 30s south.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
There will be three distinct segments to the extended forecast
period -- snow Thursday night into Friday, cold weather over the
weekend, and a warming trend early next week.

On Thursday evening, a surface cold front will still be well
upstream of the ILN CWA. Snow will likely be ongoing, with a 850mb
wave (and weak 500mb wave) moving east through the area. As this is
occurring, a more well-defined 500mb wave will be rotating southeast
out of the upper Midwest and into the Ohio Valley region. All in
all, this combination of waves -- several disparate sources of
forcing -- will eventually combine together by Friday morning,
producing widespread accumulating snow across the ILN forecast area.
It remains likely that areas of more intense snow (heavier QPF and
stronger forcing) could occur at different times and in different
locations across the region, rather than focusing on one particular
area for a longer period of time. As such, the overall expectation
for accumulations will not show a general trend toward higher snow
amounts in the eastern ILN CWA, but with no sharp gradients or
localized maxima. This looks like a 1.5" to 3.0" snow event overall.
Still cannot totally discount the probability of some higher amounts
(up to 4") if some areas do receive multiple rounds of heavier snow,
particularly given the high snow-to-liquid ratios (15-1 to 20-1). It
should be mentioned that model agreement is not particularly strong
on the specifics of this forecast -- with the NAM a noted drier
outlier.

Steady accumulating snow will end some time in the first half of
Friday, with a cold front moving through the area and cold advection
kicking in. With mid-level troughing over the Great Lakes, under
cyclonic flow and steepening lapse rates, this pattern will support
continued chances for snow showers through Friday afternoon and
night -- maybe even into Saturday morning. This would be unlikely to
produce anything more than isolated light accumulations, but PoPs
have been kept in the forecast for longer than the model blend would
suggest.

[tron777]

SPC Meso Page this morning shows a 998 MB Low off the Washington Coast. That is the main piece of energy for this system so it will be coming onshore near Seattle today. Modeling should have a good sampling of the system from this point forward.

[tron777]

6Z GEFS has 0.20" QPF for many but you can easily see the dry slot on the QPF output map and I just continue to have an uneasy feeling for our SW counties in particular as well as Cincy Metro esp S of the river. 0Z EPS had 0.15" for the Western half of our forecast area and 0.20"+ for our Eastern counties.

[tron777]

6Z Euro QPF

CVG - 0.19"
HAO - 0.16"
MGY - 0.15"
DAY - 0.17"
CMH - 0.19"
FGX - 0.20"

[tron777]

The 6Z Euro showed a bit better phasing between the two waves so the run was better overall for folks SE of I-71 versus the 0Z run. That is what we have to be on the lookout for as well as the dry slot potential as we've mentioned. I will probably make a final call this evening, but as of now my call still stands that I have already posted.

[dce]

6Z Euro QPF

CVG - 0.19"
HAO - 0.16"
MGY - 0.15"
DAY - 0.17"
CMH - 0.19"
FGX - 0.20"

Not bad. The Euro doesn't have that dry slot as much as the other models. Today's 12z runs will hopefully bring clarity. Although I'm not counting on it.

[fyrfyter]

Euro and GFS are in line with 2.4 and 2.6 in the Metro. GFS tries to give more across the state, while Euro says about 2.5 for everyone.

I like this, where we are at least getting close. See what the NAM does today. See if it gets on board, or continues with its own mind.

[Trentonwx06]

To my novice eyes, believe the SREF’s have went up at 03z and 09z runs.

[MattD41]

Would like to see 5-7 pages of posts after the runs this morning !
Have a good day everyone

[tron777]

To my novice eyes, believe the SREF’s have went up at 03z and 09z runs.

You are correct Sir. The majority of the SREF members, using CVG, are between 1-3" so the goal posts are being narrowed a bit. Hopefully, this is a sign that we'll see the 12Z NAM come around a bit more. I hope! Here are the SREF Means from the 9Z run for those interested.

CVG - 1.83"
HAO - 2.15"
ILN - 2.57"
MGY - 2.54"
DAY - 2,77"
CMH - 3.07"
ROD (Sidney, Ohio) - 3.46"

Sorry Matt, I have no stations on the SREF Plumes for Maysville or Flemingsburg. But that has always been the case.

[tron777]

Would like to see 5-7 pages of posts after the runs this morning !
Have a good day everyone

Hey Matt! We're doing the best we can buddy! Hope you have a great day also. It's always good to see you posting.

[Trevor]

Here's the SREF in map form...

[Trevor]

I will take a look at the 12z runs and make any necessary adjustments to the map. But I feel pretty good about what I came up with yesterday. Looks like its fairly similar to what ILN came up with as well. Pretty similar to our original forecast Les for 1-3" but I think most people will get 2" or more so I took out the lower end of the 1-3" range and went 2-3" instead.

[tron777]

I will take a look at the 12z runs and make any necessary adjustments to the map. But I feel pretty good about what I came up with yesterday. Looks like its fairly similar to what ILN came up with as well. Pretty similar to our original forecast Les for 1-3" but I think most people will get 2" or more so I took out the lower end of the 1-3" range and went 2-3" instead.

I am keeping the 1-3" range just because I am worried about the dry slot, especially for CVG Land. Otherwise, if it does not occur than the 2" mark is achievable.

[Trevor]

I will take a look at the 12z runs and make any necessary adjustments to the map. But I feel pretty good about what I came up with yesterday. Looks like its fairly similar to what ILN came up with as well. Pretty similar to our original forecast Les for 1-3" but I think most people will get 2" or more so I took out the lower end of the 1-3" range and went 2-3" instead.

I am keeping the 1-3" range just because I am worried about the dry slot, especially for CVG Land. Otherwise, if it does not occur than the 2" mark is achievable.

I have the dryslot on my map and that was my biggest area of uncertainty/concern. I will take a look at 12z today. I may wind up tugging the 1-2" area closer to the metro but we shall see. As ILN stated, the NAM is the driest model and an outlier for now. Then again, sometimes the outlier winds up being correct i.e. Feb 2021...that one still hurts

[tron777]

We are just getting into the hi-res range now but the 12Z HRRR has a much further north track of the low. Mainly a 1-2" event for most folks. The better snows are well north of our forecast area where the weenie frontogenic snow occurs. Kind of what we are seeing occur on past NAM runs to be honest. Now the HRRR is just beginning to see this event so that can and probably will change. But it's enough of a concern for me to leave my 1-3" call as is.

[tron777]

12Z NAM is doing the same thing. Low tracks from SE KY into WVA, which is normally good for us, but the low is weak and you can clearly see the dry slot on the QPF output. Cincy Metro and points SW get dry slotted. Best snows are north of the river.

[fyrfyter]

The 6z HRRR is weird between hours 47 & 48- is that the beginning of the transfer?

[Trevor]

HRRR QPF supportive of a couple inches locally.

[Trevor]

12z NAM continues to show our issues big time. The main reason is that the surface low is weak (what Les mentioned) and is still developing which puts us in an unfavorable position. Really just bad timing and nothing else but thats always a factor in weather. Better precip is east of us as the low begins to strengthen.

[Bgoney]

Not issuing a Screw-zone watch just yet , but it’s risen to 40% chance . Waiting for ensembles

[tron777]

I agree.... if it wasn't for bad luck, we wouldn't have any luck at all!

[mikeyp]

Looks like more and more a dusting to 1" or so. Oh well, cant win them all.. or any this winter HAHAH