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WxChallenge 2013-14


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After much thought 22/14/26/0.12"

 

The high was rather straight forward (I thought about 23), temps shouldn't rise much with clouds/snow much of the day. As the winds go strong SW or WSWrly lake modified air should move in and warm temps a tad.

 

As for the low, looking at forecast soundings from the latest GFS/NAM/RAP the lake effect strato-cu deck will in all likelihood not break up through around 10z, and winds should remain W or WSW most of the night and breezy which should keep lake modified air flowing into GRR all night. There is some potential to drop a few degrees colder between 10-13z as some models show warmer 850mb air moving in and disrupting any lake effect processes at that time, but winds should remain up which may limit how quickly things drop. I really think the low could be a degree or two warmer than I have but wasn't confident enough to go with that outright.

 

As for precip a lot of the hi-res models spit out between 0.1-0.25" of precip during the period. They only came in with 0.01" today which was shockingly low given radar and obs. As the trough rotates through they should see a period of heavy snow, with decently favorable LES conditions developing thereafter. Equilibrium levels above 800MB, moderate lake induced instability and fairly well aligned winds should support a general light to moderate snow shower pattern through most of  the afternoon. Usually the high-res models are MUCH better with lake effect QPF than say the GFS, Euro or even the 12km NAM and given a period of heavy snow and several hours of snow showers I think they'll see at least 0.10" of liquid fall (and at least 2-3" of snow given high ratios). I'm somewhat worried about the windy conditions and very fluffy nature of the snow causing some undercatch in the rain gauge so didn't go too much over 0.10".

 

They did at least 26 knots today (may have snuck up a tad higher after the preliminary climo) and they should be just as windy tomorrow. At least I hope.

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I honestly doubt they see zero measurable precip, but I really like your temps and winds. I just wasn't as ballsy as you were :lol:

 

Edit: Although I see someone here at OU went with 0.60" :axe:

They recorded nothing in the ASOS bucket once lake effect commenced today and they increased their snow depth by at least 2", but every observation from the ASOS reported 0.001. Winds will also be at the same strength as today maybe a touch stronger. With the dry consistency of the snow and the strong gusty winds, I have a hard time believing they will record anything tomorrow. It will surely be no more than 0.04. For them to record a lot, it will probably need to be a very strong lake effect band above 30dbz on radar and .25 visibility otherwise I see no change from today.

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They recorded nothing in the ASOS bucket once lake effect commenced today and they increased their snow depth by at least 2", but every observation from the ASOS reported 0.001. Winds will also be at the same strength as today maybe a touch stronger. With the dry consistency of the snow and the strong gusty winds, I have a hard time believing they will record anything tomorrow. It will surely be no more than 0.04. For them to record a lot, it will probably need to be a very strong lake effect band above 30dbz on radar and .25 visibility otherwise I see no change from today.

I think they'll see heavy snow for a time and record at least a little when that occurs. You may be right about not catching any of the snow/recording any liquid the rest of the day in which case my 0.12" would be too high, probably by a factor of 2 or 3 times. You'd really think I'd pay more attention in CLE when we get lake effect to how much liquid falls, but I really don't for some reason. I think more than 0.12" of liquid equivalent will probably fall but wasn't sure how much I wanted to undercut things due to undercatch in the rain gauge.

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I think they'll see heavy snow for a time and record at least a little when that occurs. You may be right about not catching any of the snow/recording any liquid the rest of the day in which case my 0.12" would be too high, probably by a factor of 2 or 3 times. You'd really think I'd pay more attention in CLE when we get lake effect to how much liquid falls, but I really don't for some reason. I think more than 0.12" of liquid equivalent will probably fall but wasn't sure how much I wanted to undercut things due to undercatch in the rain gauge.

I also missed that vort max swinging through for tomorrow, I was so preoccupied by what happened today. But also will the strongest band go over KGRR? Remember the ASOS is on the southeast side of the city, they also might get screwed by the buildings and everything around it due to the strong winds as well. 

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I also missed that vort max swinging through for tomorrow, I was so preoccupied by what happened today. But also will the strongest band go over KGRR? Remember the ASOS is on the southeast side of the city, they also might get screwed by the buildings and everything around it due to the strong winds as well. 

I believe a WSW flow brings the heaviest snow to GRR...winds will be SW ahead of the trough which should cause the heavier band to initially develop to the north/west of GRR. The winds then go to WSW and gradually veer to the WNW by evening. I'd expect the band to stay in tact and swing through GRR at some point during the early afternoon, how quickly it swings will be key I'd imagine.

 

I was looking at today's preliminary climo when making my forecast and it showed only 0.5" of snow...was that as of when they send out the preliminary climo or as of the most recent 6 hourly measurement (which may have been before the best lake effect got going)? Because I saw you mentioned they got at least 2" from the lake effect...if they did see 2" of snow today then that doesn't help things for tomorrow's precip forecast for anyone who went more than a few hundredths (I'm expecting something like 3-4" of snow to fall at GRR during the period).

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I believe a WSW flow brings the heaviest snow to GRR...winds will be SW ahead of the trough which should cause the heavier band to initially develop to the north/west of GRR. The winds then go to WSW and gradually veer to the WNW by evening. I'd expect the band to stay in tact and swing through GRR at some point during the early afternoon, how quickly it swings will be key I'd imagine.

 

I was looking at today's preliminary climo when making my forecast and it showed only 0.5" of snow...was that as of when they send out the preliminary climo or as of the most recent 6 hourly measurement (which may have been before the best lake effect got going)? Because I saw you mentioned they got at least 2" from the lake effect...if they did see 2" of snow today then that doesn't help things for tomorrow's precip forecast for anyone who went more than a few hundredths (I'm expecting something like 3-4" of snow to fall at GRR during the period).

Winds were same direction WSW today, so I don't know how well your logic works with strong winds like today/tomorrow. Going to be interesting to see indeed. New 0z NAM has a very small window of heavy stuff like 3 hours at most. That vortmax swings through real quick and weakens a bit.

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Winds were same direction WSW today, so I don't know how well your logic works with strong winds like today/tomorrow. Going to be interesting to see indeed. New 0z NAM has a very small window of heavy stuff like 3 hours at most. That vortmax swings through real quick and weakens a bit.

With wind blowing across the short axis of the lake, WSW winds usually won't get really heavy bands of organized snow unless instability/moisture depth are rather favorable, but that's the best direction to get the "heaviest" snow into the GRR area. Usually when a vort max or shortwave moves across a Great Lake this time of year you'll get a decent band of heavy snow that forms over the lake ahead of the trough axis and swings inland as the trough axis shifts inland. I'm better with who gets heavy snow off of Lake Erie, but similar principles usually apply to all the other lakes.

 

What I'm more concerned about at this point in time is the fact that GRR is already down to 18. The cloud tops over the lake have cooled some the past hour or two, so I'm hoping the deck is thickening a bit and will slow down the cooling here going forward.

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Given what happened at stations to their south and east when the radar echoes left (very rapid temperature drops, even after 8AM), it wouldn't surprise me if the final number is 12F, or even 11F. The 9AM obs will probably be back "up" to 13F or 14F, though.

Looks like 12F or 13F. Surrounding stations per wunderground didn't drop much lower and KGRR seems to be a warm spot of sorts. 

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Looks like 12F or 13F. Surrounding stations per wunderground didn't drop much lower and KGRR seems to be a warm spot of sorts. 

 

Depends which direction you look. I followed the back edge of the echoes on the radar, and they made it to the airport after the 7:53 obs and have only just now almost filled back in. wunderground stations that were southeast of the radar echo edge seemed to drop at 2-5 degrees an hour. That suggests to me that 12F is much more likely than 13F, and 11F is quite possible. But I've been wrong before! :P

 

EDIT: I guess not too surprisingly, we got 12F this hour. The radar echoes are just making it back in, so 11F between the 13F and 12F wouldn't shock me at all.

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Depends which direction you look. I followed the back edge of the echoes on the radar, and they made it to the airport after the 7:53 obs and have only just now almost filled back in. wunderground stations that were southeast of the radar echo edge seemed to drop at 2-5 degrees an hour. That suggests to me that 12F is much more likely than 13F, and 11F is quite possible. But I've been wrong before! :P

 

EDIT: I guess not too surprisingly, we got 12F this hour. The radar echoes are just making it back in, so 11F between the 13F and 12F wouldn't shock me at all.

You can have your 11F, but I'll take 24 and 0 :P

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