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January Pattern and Storm Discussion II


Cold Rain

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GFS definitely trended toward NAM this time. If it happens, this will make 2 times this Fall that NAM actually beat the ECMWF and GFS within 84 hours since last Fall in the Deep South regarding upper lows. This could turn into a strong system, as the trend is now what matters. The low cuts off in eastern Tx and then goes negative tilt and goes to 2 or maybe even 3 contours closed, all the way to SC now on this run, which is longer and stronger than any model has shown yet. Trends.  The only real negative against snow in the north shield is the lack of cold air. I have been saying this all along, but with dynamics and the time of day (night is best) and being on the NW side of a closed vort as strong as this, you'll be in business, especially with a little elevation, for a few hours atleast. I'd like to see GFS drop it's 850's just a couple more degrees to get more folks in the white stuff. As it stands now, I'd say the lift, dynamics, time of day and the cold all probably maximize somewhere in northern Alabama, southern to middle TN and points east to central NC, upper SC and north GA overnight.  After that, I don't know, it may weaken and lose its cold tap, which it briefly encounters, plus if it does weaken, that lessens dynamic cooling. Very VERY fascinating system to watch, but I'm still not totally sold we even have a closed system to form yet. It's going to be close, one small miscalculation and it gets sheared instead of left behind to grow into the strong ULL seen on GFS and NAM.  Trends is what matters though I suppose. Big Kudos to NAM if it gets this right though, for sure.

The other thing is areas east of the Apps won't have the surface temps areas west of the Apps have most likely, atleast not until middle of the event most likely. The cold air is as razor thin as I have ever seen it for NC, n GA and upper SC. Dynamics and lift will mean the world in this, so I wouldn't get too hopeful yet since almost always that doesn't work out for snow in most places. But the models did ok with the post Christmas event in the lee of the Apps if I recall , showing just enough dynamic cooling and 850 temps to make a little sleet upper SC, ne GA and western NC and VA regions.  If this could trend a little colder, without losing the dynamics or track then southern TN to much of NC would be nailed with a heavy wet, quick snow event....even though these 70s to 80 degrees lately won't do us any favors on accumulations.

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GFS definitely trended toward NAM this time. If it happens, this will make 2 times this Fall that NAM actually beat the ECMWF and GFS within 84 hours since last Fall in the Deep South regarding upper lows. This could turn into a strong system, as the trend is now what matters. The low cuts off in eastern Tx and then goes negative tilt and goes to 2 or maybe even 3 contours closed, all the way to SC now on this run, which is longer and stronger than any model has shown yet. Trends.  The only real negative against snow in the north shield is the lack of cold air. I have been saying this all along, but with dynamics and the time of day (night is best) and being on the NW side of a closed vort as strong as this, you'll be in business, especially with a little elevation, for a few hours atleast. I'd like to see GFS drop it's 850's just a couple more degrees to get more folks in the white stuff. As it stands now, I'd say the lift, dynamics, time of day and the cold all probably maximize somewhere in northern Alabama, southern to middle TN and points east to central NC, upper SC and north GA overnight.  After that, I don't know, it may weaken and lose its cold tap, which it briefly encounters, plus if it does weaken, that lessens dynamic cooling. Very VERY fascinating system to watch, but I'm still not totally sold we even have a closed system to form yet. It's going to be close, one small miscalculation and it gets sheared instead of left behind to grow into the strong ULL seen on GFS and NAM.  Trends is what matters though I suppose. Big Kudos to NAM if it gets this right though, for sure.

The other thing is areas east of the Apps won't have the surface temps areas west of the Apps have most likely, atleast not until middle of the event most likely. The cold air is as razor thin as I have ever seen it for NC, n GA and upper SC. Dynamics and lift will mean the world in this, so I wouldn't get too hopeful yet since almost always that doesn't work out for snow in most places. But the models did ok with the post Christmas event in the lee of the Apps if I recall , showing just enough dynamic cooling and 850 temps to make a little sleet upper SC, ne GA and western NC and VA regions.  If this could trend a little colder, without losing the dynamics or track then southern TN to much of NC would be nailed with a heavy wet, quick snow event....even though these 70s to 80 degrees lately won't do us any favors on accumulations.

 

Sounds good Robert!  We HAVE to keep that energy bundled...

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Hickory wet-bulbs to 0 C all the way down to 950 mb on this run.  With heavy enough precip rates, I think flakes would make it to the ground.  It's going to be warm on the ground though.

 

Date: 3 day AVN valid 0Z FRI 18 JAN 13Station: KHKYLatitude:   35.73Longitude: -81.38-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   186                                                                 SFC  973   412   3.0   0.4  83  2.6   1.8   5   9 278.3 279.0 276.4 289.5  4.04  2  950   602   2.4  -4.0  63  6.4  -0.1   8  20 279.6 280.1 275.6 288.0  3.00  3  900  1037   2.1 -15.7  25 17.8  -3.3   8  31 283.6 283.9 275.3 287.4  1.25  4  850  1498   1.0 -14.2  31 15.3  -3.8  15  34 287.2 287.5 277.5 291.7  1.49  5  800  1983  -0.5  -8.9  53  8.4  -3.6   9  31 290.7 291.1 280.4 297.9  2.44  6  750  2499  -0.9  -5.5  71  4.6  -2.8 359  23 295.6 296.2 283.7 305.7  3.38  7  700  3048  -3.2  -6.1  80  2.9  -4.4 353  21 298.9 299.6 285.1 309.4  3.45  8  650  3632  -5.7  -7.7  86  2.0  -6.5 338  19 302.5 303.1 286.2 312.6  3.29  9  600  4256  -8.4  -9.5  92  1.1  -8.8 308   9 306.4 307.0 287.5 316.1  3.10 10  550  4927 -12.4 -12.7  98  0.3 -12.6 196  12 309.3 309.8 288.0 317.6  2.61 11  500  5649 -17.0 -17.2  98  0.2 -17.0 206  21 312.4 312.7 288.3 318.9  1.99 12  450  6432 -21.6 -22.0  97  0.4 -21.7 201  33 316.0 316.3 289.0 320.9  1.46 13  400  7290 -27.3 -27.8  95  0.5 -27.4 196  49 319.5 319.7 289.6 322.9  0.97 14  350  8238 -33.9 -34.3  96  0.4 -34.0 198  63 323.0 323.1 290.3 325.1  0.60 15  300  9296 -43.7 -44.3  94  0.6 -43.7 198  66 323.8 323.8 290.2 324.7  0.25 16  250 10495 -51.8 -52.9  88  1.0 -51.9 204  97 329.0 329.0 291.6 329.4  0.11 17  200 11924 -56.2 -68.6  20 12.4 -56.3 214  99 343.8 343.8 295.3 343.9  0.02 18  150 13750 -58.3 -70.7  19 12.4 -58.5 242  76 369.6 369.6 300.5 369.7  0.02 19  100 16242 -65.4 -78.2  15 12.8 -65.5 232  68 401.4 401.4 305.4 401.4  0.01TRP                                             0                              WND                                             0                              Sounding variables and indices1000-500 mb thick:      5463.04 mFreezing level:          815.46 mb =  1832.84 m =  6013.18 ftWetbulb zero:            951.14 mb =   592.10 m =  1942.57 ftPrecipitable water:        0.59 inches
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Ukie has strong 5h low, but quite a bit farther south than GFS/NAM -- 1012 surface low on far eastern Fla/Ga. line. Temps WAY too warm, though, at 72 hours. 850 0c line just clips northern Tenn. and the northern half of va. 850 closed low way down over SE Ga. Interesting.

Can you post an image or link of that please?

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I am REALLY questioning that sounding profile in the lowest layers...especially the dewpoint trace...

Hickory wet-bulbs to 0 C all the way down to 950 mb on this run.  With heavy enough precip rates, I think flakes would make it to the ground.  It's going to be warm on the ground though.

 

Date: 3 day AVN valid 0Z FRI 18 JAN 13Station: KHKYLatitude:   35.73Longitude: -81.38-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   186                                                                 SFC  973   412   3.0   0.4  83  2.6   1.8   5   9 278.3 279.0 276.4 289.5  4.04  2  950   602   2.4  -4.0  63  6.4  -0.1   8  20 279.6 280.1 275.6 288.0  3.00  3  900  1037   2.1 -15.7  25 17.8  -3.3   8  31 283.6 283.9 275.3 287.4  1.25  4  850  1498   1.0 -14.2  31 15.3  -3.8  15  34 287.2 287.5 277.5 291.7  1.49  5  800  1983  -0.5  -8.9  53  8.4  -3.6   9  31 290.7 291.1 280.4 297.9  2.44  6  750  2499  -0.9  -5.5  71  4.6  -2.8 359  23 295.6 296.2 283.7 305.7  3.38  7  700  3048  -3.2  -6.1  80  2.9  -4.4 353  21 298.9 299.6 285.1 309.4  3.45  8  650  3632  -5.7  -7.7  86  2.0  -6.5 338  19 302.5 303.1 286.2 312.6  3.29  9  600  4256  -8.4  -9.5  92  1.1  -8.8 308   9 306.4 307.0 287.5 316.1  3.10 10  550  4927 -12.4 -12.7  98  0.3 -12.6 196  12 309.3 309.8 288.0 317.6  2.61 11  500  5649 -17.0 -17.2  98  0.2 -17.0 206  21 312.4 312.7 288.3 318.9  1.99 12  450  6432 -21.6 -22.0  97  0.4 -21.7 201  33 316.0 316.3 289.0 320.9  1.46 13  400  7290 -27.3 -27.8  95  0.5 -27.4 196  49 319.5 319.7 289.6 322.9  0.97 14  350  8238 -33.9 -34.3  96  0.4 -34.0 198  63 323.0 323.1 290.3 325.1  0.60 15  300  9296 -43.7 -44.3  94  0.6 -43.7 198  66 323.8 323.8 290.2 324.7  0.25 16  250 10495 -51.8 -52.9  88  1.0 -51.9 204  97 329.0 329.0 291.6 329.4  0.11 17  200 11924 -56.2 -68.6  20 12.4 -56.3 214  99 343.8 343.8 295.3 343.9  0.02 18  150 13750 -58.3 -70.7  19 12.4 -58.5 242  76 369.6 369.6 300.5 369.7  0.02 19  100 16242 -65.4 -78.2  15 12.8 -65.5 232  68 401.4 401.4 305.4 401.4  0.01TRP                                             0                              WND                                             0                              Sounding variables and indices1000-500 mb thick:      5463.04 mFreezing level:          815.46 mb =  1832.84 m =  6013.18 ftWetbulb zero:            951.14 mb =   592.10 m =  1942.57 ftPrecipitable water:        0.59 inches
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The position of the 500mb vort really hasn't changed over the last 2 days. Some of the mod's are shearing it out too fast which is common place in this situation. I think this favors a SLP track from the n-central GOM into southeastern GA and then up the coastline. The SE ridge is very strong lately and it's not surprising to see a slight trend to the NW. Also the sfc is starting to match the upper levels better. The euro really seems too flat to me.

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If you're directly under and north of the upper vort, you'll have the best shot to switch from rain to snow, especially if the timing occurs at dark in your area. Now, if you consider the trends on NAM and GFS tonight, this is trending stronger, longer and with more dynamics in play, with more QPF. Overall, this is almost always how upper lows trend across the Southeast. Look at March 2009 (that one was much colder though). Many upper lows in 2005, 2006, 2007 and 2008, even in the worst and warm Winters, had snow under the core. Still, I'd say if the GFS is right, and we do indeed have a 2 contour upper low that tracks from La to middle Ga or middle SC, then folks under and north of that track will have a great shot at switching to wet snow and/or sleet.  That's just simply how upper lows always work, if the 850 temps are anywhere near threshold, and since this is winter, and they're "close" , I see no reason to think otherwise on this one. I'm still not totally sold this upper low forms though, but we'll know by this time tomorrow by looking at the vapor I think, atleast the beginning stages of it.  The trends are in favor thats for sure. And I won't be surprised to see ECMWF NOT come on board with this.

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following the models is fun and all, but we are basically dead-set on being optimistic that this upper level energy can sustain itself as a 2-contour cutoff all the way across to be able to manufacture some real heavy precip rates

 

as I mentioned earlier today, this system doesn't have much of a ceiling as far as how cold it can go at around 5000ft... and those temperatures are critical in snow-growth

 

as someone said earlier, "may the odds be in your favor" that you happen to be positioned under the heaviest rates in overcoming an otherwise marginal/shoddy boundary layer and 925mb temperature scheme as the column dynamically cools and smacks you around with :snowing: for a 3-6 hour window

 

it will only take a short time for some real heavy, sustained snow to accumulate... but, if the snow doesn't fall heavily enough or consistently enough... it won't stick

 

if you aren't within the heavy precip rates... enjoy the rain (as many will see)

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I mean that I doubt dewpoints will change 10 to 11 degrees over the course of 100 mbs of atmosphere with NO strong high pressure to the north (1020 mb)...

Can you clarify?  Do you mean that you think that sounding is inaccurate?  Or do you mean that you don't think it's likely even though the model did output that data?

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A lot of people are mentioning march 09 with this event. From what I understand that event was just a big closed low. I don't remember much about it as I didn't know squat about winter weather back then, I only knew how to check the NWS forecast for MBY every 10 minutes. Anyway, I clearly remember ILM being forecasted for a 70% chance of snow 36 hours before the event, and it ended up being a total bust as we did not receive anything. Was there a big north shift in the last day or so with that storm that caused this bust, or did it just trend warmer? And can a similar thing happen with this upcoming storm? These ULL's look like they're much more finicky to forecast than your typical miller A.

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following the models is fun and all, but we are basically dead-set on being optimistic that this upper level energy can sustain itself as a 2-contour cutoff all the way across to be able to manufacture some real heavy precip rates

 

as I mentioned earlier today, this system doesn't have much of a ceiling as far as how cold it can go at around 5000ft... and those temperatures are critical in snow-growth

 

as someone said earlier, "may the odds be in your favor" that you happen to be positioned under the heaviest rates in overcoming an otherwise marginal/shoddy boundary layer and 925mb temperature scheme as the column dynamically cools and smacks you around with :snowing: for a 3-6 hour window

 

it will only take a short time for some real heavy, sustained snow to accumulate... but, if the snow doesn't fall heavily enough or consistently enough... it won't stick

 

if you aren't within the heavy precip rates... enjoy the rain (as many will see)

 

POST of the YEAR!!!  Please people, don't get your hopes up too much.  I am really not trying to be debbie downer, but this event is marginal still at best...

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There are a lot of positives to take away from this run. The main one being the trend to keep this closed off all the way to the carolinas. That will throw back plenty of moisture as it pivots to a netural/negative tilt over Georgia. The profiles will resolve after we good handle on how long this stay's closed off and how much QPF is possible. I like the timing being at night as well. Marginal temps at night w/ heavy snow can accumulate pretty quickly.

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Date: 3 day AVN valid 0Z FRI 18 JAN 13Station: KHKYLatitude:   35.73Longitude: -81.38-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   186                                                                 SFC  973   412   3.0   0.4  83  2.6   1.8   5   9 278.3 279.0 276.4 289.5  4.04  2  950   602   2.4  -4.0  63  6.4  -0.1   8  20 279.6 280.1 275.6 288.0  3.00  3  900  1037   2.1 -15.7  25 17.8  -3.3   8  31 283.6 283.9 275.3 287.4  1.25  4  850  1498   1.0 -14.2  31 15.3  -3.8  15  34 287.2 287.5 277.5 291.7  1.49  5  800  1983  -0.5  -8.9  53  8.4  -3.6   9  31 290.7 291.1 280.4 297.9  2.44  6  750  2499  -0.9  -5.5  71  4.6  -2.8 359  23 295.6 296.2 283.7 305.7  3.38  7  700  3048  -3.2  -6.1  80  2.9  -4.4 353  21 298.9 299.6 285.1 309.4  3.45  8  650  3632  -5.7  -7.7  86  2.0  -6.5 338  19 302.5 303.1 286.2 312.6  3.29  9  600  4256  -8.4  -9.5  92  1.1  -8.8 308   9 306.4 307.0 287.5 316.1  3.10 10  550  4927 -12.4 -12.7  98  0.3 -12.6 196  12 309.3 309.8 288.0 317.6  2.61 11  500  5649 -17.0 -17.2  98  0.2 -17.0 206  21 312.4 312.7 288.3 318.9  1.99 12  450  6432 -21.6 -22.0  97  0.4 -21.7 201  33 316.0 316.3 289.0 320.9  1.46 13  400  7290 -27.3 -27.8  95  0.5 -27.4 196  49 319.5 319.7 289.6 322.9  0.97 14  350  8238 -33.9 -34.3  96  0.4 -34.0 198  63 323.0 323.1 290.3 325.1  0.60 15  300  9296 -43.7 -44.3  94  0.6 -43.7 198  66 323.8 323.8 290.2 324.7  0.25 16  250 10495 -51.8 -52.9  88  1.0 -51.9 204  97 329.0 329.0 291.6 329.4  0.11 17  200 11924 -56.2 -68.6  20 12.4 -56.3 214  99 343.8 343.8 295.3 343.9  0.02 18  150 13750 -58.3 -70.7  19 12.4 -58.5 242  76 369.6 369.6 300.5 369.7  0.02 19  100 16242 -65.4 -78.2  15 12.8 -65.5 232  68 401.4 401.4 305.4 401.4  0.01TRP                                             0                              WND                                             0                              

 

hmph

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I mean that I doubt dewpoints will change 10 to 11 degrees over the course of 100 mbs of atmosphere with NO strong high pressure to the north (1020 mb)...

 

Thanks for the response.

 

The 00Z GFS looks pretty frigid in the long-range.  Beginning about hour 130ish, 850s are below freezing for TN/NC out until at least hour 200 or so.  I can't see any further yet.  Of course, with those cold temps comes the dry air.  It's just how we roll down here in the SE...

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following the models is fun and all, but we are basically dead-set on being optimistic that this upper level energy can sustain itself as a 2-contour cutoff all the way across to be able to manufacture some real heavy precip rates

 

as I mentioned earlier today, this system doesn't have much of a ceiling as far as how cold it can go at around 5000ft... and those temperatures are critical in snow-growth

 

as someone said earlier, "may the odds be in your favor" that you happen to be positioned under the heaviest rates in overcoming an otherwise marginal/shoddy boundary layer and 925mb temperature scheme as the column dynamically cools and smacks you around with :snowing: for a 3-6 hour window

 

it will only take a short time for some real heavy, sustained snow to accumulate... but, if the snow doesn't fall heavily enough or consistently enough... it won't stick

 

if you aren't within the heavy precip rates... enjoy the rain (as many will see)

I hope you read my post correctly. 

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There are a lot of positives to take away from this run. The main one being the trend to keep this closed off all the way to the carolinas. That will throw back plenty of moisture as it pivots to a netural/negative tilt over Georgia. The profiles will resolve after we good handle on how long this stay's closed off and how much QPF is possible. I like the timing being at night as well. Marginal temps at night w/ heavy snow can accumulate pretty quickly.

agree. I wouldn't worry or expect accums anywhere, but if it occurs long enough or heavy enough, it would happen. Obviously car tops and bushes are number 1 choice, but with super duty rates, which is always possible in upper lows that go neg. tilt before dying, that throws a small geographic region in some serious snow rates for a few hours, and that would cover the ground, if only for a few hours. I recall the March 09 event here when it was basically flooding rains for 2 days, then a switch to silver dollars for 7 hours beginning at dark. I had 10" fall  and the highest ground measurement was 9.5" . It was devastating to trees. The roads covered quickly (since sfc temps went to 30) but the next day snow melted very fast. Still I think folks would just like to see any flakes fall, after 2 long years without any. I'm NOT saying March 09 is on the way!

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Date: 3 day AVN valid 0Z FRI 18 JAN 13Station: KHKYLatitude:   35.73Longitude: -81.38-------------------------------------------------------------------------------LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg-------------------------------------------------------------------------------  0 1000   186                                                                 SFC  973   412   3.0   0.4  83  2.6   1.8   5   9 278.3 279.0 276.4 289.5  4.04  2  950   602   2.4  -4.0  63  6.4  -0.1   8  20 279.6 280.1 275.6 288.0  3.00  3  900  1037   2.1 -15.7  25 17.8  -3.3   8  31 283.6 283.9 275.3 287.4  1.25  4  850  1498   1.0 -14.2  31 15.3  -3.8  15  34 287.2 287.5 277.5 291.7  1.49  5  800  1983  -0.5  -8.9  53  8.4  -3.6   9  31 290.7 291.1 280.4 297.9  2.44  6  750  2499  -0.9  -5.5  71  4.6  -2.8 359  23 295.6 296.2 283.7 305.7  3.38  7  700  3048  -3.2  -6.1  80  2.9  -4.4 353  21 298.9 299.6 285.1 309.4  3.45  8  650  3632  -5.7  -7.7  86  2.0  -6.5 338  19 302.5 303.1 286.2 312.6  3.29  9  600  4256  -8.4  -9.5  92  1.1  -8.8 308   9 306.4 307.0 287.5 316.1  3.10 10  550  4927 -12.4 -12.7  98  0.3 -12.6 196  12 309.3 309.8 288.0 317.6  2.61 11  500  5649 -17.0 -17.2  98  0.2 -17.0 206  21 312.4 312.7 288.3 318.9  1.99 12  450  6432 -21.6 -22.0  97  0.4 -21.7 201  33 316.0 316.3 289.0 320.9  1.46 13  400  7290 -27.3 -27.8  95  0.5 -27.4 196  49 319.5 319.7 289.6 322.9  0.97 14  350  8238 -33.9 -34.3  96  0.4 -34.0 198  63 323.0 323.1 290.3 325.1  0.60 15  300  9296 -43.7 -44.3  94  0.6 -43.7 198  66 323.8 323.8 290.2 324.7  0.25 16  250 10495 -51.8 -52.9  88  1.0 -51.9 204  97 329.0 329.0 291.6 329.4  0.11 17  200 11924 -56.2 -68.6  20 12.4 -56.3 214  99 343.8 343.8 295.3 343.9  0.02 18  150 13750 -58.3 -70.7  19 12.4 -58.5 242  76 369.6 369.6 300.5 369.7  0.02 19  100 16242 -65.4 -78.2  15 12.8 -65.5 232  68 401.4 401.4 305.4 401.4  0.01TRP                                             0                              WND                                             0                              

 

hmph

Text extraction says all rain for hickory and charlotte. well that excitement was fun while it lasted.  

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