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The Big One - Forecast & Discussion


Wow

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A little speechless.. It is the NAM.. probably overdone. But wow.  Widespread 12"+ across the foothills and W piedmont.

 

NAM looks more realistic to me. You can probably cut totals by 1/3....but I suspected there would be more cold air with this system then models were saying. I still feel that and once the wedge sets up it's game time. Of course the NAM is probably going to have a different look every run until tomorrow when that northern energy is fully sampled. Keeping that energy in the south positively tilted really helped on this run compared to the 6z. 

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A little speechless.. It is the NAM.. probably overdone. But wow.  Widespread 12"+ across the foothills and W piedmont.

I'm really at a loss for words too man. Good grief. Between areal coverage and the extreme totals...it could be a once a lifetime storm. And I'm not just saying this because of the nam..but because all the models are showing really widespread and really high snow, sleet and freezing rain. Folks should soak all this in and enjoy it.

 

And also, we should all start saving maps. Maybe after it's over we could put them all in a thread and in the future we could look back it. I know I'm saving some.

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Speaking of maps.

Here is the total through 84 on the NAM 12Z:

namUS_sfc_precacc_084.gif

I'm really at a loss for words too man. Good grief. Between areal coverage and the extreme totals...it could be a once a lifetime storm. And I'm not just saying this because of the nam..but because all the models are showing really widespread and really high snow, sleet and freezing rain. Folks should soak all this in and enjoy it.

 

And also, we should all start saving maps. Maybe after it's over we could put them all in a thread and in the future we could look back it. I know I'm saving some.

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question on NAM thermal profiles......The NAM was a great hit for everyone at face value but if you look at the bufkit for the I-85 corridor up to Charlottle, over half of the precip was ZR plus quite a bit of IP and very little actual snow........so how does the NAM actually do with the thermal stack up of the column in CAD regimes in this time frame?  Is it reasonable to expect that it is underplaying the cold or is it historically pretty accurate?  Thanks

 

EDIT:  I think I this is still the 6Z and the 12Z has not updated yet.

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guys the trends this morning was north and west and now some say south and east, anyone know which one it is, lol this is crazy jumping around.  :whistle:

Umm the 0z Euro and 0z-6z NAM were north and west of previous guidance and now the 12z NAM has moved back east somewhat.  The GFS is farther east than most (all?) other guidance.  

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question on NAM thermal profiles......The NAM was a great hit for everyone at face value but if you look at the bufkit for the I-85 corridor up to Charlottle, over half of the precip was ZR plus quite a bit of IP and very little actual snow........so how does the NAM actually do with the thermal stack up of the column in CAD regimes in this time frame? Is it reasonable to expect that it is underplaying the cold or is it historically pretty accurate? Thanks

NAM bufkit hasn't come out yet.

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Very strong Disco coming from KILM!..

Whoa..

 

Synopsis...
a major winter weather event is expected across most of the area.
The risk for severe icing Tuesday night and Wednesday...away from
the coast is increasing. Light mixed precipitation may begin as
early as near daybreak Tuesday. A cold front will push south of the
area early this morning and stall along the Gulf Coast and offshore
this evening. Arctic high pressure will nose its way into the area
in the wake of the front. A series of low pressure systems will
develop and track along the stalled front Tuesday through Thursday.
Drier weather will finally return to the area Friday and persist
through the weekend.

&&

Near term /through tonight/...
as of 6 am Monday...it is going to be a very interesting next
60 hours across the eastern Carolinas. The risk for a significant
and perhaps lengthy winter weather event continues to increase. A
severe ice storm is certainly plausible with the odds of this
greatest across the more southern and western portions of the
forecast area. We will have to watch this very closely...and we
advise our customers to keep checking back for the latest forecasts.
A Winter Storm Watch has been issued for the vast majority of the
area away from the coast and it is time to prepare for dangerous
winter weather whose aftermath may last for many days...if not weeks
in the worst case
scenario.

A backdoor cold front was moving across the forecast very early this
morning. This front will stall along the Gulf Coast and offshore
this evening. The front will be shallow in nature...with the cold air
very slowly deepening through the period as Arctic high pressure
centered across the northern plains begins to wedge into the
southeast states. Developing NE winds will slowly deepen from the
surface through 2 to 4 kft...deepest across the northern portions of
the forecast area.

There will be a steady cold push through tonight as 925 mb temperatures
drop to zero to 2 degree c and as cold as minus 2 degree c from udg to eyf
and points north and west. The column will begin to support frozen
precipitation across the northern three-quarters of our forecast
area toward Tuesday morning. Developing isentropic lift will initially
be weak tonight...and the column is not expected to significantly
moisten...especially in the lowest levels making it tough for any
precipitation to reach the ground. The exception will be across the
more southern portions of the forecast area...where the column does
moisten substantially down through 1200 feet. Will begin introducing
slight chance/small probability of precipitation after midnight...first across southern and
western portions of the Pee Dee and then spreading to the coast
before daybreak. Will confine mention of measurable precipitation to
areas along and south of a ilm to bbp line. A mix of light sleet and
light snow is possible before daybreak Tuesday. Pockets of frozen
precipitation may accumulate to a trace overnight and early Tuesday
morning in these areas. Will keep mention of only rain from about
Kingstree to Bald Head Island and southward before daybreak.

Temperatures today will be held down by increasing cloud cover and cold air
advection. Expect a significant temperature gradient from north to S. We are
forecasting highs in the upper 40s across the far north and as warm as
the upper 50s across the far south. Lows tonight will be in the middle
and upper 30s. However...lows will be near freezing along and north of a
line from bbp to lbt to eyf to Watha. In these areas...temperatures are not
expected to reach near freezing until after 3 or 4 am.

&&

Short term /Tuesday through Tuesday night/...
as of 3 am Monday...

Significant winter storm still expected. Watches being issued.
Concerned about major ice storm over far western zones. Coastal
locales likely escaping most if not all of the hazardous weather.

The high level of uncertainty has been stressed regarding this storm
for several iterations of the afd thus far and it bears repeating.
Isentropic upglide overrunning surface cool wedge on Tuesday causing
light precipitation to break out from south to north as the day wears on.
Southernmost zones will be warm enough for all rain but traveling
farther north the increasing depth of the cold air will favor more
ice pellets and then snow/ip. To say the least whenever ice pellets is
involved forecasting accums is difficult. Further complicating
Tuesday snowfall forecast is that best Omega lies mostly over rain and
transition zone. Still...far northern zones may get an inch or so.
Tuesday night into Wednesday two key things happen that will need to
be monitored closely as a very dangerous icing situation appears to
be shaping up. The surface airmass asserts itself and lowers
freezing levels while offshore cyclogenesis strengthens the
isentropic lift. Over NC this means that the sleet/snow will push
further south...possibly getting into some coastal sections but
likely not long enough for much accumulations. The snow/ice pellets will
continue over northern and western zones while grand strand and far southern zones
hard pressed to see anything but rain. Meanwhile in between there
will be an increasingly large Battle Ground where the cold air is
just thin enough for freezing rain. This should start over northern flow
and Darlington County late Tuesday night and burgeon almost due eastward
into daybreak Wednesday and then expand northward with the warm air advection Wednesday
morning. Where this persists the longest...across much of the Pee
Dee as well as into interior NC counties...the potential exists for
a dangerous ice storm with freezing rain accums in the 0.25-0.50 inch range.
Unfortunately there is even indication that should the dry air be
sufficiently overwhelmed by the overrunning warm air advection and Gomex moisture
an even more damaging ice storm (0.5-0.75" of fzra) cannot be
ruled out. Such ice storms often lead to extensive tree damage and
power outages lasting weeks.

 

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question on NAM thermal profiles......The NAM was a great hit for everyone at face value but if you look at the bufkit for the I-85 corridor up to Charlottle, over half of the precip was ZR plus quite a bit of IP and very little actual snow........so how does the NAM actually do with the thermal stack up of the column in CAD regimes in this time frame?  Is it reasonable to expect that it is underplaying the cold or is it historically pretty accurate?  Thanks

 

EDIT:  I think I this is still the 6Z and the 12Z has not updated yet.

 

12z NAM is all snow in Greenville, SC area from hr54 on (the main show) according to soundings.

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guys the trends this morning was north and west and now some say south and east, anyone know which one it is, lol this is crazy jumping around. :whistle:

Actually I believe all in all even if it does go a little south and east from yesterday nam and euro wise I agree with what Bob Chill is referring to in the MA forum that northwest precip will be more expansive due to the phasing and subsequent strong low forming with The moisture transport already occurring and gulf origins this thing should be huge for everyone!
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