Severe Weather/Winter Storm - 3/26 to 3/28

[venture]

Gonna give this one its own thread. Concern for our state is now on the developing winter storm that is pegged to come in over the next couple days. Norman WFO has tossed up a Winter Storm Watch (National Weather Service Watch Warning Advisory Summary) for the counties expected to be most effected. Snow fall forecasts seem to be up in the air since some models are extremely aggressive (upwards of 20 inches) and others are just terrible with winter storms. Ground temperatures are all in the low to mid 50s throughout the state, so the rate of snowfall would need to be great for it to stick - which it should be.

I'm going to focus on the OKC metro for this first post. Going to throw up what a model is thinking (will get more when I have time to take a closer look). My thought son snowfall rates will be mitigated a bit...living in the Great Lakes for several years, these type of forecasts are the hardest to do.

GFS has OKC falling below freezing in the late afternoon on Friday. Precip will already be ongoing at this time with some light to moderate rain. This will likely mix over and change to show, upper levels will be cold enough to have frozen precip all the way down. Through the course of the event (Saturday morning) total water content will be around .4" to 1.00", which typically would translate into 4 to 10 inches of snow (this isn't the north where you have a higher water to snow ratio). However, this snow is likely to be pretty heavy with a lot of water content, so with compacting in mind ground accumulations would likely be anywhere from 2 to 5 inches. Higher values on the north side, lower from Norman south. Winds will be on the order of 15-25mph with much higher gusts during the event, so visibilities will be low.

I won't post regarding WRF, since it keeps temps no lower than 40 here in Central Oklahoma which would lead to just cold rain. Will update with the new model runs later this evening.

[westsidesooner]

I just posted a snowfall forecast chart in another thread. I wouldn't be surprised to see the watch upgraded by tomorrow, if the models are correct. The SPC has also expanded the severe weather area for tomorrow to include most of central and eastern Oklahoma. Mostly for hail. Gotta love spring.

[venture]

Yeah, it is almost a given the watch area will get upgrade. Granted the criteria used here is completely different than back north which really annoys me to a point - a flurry doesn't require a winter weather advisory (yes...not f'n travelers advisory Gary and Mike).

Here is the SPC Outlook Westside pointed out.

...SOUTHERN PLAINS INTO THE OZARK PLATEAU...
WARMING MID-LEVELS AHEAD OF STRONG DIGGING UPSTREAM TROUGH WILL CONTRIBUTE TO INCREASED INHIBITION ACROSS MUCH OF THE SOUTHERN PLAINS...PARTICULARLY SOUTH OF THE WARM FRONT FORMING NEAR THE RED RIVER...TO THE EAST OF THE DEVELOPING SURFACE CYCLONE. IT IS POSSIBLE THAT ISOLATED CONVECTIVE DEVELOPMENT...IN AN ENVIRONMENT FAVORABLE FOR SUPERCELLS...MAY OCCUR NEAR THE DRY LINE/WARM FRONT INTERSECTION ACROSS PARTS OF NORTH CENTRAL TEXAS/SOUTH CENTRAL OKLAHOMA LATE THURSDAY AFTERNOON. BUT...IT APPEARS MORE PROBABLE THAT THE PRIMARY CONVECTIVE DEVELOPMENT WILL OCCUR AFTER DARK... BASED IN AN ELEVATED WARM ADVECTION REGIME TO THE NORTH OF THE FRONT...ACROSS PARTS OF CENTRAL/EASTERN OKLAHOMA INTO ARKANSAS. SHEAR SHOULD STILL BE FAVORABLE FOR SUBSTANTIAL UPDRAFT ROTATION ...WHICH WILL ENHANCE THE RISK FOR LARGE HAIL IN THE MOST VIGOROUS STORMS.

[Thunder]

Hey, Venture, have there ever been a tornado in a snowstorm? A real tornado with snow falling? Is that ever possible?

[venture]

There has, I would have to dig up the article. I know of a few cases, but some get a little complicated. Where it would be an elongated storm with snow on one end, and the tornado on the other. Really it just comes down to instability, moisture, and shear to get the setup to happen. I'll do some digging and see what I can find.

Quick update - storms are ongoing and developing northward today. Marginal risk of hail with these storms, but nothing horrible.

[westsidesooner]

Not a tornado, just a "snow-devil"...but this is cool. YouTube - Snow Devil / Twister at Jackson Hole, Wyoming

[Thunder]

Venture, what storms? Are you saying that the energy is now tracking to the north of us rather than hitting us head on?

[OKCisOK4me]

Venture, what storms? Are you saying that the energy is now tracking to the north of us rather than hitting us head on?

No, he's saying that there are storms down in Texas that are building/developing northward. Nothing on the scale of Monday, just some rain basically...

[Luke]

So, what are we lookin' at as far as snow? The lines on the map in the other thread were kinda all bunched... anywhere from 1 inch to 4 inches?

[venture]

I would say...2-5" is pretty good estimate right now, but the effect of ground temps (melting) and snow compacting (heavy wet snow) will influence those numbers. There could be 5 inches worth of snow that falls, but only an inch is actually on the ground. Snow fall forecasts are typically going to be pretty inaccurate more than 12-24 hours out unless you have a boring, typical setup (cold ground, winter, no difference in temps going up, etc).

[Insider]

Here is what the NFO is saying...

[rod4soonrs]

[Stinger]

I'm wanting to throw some grass seed down in my yard real soon. Is this the kind of moisture that will be good for that? (slow and steady so it won't all wash down the street. The snow may even help keep it in my yard).

[rod4soonrs]

Most of our attention today has been devoted to the upcoming storm
system progged for friday. The approaching s/w trough may be
identified on water vapor imagery touching off some lightning in
id/mt/wy. 12 utc model runs from today show somewhat of a more
southerly track than previous runs...moving the surface low along or
south of the red river.nam/ukmet are considerably slower than the
gfs...and with such an intense and deepening low this solution is
not out of the question. With more than sufficient instability and
shear...among other ingredients...the environment in southeast
oklahoma and back into western north texas could be favorable for
severe thunderstorms as early as thursday afternoon. If the low
tracks more southerly...better moisture may remain further south in
texas. A more northerly track would mean larger coverage of severe
storms...but could also keep accumulating snow further to the north.
The winter storm watch was expanded a little further south and east
to cover areas where greater snow accumulation is expected on friday
into saturday...based on a low track further south. With high wind
speeds...blowing snow reducing visibility especially in northwest ok
may be a concern and this has been added to the forecast.

[bandnerd]

Guess I'd better bring the strawberry pots in...and find some way to cover my parsley. Looks like mom was right--don't plant ANYTHING until after April 15.

[rod4soonrs]

Major March Snow on the Way
Posted on March 25, 2009 by Jonathan Conder

I hope you are ready for some good old March Snow, because it is on the way. A Upper Level Low currently over British Columbia, is on a bee line for Oklahoma and it is going to bring cold air and heavy precipitation. This looks like the biggest snowfall I have ever forecasted for Oklahoma in the last 5 years. I am not ready quite yet to hang my hat on snowfall amounts, but I would not be surprised if parts of Northwestern Oklahoma pick up over a foot of snow. Yes, I said it, a Foot! I also think OKC will pick up measurable snowfall, but the big question is what time will the rain change over to snow on Friday? That will make all the difference in the accumulations in the metro.

So, get out today and enjoy the lighter winds in the metro with highs in the lower 60s. Tomorrow is not bad either, with highs in the mid 60s. Rain is likely to begin in OKC very early Friday morning and changing over to snow during the day. It should continue to snow through Midday Saturday.

Again, I am not ready to put out an exact snowfall forecast, but this will give you an idea where I think the heaviest snowfall will occur:

[rod4soonrs]

[Bostonfan]

Sure hope we see some good snow in OKC. Been a long time since we've seen it without all the ice. I'm keeping my fingers crossed, but not getting too hyped about it. I've seen too many close calls where it looked great for getting snow, and we ended up getting all rain.

Also, this is a great thread, please keep it updated!!

[rod4soonrs]

[rod4soonrs]

We will not make any changes this evening to the winter storm
watch. 00z nam is just arriving. This system still has potential
to be a particularly significant and disruptive heavy snow event
for parts of the area... Especially for so late in the season. Nam
and gfs have been sticking to their guns with run-total snowfall
in the range of 20+ inches in parts of nw ok and adjacent ks/tx -
which is hard to believe at any time of the year much less the
first week of spring. 00z nam has double-digit totals into extreme
nw ok by mid-evening friday... 15-20 inches into harper county by
09z sat... And again dumps an extraordinary 30+ inches in sw ks.
This run-to-run and model-to-model consistency is leading to
increasing concern that this snow event will be one for the
ages... And that we need to ramp it up further with what amounts
to a "pds" winter storm watch. Updated wsw will trend that way
and should be out by 10 pm. Strong winds and related blowing/drifting
easily could make this one of the most crippling s-plains
snowstorms in recent history... Although current indications are
that wind speeds are unlikely to attain blizzard criteria. All
users are urged to take this developing situation seriously and
prepare as well as possible for what may end up being essentially
an unprecedented late-season heavy snow event in nw ok. 24

[bluedogok]

The north side of Austin got hammered by storms today, Marble Falls got so much hail it closed US 281 through there. Other parts had up to baseball size hail, lucky we got out of that side of town before it hit at evening rush hour.

Y'all be careful and stay warm.

[Bostonfan]

Still looking the same for OKC?

[venture]

New model runs are still in process. I'll be posting my thoughts and precip forecast after I see all those. This will probably be around Midnight when the run is complete.

[Thunder]

4 hours past midnite. Anything?

I've just noticed that KFOR is putting us on the lite side.

[rod4soonrs]

We will upgrade the winter storm watch to a warning for our far
northwest counties... Beginning at 7 am tomorrow... Due to the
relative certainty of that area receiving winter storm quantities
of snow. There is still too much uncertainty elsewhere to upgrade
at this time. We also will add a row or two of counties to the
southern edge of the watch area from 7 am friday through 1 pm on
saturday.

The surface low will track east into the arklatex region by friday
evening... While the upper low moves into the area just south of
the texas panhandle. Cold air will continue to deepen across
oklahoma and western north texas... As the precipitation changes
from rain... To sleet... To snow across about the western 2/3 of
oklahoma and western north texas. There is also a possibility of
freezing rain or drizzle across parts of central oklahoma... If
surface temperatures fall faster than expected.

Any snow that falls on friday will be blown around by strong north
winds. Wind speeds look like they will remain below blizzard
strength... But this will need to be watched as newer model data
arrive.

Snow should begin to taper off friday night and end during the day
on saturday. Storm totals will likely exceed a foot somewhere in
the northwest half of oklahoma... But it is still far too early to
pinpoint the location. Convective snow bands will be possible...
Which may leave narrow bands of much heavier snowfall... Compared
with the overall snow field.