Archive for March, 2009

Incredible late season snow storm and blizzard

An unprecedented late season snow storm with blizzard conditions will affect KS, NWestern TX and most of west and central OK. A mid to upper-level closed low ejects into southern Plains today with very impressive and strong storm system hitting central Plains with strong cold front crossing TX/OK from NW during the Friday into Saturday.

First of all, this storm will bring severe weather into lower Mississippi valley with quite impressive wind shear and instabillity values that overlap in the warm sector. Storm Prediction Center has issued a MDT risk for parts of LA/MS/AR.

MDT risk

The second thing, which will likely be the historical event from this system, is the backside of the system with heavy snowstorm with expected snow accumulations up to 15″ or even more. And to make things even more impressive and dangerous, there will also be blizzard conditions with strong winds blowing snow and making drifts up to two feet.

snow accumulations

As impressive as it is, there were tornadoes reported last night around Red River while snow is expected today’s afternoon and evening time there. Certainly something you cannot see everyday, even thats in America.

Here is the map with the timeline over OK with eastwards moving cold front and changing precipitation type from rain to snow, likely there will be some sleet and freezing rain in that hour or two before it starts to snow. Currently there are storms ongoing in central OK.

precips change timeline

This is definatelly one of the most impressive storm system affecting central and southern Plains lately and will be closely monitored in the next 48h as the cold front races eastwards. Stay tuned for future updates on this system!

March 25rd 2009 outlook – south TX

Another healthy looking setup for southern Plains into lower Mississippi valley. Rather stationary cold frontal boundary in southern TX will be the focus for today’s severe weather while it transforms into a warm front and retreats back NWwards during the afternoon. Increasing low-level winds with rich boundary layer moisture near the gulf will slowly move NWwards and destabilization will occur along the frontal boundary. First, mostly elevated storms are expected in central TX with threat for hail and severe gusts while in the afternoon, also surface based convection is expected due to steeper lapse rates and strong surface heating which should lead in at least 1500-2000 of MLCAPE. Improving low to mid-level wind profiles with strong curved hodographs become supportive for surface-based supercells with tornadoes possible.

The Storm Prediction Center issued a SLGT risk extending from south TX into MS/AL, with hatched 10% for tornadoes and 30% for large hail:

SPC outlook

Surface frontal boundary can be very well seen on this SFC theta-e map:

theta-e

Impressive values of 0-3km SR helicity; 300-500m^2/s^2 in ESE TX!

SRH3

Due to impressive enhanced values of SR helicity and rapidly improving low-level wind shear profiles a chance for a few long-lived supercells with strong tornadoes is in place along the warm frontal boundary especially in eastern TX into MS during the afternoon into early evening timeframe.

March 23rd 2009 outlook

An interesting severe weather/tornadic setup is shaping up over central Plains today. A deep and large scale upper-level trough over western Conus effects central Plains with deepening surface low from CO through NW KS into NE and SD with extending cold front from NE into central KS while dryline is mixing out eastwards from TS/OK Panhlandle into central OK and southern KS. At the evening hours the surface cold front overtakes the dryline from central KS E/SE-wards.

Storm Prediction Center issued a MDT risk over parts of SE KS into NE OK:

SPC outlook

An impressive wind shear profiles are noticed on the models across whole warm sector from east of I35 northwards into eastern NE/SD with healthy looking LL moisture depth only down in eastern OK. According to latest model runs the strong cap should prevent early storm initiation in these areas with better moisture while more northwards into east KS and NE initiation is not a concern. However, its only late March so the cap isn’t such a problem yet.
 
This WRF/NAM 12z map shows the tripple point positioned near Pratt, KS by 00z today which should be the best area today.

theta-e

Very impressive hodographs with very high tornadic potential as strong deep-layer wind shear and still rather deep LL moisture overlap together. More south-north oriented surface frontal boundary should allow cell to become more dicerete and move off the boundary as soon as they fire along this boundary.

I am monitoring the situation overseas for now, but my virtual preliminary target would be Pratt, KS today as it has great road network when needed to go in any direction. First I was thinking if making a start around Enid, OK but cap could be a problem and initiation can be at or after the dark, so I am playing an earlier initiation in central KS.