Rain the Bigger Focus Sunday than Severe

<TL;DR> – Here is our risk outlook, combining SPC probabilities of any severe weather and our risk and impact forecasts.

KSStorm.info Risk Outlook for Sunday, March 18, 2018. SPC percentages plotted on Google Earth, remainder (c) KSStorm Media

Sunday Analysis

For this forecast I’m using a blend of the NAM-WRF, the ECMWF, the UKMET and the GFS. The models are really in decent agreement, with the lee-side low developing rapidly in southeast Colorado or the Colorado Plains and moving rapidly east-southeast.

Here’s an example loop, from the UKMET, for the period Sunday noon to Monday morning:

UKMET Barometric Pressure Loop, Sunday noon through Monday early morning

What jumps out at me is how rapidly the low plows east. If it developed in the lee of the Rockies and sat there for 6-8 hours rather than immediately plowing east, I think we’d have b it different scenario.

My Primary Concern is Moisture Return

We just had a very strong system exit the region overnight Friday into this morning. That was the system responsible for 60+ mph wind gusts all afternoon yesterday. That gives a maximum of 36 hours for Gulf moisture to recover into the area…and with the lee low not really forming until early afternoon Sunday, there’s just not much time. Here’s two loops showing moisture return (NAM-WRF, then ECMWF)

Of positive note: both models develop a strong dryline. The Euro keeps it mostly in the panhandles and far southwest Kansas while the NAM-WRF lines it up along US 83 between Garden City and Liberal and charges the southern end east as the low moves out. But even with the sharp dryline, there just isn’t a lot of energy available in the form of moisture. I think we need 55-degree dew points to get meaningful severe weather in this scenario.

To illustrate my concerns, where’s the NAM-WRF loop of CAPE (Convective Available Potential Energy) . Note there is a three-hour bubble of 1000 j/kg CAPE that hovers over Gray, Meade, Clark and Ford counties at about 9pm CDT. That might be where some elevated storms fire, in my opinion (if that model is the one most resembling what happens)

SPC/NWS Highlights

Here are a couple of highlights from the SPC Day2 outlook and this morning’s forecast discussions from Dodge City and Wichita:

SPC:

(S)trong heating will occur across the High Plains, where surface convergence will rapidly increase as the low deepens. Cooling aloft will overspread this warm air mass, resulting in steep lapse rates. Wind profiles will support supercells. However, instability will be weak, as dewpoints only rise into the 40s F. Still, strong lift will result in an arcing line of storms by around 00Z, with hail and wind possible. A tornado cannot be ruled out given the vorticity-rich environment, steep lapse rates, and ample low-level shear, mainly over southwest KS into far northwest OK.

I think any brief tornado chance is limited to the area Woodward, OK to just east of Liberal. Based on what I’m seeing now, a tornado in Kansas would be a surprise.

NWS Dodge City:

There is still the possibility of a severe storm or two late Sunday evening/Sunday night, mainly east/southeast of DDC, especially if the southern track of the mid level cyclone is preferred.

* Sunday
  - Lightning: Limited risk
  - Severe thunderstorm: Elevated risk
  - Non thunderstorm wind: Elevated risk
  - Snow: Limited risk
  - Fire weather: Significant risk

NWS Wichita:

(S)cattered thunderstorms across the region but not sure how much precipitation will accompany this activity. We may be looking at a high base, low-precipitation supercell type thunderstorms for most of the region Sunday afternoon/evening and into Monday morning. While this will reduce the flood threat it will not reduce the wind threat as set up looks more like a severe wind rather than hail as CAPE values remain rather low during this period.

A very high Grassland Fire Danger is expected for Sunday afternoon.

Late Sunday afternoon and into the overnight hours, there is a
strong chance for some severe thunderstorms, generally along and
west of I-35. Isolated thunderstorms can`t be ruled out overnight
Sunday in areas east of I-35.

Bottom Line

No matter which model you prefer this system looks like the first reasonable chance for rainfall in much of the state. I feel any severe weather that happens will be short-lived, hail to maybe just over an inch, and brief wind gusts about as high as yesterday afternoon. If the StormBurban were 100%, i might consider going to southern Oklahoma for a shakedown. But I’m not seeing anything in Kansas worth chasing tomorrow.