Day 1 - Forecast valid from 1800 UTC 19 January to 1800 UTC 20 January 2007

Still a bit of uncertainty with the exact track of our next system. Models seem to have dropped the forecasted path southward threatening the Southern and Central Plains once again with frozen precipitation. Main guidance for this forecast was taken from the GFS/WRF. Currently, 500mb closed low is located over the Baja Peninsula and already bringing snow and rain to portions of New Mexico and Texas. Once this system enters the main jet core in the southern plains, it is progged to spread into the central US by 18Z on the 20th bringing with it the chance of additional snowfall. Ample moisture coupled with strong forcing and freezing temperatures develop over Northern Texas and Southern Oklahoma by late day 1. Strong vorticity max and impressive vertical velocities accompany the main area of forcing adding additional lift and spin to the system. Weak frontogenesis couplets are also present across central Texas and into Southern Oklahoma. Soundings from northern Texas and Southern Oklahoma show temperature profiles within the desired 0 C to -10 C temp range for lightning production with saturated profiles and strong omega (-16 ub/s) values. Cross sections from HHF to LBF in northern TX reveal a well saturated atmosphere with regions of elevated (700-500 mb) CSI surrounded by additional CI and PI. Convective instability spills over into day 2 as the dynamic closed low continues to track E-NE. Lapse rates in both plan view and soundings are not very strong with highest values reaching to 5.8 C/km, which implies this system may not have the dynamics needed for a lightning producer. However, once the system is influenced by the low level jet pumping additional moisture in from the Gulf, and with all the other necessary elements present in this system, some lightning activity in the cold air is possible.


Day 2 - Forecast valid from 1800 UTC 20 January to 1800 UTC 21 January 2007

A continuation of day 1 spreads the wintertime activity further northeast into portions of Missouri, Iowa, and Illinois as the closed low comes under the influence of the sub-tropical jet. While sfc cyclone really never takes form, increasing moisture at the nose of 850-mb LLJ will help to enhance vertical wind shear with 700-mb theta-e following dynamic form of 500-mb low. Models have continued to track the low farther north, but 12Z/19 runs of the GFS have began to balance out as it shifts back towards the south slightly agreeing with model runs earlier in the week.

Convective snow anticipated.