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Warmer conditions reaching the lower 70s are expected for the weekend. Go out enjoy the warm temperatures Saturday, while it is dry. Showers and thunderstorms will move in Saturday night and going into Sunday afternoon. Uncertainty exist on how strong these thunderstorms may be. A cold front move through Sunday after midnight which will bring drier conditions and clear skies over the area by Monday.
Forecasters: Johnston, Rojas, Sumrall, and Hirsch
Issued: 5:00 p.m., 5 April 2019
Technical Discussion (The nerdy stuff we are discussing in class!)
Weather Prediction Center Model Diagnostics has average confidence in a blend of 12Z GFS and NAM, 0Z ECMWF and UKMET with less weight on the NAM and UKMET. So due to difficulty of accessing ECMWF and suggestions from the Weather Prediction Center we used the GFS.
Satellite currently shows the bulk of our clouds moving out of Missouri just leaving some scattered clouds moving in from southwest Missouri. The soundings for overnight are mostly dry. However early Saturday morning from 09Z to 12Z soundings show some moisture near the surface. With this moisture and calm winds fog is possible, but confidence is on the lower end due to how dry the sounding is aloft. By 15Z the sounding is dry below 350 mb and remains dry, indicating mostly clear skies for Saturday. High pressure currently resides over us. However a trough over the four corners will push the high pressure eastward. This trough has divergence downstream of it on the 250 mb over northern Texas and western Texas has a warm front to the south of it. This trough will move eastward toward our area, which is what will brings us rain and thunderstorms late Saturday night into Sunday.
On Sunday the upper-level maps (250mb) shows a jet core way far to the northwest side of the CONUS and the upper-level trough with its axis down into Texas. As we are located downstream of this trough a lot of divergence areas are associated to this feature along with wind speed around 100kt. Going down to 500mb, a shortwave will reach our area by Sunday 06Z, leaving the area by 18Z the same day along with maximum values of vorticity. That would be our main weather maker for Sunday. An extremely dry layer from 600 mb and 840 mb forms at 0Z Sunday that erodes away by 06Z Sunday. After the dry air erodes away the winds shift from the south to the southwest. At 09Z there is sufficient upward motion and relative humidity at 700 mb, so we will experience showers and thunderstorms, but these conditions dissipate later. At 18 Z the maximum values of omega are north of us, a relative wet layer in the lower troposphere, a dry mid-troposphere, and a saturated upper troposphere layer are present but the values of omega are around -1 mb/s. At the same time some unstable conditions start to develop. Looking up the soundings with the most unstable parcel conditions, a dominant westerly flow is observed, the values of CAPE at that time are 1004 J/Kg and the lifted index (LI) is -4 °C suggesting that the parcel is warmer than the environment. At 21Z, CAPE increases up to 1406 J/kg as well as LI (-6 °C), K index remains below 60% and the total totals reach 51, theta-e profiles indicates unstable conditions for the mid-troposphere but still not enough upward motion to support the updraft. If the wide dry layer that exists from the surface to around 500 mb is overcome by moisture, we could expect severe weather as the GFS show severe potential. The SPC convective severe thunderstorm outlook locates us in the border of slight and marginal risk.
A cold front will cross the area after Sunday midnight. On Monday the conditions start with a dry lower layer and moist upper troposphere, the cold front will dry out the entire column during the day. Thus we could see sky conditions with high clouds during the morning being dissipated by the end of the day.