Monday, March 11, 2019

Monday Night - Increasing clouds. Low 34-38.

Tuesday Morning - Cloudy. Showers developing in the afternoon. High 48-52.

Tuesday Night - Cloudy with showers, mainly before midnight. Low 48-52.

Wednesday - Cloudy with showers, mainly after noon. Thunder possible. Becoming windy during the afternoon. High 60-64.

 Thursday - Partly cloudy. Windy. High: 38-42.

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Active weather will define the start to the work week. There may be some breaks in the clouds today, especially during the afternoon, before the skies become overcast for good overnight tonight. Our next system will produce precipitation in two waves: the first wave will move through Tuesday afternoon and evening, and the second will move through Wednesday afternoon. Although both waves are expected to contain mainly showery rains, a thunderstorm or two will be possible Wednesday afternoon. Temperatures will be near average both today and Tuesday, with well above average temperatures expected Wednesday ahead of the cold front. However, Thursday temperatures will decrease back down to the 40s after the cold front passes.
Forecasters: Danaher and Brown
Issued: 4:30 p.m.March 11, 2019

Technical Discussion (The nerdy stuff we are discussing in class!)

This forecast period brings with it another week of active weather for the Midwest. With Models in good agreement regarding a strong closed low affecting much of the central CONUS by midweek, went primarily with GFS guidance.

The brief ridging set up over the eastern CONUS will breakdown as the next LW trof digs in from the west. Zonal flow at 500 hPa over the Midwest will transition to quasi-meridional a         Wednesday Night - Cloudy with showers. Thunder possible. Windy overnight. Low - s the system approaches. Monday night 850 hPa flow shifts from due west to SSW beginning the strong WAA over the next few days. Clouds will increase overnight becoming completely overcast by midnight.

Tuesday, several vort         Wednesday Night - Cloudy with showers. Thunder possible. Windy overnight. Low - icity maxima propagate into Missouri out ahead of the LW and following the southwesterly flow at 500 hPa. With them, the chances for precipitation lingers during the day Tuesday. GFS soundings show a quickly moistening column after 12z Tuesday morning, however, with little lift and a dry layer at the sfc, the precip, if any is to occur, will show itself in the form of mainly drizzle. By 21z Tuesday, soundings show complete saturation with moderate lift indicating presence of more moderate showers associated with the aforementioned vort maxima. Rain will persist into Tuesday night, but slight drying out at the lower and mid levels of the troposphere suggest a break in precipitation before our main system of focus moves in.

Our main focus for the forecast period is the closed low moving onshore into California. As the longwave digs into the western CONUS, the trof rapidly turns negatively tilted with about a 45 degree negative tilt. This strong negative tilt as the system comes off of the Rocky Mountains will favor strong cyclogenesis. This cyclone has the potential to be a bomb as GFS sfc maps favor rapid deepening immediately exiting the Rockies. Sfc maps indicate a 20 hPa drop in 24 hours, dropping to 976 hPa by the time it reaches western KS. This system shows signs of early occlusion. GFS shows 7 closed isobars as it sits over western KS. This is significantly more than the 4 isobars that the Bergeron Rule states indicates occlusion. Needless to say, when this cyclone develops, it will already be mature as it approaches the region. Impressive moisture and lift at 700 hPa will move into mid-Missouri by Wednesday at 18z. As of the 06z run of the GFS and ensemble guidance, CAPE is small. This will mainly be a widespread rain event. That being said, with the impressive lift, and about 100 J/kg of CAPE that both SREF and GEFS want to put out for Wednesday do not rule out the possibility for thunder. Early GEFS QPF mean sits at 0.85 inches of precip and SREF sits at 0.75 inches. Will defer to subsequent shifts to narrow down rain accumulations with better model guidance.

After this storm passes on Thursday, southerly flow is expected to switch to NW flow with winds reaching 15-30kts (due to a strong PGF) according to the 12Z GFS sounding. Temperatures will gradually decrease back to the 40s throughout the day Thursday.

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