Thursday, May 9, 2019

Tonight - Clouds begin to clear. Low: 40-44

Friday - Mostly sunny with clouds building in in the afternoon. High: 62-66

Friday Night - Overcast with showers later in the night. Low: 40-44

Saturday - Mostly cloudy with morning showers.  High: 56-60

Sunday - Overcast with small isolated showers.  High: 62-66

Thanks to for the icons!

Don't retire those umbrellas just yet, more rain is on the way this weekend! Tonight brings a break in the clouds with a calm night and milder temps through tomorrow morning. Friday brings similar conditions to Thursday as clouds begin to build back in ahead of the incoming cold front Friday night. Showers will take form in the latter hours of Friday night through Saturday morning with rain totals hovering just around a quarter of an inch. Temps cool off a bit with the rain and cloud coverage, but winds will stay calm and breezy. Clouds remain prominent through the later hours of Saturday with another chance for rain coming Sunday. Right now rain totals for Sunday sit in trace amounts under a tenth of an inch with a low pressure system looming over the Great Lakes to Missouri's NE. Hopefully the later days of May can keep the clouds away!

Forecasters: Doll, Myers and Bongard
Issued: 4:20 p.m.; 9 May 2019

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

Mid Missouri finally sees a break for rain tonight.  At 250-mb, southwesterly flow is continuing to bring moisture into the midwest.  The jet max is situated over the Great Lakes rounding the ridge that is continuing to make its way east.  As the night progresses, the flow will become more zonal.  A trough that is stationed over the NW portion of the CONUS deepens as we begin to see confluence from the polar and tropic upper level jets over Colorado. This 250-mb upper level jet develops 2 jet streaks indicating cyclonic development with the axis sitting over South Dakota. Moisture will slowly dissipate overnight, especially at the 700-mb level.  There is disagreement in the models, as the GFS has significantly more drying than the NAM through Missouri.  More moisture will be prevalent closer to the surface.  The decrease in cloud cover overnight will allow for temperatures to drop down into the mid 40s. 

For Friday, zonal flow at 250-mb will persist throughout the day.  There is a jet max situated to the north over Iowa and northern Illinois in the area where confluence is still prevalent.  A center of low pressure develops off the coast of California as a shortwave trough begins to take shape.  At 500 mb, bands of vorticity stay to the north of Missouri, sitting along the Iowa/Missouri border.  Conditions at 700-mb will stay dry for the majority of Friday with the moisture building back in overnight. Clouds build back in along with this moisture as well as our next round of showers coming from the low to Missouri's north. The rain will come in small amounts Saturday morning but the models are in disagreement about timing.  The NAM has the system reaching mid Missouri early Saturday around 9Z where as the GFS has the timing later at 12Z. Both models agree that we will see less than a tenth of rain for Saturday morning.

A shortwave riding the southwesterly flow will eject out of the Southern Plains into the Midwest Saturday morning. This already moistened profile will set up precipitation development by 15Z as this wave slowly traverses through the area Saturday. Model disagreement shows as NAM moistens the atmosphere sooner than GFS and unsaturated sooner Saturday afternoon. GFS will not saturate completely until after 18Z Saturday but will continue rainfall into the evening hours. Therefore rainfall accumulation from GFS is around 0.25 inches while NAM is more conservative with 0.1 inch of rainfall. Convection looks to be limited as instability values with CAPE stay minimal to none and BRN values coast below 10 for the day. Cloudy skies will dominate the area for the entirety of the day will temperatures struggling to reach 60F Saturday afternoon.

GFS depicts a classic low pressure development takes place over Arizona late Saturday evening with a clockwise circulating upper level polar jet coming into Missouri down from North Dakota. What really paints this low pressure picture is a high pressure system in the lower levels of the atmosphere that develop in the later hours of Sunday out front of the low pressure system in Oklahoma. This indicates baroclinic instability setting all of this development up. Winds in Missouri stay northwesterly at 925-mb with cold air advection sweeping its way through and setting up high pressure conditions. Both NAM and GFS show central Missouri receiving trace amounts of rain early afternoon on Sunday. This is due to the confluence driving low that also develops over the Great Lakes. Single cell convection is the driving factor for this particular system with Missouri being caught on the SW divergence section. With Missouri being caught right in the middle of the low pressure system to the NE and the high pressure to the SW, it'll be interesting to see how the models depict out this deformation zone as we get closer to Sunday. However looking at GFS model soundings, Columbia lacks shear, instability, and moisture for good rain development Sunday afternoon. The only saturated level sits at 800mb with a dew-point temp of 33.0 degrees F and a temp of 35.3 degrees F. Beyond that, there's only half an inch of precipitable water, giving possible conditions for light rain, but not likely.

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