Thursday, March 7, 2019

Thursday Night - Cloudy with freezing drizzle in the early AM. Low: 29-33

 Friday - Mostly cloudy. High: 43-47

 Friday Night - Cloudy. Low 39-43 

Saturday - Cloudy with rain coming in the early AM and thunderstorms possible. High: 58-62

Sunday - Partly Cloudy. High: 45-49

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We are in store for a warm up this weekend.  Tonight we expect to see chances of freezing drizzle into the early morning.  However, our Friday is looking to warm up drastically compared to what we've been feeling this last week with high temperatures in the upper 40s.  Our lower level atmosphere will remain moist so we will be seeing cloud cover for most of the day.  Overnight Friday, we see a trough really push into the Midwest. With this we see a warm front make its way into Missouri that will bring rain chances for our Saturday and keeps temps in the upper 50s.  We expect to see this rainfall start in the morning hours and continue into the late afternoon.  This system does have to potential to give us some thunderstorms with rain totals looking well over an inch.  A cold front quickly follows behind this system that will help to dry things out for Sunday but doesn't affect our temperatures as we continue to see high temps in the upper 40s.
Forecasters: Myers, Doll, and Bongard
Issued: 4:00 p.m.March 7, 2019

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

With temperatures warming up, precipitation is still on the way in the near future. Tonight we see a very zonal flow at the 250mb level among both the GFS and NAM as well as a decent amount of vorticity at 500 mb through Columbia extending into northern Missouri. Snow will stay to the north-northeast over the Moberly area through the night while we remain somewhat saturated at the lower levels in the atmospheree. This saturation is coming from both the southwest CONUS as well as the Gulf of Mexico where a high pressure system lingering. With the lower atmosphere staying saturated, the GFS has the mid levels of the atmosphere warming up through the night with the lower-surface levels dropping to freezing in model sounding comparisons. This brings a very good chance for trace amounts of freezing drizzle later tonight-early tomorrow morning. The NAM however keeps the mid levels colder, bringing in trace amounts of snow tonight through tomorrow morning. In terms of model agreement, we are leaning towards the GFS forecast of trace amounts of freezing drizzle because of the recent success of GFS earlier this week.
Tomorrow we see a shortwave ridge moving through the central CONUS having its axis over Columbia around 0000Z tomorrow evening. With this ridge moving in, the freezing drizzle is expected to move out of the Columbia area by 2000Z tomorrow. The mid levels of the atmosphere remain dry throughout the day while the 850mb level begins to dry out later in the evening with a SW flow bringing both dryer and warmer air seen over the ArkLaTex area. Looking at sounding comparisons, Low-Surface levels remain saturated throughout the day keeping lower level clouds overhead in the GFS models. Tomorrow, GFS and NAM generally agree with the saturation among the lower levels.
As Friday night draws closer, a trough over the Rockies begins to build in until really catching up to the ridge that passes over Mid-Missouri earlier that day. This trough deepens keeping vorticity values noticeable all the way down to the 700mb level creating a low pressure system over western Kansas. At the time the warm front passes over Columbia, MO ahead of the oncoming low pressure system. Temperatures will rise throughout the night Friday while we stay saturated at the lower levels of the atmosphere bringing in small amounts of rain later in the night beginning around 0600Z until really picking up in rate around 1200Z. Looking at model sounding comparisons, both the NAM and GFS are in good agreement in terms of saturation as well as precipitation amounts. However they do disagree quite a bit on the surface temperature  Biggest thing to note is how quick the dry layer in the mid-upper levels saturate throughout the night, bringing in the sudden change of light to heavy rain later in the early AM. 
As the rain continues Saturday morning, CAPE values hover around 450 J/Kg having the system being quite unstable in model soundings at its peak. But the chances for thunderstorms are small, primarily because of the timing of this system. However, SPC has us placed in a marginal chance for thunderstorms at this time. Comparing the rain for GFS compared to NAM: NAM has the same amount of precipitation but has the precipitation pushed east a little earlier than GFS which has the rainfall rate a bit heavier. Following the chances for a thunderstorm, the rain will die out by 2200Z at the latest. The trough that moved through the central CONUS completely swings through the mid-west by noon keeping the rain steady until departure. A big dry layer associated with the cold front in the mid-lower atmosphere moves through mid-Missouri bringing in winter conditions once again shortly after Saturday night. This cold dry air reaches just above freezing temps at the surface, limiting the chance for this rain to turn into hazardous conditions for the road.
The jet streak will position itself right over Columbia, MO Sunday morning moving the zonal flow somewhat quickly through the central CONUS. Post frontal regime comes through mid-Missouri at the 850mb level early Sunday morning moving winds from Minnesota and drying us out at the mid-lower atmospheric levels while the upper level remains somewhat moist in model sounding comparisons. Sunday will be a nice stable wrap up to the crazy weekend.

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