====================================================
Discussion:
The main focus for this weekend is another round of rain affecting Missouri. The driving force for our weather in Central Missouri is a low pressure system coming into the area originating over Colorado. As that low approaches, clouds in our area will begin to build along with good chances of showers starting Friday afternoon into Saturday. This is due to a build-up of moisture from the Gulf of Mexico. The rain should peak Friday afternoon with isolated thunderstorms possible during that time. Total precipitation amounts will be around 1.00in-1.25in. The low pressure system as well as the moisture should completely leave the area by early Saturday afternoon. As a result, we will be left in the wake of high pressure and a dry atmosphere for the remainder of the weekend.
====================================================
Forecaster: Lamb, Nixon, Travis
Issued: 6:00PM CST 22 April 2021
Technical Discussion (The nerdy stuff we are discussing in class):
Both models struggled with various plots in the forecasting period. Overall,
NAM40 was chosen for this forecast period due to its handling of
temperatures and surface pressure predication compared to observed
values. SREF plumes and NAM soundings were also used for QPF and
temperatures. The defining feature for this forecast is the stacked low
pressure system and accompanying precipitation that passes over the area
on Friday.
The
200-mb plot of wind divergence and heights depict a ridge over the area
until early Friday morning, keeping the atmosphere pleasant for most of
Thursday night. On early Friday a positively tilted trough passes over
the Central Plains region, becoming negatively tilted as it progresses
eastward. Ahead of the trough, there is significant divergence aloft
covering the entire state of Missouri. The upper level divergence will
cause convergence in the lower levels, which will help aid in the
expected precipitation. The trough is expected to push northeast out of
the area late Saturday evening. In its wake zonal flow will dominate the
forecast for Sunday.
In
the vorticity and height plots at the 500-mb level, Missouri is still
under the influence of the upper level ridge. The well-defined trough
begins to influence the area early Friday morning, as circulations
branching off from the trough penetrate Central Missouri. As the trough
axis passes through the area on Saturday morning, multiple vorticity
maxima materialize throughout the state. As the trough exits the area,
we are left with zonal flow once again dominating the rest of the
forecast period.
Looking
at the 700-mb plot of relative humidity and heights, a large influx of
moisture covers the state on early Friday morning. On Friday afternoon,
there is a small period of time where the atmosphere slightly dries, but
is short-lived as it quickly saturates again Friday evening. The
atmosphere remains saturated with the passage of the trough, but swiftly
dries as the trough progresses east. Soundings confirm deep saturation from the surface to the 500-mb level for most of Friday and Saturday morning.
At
the 850-mb plot of winds and heights, a strong low-level jet reaching
up to the Upper Mississippi Valley is visible. The jet will aid in
strong moisture transport and WAA throughout Friday, as the jet shifts
from southerly to southwesterly. On Friday afternoon, a warm front
branching off from the low-pressure system over Southern Oklahoma and
the Texas panhandle infiltrates the area. This warm front brings
isolated storms into the area starting late afternoon. The low-pressure
system reaches Missouri late Friday evening into Saturday morning. The
system will continue to aid in precipitation until it pushes northeast
out of the area on early Saturday morning. A high-pressure system
replaces the low shortly after, helping the atmosphere to stabilize.
Surface plots of MSLP and 1000-500mb thickness show strong WAA lasting from Thursday through Friday evening. As the low pressure system progresses into the area the winds shift from SSW to Northerly. Winds are expected to dissipate as the low-pressure system progresses out of the area. Late Sunday afternoon sees an increase in southerly winds and WAA as the weekend draws to a close.
The next forecast period should focus on the development of the low-pressure system over the Rocky Mountains on Sunday evening.
No comments:
Post a Comment