Friday Night - Clouds increasing. Low: 52 - 56.
Saturday - Cloudy, with light showers in the morning. High: 68 - 72.
Saturday Night - Partly cloudly. Low: 34 - 38.
Sunday - Clouds increases through out the day. With late overnight showers possible. High: 60 - 64.
Monday - Cloudly with showers likely. High: 62 - 66.
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Discussion:
The
low temperatures tonight will not drop too much as the increase in
cloud cover will help us to keep the warm
air. The cloud formation is due to the southerly flow that will bring
moisture and warmer conditions to the area. Light showers are expected
after midnight and early Saturday with no significant accumulation. The
cloudy conditions will remain along Saturday,
with an, for a short time though increase in wind speeds by the afternoon. Saturday evening a
cold front will pass across the area, drying out the mid and upper
atmosphere allowing clear skies, for a short time Saturday’s night. Moisture works its way
back in to get cloud formation, then we get enough
moisture in the atmosphere to get showers late Sunday night that
will last through out Monday.
Forecasters: Johnston, Rojas, and Summall.
Issued: 5:30 p.m.; 26 April 2019
Technical Discussion (The nerdy stuff we are discussing in class!)
The WPC Model Diagnostics suggested a general model blend for the CONUS, excluding the NAM and CMC with a slightly
above average confidence. Based on that, the following discussion is using GFS 12Z.
The
dry conditions associated with high pressure system formed west of the
departing upper level trough were
dominant during Friday but as the northerly winds shift southerly
tonight, the veering profile confirms warm advection as the southerly
flow, the increase in moisture. We can expect an increase of clouds
along tonight, which will be acting as a blanket, avoiding
the escape of warm air. As a result the temperatures will not descend
too much, leaving us mild temperatures Friday’s night.
A
short wave approaches to our area by 6Z on Saturday along with
unorganized areas of vorticity, seen at 500
mb –height. The column in the atmosphere starts to moist from upper to
lower levels by 09Z.A low level jet will be responsible for the warm
advection and the increase in moisture over the area, an absence of
vertical motion will indicate more light showers.
This LLJ with wind velocities of 40 to 50 kts at 925 and 850 mb-height
respectively, will also bring breezy condition in the afternoon. Rain is
expected to last from 09Z to 18Z. The GFS does not indicate significant
accumulated precipitation, just trace. The
NAM is being a little bit more optimistic with values of 0.02, the rain
expected will not be significant. At 12Z the center of the deep low
pressure system would be east of Nebraska and North of Missouri by 18Z.
Along with the low pressure system we will have
a tight pressure gradient that will increase the wind speed at surface
around 20 kts during the early evening. Same time, the deep low will
drag a cold front through the area which literally will sweep the
moisture, leaving us a dry atmosphere at the end of
the day, for a short time though.
A
low pressure system over the Rockies Sunday morning will be the cause
of our precipitation Sunday night through Monday. Sunday night near
midnight the core of the low
pressure system is over eastern Colorado and western Kansas. The low
pressure system reaches northwest Missouri by noon on Monday. We start
off Monday with southerly winds allowing warmer temperatures through the
start of the afternoon before the winds begin
to shift northerly. This wind shift indicates frontal passage.
Soundings
show moistening aloft increasing through out the day on Sunday to
support increasing cloud cover. Near 21Z on Sunday, soundings have CAPE
values above 500 J/kg
and CIN values at -61 J/kg. The CIN provides a small cap, which can be easily eroded when moisture
reaches the surface in the next few hours. Some thunder is possible 09Z
Monday when high omega values stretch from near the
surface up to 250 mb along with a 500 vorticity max moving through
Mid-Missouri during that same time. The moisture remains near the
surface all through the end of our forecast period. Along with CAPE
values ranging from 500 – 1000 J/kg during this time with
low CIN values which supports shower activity for our area. SREF plumes
has a total QPF mean of 0.46 inch through Monday. Future forecasters
will need to look at rainfall totals and rates for next week to monitor
for a risk of flash flooding.
