Tuesday, April 28, 2020

Tuesday Night - Cloudy with rain/storms. Low: 48-52

Wednesday - Cloudy with scattered rain. High: 56-60

Wednesday Night - Cloudy with scattered rain. Low: 46-50

Thursday - Sunny. High: 66-70

Friday - Mostly Sunny. High: 74-78

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The sunny skies and above average temperatures that occurred this afternoon will
transition to cloudy skies with rain and thunderstorms late this afternoon. A cold front will
follow these storms and sweep through the region between 9:00pm and 12:00am. After
that, lingering rain will remain throughout most of the afternoon tomorrow along with
afternoon temperatures nearly 25 degrees colder than today. Skies will clear out
night and temperatures will warm back up to near average for Thursday and Friday
under sunny skies both days. 
Forecasters: Gallahan, Munley
Issued:  5:oopm: April 28, 2020.
Technical Discussion (The nerdy stuff we are discussing in class)

A 12z blend of ECMWF and GFS were recommended via the WPC. ECMWF was
used for the short-term and GFS was used for Thursday and Friday.

The main topic of concern for this forecast period are the rain and storms forecast
to push through the area this evening ahead of a cold front passing through the area
overnight, and the clearing skies for Thursday and Friday and a return to average
temperatures for those days as well.

With the approaching cold front and storms associated with the front, the variables
used were 500mb vorticity, 700mb RH and UVM, 850mb winds to indicate low level
support to feed these storms. CAPE values for potential uplift an helicity for potential
rotation. Starting out at 500mb vorticity, there is definitely some strong circulation
pushing through the region indicating a potential longwave. That longwave will be followed
by a deepening trough. This indicates a potential change in wind direction which is an
indication of a possible cold front.

700mb UVM and RH values begin to kick up to 25-35 ubar/s and 100% respectively.
This indicates 700mb moisture and lift needed for rain and storm development.

850mb winds indicate good low level support which allows for the southerly moisture
to fuel these storms. This will allow for very good storm development as this low level
moist air will clash with the cold dry air associated with the passing cold front.

The last two ingredients that were looked at were CAPE for potential updraft and helicity
for potential rotation. CAPE values begin to pick up late this afternoon associated with
afternoon heating because of temperatures reaching the low 80s. These CAPE values will
reach as high as 2100 J/Kg which is an indication of good updraft. Helicity values do remain
relatively low throughout, so rotation in these storms look minimal. With that being said,
the main threats are going to be straight-line winds and hail. Total rainfall out of these storms
look to be along the lines of 0.5 to 0.75 inches.

After these storms, winds will begin to back wit height which will usher in CAA and cool
temperatures off for tomorrow by nearly 25 degrees. Rain showers look to remain for most
of the afternoon tomorrow as well. Tomorrow night, skies will clear out due to the previously
passed cold front. Winds will change direction again tomorrow night as well and will begin
to veer with height and usher in WAA and warm southerly air. This will warm temperatures
for Thursday back to average and 5 to 10 degrees above average for Friday.

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