April 2021

General Weather Discussions and Analysis
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jasons2k
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Re: April 2021

Post by jasons2k » Thu Apr 22, 2021 1:42 pm

Ruh roh - best I could draw on my phone
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Houstonkid
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Re: April 2021

Post by Houstonkid » Thu Apr 22, 2021 2:00 pm

Appears NWS removed Severe wording from the forecast for us in Harris Co.. Pretty sure I saw it there this morning.

unome
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Re: April 2021

Post by unome » Thu Apr 22, 2021 2:05 pm

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
321 PM EDT Thu Apr 22 2021
...

Day 2
Valid 12Z Fri Apr 23 2021 - 12Z Sat Apr 24 2021

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS THE LOWER
MISSISSIPPI VALLEY AND THE GULF STATES...

There continues to be a strong signal for a heavy rainfall event
developing over eastern Texas and Oklahoma that spreads east
across the Lower Mississippi Valley and the central Gulf Coast
states. PW values build to 1.5"+ (nearing 2 standard deviations
above normal for late April) along the Gulf Coast while continuing
to transport northward into the central U.S.
A low pressure system exiting the Rockies will track across the
southern tier states, lifting a warm front up the Mississippi
Valley while a cold front sweeps in a few hours later. The upper
level jet will be passing overhead and provide divergence
aloft/enhanced vertical motion in the low/mid levels of the
atmosphere. Low-level inflow rises to 40-60 knots (with effective
bulk shear to match), close to the value of the mean 850-400 hPa
wind. Instability will be increasing across the Southern Plains
ahead of the cold front with CAPE values of 1500+ J/Kg supporting
periods of heavy rainfall.

There is some degree of spread on where the maximum values will
occur, but the overall consensus suggests a fairly large area
where 2-4 inches will fall with very isolated maximums of 5-6
inches possible. Although some locations have had several days to
recover from recent soaking rains, rain of this magnitude may
quickly become problematic, thus increasing the threat for flash
flooding. The Slight Risk area was slightly reshaped for this
update, but remains about the same. The Marginal Risk area spans
from eastern Texas to Alabama and from central Oklahoma into the
Midwest. The LCH/Lake Charles LA, SHV/Shreveport LA, and
LIX/Slidell LA forecast offices were consulted in this update.

Roth/Campbell


I'll be happy with 1/2"
fill_94qwbg - Copy.gif

txbear
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Re: April 2021

Post by txbear » Thu Apr 22, 2021 2:10 pm

jasons2k wrote:
Thu Apr 22, 2021 1:42 pm
Ruh roh - best I could draw on my phone
jason - those are some decently high SigTor probabilities. the ingredients seem like they'll definitely be there for things to get a bit sporty if/when capping can be overcome especially with the amount of shear that will be in place. think SPC will upgrade the outlook to have a small bullseye of moderate risk a day out?

i'm hoping that we can get some good rumbles of thunder and a good soaking, with the severe roaming about in rural areas avoiding folks.

Cromagnum
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Re: April 2021

Post by Cromagnum » Thu Apr 22, 2021 2:16 pm

unome wrote:
Thu Apr 22, 2021 2:05 pm
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
321 PM EDT Thu Apr 22 2021
...

Day 2
Valid 12Z Fri Apr 23 2021 - 12Z Sat Apr 24 2021

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS THE LOWER
MISSISSIPPI VALLEY AND THE GULF STATES...

There continues to be a strong signal for a heavy rainfall event
developing over eastern Texas and Oklahoma that spreads east
across the Lower Mississippi Valley and the central Gulf Coast
states. PW values build to 1.5"+ (nearing 2 standard deviations
above normal for late April) along the Gulf Coast while continuing
to transport northward into the central U.S.
A low pressure system exiting the Rockies will track across the
southern tier states, lifting a warm front up the Mississippi
Valley while a cold front sweeps in a few hours later. The upper
level jet will be passing overhead and provide divergence
aloft/enhanced vertical motion in the low/mid levels of the
atmosphere. Low-level inflow rises to 40-60 knots (with effective
bulk shear to match), close to the value of the mean 850-400 hPa
wind. Instability will be increasing across the Southern Plains
ahead of the cold front with CAPE values of 1500+ J/Kg supporting
periods of heavy rainfall.

There is some degree of spread on where the maximum values will
occur, but the overall consensus suggests a fairly large area
where 2-4 inches will fall with very isolated maximums of 5-6
inches possible. Although some locations have had several days to
recover from recent soaking rains, rain of this magnitude may
quickly become problematic, thus increasing the threat for flash
flooding. The Slight Risk area was slightly reshaped for this
update, but remains about the same. The Marginal Risk area spans
from eastern Texas to Alabama and from central Oklahoma into the
Midwest. The LCH/Lake Charles LA, SHV/Shreveport LA, and
LIX/Slidell LA forecast offices were consulted in this update.

Roth/Campbell


I'll be happy with 1/2"

fill_94qwbg - Copy.gif
If it does that, I'll be dragging the hose around again on Saturday.

cperk
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Re: April 2021

Post by cperk » Thu Apr 22, 2021 2:56 pm

Cpv17 wrote:
Thu Apr 22, 2021 10:42 am
I’m not sure what y’all are seeing saying we won’t be getting much rain over the next week or so. Models are showing 2-4” for most of us over the next 10 days.
I sure hope that’s the case I’ve sent two back breaking days filling in low spots in my yard with bank sand.

Cpv17
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Re: April 2021

Post by Cpv17 » Thu Apr 22, 2021 4:29 pm

Dew points better start rising. It sure doesn’t feel like any severe weather is coming anytime soon.

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jasons2k
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Re: April 2021

Post by jasons2k » Thu Apr 22, 2021 4:51 pm

My dew point has risen 20 degrees since this morning...the airmass is definitely modifying with the return flow in place now.

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Katdaddy
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Re: April 2021

Post by Katdaddy » Thu Apr 22, 2021 5:09 pm

Hopefully just some more well needed rainfall in NW Galveston County without any excitement.

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DoctorMu
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Re: April 2021

Post by DoctorMu » Thu Apr 22, 2021 6:19 pm

jasons2k wrote:
Thu Apr 22, 2021 4:51 pm
My dew point has risen 20 degrees since this morning...the airmass is definitely modifying with the return flow in place now.
Same here. I'm going out walking/running with the dog before it gets too humid!

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