April 2021
Ruh roh - best I could draw on my phone
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Houstonkid
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Appears NWS removed Severe wording from the forecast for us in Harris Co.. Pretty sure I saw it there this morning.
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"
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"
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.
If it does that, I'll be dragging the hose around again on Saturday.unome wrote: ↑Thu Apr 22, 2021 3:05 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
I sure hope that’s the case I’ve sent two back breaking days filling in low spots in my yard with bank sand.
Dew points better start rising. It sure doesn’t feel like any severe weather is coming anytime soon.
My dew point has risen 20 degrees since this morning...the airmass is definitely modifying with the return flow in place now.
The HRRR looks pretty active for tomorrow. And the 0z NAM also.
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I’m hoping we can get some of these storms to actually form south of I-10 for a change. It’s so aggravating and annoying for us in the southern counties.
Man, what a horrible trend on the models since yesterday when I said they looked good. Geez 
HRRR is still looking very active this afternoon.
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Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1251 AM CDT Fri Apr 23 2021
Valid 231200Z - 241200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO TONIGHT ACROSS PARTS OF EASTERN TEXAS...MUCH OF
CENTRAL AND NORTHERN LOUISIANA...ADJACENT SOUTHERN ARKANSAS AND
SOUTHWESTERN MISSISSIPPI...
...SUMMARY...
Severe thunderstorms are possible today across the southern Great
Plains into the lower Mississippi Valley. This may include the
evolution of large, organized cluster of storms across the Piney
Woods vicinity into the lower Mississippi Valley by this evening,
which could produce a swath or two of damaging wind gusts and
perhaps a couple of tornadoes.
...Synopsis...
Deep mid-level troughing, with a developing embedded low, has
emerged from the Arctic latitudes and is forecast to become
entrenched across much of interior Canada during this period,
downstream of a blocking mid-level high which has become centered
across Alaska. To the southeast of the low, a similar preceding
perturbation, and associated deep surface cyclone, appear likely to
gradually turn northward across and north of the Canadian Maritimes.
As this lead system gradually loses influence on the Northeast,
models indicate that a belt of westerlies emanating from the
mid-latitude Pacific will continue to become a more prominent
influence across much of the remainder of the United States. This
regime includes a significant short wave trough now turning eastward
across parts of the Southwest and northwestern Mexico, as it comes
in phase with a belt of westerlies emanating from the subtropical
eastern Pacific. It appears that this feature will accelerate
east-northeastward, across southern portions of the Great Plains
into the lower Mississippi Valley by late tonight.
In lower levels, while another intrusion of cold air surges south of
the Canadian/U.S. border, to the east of the northern Rockies,
through much of the northern Great Plains, potentially cold air
associated with a preceding intrusion will, at least initially, be
slow to lose influence across much of the Southeast into lower
Mississippi Valley. However, a substantive return flow of moisture
is ongoing off the western Gulf of Mexico into the southern Great
Plains, and this will tend to spread east-northeastward in advance
of the impulse emerging from the Southwest/Mexican Plateau, and
broad surface troughing developing eastward across the southern
Great Plains.
...Southern Great Plains through the central Gulf states...
Beneath steep mid-level lapse rates associated with elevated
mixed-layer air, daytime heating is expected to contribute to
moderately large mixed-layer CAPE, in at least a narrow corridor
along a developing dryline from the eastern Texas Panhandle into the
Hill Country vicinity by this afternoon. Low clouds may slow
destabilization within a developing wedge of returning
boundary-layer moisture across central/southeast Texas into the
north central Gulf coast vicinity, while trajectories emanating from
surface ridging slow boundary-layer moistening across and northeast
of the lower Mississippi Valley.
Further complicating warm sector boundary-layer destabilization,
various model output suggests that thunderstorm activity may
initiate by midday east of the dryline, across parts of central
Texas into the Texas coastal plain. It appears that this may occur
in response to forcing associated with a subtropical perturbation
preceding the primary short wave trough, aided by lower/mid
tropospheric warm advection, and guidance indicates a steady
increase in thunderstorm development while spreading
east-northeastward through the afternoon.
NWS Storm Prediction Center Norman OK
1251 AM CDT Fri Apr 23 2021
Valid 231200Z - 241200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO TONIGHT ACROSS PARTS OF EASTERN TEXAS...MUCH OF
CENTRAL AND NORTHERN LOUISIANA...ADJACENT SOUTHERN ARKANSAS AND
SOUTHWESTERN MISSISSIPPI...
...SUMMARY...
Severe thunderstorms are possible today across the southern Great
Plains into the lower Mississippi Valley. This may include the
evolution of large, organized cluster of storms across the Piney
Woods vicinity into the lower Mississippi Valley by this evening,
which could produce a swath or two of damaging wind gusts and
perhaps a couple of tornadoes.
...Synopsis...
Deep mid-level troughing, with a developing embedded low, has
emerged from the Arctic latitudes and is forecast to become
entrenched across much of interior Canada during this period,
downstream of a blocking mid-level high which has become centered
across Alaska. To the southeast of the low, a similar preceding
perturbation, and associated deep surface cyclone, appear likely to
gradually turn northward across and north of the Canadian Maritimes.
As this lead system gradually loses influence on the Northeast,
models indicate that a belt of westerlies emanating from the
mid-latitude Pacific will continue to become a more prominent
influence across much of the remainder of the United States. This
regime includes a significant short wave trough now turning eastward
across parts of the Southwest and northwestern Mexico, as it comes
in phase with a belt of westerlies emanating from the subtropical
eastern Pacific. It appears that this feature will accelerate
east-northeastward, across southern portions of the Great Plains
into the lower Mississippi Valley by late tonight.
In lower levels, while another intrusion of cold air surges south of
the Canadian/U.S. border, to the east of the northern Rockies,
through much of the northern Great Plains, potentially cold air
associated with a preceding intrusion will, at least initially, be
slow to lose influence across much of the Southeast into lower
Mississippi Valley. However, a substantive return flow of moisture
is ongoing off the western Gulf of Mexico into the southern Great
Plains, and this will tend to spread east-northeastward in advance
of the impulse emerging from the Southwest/Mexican Plateau, and
broad surface troughing developing eastward across the southern
Great Plains.
...Southern Great Plains through the central Gulf states...
Beneath steep mid-level lapse rates associated with elevated
mixed-layer air, daytime heating is expected to contribute to
moderately large mixed-layer CAPE, in at least a narrow corridor
along a developing dryline from the eastern Texas Panhandle into the
Hill Country vicinity by this afternoon. Low clouds may slow
destabilization within a developing wedge of returning
boundary-layer moisture across central/southeast Texas into the
north central Gulf coast vicinity, while trajectories emanating from
surface ridging slow boundary-layer moistening across and northeast
of the lower Mississippi Valley.
Further complicating warm sector boundary-layer destabilization,
various model output suggests that thunderstorm activity may
initiate by midday east of the dryline, across parts of central
Texas into the Texas coastal plain. It appears that this may occur
in response to forcing associated with a subtropical perturbation
preceding the primary short wave trough, aided by lower/mid
tropospheric warm advection, and guidance indicates a steady
increase in thunderstorm development while spreading
east-northeastward through the afternoon.
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I had a hunch based on jasons2k's post yesterday on SigTor probabilities that SPC might upgrade a portion to an enhanced risk (full disclosure - I said moderate not realizing i had mistakenly skipped the "enhanced" level).
HRRR sounding for my general area looks a bit better as far as not teetering on the edge of capped situation. Appears to really have some potential for surfaced based convection to get going, but I'm curious how much things will be limited with the low level cloud deck in place.
ETA: Definitely a day to keep tabs on things.
HRRR sounding for my general area looks a bit better as far as not teetering on the edge of capped situation. Appears to really have some potential for surfaced based convection to get going, but I'm curious how much things will be limited with the low level cloud deck in place.
ETA: Definitely a day to keep tabs on things.
Great. More "North of I-10" crap.
I know. I've drug my sprinkler out several times this spring already. My ground is cracked everywhere.
Judging by how the clouds are hanging low and cruising very quickly off towards the north with high humidity, I'm sure someone is going to have a rough day somewhere though.
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