Convective Outlook

SPC 0730Z Day 3 Outlook
Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0220 AM CDT Tue Sep 17 2019

Valid 191200Z - 201200Z


At least isolated storms producing large hail are possible Thursday
evening and overnight over the northern High Plains.

An upper trough will continue to slowly move east across the Great
Basin and toward the Rockies with increasing south/southwest flow
aloft into the northern High Plains. Meanwhile, an upper high will
remain situated over the Southeast, with a surface high over the Mid
Atlantic maintaining dry conditions there. Southerly winds over the
Plains will maintain 65-70 F dewpoints from TX to MN, with a
tropical disturbance possibly over eastern TX. The slow-moving
western trough will also create lift over the northern High Plains
as a cold front encounters an unstable air mass Thursday afternoon
into Friday.

...Northern High Plains...
Low pressure will develop over eastern WY during the afternoon with
a wind shift over eastern MT. Southeast surface winds will maintain
moist and unstable conditions over the Dakotas and Nebraska during
the day, with continued northwestward warm advection during the
evening with a 40-50 kt low-level jet. Steepening lapse rates aloft
combined with sufficient deep-layer shear will support at least
isolated severe storms capable of damaging hail. Locally damaging
winds cannot be ruled out, although the majority of the storms are
expected overnight.

..Jewell.. 09/17/2019

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Updated 17 September 2019 | 2:25 am

SPC 0600Z Day 2 Outlook
Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1234 AM CDT Tue Sep 17 2019

Valid 181200Z - 191200Z


A few strong thunderstorms are possible across parts of the Upper
Midwest Wednesday afternoon and evening, but the risk for severe
weather appears low.

An upper trough will shift east across the Pacific Northwest and
Great Basin, with strong upper-level southwesterlies and cooling
aloft approaching the Rocky Mountains into Thursday morning. Ahead
of this trough, a fast-moving, compact shortwave trough will move
from MN into Ontario while an upper ridge remains over the mid and
lower MS Valley. Beneath the upper ridge, a warm core disturbance is
forecast to move into southeast TX, providing heavy precipitation.

At the surface, a weak front will stall over the northern Plains
behind the leading wave, with a moist air mass extending southwest
to the Gulf of Mexico. 

...Eastern NE into western WI...
Storms may be ongoing Wednesday morning associated with a low-level
jet and warm advection from IA into MN and northwest WI. Shear will
be weak but plenty of instability will support heavy rain, gusty
winds. Severe weather is not anticipated, but a locally strong wind
gust or marginal hail report cannot be ruled out during the
afternoon as isolated storms regenerate along the weak boundary.

...Upper TX Coast...
A disturbance in the northwest Gulf of Mexico is forecast to move
northwestward into southeast TX, with the primary concern very heavy
rainfall. Predictability is low regarding wind fields and thus
tornado risk. Should the system become stronger than currently
forecast, shear profiles may necessitate low tornado probabilities
in later outlooks.

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Updated 17 September 2019 | 12:49 am

SPC 1200Z Day 1 Outlook
Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1236 AM CDT Tue Sep 17 2019

Valid 171200Z - 181200Z


A few strong/severe storms are expected across the northern high
Plains area afternoon/early evening, and may evolve overnight into
the Upper Midwest.  Hail and locally damaging winds will be

...Northern Plains to the Upper Midwest...

A shortwave impulse over SD early this morning will continue to lift
northeast across MN. Ongoing convection associated with this feature
will spread across MN through midday and should remain elevated.
This activity is not expected to be severe given the elevated nature
of convection. 

Further southwest, a compact shortwave trough is forecast to lift
northeast from the Great Basin to the eastern Dakotas/western MN by
Wednesday morning. A surface low near the eastern MT/western ND/SK
border will deepen during the afternoon as height falls begin to
overspread the region. a surface trough/dryline will extend
southward through the northern/central High Plains while a cold
front shifts east across eastern MT by 00z. Deep layer flow will
strengthen considerably as a mid/upper level jet streak overspreads
the central High Plains and steep midlevel lapse rates will aid in
modest destabilization by late afternoon. However,
coverage/intensity of storms remains somewhat uncertain given a
considerable dry slot and capping on the western fringes of the
Midwestern upper ridge. Nevertheless, at least a few storms are
expected near the triple point over eastern MT into northeast WY.
Strong gusts and marginal hail will be possible with the strongest
cells as they shift east/northeast.  Additional storms are expected
to develop over eastern SD into MN after 03z ahead of the
eastward-surging cold front. Storms should quickly grow into
clusters or line segments as a 40-50 kt southwesterly low level jet
increases. Strong gusts will be possible with the strongest cells,
though forecast soundings suggest convection may remain elevated.

..Leitman.. 09/17/2019

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Updated 17 September 2019 | 12:45 am