LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Mon Jul 10 2023
Valid 101200Z - 111200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY INTO TONIGHT
ACROSS PARTS OF WESTERN UPPER MICHIGAN...CENTRAL
WISCONSIN...SOUTHERN MINNESOTA...NORTHERN IOWA...SOUTHEASTERN SOUTH
DAKOTA...NORTHEASTERN THROUGH SOUTH CENTRAL NEBRASKA...NORTHWESTERN
INTO CENTRAL KANSAS...PARTS OF SOUTHEASTERN COLORADO...EASTERN NEW
MEXICO...THE OKLAHOMA AND TEXAS PANHANDLES INTO SOUTHWESTERN
OKLAHOMA AND THE TEXAS SOUTH PLAINS...
...SUMMARY...
Scattered strong thunderstorms and a couple of organizing storm
clusters may pose a risk for severe hail and wind across parts of
the Upper Midwest into Great Plains this afternoon into tonight.
...Synopsis...
As a blocking mid-level high remains prominent east/northeast of the
Canadian Maritimes vicinity, there appears likely to be little
eastward progression of a broad, anomalously deep upstream mid-level
low through this period. The center of the low may shift from
southwest of Hudson Bay northeastward into Hudson Bay, mostly in
response to significant perturbations pivoting around its periphery.
While an associated occluding cyclone migrates northward through
Hudson Bay, its notable trailing cold front is forecast to surge
southward through much of the remainder of the Upper Great Lakes,
Upper Midwest and northern Great Plains by daybreak Tuesday.
A preceding front appears likely to stall and weaken further near
the south Atlantic Seaboard through the Gulf States, while broad,
weak mid-level troughing as far south as the Gulf Coast/northern
Florida vicinity continues to slowly shift east of the lower
Mississippi Valley and off the Atlantic Seaboard. Models indicate
that the western flank of this front will become better defined
during the day today across eastern Texas into the Raton Mesa
vicinity. This will occur as strong heating occurs to its
southwest, beneath warming elevated mixed-layer air advecting east
of the southern Rockies, to the north and east of a prominent
mid-level subtropical high centered near/west of southwestern Texas.
To the northwest through north of this high, a series of short wave
perturbations will slowly progress through one branch of westerlies
offshore of the Pacific Northwest through the northern Rockies.
...Central Great Plains into Upper Midwest...
A corridor of stronger pre-frontal heating is forecast to become
characterized by moderate CAPE of 1500 J/kg, across southern
Minnesota through much of north central Wisconsin. Models indicate
similar destabilization southwestward across the middle Missouri
Valley into central Nebraska, to the east of lee surface troughing.
Perhaps aided by increasing forcing for ascent downstream of a short
wave impulse pivoting around the southwestern periphery of the
Canadian mid-level low, this instability is forecast to support
increasing and intensifying thunderstorm development by late this
afternoon. This may tend to occur to the south of the stronger
mid/upper flow, but deep-layer shear may still be sufficient to
support isolated supercell structures initially, before convection
consolidates into one or two upscale growing and organizing
clusters, posing a risk for severe hail and wind into this evening.
Warmer mid-levels, with stronger inhibition and more subtle forcing
for ascent, result in more uncertain thunderstorm initiation to the
southwest of (roughly) the Cheyenne ridge into Kansas/Nebraska
border area. However, there is a signal in at least some model
output that a perturbation emerging from the Great Basin may support
a developing cluster of storms along this corridor by early this
evening. Aided by a northwesterly component to the mid-level flow
across this vicinity, it is possible that this activity may develop
a southeastward propagation into a more moist and potentially
unstable environment beneath the strong capping across northwestern
Kansas. If this occurs, the development of an MCV with
strengthening rear inflow and increasing potential for strong
surface gusts is possible late this evening into the overnight
hours.
...Southern Great Plains...
Beneath the warmer and more strongly capping mid-level environment,
the higher terrain of southeastern Colorado into northeastern New
Mexico may provide a focus for thunderstorm initiation. It is
possible that this will be supported by a weak perturbation
progressing around the northeastern periphery of the subtropical
high, and modest northwesterly mid-level flow will aid propagation
of a consolidating cluster of convection into Texas Panhandle
vicinity. As this occurs, inflow of air characterized by moderate
to large CAPE may contribute to intensification into an organizing
cluster posing a risk for strong wind gusts this evening into the
overnight hours.
...Montana...
An environment becoming characterized by modest destabilization and
shear, ahead of a lead short wave trough progressing into the
northern Rockies, may become supportive of organized convection
spreading across the mountains of western through south central
Montana late this afternoon into tonight. It appears that this
activity could become at least marginally supportive of severe hail
and wind before weakening overnight.
...Southern New England...
A mid-level short wave trough and weak surface low may provide
support for thunderstorm development overspreading much of southern
New England today. Despite generally weak low-level wind fields and
instability, seasonably high moisture content may contribute to
locally heavy precipitation loading and a couple of strong
downbursts.
...Eastern Gulf coast vicinity/northern Florida...
Modest mid-level speed maxima (on the order of 20-30+ kt) within the
broadly cyclonic westerly flow may contribute to potential for
locally damaging wind gusts in scattered strong thunderstorm
development today.
..Kerr/Thornton.. 07/10/2023
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