A Mesodiscussion is issued by the National Weather Service's Storm Prediction Center when there is a chance of a significant weather event impacting an area. These are routinely issued before weather watches or as updated to weather watches.

SPC MD 1357

MD 1357 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHERN NEW YORK AND VERMONT
MD 1357 Image

Mesoscale Discussion 1357
NWS Storm Prediction Center Norman OK
0503 PM CDT Mon Jul 26 2021

Areas affected...Northern New York and Vermont

Concerning...Severe potential...Watch unlikely 

Valid 262203Z - 262330Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated large hail or a damaging wind gust is possible
this evening.

DISCUSSION...Storms have developed in eastern Ontario and St.
Lawrence counties over the past few hours. These storms have stayed
below severe limits thus far and are mostly expected to remain that
way given the somewhat weak shear and MLCAPE only around 500 to 1000
J/kg. If storms congeal/collide, a stronger updraft may be possible
which could pose a threat for isolated damaging winds/large hail.
Overall, expect most of these storms to produce sub-severe
winds/hail over the next few hours.

..Bentley/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GYX...BTV...ALY...BUF...

LAT...LON   45027491 45057306 45047241 45037177 44907161 44687162
            44337192 44047205 43757235 43717310 43647354 43757472
            43927538 44207574 44417601 45027491 

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SPC MD 1356

MD 1356 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHWEST UT INTO SOUTHERN NV
MD 1356 Image

Mesoscale Discussion 1356
NWS Storm Prediction Center Norman OK
0501 PM CDT Mon Jul 26 2021

Areas affected...Southwest UT into southern NV

Concerning...Severe potential...Watch unlikely 

Valid 262201Z - 270000Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorm clusters capable of locally strong/severe
wind gusts and perhaps some hail will continue through the
afternoon.

DISCUSSION...A few areas of stronger thunderstorms have developed
across portions of southwest UT into southern NV, within an
environment characterized by MLCAPE of 1000-1500 J/kg and effective
shear generally ranging from 15-25 kt, per recent objective
mesoanalyses. While this environment is only supportive of transient
storm organization, modestly-enhanced steering flow to the north of
the weak midlevel trough over southern CA may support a couple of
outflow-driven clusters capable of isolated strong/severe wind
gusts. Instability may also be sufficient to support a marginal hail
risk with the strongest updrafts.

..Dean/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...SLC...VEF...LKN...

LAT...LON   38751243 38251139 37611130 37131194 36841333 36851384
            36991603 37211745 37281755 38271766 38501712 38931461
            38931361 38751243 

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SPC MD 1355

MD 1355 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR NORTH-CENTRAL AND NORTHEAST MINNESOTA
MD 1355 Image

Mesoscale Discussion 1355
NWS Storm Prediction Center Norman OK
0500 PM CDT Mon Jul 26 2021

Areas affected...north-central and northeast Minnesota

Concerning...Severe potential...Severe Thunderstorm Watch likely 

Valid 262200Z - 270000Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorms capable of very large hail, gusty
thunderstorm winds, and a tornado or two will be possible across the
area this afternoon and evening. A watch will likely be needed for
portions of the area later today.

DISCUSSION...A cluster of thunderstorms persist across north-central
Minnesota this afternoon associated with modest warm-air advection
along a west-northwest to east-southeast warm-front draped across
northern Minnesota. Although temperatures have warmed into the
mid-to-upper-80s F along both sides of the warm front, surface
moisture, as measured by dewpoints, dramatically increases to the
south, rising from mid 50s F north to mid 60s F south. The result is
a strongly unstable airmass along and south of the warm front.
Strong deep-layer shear across the region will likely sustain
thunderstorm intensity and organization into he evening hours, with
supercell thunderstorms possible. 

Warm-air advection is expected to continue through the evening
hours, even strengthening after 00Z. The result should be one or
more rounds of thunderstorms across the region. Given the degree of
instability and strong shear, very large hail and gusty thunderstorm
winds will be likely with any intense thunderstorm. Additionally,
the presence of a warm-front across the area will result in the
potential for a tornado or two with any surface-based or
near-surface-based supercell that interacts with the warm front.

A watch will likely be needed this afternoon or evening across
portions of the area.

..Marsh/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DLH...MPX...FGF...

LAT...LON   47809584 48309571 48549430 48319312 47879203 47279165
            46519166 45699292 46009468 47069564 47809584 

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SPC MD 1354

MD 1354 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR FAR NORTHEAST NORTH CAROLINA AND FAR SOUTHEAST VIRGINIA
MD 1354 Image

Mesoscale Discussion 1354
NWS Storm Prediction Center Norman OK
0443 PM CDT Mon Jul 26 2021

Areas affected...Far northeast North Carolina and far southeast
Virginia

Concerning...Severe potential...Watch unlikely 

Valid 262143Z - 262315Z

Probability of Watch Issuance...20 percent

SUMMARY...There will be an isolated damaging wind threat across far
southeast Virginia and far northeast North Carolina over the next 1
to 2 hours. No watch is anticipated.

DISCUSSION...The cluster of storms which produced some damaging wind
across eastern Virginia has shown some weakening as it moves
southward toward areas with decreasing effective shear. However, the
airmass ahead of these storms is still quite unstable with MLCAPE
around 2500 J/kg. Therefore, an isolated severe wind threat may
persist as this activity moves southeastward out of watch 392.
However, a more organized threat is not anticipated, and therefore,
no downstream watch is planned.

..Bentley/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...AKQ...MHX...

LAT...LON   36697700 36757631 36707588 36307565 36137563 35857560
            35777578 35767614 35787669 36007691 36237711 36497728
            36697700 

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SPC MD 1353

MD 1353 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EASTERN NORTH DAKOTA
        
MD 1353 Image
Mesoscale Discussion 1353
NWS Storm Prediction Center Norman OK
0442 PM CDT Mon Jul 26 2021

Areas affected...eastern North Dakota

Concerning...Severe potential...Watch possible 

Valid 262142Z - 262345Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms may develop this afternoon across central
and eastern North Dakota. Very large hail and strong thunderstorm
outflow winds will be possible with any thunderstorm. A watch may
become necessary should confidence in initiation increase.

DISCUSSION...Recent visible satellite imagery depicts clumping
cumulus developing across Burleigh and Morton counties in central
North Dakota. This is in response to sustained low-level convergence
along a weak surface boundary within a broad area of lower pressure
across the northern Plains. Surface temperatures in the mid-to-upper
90s F coupled with dewpoints in the mid-60s to around 70 F have
resulted in a very unstable airmass, characterized by most-unstable
CAPE values in excess of 3500 J/kg and decreasing convective
inhibition. Some high-resolution guidance develops robust convection
within this area of sustained low-level convergence and decreasing
inhibition over the next couple of hours. Strong deep-layer shear
greater than 40 knots and mid-level lapse rates around 8 C/km will
support vigorous updrafts capable of producing very large hail and
gusty thunderstorm winds with any thunderstorm. 

If confidence in convective initiation increases, a watch may be
required for portions of eastern North Dakota. This area will
continue to be monitored.

..Marsh/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FGF...BIS...

LAT...LON   46690103 47380046 47619940 47619820 47139688 46469669
            46079699 46049828 46009983 46190089 46400099 46690103 

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SPC MD 1352

MD 1352 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTHEAST WISCONSIN
MD 1352 Image

Mesoscale Discussion 1352
NWS Storm Prediction Center Norman OK
0431 PM CDT Mon Jul 26 2021

Areas affected...Portions of northeast Wisconsin

Concerning...Severe potential...Watch unlikely 

Valid 262131Z - 262300Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated severe storms may pose a large hail and damaging
wind threat over the next 1 to 2 hours.

DISCUSSION...Temperatures have warmed into the mid 80s with
dewpoints in the mid 60s across north central Wisconsin. This
destabilization has been sufficient to erode surface inhibition
according to SPC mesoanalysis with MLCAPE around 1500 J/kg. Flow is
less than 30kts in the lowest 5km, but strengthens to near 50 knots
above 8km per KGRB VWP. Given storm depth around 12km, and the
observations from the VWP, the effective shear is probably greater
than the 25 knots shown on SPC mesoanalysis. Stronger effective
shear would also explain the organization of the large supercell
north of Green Bay. This supercell currently shows MESH around 1.5
inches. This cell has turned right and may try to continue southward
along the instability gradient. However, expect this supercell to
eventually move eastward over Lake Michigan and into an airmass with
decreasing instability and increasing inhibition which should limit
storm intensity. Given the small temporal and areal threat from this
storm activity, no watch is anticipated, but some large hail and
damaging winds may be possible over the next 1 to 2 hours.

..Bentley/Grams.. 07/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MQT...GRB...MKX...

LAT...LON   45698838 45478757 45258730 44958721 44488725 44238741
            43798769 43838813 43978841 44148870 44428889 44798883
            45698838 

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