RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Wed Jun 19 16:49:01 UTC 2019.
MD 1133 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF CENTRAL AND EASTERN ILLINOIS...INDIANA...AND WESTERN OHIO
Mesoscale Discussion 1133
NWS Storm Prediction Center Norman OK
1134 AM CDT Wed Jun 19 2019
Areas affected...Parts of central and eastern
Illinois...Indiana...and western Ohio
Concerning...Severe potential...Watch possible
Valid 191634Z - 191830Z
Probability of Watch Issuance...40 percent
SUMMARY...A gradual increase and intensification of thunderstorms
could yield at least some increase in risk for potentially damaging
wind gusts by 3-5 PM EDT. While it is not yet certain that a severe
weather watch will be needed, trends will continue to be monitored
for this possibility.
DISCUSSION...An increase in thunderstorm development has become
evident within an arcing corridor, east-southeast of a remnant
elongated cyclonic mid-level circulation, across central through
southeastern Illinois. This is coinciding with diurnal boundary
layer destabilization within the warm sector of a broad weak area of
low pressure now centered over north central Missouri, and forecast
to only slowly shift eastward today.
West-southwesterly deep layer mean ambient wind fields across much
of Illinois and Indiana into Ohio are only on the order of 20-25 kt,
with substantive strengthening associated with a mid-level speed
maximum propagating east of the south central Plains likely to
remain to the southwest of the region. This seems likely to limit
severe weather potential, in general. However, as inhibition
continues to weaken for warming, seasonably moist boundary layer
parcels characterized by CAPE up to around 1500 J/kg, there appears
potential for further intensification and upscale growth of
convection that could gradually become accompanied by at least some
increasing risk for potentially damaging wind gusts through 19-21Z.
..Kerr/Guyer.. 06/19/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ILN...LMK...IWX...IND...PAH...LOT...ILX...LSX...
LAT...LON 40868738 41128566 40818466 40298364 39148398 38248585
38438719 39328896 39699052 41018983 40868738
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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Wed Jun 19 2019
Valid 191300Z - 201200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS
NORTH-CENTRAL/NORTHEAST TX...NORTHWEST LA...SOUTHWEST AR...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LEE OF THE BIG
HORN MOUNTAINS TO THE BLACK HILLS...
...SUMMARY...
Severe thunderstorms are most likely across north-central/northeast
Texas and the Ark-La-Tex region during the late afternoon and
evening. Destructive hail and wind, along with a few tornadoes are
possible.
...TX to the MS/OH/TN Valleys...
Complex forecast with multiple episodes of severe storms anticipated
during the period. Primary changes are to increase damaging wind
(including sig) probabilities for the Enhanced Slight Risk, expand
Marginal and Slight Risk areas in parts of LA/MS/TX, and expand
tornado probabilities into the Lower/Mid-MS Valleys. An upgrade to
Moderate Risk via wind and/or hail may be needed in later outlooks.
A decaying MCS is ongoing, recently splitting into two active areas
of convection in the Ozarks and Ark-La-Tex. Reintensification is
possible with the Ark-La-Tex complex as boundary-layer heating
increases. Even if full decay occurs, redevelopment along remnant
outflows is likely towards midday/early afternoon downstream of both
areas across the Lower/Mid-MS Valleys as the downstream air mass
characterized by upper 60s to mid 70s surface dew points
destabilizes. 25-35 kt 500-mb westerlies will support several
multicell clusters with scattered damaging winds as the primary
hazard this afternoon into the OH and TN Valleys.
Remnant west/east-oriented outflow boundary in the wake of the
morning MCS should drift north across north-central/northeast TX
into perhaps southeast OK by late afternoon. South of this boundary,
intense diabatic heating coupled with a plume of 70s surface dew
points over east TX will support a strong to extremely unstable air
mass with MLCAPE in excess of 3500 J/kg. By late afternoon, ascent
should increase downstream of a minor mid-level impulse that is
currently approaching from the southern Rockies. This should aid in
convective initiation along the outflow boundary, as well as near
the dryline bulge in the TX Big Country. 40-50 kt effective shear
with pronounced speed shear in the mid to upper-levels will support
a risk for very large hail with initial supercells. This activity
should consolidate into yet another MCS during the evening, aided by
a strengthening southwesterly low-level jet, with an increasing
threat for severe wind gusts (a few could be significant given the
large buoyancy). Tornado risk should be maximized during the first
couple hours of supercell formation in a relatively narrow corridor
near the outflow boundary.
Later tonight, this MCS may spread east or separate clusters will
develop east as warm advection strengthens eastward into the TN
Valley. An isolated threat for severe hail/wind may persist along
the eastern periphery of the elevated mixed-layer.
Near the confluence of the MS/OH rivers, in the wake of early-day
convection, a separate cluster of severe storms may develop towards
early evening. This region will lie south of the primary surface
cyclone that should consolidate and gradually deepen as it tracks
east along the I-70 corridor. If adequate boundary-layer heating can
occur in the absence of substantial overturning from the morning
convective activity, a few supercells are possible with a risk for
all hazards.
...Northern WY to western SD...
Have upgraded to Slight Risk given the potential for a couple
long-track supercells this evening into tonight.
A shortwave trough will amplify from British Columbia across the
northern Rockies as a 50-60 kt mid-level jet spreads east across the
Northwest. This will strengthen forcing for ascent and yield
sustained thunderstorm development by late afternoon along the WY/MT
border. While boundary-layer moisture will be limited and the
boundary-layer will not be particularly warm, increasingly elongated
hodographs will favor potential for splitting supercells, a couple
of which could be long tracked. A swath of severe hail with
localized severe wind gusts appears possible.
..Grams/Gleason.. 06/19/2019
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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1143 AM CDT Wed Jun 19 2019
Valid 191630Z - 201200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS NORTH
TEXAS/SOUTHEAST OKLAHOMA AND ARKLATEX REGION...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MID-SOUTH/OHIO VALLEY AND NORTHERN HIGH PLAINS...
...SUMMARY...
Severe thunderstorms are most likely across north-central/northeast
Texas and the Ark-La-Tex region during the late afternoon and
evening. Destructive hail and wind, along with a few tornadoes are
possible. Severe thunderstorms are also expected across the
Mid-South and Ohio Valley.
...North-central/northeast TX and southeast OK/ArkLaTex...
In the wake of a decaying MCS across the Lower Mississippi River
Valley, a northwestward-extending outflow boundary will continue to
modify/drift northward with rapid/strong destabilization this
afternoon particularly along and south of it. A quick
reestablishment of lower/some middle 70s F surface dewpoints will
occur into prior-MCS-impacted areas, with MLCAPE in excess of 4000
J/kg expected for parts of north-central/northeast Texas into far
southeast Oklahoma and the nearby ArkLaTex. Special 19Z observed
soundings are expected from Fort Worth/Shreveport to help better
gauge/confirm this destabilization trend and the degree of capping.
By late afternoon, ascent should increase downstream of a minor
mid-level impulse that is currently approaching from the southern
Rockies. This should aid in convective initiation along the outflow
boundary, as well as near the dryline bulge in the Texas Big
Country. 40-50 kt effective shear with pronounced speed shear in the
mid to upper-levels will support a risk for very large hail with
initial supercells. The tornado risk should be maximized during the
first couple hours of supercell formation in a relatively narrow
corridor near the outflow boundary, where the influence of the
boundary and strong instability will somewhat compensate for
modest-strength low-level winds. With time, this activity should
consolidate into another southeastward-moving MCS during the
evening, aided by a strengthening southwesterly low-level jet, with
an increasing threat for severe wind gusts, a few of which could be
significant given the large buoyancy and ample shear by mid-June
standards.
...Ohio/Tennessee Valleys and Mid-South...
Regarding the Ohio Valley, for short-term details see Mesoscale
Discussion 1133. An MCV-related enhanced belt of
low/mid-tropospheric flow will shift eastward across these regions
through the afternoon and evening, with the strongest
destabilization expected this afternoon along and south of the Ohio
River. Gradually increasing vertical shear will commonly support
multicells, along with some supercells, capable of damaging
winds/hail and possibly a tornado risk.
...Northern High Plains...
A shortwave trough will amplify from British Columbia across the
northern Rockies as a 50-60 kt mid-level jet spreads east across the
Northwest. This will strengthen forcing for ascent and yield
sustained thunderstorm development by late afternoon along the
Wyoming/Montana border and in eastern Montana. While boundary-layer
moisture will be limited and the boundary layer will not be
particularly warm, increasingly elongated hodographs will favor
potential for splitting supercells, a couple of which could be long
tracked. This would particularly be across northern Wyoming into
western South Dakota, where a swath of severe hail with localized
severe wind gusts appears possible.
..Guyer/Bentley.. 06/19/2019
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SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1136 AM CDT Wed Jun 19 2019
Valid 191700Z - 201200Z
...CRITICAL FIRE WEATHER AREA FOR COLUMBIA BASIN VICINITY...
The elevated area in the Southwest has been removed. Morning surface
observations indicate very poor RH recovery as well as 12Z Phoenix
and Tucson soundings indicating very dry, lower-tropospheric columns
that will allow very low RH this afternoon. However, both regional
vertical wind profiles and model guidance indicate a decreasing
trend in 700-500 mb winds through the afternoon. All but the most
aggressive high-resolution guidance generally depict locally
elevated conditions occurring this afternoon.
In the Pacific Northwest, model guidance continues to be a touch
higher than observations with regard to RH. Stronger winds will
continue to push into the Columbia Basin as the boundary layer
deepens with time. Locally critical conditions will be possible
within the highlighted elevated area where terrain enhanced surface
flow occurs.
..Wendt.. 06/19/2019
.PREV DISCUSSION... /ISSUED 0115 AM CDT Wed Jun 19 2019/
...Synopsis...
A mid-level shortwave trough will amplify across the Pacific
Northwest, with surface low pressure deepening across the Northern
Rockies during the afternoon hours. Upper-level ridging will flatten
across the Great Basin and the Four Corners region, with surface low
pressure developing across the Four Corners as well. A relatively
strong west-to-east pressure gradient will become established across
the Pacific Northwest into the Northern Rockies, promoting breezy,
dry conditions across portions of the northwest CONUS, where
conditions will be favorable for wildfire spread.
...Pacific Northwest...
With the onset of afternoon heating and mixing of the boundary
layer, downslope westerly flow will prevail along the lee of the
northern Cascades. 15-25 mph sustained westerly surface winds are
expected to occur during the afternoon hours, coincident with RH
dropping to 20-25%. With drying fuels becoming prevalent across the
Columbia Basin, conditions will become relatively favorable for
wildfire spread, where a critical delineation has been maintained.
...Southeast New Mexico into southwest Arizona...
While stronger flow aloft will be confined farther to the north,
very deep tropospheric mixing will encourage breezy
west-southwesterly surface flow, with winds potentially exceeding 15
mph during the afternoon hours, amidst RH dropping to 10%. Fuels in
this area are critical, and given the lack of recent rainfall across
the region, combined with the aforementioned surface wind/RH
conditions, an elevated area was delineated.
...Montana...
Widespread elevated to locally critical meteorological conditions
will be present across much of western into central Montana during
the afternoon hours, as deep boundary layer mixing (up to 700 mb)
will encourage downward momentum transport of the stronger flow
aloft, promoting 20+ mph sustained westerly winds and 20-30% RH.
While modest drying of the finer fuels has been ongoing across the
area, recent rainfall from scattered showers/thunderstorms, along
with additional rainfall possible during the period, introduces
uncertainty regarding the receptiveness of the aforementioned finer
fuels, precluding delineations at this time.
...Please see www.spc.noaa.gov/fire for graphic product...
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