000
acus01 kwns 190600
swody1
Storm Prediction Center ac 190559
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1259 am CDT Wednesday Jun 19 2013
Valid 191200z - 201200z
..there is a slight risk of severe thunderstorms across central and eastern Montana into
western ND this afternoon through tonight...
..there is a slight risk of severe thunderstorms across parts of the central and
southern High Plains this afternoon and evening...
..synopsis..
a closed low centered along or just off the Washington/Oregon coasts per 19/00z
upper air analysis will move inland today...while a potent shortwave
trough moves through the southern and eastern peripheries of this system.
This latter feature will acquire a negative-tilt as it tracks from
the northern Great Basin into the northern rockies/High Plains region this
afternoon through 12z Thursday. Downstream height rises and
midlevel warming will occur as a ridge builds eastward across the plains.
Aside from the Great Lakes to New England...midlevel winds are
expected to weaken as a trough moves off the eastern Seaboard into the
western Atlantic. A Lee cyclone is forecast to deepen over southeastern Montana
through the early half of the forecast period...with a Lee
trough/dryline extending southward through the central and southern High Plains.
A cold front will accelerate eastward across the northern High Plains this
evening through tonight and should reach the western Dakotas by 12z
Thursday.
..central and eastern Montana into western ND...
Surface dew points in the 50s were observed across much of central
and eastern Montana Tuesday afternoon/evening. Strengthening southeasterly low level
winds east-north of the deepening southeastern Montana surface low will support further
moisture advection with dew points in the middle-upper 50s expected
this afternoon across central/north central Montana and around 60 in eastern
Montana/western Dakotas. This increase in moisture /I.E. Precipitable water
values to over 1 inch/...surface heating and steep lapse rates will
result in MLCAPE of 1500-2500 j/kg...and possibly up to 3000 j/kg
over eastern Montana and part of the adjacent Dakotas.
An increase in diffluent flow aloft across the northern rockies/High
Plains suggests initial thunderstorms may develop over the higher terrain of
the northern rockies with the approach of the negatively-tilted shortwave
trough. These storms are expected to increase in intensity and
severe weather threat as they track northward/northeastward into central Montana by
middle-late afternoon where the environment will be moderately unstable
and strongly sheared. These storms will be capable of producing
large hail...some very large...given the presence of steep lapse
rates and sizable cape in the -10 to -30 c layer shown in forecast
soundings with the more intense updrafts /supercells/. Damaging
winds will be a threat...especially this evening through
tonight...as cold pools merge with clusters of storms moving
northeastward/eastward into eastern Montana/western ND...potentially evolving into a linear
mesoscale convective system. A strengthening southeasterly low level jet into eastern/northestern Montana by evening may
increase a tornado threat across these areas as low level
shear/hodograph size increases.
..central and southern High Plains...
Much of the Great Plains is expected to become moderately to
strongly unstable today...but given height rises/warming midlevel
temperatures there remains uncertainty with the potential
development of thunderstorms across a large portion of the plains. The
exception appears to be along the Lee trough/dry line across the
central/southern High Plains...where the 12z European model (ecmwf)/00z NAM suggest thunderstorms
will develop later this afternoon into the evening. Moderate to
strong instability and effective bulk shear to at least 40 knots will
support supercells. The presence of steep lapse rates and sizable
cape in the -10 to -30 c layer shown in forecast soundings with the
more intense updrafts /supercells/ will support large hail...some
very large. Damaging winds will also be a threat with the stronger
storms.
..Dakotas/central and eastern Nebraska/southwestern Minnesota...
Aside from the strong to severe storms moving into western ND later
tonight...a strengthening southerly low level jet up to 40-50 knots extending from
central Kansas/Nebraska into South Dakota will result in an increase in warm air advection across the
Dakotas...central-ern Nebraska into southwestern Minnesota after dark. This should
prove favorable in supporting elevated thunderstorm development...though
coverage may be somewhat limited given the background height rises
with the upper ridge. A Reservoir of moderate-strong instability
and increasing effective bulk shear should support a few stronger to
severe storms with hail and strong wind gusts being the primary
threats. Given uncertainty in the overall coverage of a severe
weather threat...only low severe hail/wind probabilities will be
included with this outlook.
.Peters/Rogers.. 06/19/2013
Mesoscale Discussion
000
acus11 kwns 190221
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 190221
mtz000-190315-
Mesoscale discussion 1127
National Weather Service Storm Prediction Center Norman OK
0921 PM CDT Tuesday Jun 18 2013
Areas affected...western Montana
Concerning...Severe Thunderstorm Watch 326...
Valid 190221z - 190315z
The severe weather threat for Severe Thunderstorm Watch 326
continues.
Summary...severe threat is diminishing across western Montana.
Discussion...a few strong updrafts remain across Toole
County...otherwise thunderstorm activity is diminishing in intensity and
areal coverage. Aside from isolated hail or perhaps gusty winds it
appears severe threat is minimal across most of ww326.
.Darrow.. 06/19/2013
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...tfx...mso...
Latitude...Lon 46181412 48961435 48951040 46181036 46181412
