Flooding Continues in Arenac County Along the Rifle River

423
ACUS01 KWNS 211945
SWODY1
SPC AC 211944

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 PM CDT Mon May 21 2018

Valid 212000Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
OHIO VALLEY...AND PARTS OF NEW MEXICO...

...SUMMARY...
Isolated to widely scattered strong to severe thunderstorms are
possible across the Ohio Valley as well as portions of New Mexico
and southwest Texas, and over parts of the central High Plains.
Damaging wind and large hail will likely be the main severe threats.

...20Z Update...
Only minor changes were needed to the outlook as the overall
evolution of storms across the CONUS has occurred as anticipated in
the previous outlook (discussion appended below). Slight risk was
extended northward in NM where increasing thunderstorm coverage
supports higher probabilities of damaging wind gusts and/or severe
hail. Potential for a few bowing segments capable of damaging wind
gusts will persist across the OH Valley into the evening. Recent
development across southwest IN and adjacent portions of far
southwest KY are indicative of better forcing for ascent moving into
the region. These storms will gradually move northeastward with
additional development also expected later this afternoon across
more of IN and into OH. Recent development across southeastern OH
may produce isolated damaging wind gusts and/or hail. More
information about southeastern OH and northwest WV is available in
MCD 481.

..Mosier.. 05/21/2018

.PREV DISCUSSION... /ISSUED 1128 AM CDT Mon May 21 2018/

...Parts of New Mexico into southwest Texas...
Moisture has increased into much of central and eastern New Mexico
in response to southeasterly low-level flow, in advance of an upper
low moving slowly across the lower Colorado River Valley.  Surface
dew points into the low 50s F extend across the Rio Grande Valley in
New Mexico, and with 12Z soundings at EPZ and ABQ showing lowest 100
mb mean mixing ratios of 9.1 and 7.4 g/kg, respectively, PBL
moisture is not expected to mix substantially as strong diabatic
heating occurs this afternoon.  Steep lapse rates will contribute to
an unstable environment with MLCAPE of 1000-1500 J/kg.

Model guidance including 12Z CAMs indicate convective initiation
will occur by early afternoon over the mountains of north central
New Mexico and the develop southward toward the south central part
of the state.  The region will be on the eastern periphery of the
stronger flow aloft to the east of the southwest US upper low, with
25-35 kt of deep-layer shear over the area.  This will promote
organized multi-cell storms and clusters, with potential for a few
supercells to also form, especially during the earlier phases of
storm development when discrete cells are the more likely mode.  The
activity is expected to spread eastward and southeastward later this
afternoon and evening before slowly diminishing after 03-04Z.
Stronger cells will be capable of producing large and damaging
winds, with the wind possibly becoming the primary threat by this
evening as cells grow upscale into small clusters.

...Ohio Valley Region...
A broad region of large scale ascent is evident in satellite imagery
from the middle Mississippi Valley into the western Great Lakes in
advance of a short wave trough and upper low over the upper Midwest.
The low amplitude trough is forecast to move eastward across the
Ohio Valley and southern Great Lakes and enhance convective
potential over the area.

At the surface, a warm front extends from a low over southeast Iowa
across central Illinois and southern Ohio.  The front is expected to
lift northward this afternoon and provide a focus for stronger storm
development.  Visible imagery shows more limited clouds from
southern/eastern Indiana into Ohio where stronger diabatic heating
and destabilization will occur, downstream from developing weak
convection over northern and central Indiana.  Modest lapse rates
will temper the magnitude of afternoon instability with MLCAPE of
1000-1500 J/kg expected.

Storms are expected to increase near and just north of the warm
front by early to mid-afternoon over parts of Indiana and western
Ohio.  This region will be located along the southern edge of
stronger westerly winds aloft and vertical shear, which will support
development of organized multi-cell clusters or short line segments.
There will also be potential for a few embedded supercells to form,
especially along and north of the retreating warm front.  Strong to
severe wind gusts will be the primary threat as activity moves
eastward into the evening hours.  Other strong to isolated severe
storms will be possible farther southwest over the Ohio Valley but
decreasing vertical shear with southward extent is expected to limit
the threat for organized severe storms.

...Central High Plains...
Gradual lee-side cyclogenesis will influence weak upslope
trajectories with a modest influx of low-level moisture through the
day. While upper heights will generally rise, weak low-level upslope
flow and differential heating along the mountains/higher terrain
should yield isolated east/southeastward-drifting thunderstorms this
afternoon. Sufficient low-level moisture and effective shear (30-40
kt) coincident with very steep lapse rates could support some strong
multicells/brief supercells capable of severe hail/gusty winds on a
very isolated basis.

$$

000
ACUS02 KWNS 211714
SWODY2
SPC AC 211714

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1214 PM CDT Mon May 21 2018

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE HIGH PLAINS...OH VALLEY...AND NORTHERN MID-ATLANTIC...

...SUMMARY...
Isolated strong to severe thunderstorms are expected Tuesday across
portions of the High Plains from west Texas into southeast Montana.
A few strong to severe storms may also develop across the Ohio
Valley into the northern Mid-Atlantic.

...Synopsis...
Upper low, embedded within the larger upper trough currently
extending from the Pacific Northwest through southern CA, is
expected continue gradually southeastward today before arcing more
northward/northeastward on Tuesday. As this occurs, a mid-level jet
streak will round the base of the low, ejecting into the southern
and central Rockies late Tuesday afternoon. Southwesterly flow aloft
ahead of this jet streak as well as large-scale forcing for ascent
will result in a deepening surface lee trough and eventual
cyclogenesis Tuesday evening.

Farther east, upper ridging will cover much of the Southeast with
more confluent flow across the OH Valley into the Northeast south of
the upper troughing moving across eastern Canada. A shortwave trough
is expected to move eastward within this confluent, slightly
enhanced upper flow from the upper Great Lakes into the Northeast.

...High Plains Tuesday afternoon and evening...
Modest low-level moisture advection is anticipated across the Plains
and High Plains on Tuesday as lee troughing supports a tightening
surface pressure gradient and southerly 850mb flow persists.
However, despite this favorable return flow, strong boundary-layer
mixing is anticipated, likely resulting in low 50s dewpoints during
the afternoon. Steep mid-level lapse rates atop this modest moisture
will moderate instability with MLCAPE expected to be around
1500-2000 J/kg across portions of the southern and northern High
Plains. Lower instability is anticipated across the central Plains
where stronger mixing is expected.

Thunderstorms will likely develop in areas of relatively stronger
surface convergence and greater instability (i.e. across the
southern and northern High Plains). Thunderstorms are not as likely
across the central High Plains where less surface convergence and
lower afternoon dewpoints are anticipated. Weak mid-level flow and
relatively dry mid-levels suggest storms will quickly become outflow
dominant. Even so, a few strong updrafts capable of hail and
damaging wind gusts are possible.

...Middle MO Valley late Tuesday night into early Wednesday
morning...
A strengthening low-level jet will contribute to increasing
isentropic ascent across the warm frontal zone stretching from the
low near the NE/WY/SD border intersection eastward into western IA.
Modest elevated instability and vertical shear will support a few
storms capable of large hail.

...Upper OH Valley and northern Mid-Atlantic Tuesday afternoon...
Broadly confluent surface winds augmented by favorable jet dynamics
(i.e. region is beneath the right entrance region of the upper jet)
amidst modest low-level moisture and instability will likely result
in scattered thunderstorms across the region during the afternoon.
Multiple linear bands are possible along areas of stronger
confluence, with a few storms in these bands capable of damaging
wind gusts.

...MAXIMUM RISK BY HAZARD...
Tornado:   2%     - Marginal
Wind:      5%     - Marginal
Hail:      5%     - Marginal

..Mosier.. 05/21/2018

$$

000
FXUS63 KAPX 211943
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
343 PM EDT Mon May 21 2018

.NEAR TERM...(Through Tonight)
Issued at 340 PM EDT Mon May 21 2018

...Little bit of rain, fog, and low clouds tonight...

High impact weather potential: Minimal.

Pattern synopsis/forecast: Convectively enhanced wave (wave itself
is shearing out/weakening) responsible for driving a rather large
area of light to moderate showers into the central Great Lakes this
afternoon. Dry air tied to Lake Superior high pressure doing a
number on the northward advance of this rain, with a noticeable
decrease in organization and intensity on its northern periphery.
Still, saturation has become deep enough to allow rain to reach the
surface in our southwest areas, with high pressure keeping
conditions dry, albeit with quite a bit of high clouds, further
north.

Wave cuts across the region tonight, continuing to de-amplify in the
process. Light showers will follow suite, targeting a good portion
of northern lower Michigan for some light rain amounts.

Primary forecast concerns/challenges: Addressing that shower
potential, as well as potential for some fog and overnight
temperature trends.

Details: Light showers will continue to advance northeast the
remainder of this afternoon and evening as overall forcing and
deepest moisture axis shear out. Still question just how far north
the rain advances as northern Lakes ridge axis simply refuses to
yield. Simple radar/satellite extrapolation confirms high res-
guidance of drifting some rain potential to at least the M-68
corridor, with the best coverage of rain remaining along and south
of M-72. Rain amounts look to remain light as any deep convective
potential/thunderstorms focus south of our region. Areas north of
the big bridge should stay dry as low level dry air stays steadfast.
More "organized" rains expected to depart overnight, leaving behind
low clouds and potential for a bit of drizzle. Where better rain
occurs, may see a bit of fog develop overnight as low levels become
increasingly "soupy" and with light winds. Don`t think this will get
to out of hand, with only brief restrictions to visibility expected.
Overnight lows range from the mid 40s north, to near 50 degrees
along/south of the M-55 corridor.

&&

.SHORT TERM...(Tuesday through Thursday)
Issued at 340 PM EDT Mon May 21 2018

...High pressure returns...

High Impact Weather Potential: Elevated fire danger possible.

Pattern Forecast: Clouds and any lingering rain showers will
diminish Tuesday from north to south as high pressure centered
over Hudson Bay along with, accompanied dry air, push in behind a
departing low pressure system. Said high pressure will build over
the Great Lakes and provide precipitation free weather and warm
temperatures Tuesday through Thursday. Highs will be in the upper
60s to near 70 Tuesday and then mid 70s to around 80 Wednesday and
Thursday (low to mid 70s over eastern upper). Of course temperatures
will be cooler along the lake shores once lake breezes form during
the afternoons with daytime heating. Lows will generally be in the
mid to upper 40s. Winds will continue to remain on the light side
through the forecast period as high pressure is overhead and
pressure gradients remain relaxed. Thursday may mix out enough to
reach near critical thresholds for relative humidity. With the lower
humidity levels and temperatures forecast to be near 80 fire danger
could be elevated.

&&

.LONG TERM...(Thursday night through Monday)
Issued at 340 PM EDT Mon May 21 2018

Rain chances return late Thursday night/early Friday morning and
last through the weekend and possibly into Monday as long range
models have consensus on an area of low pressure meandering over the
upper Great Lakes region. Won`t be a washout weekend, but will be
partly to mostly cloudy with periodic rain showers and possibly some
thunder. Highs will be in the mid 70s to near 80 (eastern upper only
in the upper 60s to low 70s). Lows will be in the upper 40s to upper
50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 138 PM EDT Mon May 21 2018

Conditions to slowly deteriorate as area of light rain and lower
clouds advance northeast later this afternoon and overnight.
Primary impact expected at KTVC and KMBL where cigs will lower to
MVFR and there is potential for some late night fog/mist. Current
trends support VFR conditions continuing at KPLN, with KAPN right
on the border between VFR and MVFR conditions. Similar conditions
expected to start Tuesday, with cigs slowly scattering out from
north to south during the late morning and afternoon.

&&

.MARINE...
Issued at 340 PM EDT Mon May 21 2018

A weak pressure gradient will hold over the region for the
next several days, resulting in minimal chances for any wind/wave
issues. Weak low pressure does cross srn Lakes Michigan and Huron
into this evening for some potential light rain showers. Otherwise,
next chance of rain arriving mainly Thursday night-Saturday.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...MB
SHORT TERM...TL
LONG TERM...TL
AVIATION...MB
MARINE...MB

454
ACUS11 KWNS 212029
SWOMCD
SPC MCD 212029
NMZ000-212230-

Mesoscale Discussion 0483
NWS Storm Prediction Center Norman OK
0329 PM CDT Mon May 21 2018

Areas affected...portions of Northern and Central New Mexico

Concerning...Severe Thunderstorm Watch 112...

Valid 212029Z - 212230Z

The severe weather threat for Severe Thunderstorm Watch 112
continues.

SUMMARY...Threat for marginally severe wind and hail continues
across WW 112

DISCUSSION...Visible satellite imagery at 2030Z shows a large area
of anvil clouds overspreading WW 112. This has stunted surface
heating and generally limited further destabilization within the
area. However, mid- and upper-level winds have been modestly
increasing, per KABX and KHDX VAD profiles, as the the upper-level
trough pushes slowly eastward. Effective bulk shear remains 25-30
kts and will support enough storm organization for isolated,
marginally severe hail and wind gusts.

..Wendt/Elliott.. 05/21/2018

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

ATTN...WFO...ABQ...EPZ...

LAT...LON   36310742 36610707 36690600 35910542 34150511 33360549
            33260660 33720705 35040725 36310742