Severe Weather - Flooding

249
ACUS01 KWNS 121630
SWODY1
SPC AC 121628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Wed Aug 12 2020

Valid 121630Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS PARTS OF WESTERN AND NORTHERN NORTH
DAKOTA...

...SUMMARY...
Widely scattered strong storms may impact portions of the the
northern and central Great Plains late this afternoon into tonight,
accompanied by at least some risk for severe hail and wind.  Other
thunderstorms with locally strong wind gusts are possible near and
east of the Blue Ridge Mountains into the northern Mid Atlantic
coast vicinity.

...Synopsis...
A belt of westerlies emanating from northern mid-latitude Pacific
has undergone some amplification, and this appears likely to
transition eastward near/north of the Canadian/U.S. border today
through tonight.  This includes large-scale troughing across western
Canada and the Pacific Northwest, gradually shifting east of the
Canadian and northern U.S. Rockies, through the Canadian Prairies
and higher portions of the northern U.S. Great Plains.  Downstream
ridging is forecast to continue to build across lower portions of
the northern Great Plains, Upper Midwest and adjacent Great Lakes
region through the Hudson Bay vicinity.

In lower latitudes, mid-level subtropical ridging will remain
influential across much of the central and southern tier of the
U.S., including a prominent high centered over parts of the
Southwest into the southern Great Plains.

Steep lower/mid tropospheric lapse rates associated with a plume of
warm and capping elevated mixed-layer air will be maintained across
much of the Great Plains.  Seasonably high moisture content lingers
south of a weak surface front extending across parts of the
Northeast into the Ohio Valley, and generally to the east of weak
mid/upper troughing within the larger-scale ridging across the lower
Mississippi Valley.

...Great Plains...
Coverage of thunderstorm development and associated severe weather
potential remain unclear for today through tonight.  Stronger
forcing for ascent associated with a short wave impulse migrating
northeastward out of the base of the larger-scale troughing appears
likely to remain mostly north of the international border, but could
perhaps extend southward into the vicinity of lee surface troughing
across parts of northwestern North Dakota late this afternoon and
evening.  Otherwise, the lee surface trough extending southward
through central portions of the higher plains could provide a focus
for widely scattered late afternoon and early evening thunderstorm
initiation.  Additional thunderstorms may initiate, aided by warm
advection, later tonight, east of the warmer and more strongly
capping elevated mixed-layer air across parts of northern and
central Minnesota, as well as portions of the central Great Plains.

Where storms form, thermodynamic profiles characterized by steep
mid-level lapse rates and sizable CAPE, coupled with perhaps modest
shear, may provide support for severe hail and locally strong
surface gusts.

...Northern Mid Atlantic into central Appalachians...
Orographic forcing along the Appalachians may provide the primary
support for thunderstorm initiation this afternoon, along with
perhaps weak pre-frontal low-level convergence extending east of the
higher terrain, across southern Pennsylvania into the northern Mid
Atlantic coast region.  Although deep-layer ambient mean flow is
generally on the order of 10 kt or less, seasonably high moisture
content and sizable CAPE may contribute to heavy precipitation
loading and the risk for potentially damaging wind gusts in the
stronger storms.

..Kerr/Cook.. 08/12/2020

$$

888
ACUS02 KWNS 121721
SWODY2
SPC AC 121720

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1220 PM CDT Wed Aug 12 2020

Valid 131200Z - 141200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
NORTHWEST MINNESOTA AND PARTS OF EASTERN NORTH DAKOTA...

...SUMMARY...
Severe thunderstorms with large hail and damaging wind are likely
from North Dakota and northern South Dakota into northern Minnesota,
with isolated activity to the south and west. Isolated severe storms
are also possible from eastern Kansas and Oklahoma into western
Arkansas.

...Synopsis...
An upper trough will move from the northern Rockies into the
northern Plains with the main speed max and strongest lift moving
across MT, WY, and the Dakotas from evening into the overnight.
Meanwhile to the south, an upper high will remain over AZ,NM and
west TX, with enhanced northwesterly winds aloft from the central
Plains into the Ozarks.

At the surface, a front is forecast to extend from the Red River of
ND/MN into western NE during the afternoon, with low pressure
redeveloping over eastern MT/WY in advance of the upper trough.
Southerly winds will maintain a moist and very unstable air mass
east of the low, from the Dakotas into MN. The combination of
instability and increasing lift should result in damaging wind and
hail over parts of the region.

...Northern Plains...
MUCAPE in excess of 4000 J/kg is likely over a large area from the
eastern Dakotas into MN, east of the front/wind shift and beneath
persistent southerly 850 mb winds which will increase boundary-layer
moisture depth. Explosive development is likely along the boundary,
from northwest MN into eastern ND and northeast SD. Damaging winds
appear likely, and areas of large hail will be possible as well
despite weak shear, mainly with the initial development.

Other severe storms with large hail are expected as the main lobe of
forcing for ascent moves from southeast MT into North Dakota.
Lengthening hodographs and cold temperatures aloft will favor large
hail, and a few of these storms may also produce damaging winds.

...KS/OK/MO/AR Borderlands...
Enhanced midlevel northwesterlies of 35-40 kt are forecast from KS
into AR, around the eastern periphery of the upper ridge. Hot
temperatures will develop from TX into southwest OK near a surface
low, with a very moist air mass farther northeast where surface
winds will remain backed. Strengthening warm advection during the
evening will likely induce a swath of storms from southeast KS into
AR, oriented northwest to southeast. Veering winds with height in
the effective cloud layer suggest isolated supercells will be
possible, most likely elevated. If sufficient storm coverage can
form, cold pool generation may support a few strong gusts as well.

..Jewell.. 08/12/2020

$$

000
NWUS53 KAPX 111356
LSRAPX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GAYLORD MI
956 AM EDT TUE AUG 11 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 AM     HEAVY RAIN       2 W LEWISTON            44.88N 84.37W
08/11/2020  M2.30 INCH       MONTMORENCY        MI   CO-OP OBSERVER

            CO-OP OBSERVER STATION LEWM4 LEWISTON 3 W.

0700 AM     HEAVY RAIN       1 SW ATLANTA            44.99N 84.16W
08/11/2020  M2.26 INCH       MONTMORENCY        MI   CO-OP OBSERVER

            CO-OP OBSERVER STATION ATLM4 ATLANTA 1 SW.

0800 AM     HEAVY RAIN       1 NW WATERS             44.91N 84.72W
08/11/2020  M1.20 INCH       OTSEGO             MI   CO-OP OBSERVER

            CO-OP OBSERVER STATION APXM4 GAYLORD 9 SSW.

0850 AM     HEAVY RAIN       1 NNE OSSINEKE          44.92N 83.43W
08/11/2020  M1.03 INCH       ALPENA             MI   COCORAHS

            COCORAHS STATION MI-AP-2 OSSINEKE 1.0 NNE.


&&

$$

056
FXUS63 KAPX 121839
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
239 PM EDT Wed Aug 12 2020

.NEAR TERM...(Through Thursday)
Issued at 238 PM EDT Wed Aug 12 2020

...Quiet stretch of weather...

High Impact Weather Potential: None.

Pattern Synopsis/Forecast: Short-wave ridging extends through the
central and northern Plains into Canada with downstream westerly
mid level flow through the Great Lakes. A couple of smaller scale
waves are embedded in the flow; one sliding into northern Lower
Michigan with little more than patchy clouds. Second convectively
induced wave is moving through Minnesota into Wisconsin along with
a compact round of showers/storms.

At the surface, large expanse of surface high pressure and dry
air encompasses all the Great Lakes providing lots of sunshine and
quiet weather across the region. Southerly return flow of
moisture/instability extends northward through the Plains with
aforementioned compact round of showers/storms occurring along the
very eastern edge of the instability gradient.

Primary Forecast Concerns: Minimal.

Upstream wave in Minnesota will slowly track across northern
Michigan later tonight through Thursday. Ongoing convection will
continue to move slowly eastward into the U.P. tonight although
weaken substantially as it outpaces it`s supporting instability
axis further to the west. But there may be some remnant cloud
cover (maybe a shower?) that tracks through the region late
tonight through Thursday. I`ll keep the forecast dry...but I have
nudged cloud cover upward just a bit late overnight through
Thursday, particularly across eastern Upper MI.

Overnight lows will dip into the 50s for most areas, possibly a
few upper 40 degree readings. Highs Thursday will once again span
the 80s with the warmest readings in the SW counties owing to
easterly downsloping flow.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 238 PM EDT Wed Aug 12 2020

High impact weather potential: Thunder possible Saturday night,
although none expected to become severe at this time.

Pattern synopsis/forecast:

Surface high pressure and upper level ridging continues to dominate
northern Michigan`s weather through at least Saturday afternoon.
This ridge of high pressure begins a push eastward and allows a weak
cold front associated with an area of low pressure over Canada to
begin an approach into the Great Lakes region Saturday evening and
provides the next chances for some rain showers...beginning in
eastern upper and progressing to the east and southward through the
night. Thunder will be possible late Saturday into the overnight
hours and possibly into the next forecast period. Don`t expect any
severe storms at this time due to weak shear and instability.
Daytime temperatures will be in the mid 80s and a bit more humid
Saturday with southerly flow advecting low level moisture into the
forecast area. Nighttime lows will be in the mid 50s to near 60.
Winds will continue to be light out of the south to southwest under
high pressure through Saturday night...until the aforementioned cold
front passes Sunday, then the winds will veer to northwesterly.

&&

.LONG TERM...(Saturday night through Wednesday)
Issued at 238 PM EDT Wed Aug 12 2020

High Impact Weather Potential: Minimal...

Amplified ridging in place across Ontario will give way to troughing
approaching from the west Sunday. This troughing looks to dig into
the Great Lakes, supporting a cyclone that is expected to move
across Hudson Bay over the weekend. An associated cold front will
likely sweep down across the region from Canada in the Sunday
timeframe. This will provide the next chance for rain and possibly
thunder across northern Michigan. While southerly low-level flow
should bring some mid 60s dewpoints into the area, meager upper-
level shear will work against the potential for stronger, organized
thunderstorms over the weekend. This frontal passage would wipe
favorable low-level moisture from the Great Lakes and, along with
surface high pressure building in behind, bring the return of rain-
free weather to northern Michigan. High temperatures look to drop
back down into the low to mid 70s behind the front, making for a
cooler start to next work week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 109 PM EDT Wed Aug 12 2020

High pressure and dry air across the region will solidify VFR
conditions across northern Michigan through Thursday, although a
little patchy fog is possible overnight at MBL. Upstream, small
area of showers/storms is pressing into western Wisconsin. Showers
and storms are expected to dwindle through tonight, but remnant
mid and high cloud cover will slide through the region late
overnight through Thursday bringing a little bit of cloud cover.


&&

.MARINE...
Issued at 238 PM EDT Wed Aug 12 2020

High pressure across the Great Lakes will maintain overall light
winds and waves on the lakes through Thursday. System will weaken
a bit later Thursday into Friday while low pressure deepens
through the Ohio Valley. This will lead to a little stronger east
to southeasterly flow, although winds/waves will remain below any
headline criteria.

&&

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

$$

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

000
ACUS11 KWNS 121715
SWOMCD
SPC MCD 121715
NJZ000-NYZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-NCZ000-121915-

Mesoscale Discussion 1471
NWS Storm Prediction Center Norman OK
1215 PM CDT Wed Aug 12 2020

Areas affected...Portions of Virginia northeastward through New
Jersey

Concerning...Severe potential...Watch unlikely

Valid 121715Z - 121915Z

Probability of Watch Issuance...20 percent

SUMMARY...Gradually deepening convection will pose a risk of
damaging wind gusts through the afternoon.  The isolated nature of
the threat precludes a WW issuance.

DISCUSSION...Strong buoyancy has developed along and south of a weak
surface boundary over southern Pennsylvania/New York, where
mid/upper 70s F surface dewpoints was contributing to 3000+ J/kg
MUCAPE.  This unstable, uncapped airmass has supported isolated to
scattered convective development, although deep layer shear is quite
weak.  The environment should support occasional, `pulse-type`
storms that pose a brief damaging-wind threat but migrate/propagate
erratically in and near the discussion area through the afternoon.
The threat should be too isolated to necessitate a WW issuance, and
the threat should persist through the early evening until nocturnal
boundary layer stabilization commences.

..Cook/Kerr.. 08/12/2020

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

ATTN...WFO...OKX...PHI...AKQ...CTP...LWX...RAH...RNK...RLX...
GSP...

LAT...LON   37108104 37968012 39527797 40177628 40587480 40457400
            39937396 39367449 38677605 37847718 36757863 36068003
            35868125 36238174 37108104

000
WGUS53 KAPX 110112
FFWAPX
MIC011-051-129-143-110515-
/O.NEW.KAPX.FF.W.0013.200811T0112Z-200811T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Gaylord MI
912 PM EDT Mon Aug 10 2020

The National Weather Service in Gaylord has issued a

* Flash Flood Warning for...
  Northwestern Arenac County in northern Michigan...
  Northern Gladwin County in northern Michigan...
  Southwestern Ogemaw County in northern Michigan...
  Southeastern Roscommon County in northern Michigan...

* Until 115 AM EDT.

* At 912 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Between 1 and 3 inches of rain
  have fallen. Flash flooding is ongoing or expected to begin
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Doppler radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets and underpasses as well as other
           drainage and low lying areas.

* Some locations that will experience flash flooding include...
  Gladwin, Bowmanville, Skeels and Skidway Lake.

Additional rainfall amounts of 1 to 2 inches are possible in the
warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be especially cautious at night when it is harder to recognize the
dangers of flooding.

&&

LAT...LON 4408 8461 4425 8427 4425 8412 4417 8406
      4386 8461

FLASH FLOOD...RADAR INDICATED

$$

Cornish