- Day Three
acus01 kwns 301249
Storm Prediction Center ac 301247
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0747 am CDT Sat may 30 2015
Valid 301300z - 311200z
..there is a slight risk of severe thunderstorms over northern ME...
..There is a slight risk of severe thunderstorms over parts of the lower Ohio and Tennessee
..there is a marginal risk of severe thunderstorms from southern and eastern Texas northeastward into
the lower Great Lakes/New England...
..there is a marginal risk of severe thunderstorms over parts of the northern rockies and
northern High Plains...
Scattered thunderstorms...some with strong to possibly severe winds
and hail...will develop near and ahead of a cold front from parts of
the northeast and Ohio Valley southwest into Texas. A few strong to
possibly severe storms also are expected over parts of New
Mexico...and central and eastern Montana this afternoon and evening.
A multi-stream trough will progress slowly east from the plains into the
Great Lakes...Ohio Valley...and lower MS valley this period as a ridge persists
over the western Atlantic and heights rise across the Great Basin. Within
the trough...southern stream vorticity now over western Arkansas should continue NE into
western Kentucky by this evening while upstream impulse now over western Nebraska/Kansas moves
east into Iowa. At the same time...stronger northern stream disturbance now
over western ont should track east into northern/central Quebec by early
sun...strengthening existing west-southwest flow across the lower Great Lakes/New
England. A series of weak disturbances will top building ridge over
the interior west...and an mesoscale convective vortex may evolve from mesoscale convective system now over north central
At the surface...a cold front at this time extending from eastern Quebec southwestward through
the lower Great Lakes and lower Ohio Valley into west central Texas should progress
steadily east/southeast through the period. This boundary...bands of
confluence ahead of it...and surface low along the front over the lower Ohio
Valley...will serve as the primary low-level sources of lift for
thunderstorms...especially this afternoon and evening.
..upstate New York to northern ME this aftn/eve...
Surface observation and satellite data show that sufficient moisture has spread
NE across upstate New York and northern New England to support strong
storms...with precipitable water now at or above 1.50 inches. Largely unidirectional deep
west-southwesterly flow should slowly increase through the day...with the
strongest winds /700-500 mb speeds at or above 40 kts/ expected over far northern
New York and northern ME. Combination of surface heating and convergence along lake
breeze boundaries/terrain circulations should support bands of scattered
afternoon thunderstorms ahead of cold front from upstate New York east-northeast across northern New
Modest middle-level lapse rates will limit maximum buoyancy to around 1000
j/kg despite presence of increased moisture. Nevertheless...given
strength of deep west-southwesterly flow and its orientation parallel to the
sources of low-level uplift...some potential will exist for embedded
bowing segments with locally damaging wind. The storms should weaken
with nocturnal cooling early tonight.
..lwr Ohio/Tennessee valleys this aftn/eve...
Surface low now located along the Arkansas-MO border should track slowly NE
along cold front into southern Illinois by evening...in association with southern stream
upper vorticity. Band of enhanced /40+ knots/ 700-500 mb flow on east side of the
vorticity will overspread warm sector across western portions of Tennessee/Kentucky and
southern Illinois/ind today...where precipitable water will remain at or above 1.75 inches. Although
middle-level lapse rates will be weak...surface heating and confluence in the
warm sector should support development of short lines/clusters of
storms by early afternoon. These could yield a conditional risk for
locally damaging wind and a couple tornadoes through early tonight.
..TX/la this aftn/eve...
North Texas mesoscale convective system should continue generally eastward into NE Texas/northwest la by early
afternoon. New development likely will occur S and east of the system across
parts of east central and southeast Texas as surface heating boosts MLCAPE to at or above 2000
j/kg. Occasional locally damaging wind gusts and hail may occur with
embedded bowing segments in the mesoscale convective system...and with the more isolated storms
farther S. Modest deep shear /around 25 kts/
should...however...limit potential for widespread severe weather.
Elsewhere...SW Texas mesoscale convective system should move/develop south-southeast to the Texas Big Bend by
middle afternoon. This system should remain largely elevated atop outflow
from previous mesoscale convective system...although it too could yield occasional instances
of severe wind and hail given somewhat greater /30+ knots/ cloud-layer
shear present in that region. Additional scattered storms may form over
central and S Texas through tonight...ahead of trailing southern portion of
Nebraska/Kansas upper trough. While this activity could yield a instance or two
of severe hail...the wind/thermodynamic environment should be
unfavorable for a sustained severe threat.
..NE Washington/Idaho eastward into western/central Montana this aftn/eve...
Low-amplitude trough now entering western Montana will continue east across the
remainder of that state later today...while another disturbance
moves east from Oregon into Idaho. Widely scattered storms now over northern Idaho/western Montana
should move/develop mainly east through the day...affecting central/eastern
Montana by late afternoon and evening. Inverted-v thermodynamic environment may
yield a few strong/possibly severe downburst winds. Farther west...other
diurnally-enhanced storms with a conditional risk for strong winds
and perhaps marginally severe hail may occur over NE Washington and northern Idaho...in
association with Oregon upper impulse.
acus11 kwns 301551
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 301551
Mesoscale discussion 0843
National Weather Service Storm Prediction Center Norman OK
1051 am CDT Sat may 30 2015
Areas affected...S-cntrl into east-central Illinois / southwestern through central and into
Concerning...severe potential...watch unlikely
Valid 301551z - 301745z
Probability of watch issuance...20 percent
Summary...scattered thunderstorms are forecast to develop this
afternoon. A few of the stronger storms may be capable of an isolated
damaging wind risk.
Discussion...visible satellite imagery shows a swelling cumulus field
across the Wabash River valley amidst ample surface heating as temperatures
rise through the 70s and into the lower 80s with dewpoints in the
upper 60s. A shortwave trough evident in water vapor imagery over
the Ozark Plateau will move downstream to the NE towards the Ohio/MS
river confluence by middle afternoon while a surface low develops northeastward
from southeastern MO into S-central Illinois. Marginal to pockets of moderate
buoyancy /500-1200 j per kg MLCAPE/ will likely develop as the
airmass destabilizes further. 30-knots 500 mb flow on the southeast-side of the
middle-level disturbance will act to support isolated strong
quasi-discrete cells but the overall marginal shear will yield a
multicell Mode. Nonetheless...the moist airmass coupled with
moderate unidirectional southwesterly flow fields will probably yield at
least some potential for localized wind damage this afternoon.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 38068950 38728943 40638738 41058640 41108531 40748478
40298472 38398675 37838775 37748891 38068950