Alert archive / Maine / Mesoscale Discussions in 2021

Mesoscale Discussion 1052

June 21, 2021Aroostook County, Piscataquis County, Somerset County, Maine

The Storm Prediction Center issued this mesoscale discussion at Jun 21, 2021, 4:56 PM EDT for Aroostook County, Piscataquis County, Somerset County, Maine. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued
Jun 21, 2021, 4:56 PM EDT (20:56 UTC)
Expired
Jun 21, 2021, 6:30 PM EDT
In force
94 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch possible
Chance of a watch
40%

Counties Aroostook County, ME, Piscataquis County, ME, Somerset County, ME

The radar

The Caribou radar (KCBW), 126 km from the middle of the area, began a volume at 20:58 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Caribou, ME (KCAR), launched 12:00Z, 8.9 hours before the alert went out and 120 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Caribou, ME at 12:00Z on 2021-06-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Caribou, ME at 12:00Z on 2021-06-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 51 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1363 m above ground
0-6 km bulk shear
31 kt
0-1 km storm-relative helicity
51 m²/s²
0-3 km storm-relative helicity
113 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

827 
ACUS11 KWNS 212056
SWOMCD
SPC MCD 212056 
MEZ000-212230-

Mesoscale Discussion 1052
NWS Storm Prediction Center Norman OK
0356 PM CDT Mon Jun 21 2021

Areas affected...Northern Maine

Concerning...Severe potential...Watch possible 

Valid 212056Z - 212230Z

Probability of Watch Issuance...40 percent

SUMMARY...Supercells are expected to persist into the evening.

DISCUSSION...Two strong supercells are ongoing across northern
Maine. The northernmost storm is in a region of weaker instability,
but has developed a strong mesocyclone and is near the warm front.
The farther south supercell just entering Maine from Quebec appears
very healthy with a 2+ inch MRMS MESH signature and an unstable
downstream airmass. In addition, surface winds are backed in the
region given the proximity to the warm front which does increase the
chance of a tornado or two with both storms. 

Storm coverage has been isolated thus far and and it is unclear how
it will evolve through the evening. If the greater threat remains
confined to one or two supercells, a watch may not be necessary, but
a greater storm coverage may necessitate a watch.

..Bentley/Hart.. 06/21/2021

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

ATTN...WFO...CAR...GYX...

LAT...LON   46417023 47036974 47516921 47276815 47036772 46246797
            45736867 45346989 45347056 45527083 46417023

Nearby

Mesoscale Discussions in Maine, 2021Every mesoscale discussion in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.