RSS Mesoscale Discussions from Storm Prediction Center
WW 437 SEVERE TSTM MT 240230Z - 240900Z
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 437
NWS STORM PREDICTION CENTER NORMAN OK
830 PM MDT WED JUL 23 2014
THE NWS STORM PREDICTION CENTER HAS ISSUED A
* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
WEST-CENTRAL AND NORTHERN MONTANA
* EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 830 PM
UNTIL 300 AM MDT.
* PRIMARY THREATS INCLUDE...
ISOLATED SIGNIFICANT DAMAGING WIND GUSTS TO 75 MPH POSSIBLE
ISOLATED VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE
THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 55 MILES SOUTH
SOUTHWEST OF CUT BANK MONTANA TO 35 MILES EAST SOUTHEAST OF
GLASGOW MONTANA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 435...WW 436...
DISCUSSION...SVR POTENTIAL FCST TO INCREASE THROUGH REMAINDER
EVENING AS TSTMS MOVE NEWD AND AGGREGATE OVER W-CENTRAL
MT...ULTIMATELY FOLLOWING ANTICYCLONICALLY CURVING PATH ACROSS NRN
MT TONIGHT. ADDITIONAL/MORE ISOLATED SVR ALSO MAY OCCUR AHEAD OF
THAT ACTIVITY WITH CONVECTION INITIALLY BETWEEN GGW-HVR. REF SPC
MESOSCALE DISCUSSION 1452 FOR INITIAL NEAR-TERM DETAILS.
AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 25035.
...EDWARDS
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WW 0437 Status Updates
STATUS REPORT ON WW 437
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 SSW LWT
TO 45 N LWT TO 5 SE HVR TO 40 NE CTB.
..GOSS..07/24/14
ATTN...WFO...TFX...GGW...
STATUS REPORT FOR WS 437
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MTC005-027-033-041-069-071-105-240640-
MT
. MONTANA COUNTIES INCLUDED ARE
BLAINE FERGUS GARFIELD
HILL PETROLEUM PHILLIPS
VALLEY
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
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WW 0436 Status Updates
STATUS REPORT ON WW 436
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 45 NNW UTS
TO 45 WNW LFK TO 30 NW LFK.
..DIAL..07/24/14
ATTN...WFO...SHV...FWD...HGX...
STATUS REPORT FOR WS 436
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
TXC225-240440-
TX
. TEXAS COUNTIES INCLUDED ARE
HOUSTON
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
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WW 0435 Status Updates
STATUS REPORT ON WW 435
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 WSW BTM
TO 20 N MSO TO 50 W GPI TO 100 N GEG.
..BROYLES..07/24/14
ATTN...WFO...OTX...MSO...
STATUS REPORT FOR WS 435
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MTC029-039-047-053-063-240340-
MT
. MONTANA COUNTIES INCLUDED ARE
FLATHEAD GRANITE LAKE
LINCOLN MISSOULA
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
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WW 0434 Status Updates
STATUS REPORT ON WW 434
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 S GYI TO
30 ESE DAL.
..DIAL..07/24/14
ATTN...WFO...SHV...FWD...
STATUS REPORT FOR WS 434
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
TXC085-240240-
TX
. TEXAS COUNTIES INCLUDED ARE
COLLIN
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
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No Mesoscale Discussions are in effect as of Thu Jul 24 06:16:02 UTC 2014.
SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT THU JUL 24 2014
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN INTO TONIGHT ACROSS
PARTS OF EASTERN MONTANA INTO WESTERN AND CENTRAL NORTH
DAKOTA...PERHAPS PARTS OF ADJACENT NORTHERN SOUTH DAKOTA...
...SUMMARY...
A FEW SEVERE THUNDERSTORMS CAPABLE OF PRODUCING LARGE HAIL AND
STRONG WIND GUSTS ARE POSSIBLE ACROSS PARTS OF EASTERN MONTANA INTO
WESTERN AND CENTRAL NORTH DAKOTA THIS AFTERNOON INTO TONIGHT.
STRONG STORMS...WITH POTENTIAL FOR LOCALIZED DAMAGING WIND
GUSTS...MAY ALSO DEVELOP ACROSS PARTS OF THE CENTRAL AND SOUTHERN
APPALACHIANS INTO THE SOUTHERN MID ATLANTIC COAST STATES TODAY.
...SYNOPSIS...
THE SIGNIFICANT SHORT WAVE TROUGH AND EMBEDDED CLOSED LOW NOW OVER
THE PACIFIC NORTHWEST APPEAR LIKELY TO CONTINUE SLOWLY INLAND DURING
THIS FORECAST PERIOD...AS AN UPSTREAM IMPULSE PROGRESSES ACROSS THE
NORTHEAST PACIFIC...TOWARD THE BRITISH COLUMBIA COAST. WITH
SUBTROPICAL RIDGING CURRENTLY PROMINENT ACROSS MUCH OF THE
INTERMOUNTAIN WEST/ROCKIES AND PLAINS...THE LEAD SYSTEM IS FORECAST
TO TURN NORTHEASTWARD AROUND ITS CREST...ACROSS THE CANADIAN AND
NORTHERN U.S. ROCKIES...INTO ALBERTA AND SASKATCHEWAN. MODELS
SUGGEST THAT SUBSTANTIVE MID-LEVEL HEIGHT FALLS WILL GENERALLY BE
CONFINED TO MONTANA AND PORTIONS OF THE DAKOTAS...WITH ONLY MINOR
WEAKENING OF THE SUBTROPICAL HIGH...ALTHOUGH ITS CENTER MAY SHIFT
SOUTHEAST OF THE CENTRAL ROCKIES INTO THE SOUTHERN HIGH PLAINS.
OTHERWISE...LITTLE CHANGE TO THE LARGE-SCALE UPPER PATTERN IS
EXPECTED...WITH AMPLIFIED TROUGHING PERSISTING EAST OF THE
MISSISSIPPI VALLEY THROUGH THE ATLANTIC SEABOARD. THE LEADING EDGE
OF LOW-LEVEL COOLING/DRYING ASSOCIATED WITH THIS FEATURE IS EXPECTED
TO ADVANCE SOUTHEAST OF THE OHIO VALLEY INTO THE SOUTH ATLANTIC AND
GULF COAST STATES. AT THE SAME TIME...A SOUTHERLY RETURN FLOW WILL
CONTRIBUTE MOISTENING ACROSS THE CENTRAL INTO NORTHERN
PLAINS...AHEAD OF THE NORTHWESTERN UPPER TROUGHING. HOWEVER...THIS
IS GENERALLY EXPECTED TO OCCUR BENEATH VERY WARM AND CAPPING
ELEVATED MIXED LAYER AIR ADVECTING NORTHEAST AND EAST OF THE
NORTHERN AND CENTRAL ROCKIES.
HIGHEST PROBABILITIES FOR THUNDERSTORMS DURING THIS PERIOD APPEAR TO
EXIST AHEAD OF THE FRONT...ACROSS THE SOUTHEASTERN U.S...AS WELL AS
WITHIN A PLUME OF MONSOONAL MOISTURE FROM THE SOUTHERN PLATEAU
THROUGH THE CENTRAL ROCKIES. BUT AT LEAST SCATTERED THUNDERSTORM
ACTIVITY IS EXPECTED WITHIN A LOWER/MID TROPOSPHERIC WARM ADVECTION
REGIME DEVELOPING NORTHEAST OF THE MID MISSOURI VALLEY...AS WELL AS
AHEAD OF A COLD FRONT ADVANCING INTO THE WESTERN DAKOTAS BY LATE
TONIGHT.
...NORTHERN AND CENTRAL PLAINS...
STRONGER MID-LEVEL HEIGHT FALLS ARE NOT EXPECTED TO REACH EASTERN
MONTANA AND THE WESTERN DAKOTAS UNTIL AT LEAST LATE THIS
AFTERNOON...PERHAPS THIS EVENING. AND VERY WARM ELEVATED MIXED
LAYER AIR PROBABLY WILL SUPPRESS VIGOROUS CONVECTIVE DEVELOPMENT
WITHIN THE CORRIDOR OF HIGHER BOUNDARY LAYER MOISTURE CONTENT ALONG
THE PRE-FRONTAL SURFACE TROUGH ACROSS THE REGION. HOWEVER...THE
VERY STEEP MID-LEVEL LAPSE RATES ASSOCIATED WITH THIS AIR MASS WILL
CONTRIBUTE TO SIZABLE CAPE...AND A RATHER BROAD AREA WITH AT LEAST A
CONDITIONAL RISK FOR SEVERE STORMS.
IT CURRENTLY APPEARS THAT...THROUGH MUCH OF THE AFTERNOON
HOURS...ANY THUNDERSTORM ACTIVITY WILL BE WIDELY SCATTERED IN
NATURE. ACTIVITY PROBABLY WILL FORM ACROSS THE HIGHER TERRAIN
NEAR/WEST OF THE NORTH CENTRAL HIGH PLAINS...IN RESPONSE TO DAYTIME
HEATING AND OROGRAPHIC FORCING. BUT ISOLATED/WIDELY SCATTERED STORM
DEVELOPMENT MAY NOT BE OUT OF THE QUESTION WITHIN A ZONE OF ENHANCED
LOWER/MID TROPOSPHERIC WARM ADVECTION...NEAR A SOUTHERLY 850 MB
JET...ON THE EASTERN EDGE OF THE ELEVATED MIXED LAYER AIR ACROSS THE
EASTERN DAKOTAS INTO MINNESOTA/IOWA.
OTHERWISE...IT APPEARS POSSIBLE THAT FORCING ALONG/AHEAD OF AN
EASTWARD ADVANCING COLD FRONT COULD SUPPORT STORM INITIATION ACROSS
PARTS OF EASTERN MONTANA AS EARLY AS 21-23Z. ALTHOUGH THE STRONGER
MID/UPPER FLOW ASSOCIATED WITH THE APPROACHING UPPER TROUGH MAY LAG
TO THE WEST OF THE FRONT...PRE-FRONTAL VERTICAL SHEAR ACROSS EASTERN
MONTANA INTO NORTH DAKOTA STILL APPEARS SUFFICIENT FOR ORGANIZED
CONVECTIVE DEVELOPMENT...INCLUDING SUPERCELLS...GIVEN EXPECTED MIXED
LAYER CAPE OF 2000-3000+ J/KG.
THE EVOLUTION OF A MESOSCALE CONVECTIVE SYSTEM CAPABLE OF PRODUCING
ONE OR TWO SWATHS OF POTENTIALLY DAMAGING WIND GUSTS SEEMS AT LEAST
A POSSIBILITY AS UPPER FORCING SPREADS EASTWARD INTO THE NORTHERN
PLAINS THIS EVENING.
...CNTRL/SRN APPALACHIANS INTO SRN MID ATLANTIC COAST REGION...
WEAK LOWER/MID TROPOSPHERIC LAPSE RATES PROBABLY WILL LIMIT CAPE
ALONG/AHEAD OF THE SOUTHWARD ADVANCING FRONTAL ZONE TODAY.
HOWEVER...IN THE PRESENCE OF SEASONABLY HIGH MOISTURE
CONTENT...MODEST WESTERLY MID-LEVEL FLOW MAY ENHANCE CONVECTIVE
DEVELOPMENT...SUPPORTING AT LEAST LOW PROBABILITIES FOR STORMS
CAPABLE OF PRODUCING POTENTIALLY DAMAGING WIND GUSTS.
..KERR/DIAL.. 07/24/2014
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SPC 0600Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT THU JUL 24 2014
VALID 251200Z - 261200Z
...NO SVR TSTM AREAS FORECAST...
...SUMMARY...
ISOLATED SEVERE STORMS WILL BE POSSIBLE OVER PARTS OF THE UPPER
MIDWEST TO CENTRAL HIGH PLAINS.
...SYNOPSIS...
A VIGOROUS MID-LEVEL CYCLONE IN THE LEE OF THE CANADIAN SRN ROCKIES
SHOULD GRADUALLY SHIFT E TO THE SRN SK/MB BORDER AREA BY EARLY SAT.
THIS WILL EFFECTIVELY DAMPEN THE NRN PLAINS/UPPER MIDWEST
RIDGE...TRANSITIONING TO A ZONAL FLOW REGIME WITH A MID-LEVEL
ANTICYCLONE ANCHORED OVER NM. AT THE SURFACE...A THERMALLY-AIDED
CYCLONE SHOULD BE INDUCED OVER THE LOWER MO VALLEY WITH A WARM FRONT
EXTENDING SE TO THE MID-MS VALLEY. TRAILING QUASI-STATIONARY FRONT
WILL ARC W TO THE CNTRL HIGH PLAINS WHERE LEE CYCLOGENESIS WILL
OCCUR.
...CNTRL HIGH PLAINS...
GUIDANCE DIFFERS WITH THE DEGREE OF CYCLOGENESIS INVOF SE WY FRI
AFTERNOON. THE DEEPER NAM TENDS TO FAVOR GREATER LOW-LEVEL MOISTURE
AND CONSEQUENTLY LARGER POTENTIAL BUOYANCY THAN OTHER GUIDANCE. THE
LACK OF APPRECIABLE UPSTREAM MID-LEVEL IMPULSES AND FARTHER S
MID-LEVEL JET RELATIVE TO OTHER GUIDANCE...RENDERS LOW CONFIDENCE IN
THIS SCENARIO. AT A MINIMUM...ISOLATED HIGH-BASED CONVECTION SHOULD
FORM ACROSS PARTS OF THE FRONT RANGE FRI AFTERNOON WHERE DEEP
INVERTED-V THERMODYNAMIC PROFILES AMIDST A TIGHT MID-LEVEL FLOW
GRADIENT WOULD SUPPORT LOCALIZED SEVERE WIND GUSTS. FRI
EVENING/NIGHT...LOW-LEVEL E/SELYS WILL STRENGTHEN YIELDING UPSLOPE
AND WAA THAT SHOULD RESULT IN A BAND OF ELEVATED CONVECTION
OVERNIGHT ACROSS PARTS OF SRN SD/NRN NEB. ALTHOUGH THE DEGREE OF
BUOYANCY IS UNCERTAIN...VERY STRONG CLOUD-BEARING SHEAR AND STEEP
MID-LEVEL LAPSE RATES WOULD FAVOR SEVERE HAIL PRODUCTION.
...LOWER MO AND MID/UPPER MS VALLEYS...
ROBUST LOW-LEVEL WAA SHOULD YIELD ELEVATED TSTM CLUSTERS CENTERED
OVER THE UPPER MS VALLEY AT 12Z/FRI...ALONG THE FRINGE OF A STOUT
PLAINS EML. THIS CONVECTION SHOULD SUBSIDE DURING THE DAY AS THE LLJ
WEAKENS. IN THE WAKE OF THIS ACTIVITY...PRONOUNCED CAPPING SHOULD
EXIST OVER MUCH OF THE WARM SECTOR WITH 700 MB TEMPERATURES OF 12-16
DEG C. DESPITE POTENTIAL FOR A VERY UNSTABLE AIR MASS...CONFIDENCE
IN SUSTAINING SURFACE-BASED TSTMS IS RATHER LOW. THE BEST PROSPECT
WOULD BE NEAR THE THERMAL LOW WHERE HOT SURFACE TEMPERATURES WILL
YIELD WEAKER INHIBITION AND SUFFICIENT CONVERGENCE MAY EXIST TO
INITIATE A STORM OR TWO. IF THIS OCCURS WITHIN THE PERIPHERY OF
MODERATE MID-LEVEL W/NWLYS...LARGE HAIL AND SEVERE WIND GUSTS WOULD
BE POSSIBLE. FARTHER E ACROSS PARTS OF THE MID/UPPER MS
VALLEY...ELEVATED STORMS SHOULD REDEVELOP FRI EVENING/NIGHT AS THE
LLJ STRENGTHENS. ON THE WRN PERIPHERY OF THIS DEVELOPMENT...STEEP
MID-LEVEL LAPSE RATES WOULD SUPPORT A RISK FOR MARGINALLY SEVERE
HAIL.
...NRN MN...
COOLER 700 MB TEMPERATURES RELATIVE TO AREAS FARTHER S SHOULD RESULT
IN MINIMAL INHIBITION AT PEAK HEATING. A MODERATELY FAVORABLE
COMBINATION OF INSTABILITY/SHEAR WOULD SUPPORT A RISK FOR AT LEAST
MARGINALLY SEVERE HAIL/WIND. HOWEVER...LOW-LEVEL FLOW WILL BE ANEMIC
WITH CONVERGENCE ALONG A COLD FRONT EXPECTED TO BE WEAK. CONFIDENCE
IS LOW IN THE DEVELOPMENT OF MORE THAN A COUPLE OF SURFACE-BASED
STORMS.
..GRAMS.. 07/24/2014
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