SPC

DY1 SWODY1 12:51Z

0

VALID 190100Z – 191200Z

…THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO WRN
NY…

…UPPER MS VALLEY TO LAKE WESTERN NY…

CONSIDERABLE VEERING AND WEAK LOW LEVEL CONVERGENCE APPEAR TO BE
PARTLY RESPONSIBLE FOR LACK OF STRONG CONVECTION ACROSS THE UPPER MS
VALLEY THIS EVENING. ORGANIZED DEEP CONVECTION HAS STRUGGLED TO
INTENSIFY AHEAD OF WEAK SFC LOW OVER THE ARROWHEAD OF MN BUT
APPROACHING SHORT-WAVE TROUGH IS EXPECTED TO AID DEVELOPMENT LATER
THIS EVENING NEAR THE CANADIAN BORDER.

HAVE OPTED TO LOWER SEVERE PROBS ACROSS MN/WI DUE TO THE STRUGGLING
NATURE OF THIS CONVECTION BUT TSTMS ARE STILL ANTICIPATED TO DEVELOP
SWWD ALONG THE COLD FRONT WHICH SHOULD THEN SPREAD EAST ACROSS THE
U.P. OF MI LATE TONIGHT.

DOWNSTREAM…A WELL ORGANIZED BAND OF TSTMS HAVE EVOLVED WITHIN WEAK
WARM ADVECTION ZONE ACROSS THE ERN U.P. INTO ONTARIO. THIS ACTIVITY
IS SPREADING SEWD AT ROUGHLY 35KT AND IF CONVECTION CAN REMAIN
ORGANIZED IT MAY SPREAD ACROSS LAKE ONTARIO INTO WRN NY AROUND
SUNRISE.

00Z SOUNDINGS ACROSS THE UPPER MS VALLEY INTO NRN LOWER MI REMAIN
FAVORABLE FOR MAINTENANCE OF ANY ORGANIZED BANDS OF CONVECTION THAT
EVOLVE ALONG/AHEAD OF COLD FRONT…THUS DAMAGING WINDS MAY BE THE
GREATEST SEVERE THREAT THE REST OF THE PERIOD.

..DARROW.. 07/19/2013

Mesoscale discussion

0

Severe Storm Outlook Narrative for Wrn-Nwrn Nv / Far Sern Oregon / Far Swrn Id concerning SEVERE POTENTIAL…WATCH UNLIKELY

Mesoscale discussion

0

Severe Storm Outlook Narrative for S-Cntrl/Sern Mt concerning SEVERE POTENTIAL…WATCH UNLIKELY

DY1 SWODY1 07:42Z

0

VALID 042000Z – 051200Z

…NO SVR TSTM AREAS FORECAST…

NO CHANGES WERE REQUIRED TO THE PREVIOUS OUTLOOK FOR THE MAJORITY OF
THE CONUS…THE EXCEPTION BEING NV.

…SIERRA INTO NWRN NV…
A WEAK SHORTWAVE TROUGH IS NOW MOVING ACROSS NRN CA AND INTO NW NV
WHICH IS PROVIDING COOLING ALOFT AS WELL AS ENHANCING SHEAR PROFILES
LOCALLY. STORMS WERE BEGINNING TO FORM OVER THE SIERRA AS WELL AS
OVER NRN CA INTO NWRN NV WITH PWAT AROUND 1.00 INCH. WITH CONTINUED
HEATING…STORMS WILL INCREASE IN COVERAGE…AND SHOULD PROPAGATE
GENERALLY IN AN EWD DIRECTION. DOWNDRAFTS WILL LIKELY BE COLD WITH
SOME HAIL POSSIBLE…WHICH WILL FURTHER HELP TO PRODUCE STRONG
OUTFLOW AND PERHAPS AN ISOLATED SEVERE GUST.

..JEWELL.. 07/04/2013

.PREV DISCUSSION… /ISSUED 1126 AM CDT THU JUL 04 2013/

…SYNOPSIS…

LITTLE CHANGE TO THE LARGE-SCALE PATTERN IS FORECAST THROUGH THE D1
PERIOD WITH A RIDGE-TROUGH-RIDGE CONFIGURATION EXTENDING FROM THE
SWRN DESERTS TO WRN ATLANTIC. SOME LOWERING OF MIDLEVEL HEIGHTS
WILL OCCUR OVER THE PACIFIC NW INTO NRN INTERMOUNTAIN REGION IN
CONJUNCTION WITH A POLAR-BRANCH SHORT-WAVE TROUGH MOVING ONSHORE.
IN THE LOW LEVELS…A BAROCLINIC ZONE /REINFORCED BY CLOUDS AND
PRECIPITATION/ WILL REMAIN QUASI STATIONARY FROM THE CNTRL GULF
COAST TO LOWER GREAT LAKES WHILE FARTHER TO THE W…A WEAK COLD
FRONT EDGES EWD TOWARD THE UPPER MS VALLEY.

…CNTRL/ERN GULF COAST STATES INTO TN VALLEY TODAY/TONIGHT…

A VORTICITY MAXIMUM OVER THE LOWER MS VALLEY WILL PROGRESS NNEWD
TODAY INDUCING A WEAK FRONTAL WAVE AND ENHANCING DEEP-LAYER ASCENT
ACROSS A VERY MOIST BUT ONLY WEAKLY UNSTABLE WARM SECTOR. THE NET
RESULT WILL BE A GRADUAL INCREASE IN TSTMS WITHIN THE WARM CONVEYOR
AIR STREAM ASSOCIATED WITH THE LARGE-SCALE TROUGH. LOW-LEVEL SHEAR
SHOULD CONTINUE TO STRENGTHEN WITH THE DEVELOPMENT OF A 35-45 KT LLJ
FROM ERN AL/WRN GA INTO MIDDLE/ERN TN. GIVEN THE VERY MOIST/LOW LCL
PBL…THE POTENTIAL WILL EXIST FOR EMBEDDED SUPERCELL STRUCTURES
WITH A RISK FOR A BRIEF TORNADO OR TWO IN ADDITION TO LOCALLY
DAMAGING WIND GUSTS. THE MARGINAL INSTABILITY IS EXPECTED TO
PRECLUDE A MORE ROBUST SEVERE WEATHER THREAT.

…UPPER OH VALLEY INTO NEW ENGLAND THIS AFTERNOON/EVENING…

BREAKS IN THE CLOUDS MAY ALLOW FOR STRONGER DAYTIME HEATING THAN
POINTS TO THE SOUTH WHICH WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS
IN THE UPPER 60S TO LOWER 70S WILL CONTRIBUTE TO AFTERNOON MLCAPE
VALUES OF 1000-2000 J/KG. THE WRN/NRN BOUNDS OF THIS INSTABILITY
AXIS WILL COINCIDE WITH A RIBBON OF ENHANCED MIDLEVEL FLOW /I.E.
40-45 KT AT 500 MB/…RESULTING IN A POTENTIAL CORRIDOR FOR
ORGANIZED STORM DEVELOPMENT WITH A RISK FOR ISOLATED DAMAGING
WINDS…HAIL…AND PERHAPS A TORNADO. THE PRIMARY UNCERTAINTY IS
THE COVERAGE/LONGEVITY OF ANY TSTM ACTIVITY OWING TO THE TENDENCY
FOR MIDLEVEL DRYING/SUBSIDENCE PER MORNING WATER VAPOR IMAGERY.

…NRN HIGH PLAINS THIS AFTERNOON/EVENING…

THE EWD PROGRESSION OF THE ABOVE-MENTIONED POLAR-BRANCH SHORT-WAVE
TROUGH INTO THE PACIFIC NW AND BRITISH COLUMBIA WILL INDUCE A LEE
CYCLONE/TROUGH OVER WRN/CNTRL MT LATER TODAY. THE 12Z GREAT FALLS
SOUNDING SHOWED THE PRESENCE OF A MOIST LOW-LEVEL AIR MASS WHICH
WILL COMPENSATE FOR MIDLEVEL LAPSE RATES OF GENERALLY LESS THAN 7
C/KM TO YIELD A MODERATELY UNSTABLE ENVIRONMENT BY AFTERNOON. WHILE
STRONGER FORCING FOR ASCENT ASSOCIATED WITH THE SHORT-WAVE TROUGH
WILL REMAIN TO THE WEST OF THE REGION THROUGH THE PEAK OF THE
DIURNAL HEATING CYCLE…LOW-LEVEL CONVERGENCE INVOF THE LEE
CYCLONE/TROUGH WILL FOSTER ISOLATED STORM DEVELOPMENT BY MID TO LATE
AFTERNOON WITH A RISK FOR LOCALLY DAMAGING WINDS AND/OR LARGE HAIL.

…SERN AZ INTO SRN ROCKIES AND SRN HIGH PLAINS…

HEATING ALONG THE HIGH TERRAIN WILL FOSTER SCATTERED STORM
DEVELOPMENT THIS AFTERNOON WITHIN A SIMILAR ENVIRONMENT TO PAST
DAYS. THE STRONGEST STORMS WILL BE CAPABLE OF ISOLATED OCCURRENCES
OF LARGE HAIL AND DAMAGING WINDS THROUGH THIS EVENING.

DY1 SWODY1 04:29Z

0

VALID 041630Z – 051200Z

…NO SVR TSTM AREAS FORECAST…

…SYNOPSIS…

LITTLE CHANGE TO THE LARGE-SCALE PATTERN IS FORECAST THROUGH THE D1
PERIOD WITH A RIDGE-TROUGH-RIDGE CONFIGURATION EXTENDING FROM THE
SWRN DESERTS TO WRN ATLANTIC. SOME LOWERING OF MIDLEVEL HEIGHTS
WILL OCCUR OVER THE PACIFIC NW INTO NRN INTERMOUNTAIN REGION IN
CONJUNCTION WITH A POLAR-BRANCH SHORT-WAVE TROUGH MOVING ONSHORE.
IN THE LOW LEVELS…A BAROCLINIC ZONE /REINFORCED BY CLOUDS AND
PRECIPITATION/ WILL REMAIN QUASI STATIONARY FROM THE CNTRL GULF
COAST TO LOWER GREAT LAKES WHILE FARTHER TO THE W…A WEAK COLD
FRONT EDGES EWD TOWARD THE UPPER MS VALLEY.

…CNTRL/ERN GULF COAST STATES INTO TN VALLEY TODAY/TONIGHT…

A VORTICITY MAXIMUM OVER THE LOWER MS VALLEY WILL PROGRESS NNEWD
TODAY INDUCING A WEAK FRONTAL WAVE AND ENHANCING DEEP-LAYER ASCENT
ACROSS A VERY MOIST BUT ONLY WEAKLY UNSTABLE WARM SECTOR. THE NET
RESULT WILL BE A GRADUAL INCREASE IN TSTMS WITHIN THE WARM CONVEYOR
AIR STREAM ASSOCIATED WITH THE LARGE-SCALE TROUGH. LOW-LEVEL SHEAR
SHOULD CONTINUE TO STRENGTHEN WITH THE DEVELOPMENT OF A 35-45 KT LLJ
FROM ERN AL/WRN GA INTO MIDDLE/ERN TN. GIVEN THE VERY MOIST/LOW LCL
PBL…THE POTENTIAL WILL EXIST FOR EMBEDDED SUPERCELL STRUCTURES
WITH A RISK FOR A BRIEF TORNADO OR TWO IN ADDITION TO LOCALLY
DAMAGING WIND GUSTS. THE MARGINAL INSTABILITY IS EXPECTED TO
PRECLUDE A MORE ROBUST SEVERE WEATHER THREAT.

…UPPER OH VALLEY INTO NEW ENGLAND THIS AFTERNOON/EVENING…

BREAKS IN THE CLOUDS MAY ALLOW FOR STRONGER DAYTIME HEATING THAN
POINTS TO THE SOUTH WHICH WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS
IN THE UPPER 60S TO LOWER 70S WILL CONTRIBUTE TO AFTERNOON MLCAPE
VALUES OF 1000-2000 J/KG. THE WRN/NRN BOUNDS OF THIS INSTABILITY
AXIS WILL COINCIDE WITH A RIBBON OF ENHANCED MIDLEVEL FLOW /I.E.
40-45 KT AT 500 MB/…RESULTING IN A POTENTIAL CORRIDOR FOR
ORGANIZED STORM DEVELOPMENT WITH A RISK FOR ISOLATED DAMAGING
WINDS…HAIL…AND PERHAPS A TORNADO. THE PRIMARY UNCERTAINTY IS
THE COVERAGE/LONGEVITY OF ANY TSTM ACTIVITY OWING TO THE TENDENCY
FOR MIDLEVEL DRYING/SUBSIDENCE PER MORNING WATER VAPOR IMAGERY.

…NRN HIGH PLAINS THIS AFTERNOON/EVENING…

THE EWD PROGRESSION OF THE ABOVE-MENTIONED POLAR-BRANCH SHORT-WAVE
TROUGH INTO THE PACIFIC NW AND BRITISH COLUMBIA WILL INDUCE A LEE
CYCLONE/TROUGH OVER WRN/CNTRL MT LATER TODAY. THE 12Z GREAT FALLS
SOUNDING SHOWED THE PRESENCE OF A MOIST LOW-LEVEL AIR MASS WHICH
WILL COMPENSATE FOR MIDLEVEL LAPSE RATES OF GENERALLY LESS THAN 7
C/KM TO YIELD A MODERATELY UNSTABLE ENVIRONMENT BY AFTERNOON. WHILE
STRONGER FORCING FOR ASCENT ASSOCIATED WITH THE SHORT-WAVE TROUGH
WILL REMAIN TO THE WEST OF THE REGION THROUGH THE PEAK OF THE
DIURNAL HEATING CYCLE…LOW-LEVEL CONVERGENCE INVOF THE LEE
CYCLONE/TROUGH WILL FOSTER ISOLATED STORM DEVELOPMENT BY MID TO LATE
AFTERNOON WITH A RISK FOR LOCALLY DAMAGING WINDS AND/OR LARGE HAIL.

…SERN AZ INTO SRN ROCKIES AND SRN HIGH PLAINS…

HEATING ALONG THE HIGH TERRAIN WILL FOSTER SCATTERED STORM
DEVELOPMENT THIS AFTERNOON WITHIN A SIMILAR ENVIRONMENT TO PAST
DAYS. THE STRONGEST STORMS WILL BE CAPABLE OF ISOLATED OCCURRENCES
OF LARGE HAIL AND DAMAGING WINDS THROUGH THIS EVENING.

..MEAD/PETERS.. 07/04/2013

DY1 SWODY1 12:54Z

0

VALID 041300Z – 051200Z

…NO SVR TSTM AREAS FORECAST…

…SYNOPSIS…
PATTERN WILL REMAIN AMPLIFIED ACROSS THE LWR 48 THROUGH EARLY
FRI…BUT THERE WILL BE SOME CHANGES. THE GRT BASIN RIDGE SHOULD
CONTINUE TO RETREAT SWD AS A SERIES OF IMPULSES IN THE WLYS LOWER
HEIGHTS ACROSS SW CANADA AND THE PACIFIC NW. FARTHER E…EXPECT
CNTRL U.S. UPR TROUGH/LOW TO GRADUALLY WEAKEN WHILE REMAINING NEARLY
STNRY OR DRIFTING SLIGHTLY E. AT THE SAME TIME…SATELLITE INDICATES
THAT RETROGRESSION OF THE WRN ATLANTIC RIDGE HAS ENDED. THE SYSTEM
WILL…HOWEVER…REMAIN STRONG AND MAINTAIN EXISTING TIGHT HEIGHT
GRADIENT ACROSS THE ERN U.S.

AT LWR LVLS…WEAK FRONT/INVERTED TROUGH FROM THE CNTRL GULF CST TO
THE MID-OH VLY SHOULD BECOME INCREASINGLY DIFFUSE TODAY AS WEAK LOW
PRESSURE NOW IN THE N CNTRL GULF ADVANCES NNE ALONG IT.
ELSEWHERE…ERN PART OF COLD FRONT OVER THE NRN PLNS SHOULD WEAKEN
WHILE WRN PART STALLS OVER SRN/WRN MT IN RESPONSE TO LEE TROUGHING
AHEAD OF APPROACHING PACIFIC SHORTWAVE IMPULSE.

…ERN GULF CST NNE TO LWR GRT LKS/NORTHEAST TODAY…
SEASONABLY STRONG HEIGHT GRADIENT WILL PERSIST ALONG AN ARC FROM THE
NERN GULF OF MEXICO NNE ALONG THE APPALACHIANS INTO THE UPR OH
VLY…LWR GRT LKS…AND THE NORTHEAST THROUGH TNGT. COINCIDENT WITH
THIS FLOW WILL BE A PLUME OF DEEP…MOISTURE-RICH AIR….WITH PW AOA
2 INCHES FROM ERN KY SWD TO THE GULF…AND AROUND 1.75 INCHES FROM
OH INTO NEW ENGLAND.

WITH WIDESPREAD CLOUD COVER/SHOWERS ALREADY IN PLACE FROM MUCH OF OH
SSW TO THE ERN GULF CST…SFC HEATING WILL BE MINIMAL. BUT GIVEN
MOISTURE-RICH ENVIRONMENT AND STRONG MEAN FLOW…SETUP COULD YIELD
OCCASIONAL POCKETS OF LOW-TOPPED CONVECTION/STORMS POSING A RISK FOR
ISOLD PRECIP-ENHANCED WIND GUSTS. AND…GIVEN FRICTIONALLY-DRIVEN
BACKING OF LOW-LVL FLOW…A RISK ALSO WILL EXIST FOR ISOLD
TORNADOES. THIS RISK MAY BE GREATEST OVER THE FL PANHANDLE AND CSTL
BEND…WHERE THE GREATEST LOW-LVL BUOYANCY SHOULD EXIST AND WHERE
APPROACH OF WEAK SFC WAVE FROM THE N CNTRL GULF WILL MAXIMIZE SELY
LOW-LVL WINDS.

SATELLITE SUGGESTS THAT SFC HEATING WILL BE SOMEWHAT GREATER FARTHER
NE…FROM WV AND WRN MD NEWD THROUGH PA/NY INTO NEW ENGLAND.
ANTICYCLONIC NATURE OF LARGE-SCALE FLOW WILL KEEP FORCING FOR ASCENT
LIMITED…AND LOW-LVL FLOW WILL BE WEAK. BUT SUBSTANTIAL /30-40 KT/
DEEP…SWLY MID-LVL WINDS IN THE PRESENCE OF EVEN MODERATE SFC
HEATING COULD PROMOTE THE DEVELOPMENT OF ISOLD SMALL-SCALE BOWING
SEGMENTS WITH LOCALLY DMGG WIND AND PERHAPS A TORNADO. SUCH A THREAT
SHOULD BE GREATEST WITH ANY SUSTAINED STORMS THAT DO
FORM…ESPECIALLY FROM UPSTATE NY INTO ME THIS AFTN THROUGH EARLY
TNGT.

…SW U.S. THIS AFTN/EVE…
SWD SHIFT OF GRT BASIN RIDGE INTO AZ WILL RESULT IN DIMINISHED NLY
FLOW OVER THE SRN RCKYS AND FOUR CORNERS REGION RELATIVE TO RECENT
DAYS…WITH MINIMAL CHANGE IN MOISTURE. NEVERTHELESS…SFC
HEATING/TERRAIN CIRCULATIONS SHOULD FOSTER ANOTHER ROUND OF
SCTD STRONG TO LOCALLY SVR AFTN/EVE STORMS OVER THE HIGHER
ELEVATIONS OF NM AND THE AZ RIM COUNTRY. AS THESE STORMS
MOVE/DEVELOP MAINLY S OR SWWD…POTENTIAL WILL EXIST FOR
ISOLD HAIL AND A FEW DMGG WIND GUSTS GIVEN 1000-1500 J/KG MLCAPE
AMIDST A DEEP…WELL-MIXED BOUNDARY LAYER. THE STRONGEST/MOST
SUSTAINED STORMS SHOULD OCCUR OVER CNTRL/SRN NM AND PERHAPS FAR W
TX…WHERE 20+ KT NLY 500 MB FLOW WILL CONTRIBUTE TO
35+ KT DEEP SHEAR.

…MT THIS AFTN/EVE…
ISOLD TO WDLY SCTD TSTMS SHOULD FORM NEAR STALLED FRONT OVER SRN/WRN
MT THIS AFTN…AND OVER THE HIGHER TERRAIN. WITH SFC DEW POINTS
MAINLY IN THE UPR 50S TO MID 60S F AND MODERATELY STEEP MID-LVL
LAPSE RATES…SFC HEATING SHOULD YIELD 500-1500 J/KG MLCAPE. LOW-LVL
WINDS WILL REMAIN WEAK…BUT 30+ KT WLY 500 MB FLOW WILL PROVIDE
AMPLE DEEP SHEAR FOR ORGANIZED/SUSTAINED STORMS. LARGE-SCALE FORCING
WILL BE MODEST EVEN AFTER ARRIVAL OF LEAD UPR IMPULSE /NOW IN WA/
INTO W CNTRL MT LATE IN THE DAY. WHILE STORM COVERAGE LIKELY WILL
REMAIN LIMITED…A CONDITIONAL RISK FOR SVR HAIL/WIND WILL
EXIST…ESPECIALLY FROM MID-LATE AFTN THROUGH EARLY EVE.

..CORFIDI/MOSIER.. 07/04/2013

DY1 SWODY1 06:02Z

0

VALID 041200Z – 051200Z

…NO SVR TSTM AREAS FORECAST…

…SYNOPSIS…
HIGHLY AMPLIFIED UPPER-AIR PATTERN WILL PERSIST ACROSS
CONUS…CENTERED UPON QUASISTATIONARY TROUGHING FROM LS SSWWD ACROSS
MO TO WRN GULF OF MEXICO. EMBEDDED MID-UPPER LOW — NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY OVER KS/MO BORDER REGION — SHOULD FILL
VERY SLIGHTLY WHILE DRIFTING VERY SLOWLY EWD OR NEWD ACROSS WRN MO
THROUGH PERIOD. MEANWHILE…LARGE BERMUDA-HIGH REGIME WILL REMAIN
ANCHORED OVER ATLC. FARTHER W…PERSISTENT ANTICYCLONE INITIALLY
OVER NV SHOULD BE SHUNTED SOMEWHAT SEWD ACROSS AZ…AS HEIGHTS FALL
OVER NWRN CONUS IN ADVANCE OF TROUGH NOW OFFSHORE BC.

AT SFC…REMNANTS OF OLD BAROCLINIC ZONE FROM LOWER GREAT LAKES TO
SRN MS DELTA REGION WILL BECOME MORE DIFFUSE…AS ASSOCIATED THETAE
GRADIENT LOOSENS AND RICH MOISTURE TO ITS E BEGINS TO SHIFT SLOWLY
WWD OVER MS VALLEY AND S TX. WRN SEGMENT OF WEAK COLD FRONT — NOW
OVER EXTREME NWRN ND AND ERN MT — SHOULD STALL OVER
S-CENTRAL/W-CENTRAL MT AS LEE TROUGHING OCCURS IN ADVANCE OF PAC
SHORTWAVE.

…ERN CONUS…
BUILDING OF HEIGHTS OVER ATLC WILL TIGHTEN GRADIENT ALOFT BETWEEN
CENTRAL CONUS TROUGHING AND ATLC ANTICYCLONE…RESULTING IN BROAD
FETCH OF SLIGHTLY STRENGTHENING/DEEP-TROPOSPHERIC FLOW WITH
SUBSTANTIAL SLY COMPONENT FROM NRN GULF ACROSS SRN APPALACHIANS TO
OH VALLEY. MOIST PLUME WILL BECOME SWLY TO WLY ACROSS LOWER GREAT
LAKES AND PORTIONS NEW ENGLAND. EMBEDDED WITHIN THIS
REGIME…SCATTERED TSTMS ARE EXPECTED THROUGHOUT PERIOD. AS
REFLECTED IN ENHANCED TSTM FCST…COVERAGE LIKELY WILL BE MORE
NUMEROUS AND DENSELY CLUSTERED ON MESOBETA SCALE DURING DAYTIME…AS
POCKETS OF SUBTLE DIABATIC HEATING OCCUR IN CLOUD/PRECIP BREAKS.
DAMAGING GUSTS MAY OCCUR FROM PRECIP-LOADING ENHANCED OUTFLOW IN
MOST INTENSE CELLS VIRTUALLY ANYWHERE WITHIN THIS CORRIDOR…WHILE
ISOLATED LARGE HAIL IS MORE PROBABLE FROM CENTRAL APPALACHIANS
REGION NEWD.

LOW-LEVEL SHEAR SHOULD BE RELATIVELY MAXIMIZED GENERALLY BETWEEN
04/18Z-05/06Z BENEATH 35-45 LLJ ACROSS PORTIONS E-CENTRAL GULF
COAST…GA/AL AND NWD TOWARD PORTIONS WV/OH/PA. FCST SOUNDINGS SHOW
ENLARGED 0-1 KM AGL HODOGRAPHS…THOUGH SHEAR VECTORS ASSUME
NEGATIVE VALUES FROM 850-500 MB. NONETHELESS…FAVORABLE LOW-LEVEL
WIND PROFILES COMBINED WITH VERY MOIST/LOW-LCL AIR MASS SUPPORTS
CONDITIONAL POTENTIAL. WITHIN RELATED CORRIDOR OF MRGL
UNCONDITIONAL PROBABILITIES…MESOSCALE FOCI FOR RELATIVELY ENHANCED
SRH/VORTICITY AND POSSIBLE CATEGORICAL ENHANCEMENT OF TORNADO RISK
ARE UNCERTAIN ATTM.

…SWRN CONUS…
ALTHOUGH MIDLEVEL WINDS SHOULD BE SOMEWHAT WEAKER THAN PREVIOUS
DAY…ANOTHER ROUND OF WIDELY SCATTERED TO SCATTERED AFTN TSTMS
SHOULD DEVELOP OVER PORTIONS NM AND MOVE SWD TO SWWD. POTENTIAL
EXISTS FOR ISOLATED HAIL NEAR SVR LEVELS AND A FEW DAMAGING
GUSTS…AS ACTIVITY MOVES ATOP WELL-MIXED SUBCLOUD LAYERS UNDERLYING
MLCAPE 1000-1500 J/KG…LOCALLY HIGHER. OVER 180 DEG OF VEERING
WITH HEIGHT IS FCST…WITH SLYS/SELYS AT SFC BENEATH NLY TO NNELY
FLOW AROUND UPPER 1/3 OF CAPE LAYER. EFFECTIVE SHEAR MAGNITUDES
40-45 KT THEREFORE ARE EVIDENT IN FCST SOUNDINGS DESPITE WEAK
LOW-MIDDLE LEVEL SPEEDS. POTENTIAL SHOULD DIMINISH MARKEDLY AFTER
ABOUT 04Z…AS AIR MASS STABILIZES FROM COMBINATION OF SFC DIABATIC
COOLING AND MAXIMIZED COVERAGE OF CONVECTIVE OUTFLOWS.

…MT…
ISOLATED TO WIDELY SCATTERED TSTMS SHOULD DEVELOP INVOF FRONTAL
ZONE…AND OVER SRN/WRN PORTIONS OF AREA…ALONG HIGHER TERRAIN. SFC
DEW POINTS RANGING FROM LOW 50S TO MID 60S F WILL UNDERLIE
MODERATELY STEEP MIDLEVEL LAPSE RATES…COMBINING WITH INSOLATION TO
YIELD MLCAPE IN 500-1500 J/KG RANGE. THOUGH WEAK LOW-LEVEL WINDS
ARE FCST OVER MOST OF THIS AREA…250-500 MB LAYER FLOW WILL BE
SUFFICIENT TO CONTRIBUTE TO AROUND 30-40 KT EFFECTIVE SHEAR
MAGNITUDES IN SUPPORT OF A FEW ORGANIZED TSTMS. MAIN CONCERN IS
HAIL/GUSTS NEAR SVR LIMITS BETWEEN MID-AFTN AND EARLY EVENING.

..EDWARDS.. 07/04/2013

DY1 SWODY1 01:01Z

0

VALID 040100Z – 041200Z

…THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NM…SERN AZ…FAR W
TX…

…SYNOPSIS…
ANOMALOUSLY HIGH-AMPLITUDE PATTERN PERSISTS OVER CONUS…WITH
MID-UPPER LOW INVOF MKC ANCHORING DEEP/QUASISTATIONARY SYNOPTIC
TROUGH THAT EXTENDS FROM LS TO LOWER TX COAST AND SWRN GULF OF
MEXICO. ASSOCIATED CYCLONIC FLOW IS FLANKED BY STG RIDGING FROM
ATLC BERMUDA HIGH…AND FROM SMALLER BUT STILL STG ANTICYCLONE
CENTERED OVER S-CENTRAL/SWRN NV. LITTLE CHANGE IN OVERALL PATTERN
WILL TAKE PLACE THROUGH REMAINDER PERIOD…THOUGH WEAK HEIGHT FALLS
WILL OCCUR OVER PAC NW IN ADVANCE OF SHORTWAVE TROUGH NOW APCHG BC
COAST. VERY MINOR AND PROBABLY CONVECTIVELY GENERATED/ENHANCED
PERTURBATIONS SHOULD RIPPLE NWD ACROSS LOWER GREAT LAKES…OH VALLEY
AND SRN APPALACHIANS REGIONS…EMBEDDED WITHIN BROAD PLUME OF
DEEP-TROPOSPHERIC SLY FLOW.

SFC ANALYSIS AT 23Z SHOWED WAVY…REMNANT…FRONTOLYTIC…
QUASISTATIONARY BAROCLINIC ZONE FROM LOWER GREAT LAKES SSWWD ACROSS
CENTRAL KY AND MID TN TO SERN LA…THEN SWWD ACROSS SHELF WATERS
NEAR TX COAST. THIS BOUNDARY IS MANIFEST ANYMORE PRIMARILY BY WRN
FRINGE OF LOW-LEVEL MOISTURE PLUME…E OF WHICH DEW POINTS UPPER 60S
AND 70S F ARE VERY COMMON…AND W OF WHICH LOWER-THETAE CONTINENTAL
AIR MASS UNDERGOES GREATER NOCTURNAL-DIURNAL THERMAL OSCILLATIONS.
AS SUCH…AIR MASS WAS WARMER W OF FRONT…WITH CONSIDERABLE
CLOUDS/PRECIP TO ITS E HAVING LIMITED DIURNAL SFC WARMING.

…SRN ROCKIES/SRN HIGH PLAINS TO AZ…
SCATTERED TO WIDELY SCATTERED TSTMS…SOME SVR WITH AT LEAST
TRANSIENT SUPERCELLULAR CHARACTERISTICS…HAVE DEVELOPED OVER HIGHER
TERRAIN AND MOVED SWD TO SWWD AROUND SERN RIM OF NV ANTICYCLONE
ALOFT. TSTMS MAY MOVE INTO FAVORABLY MOIST/UNSTABLE BOUNDARY LAYERS
FOR A FEW MORE HOURS WITH RISK OF SVR GUSTS AND OCNL LARGE HAIL.
REF SPC WW 391 AND RELATED MESOSCALE DISCUSSIONS FOR LATEST
NEAR-TERM GUIDANCE. REF MESOSCALE DISCUSSION 1322 FOR INFORMATION
ON ADJOINING PORTIONS SERN AZ/SWRN NM. POTENTIAL BECOMES MORE
ISOLATED/CONDITIONAL FARTHER NW INVOF MOGOLLON RIM REGION.
OVERALL…SVR POTENTIAL ACROSS REGION SHOULD DIMINISH MARKEDLY BY
ABOUT 06Z…AS BOUNDARY LAYER BECOMES PROGRESSIVELY MORE STABLE DUE
TO COMBINATION OF SPREADING OUTFLOWS AND DIABATIC SFC COOLING.

…SERN CONUS…
LOOSELY ORGANIZED BANDS OF SCATTERED TO NUMEROUS TSTMS WILL CONTINUE
OVER PORTIONS TN VALLEY SWD TO MS/AL COASTAL PLAIN…AS WELL AS
ACTIVITY MOVING NWD TO NWWD ACROSS PORTIONS GA AND FL PANHANDLE.
ISOLATED DAMAGING GUSTS REMAIN POSSIBLE WHERE PRECIP-LOADING
ENHANCED DOWNBURSTS OCCUR…AND A TORNADO CANNOT BE RULED OUT
DEFINITIVELY GIVEN POCKETS OF AT LEAST MRGLLY FAVORABLE LOW-LEVEL
SHEAR. HOWEVER…SVR POTENTIAL IS LIMITED BY RELATIVELY
MESSY/CLUSTERED OR LINEAR STORM MODES…AS WELL AS INCREASING
COVERAGE OF PRECIP-STABILIZED AIR.

..EDWARDS.. 07/04/2013

Mesoscale discussion

0

Severe Storm Outlook Narrative for Sern Az..Extreme Swrn Nm concerning SEVERE POTENTIAL…WATCH POSSIBLE

Mesoscale discussion

0

Severe Storm Outlook Narrative for Cntrl-Srn-Ern Nm / Far Wrn Tx Panhandle concerning SEVERE POTENTIAL…WATCH POSSIBLE

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