Severe Thunderstorm Warning 18, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 PM EDT MON MAY 12 2014

.SHORT TERM...THROUGH TONIGHT

SOUTHEAST MICHIGAN NOW FIRMLY POSITIONED AT THE EDGE OF THE UPPER
RIDGE AXIS ANCHORED THROUGH THE CENTRAL OHIO VALLEY AND DEEPENING
SOUTHWEST FLOW WORKING DOWNSTREAM OF A SURFACE WAVE NOW LIFTING
NORTH THROUGH IOWA.  LARGE SCALE SETUP MAINTAINING A FAVORABLE
PATTERN FOR SUSTAINED LOW AND MID LEVEL MOISTURE TRANSPORT INTO SE
MICHIGAN TODAY.  THE BROADER ASCENT /AUGMENTED BY A WEAK WAVE/
WITHIN A RELATIVELY UNCAPPED WARM SECTOR ENVIRONMENT WITH MODESTLY
STEEP MID LEVEL LAPSE RATES PROVIDING THE BACKDROP FOR ADDITIONAL
CONVECTIVE DEVELOPMENT SOUTHWEST OF AND ACROSS THE WARM FRONT. WARM
FRONT MAKING CONSIDERABLY SLOWER PROGRESS NORTHEAST...THE RAIN
COOLED ENVIRONMENT SHROUDED WITH STRATUS TO THE NORTH FORTIFYING A
POSITION THAT CURRENTLY STILL EXTENDS FROM NEAR MONROE NORTHWEST TO
JUST WEST OF HOWELL.

SLIVER OF THE WARM SECTOR TO THE SOUTH REMAINS LARGELY UNMODIFIED
FROM THE ONGOING CONVECTION...GENERALLY FROM THE I-94 CORRIDOR
SOUTHWARD.  THE ELEVATED NEAR SURFACE MOISTURE CONTENT /DEWPTS
APPROACHING 70 IN SOME LOCALES/ WILL CONTRIBUTE TO AT LEAST A
MODESTLY UNSTABLE PROFILE.  RECENT SPC ANALYSIS SHOWS MLCAPE
APPROACHING THE 1000 J/KG RANGE.  THERE REMAINS AT LEAST A WINDOW
THROUGH THIS EVENING FOR THE THERMODYNAMIC PROFILE TO BECOME
SUPPORTIVE ENOUGH TO ALLOW FOR GREATER UPDRAFT DEVELOPMENT.  THE
WIND PROFILE THROUGH 6 KM NOT OVERLY IMPRESSIVE...BUT INCREASING
SLIGHTLY WITH TIME.  HOWEVER FAVORABLY LARGE 0-1 KM SHEAR AND
CORRESPONDING HIGHER LOW LEVEL HELICITY WILL EXIST...PARTICULARLY
CENTERED AT THE INTERFACE OF THE SURFACE WARM FRONT.  GIVEN
SUPPRESSED LCL HEIGHTS...THIS STILL POINTS TOWARD A PLAUSIBLE
SCENARIO WHERE ANY STRONGER CELLS COULD QUICKLY ATTAIN BETTER LOW
LEVEL ROTATION SHOULD IT WORK ACROSS THE WARM FRONTAL ZONE.  FOR
THIS REASON...WILL MAINTAIN A MENTION OF TORNADOES ALONG WITH A
WIND/HAIL RISK THROUGH THIS EVENING.   HIGH PWAT ENVIRONMENT WILL
ALSO CONTINUE TO TRANSLATE INTO SOME HIGHLY EFFICIENT RAINFALL
RATES.

&&

.LONG TERM...TUESDAY THROUGH NEXT MONDAY

WARM AND HUMID AIRMASS WILL REMAIN ENTRENCHED OVER SOUTHEAST
MICHIGAN AT THE START OF THE DAY TOMORROW...WITH THE WARM FRONT
LYING OVER NORTHERN MICHIGAN. MAIN AREA OF UPPER ENERGY WITHIN THE
TROUGH NOW OVER THE ROCKIES WILL LIFT UP INTO THE UPPER MIDWEST AND
ONTARIO TOMORROW AND TOMORROW NIGHT...SENDING A DEEPENING AREA OF
SURFACE LOW PRESSURE UP ACROSS WISCONSIN AND INTO ONTARIO. AS THIS
SYSTEM LIFTS NORTHEAST...IT WILL SEND A STRONG COLD FRONT ACROSS
SOUTHEAST MICHIGAN. TIMING ON THE FRONTAL PASSAGE ACROSS THE AREA
CURRENTLY LOOKS TO BE BETWEEN 20-02Z (4PM-10PM). HIGHER-RES MODELS
ARE HINTING A PRE-FRONTAL TROUGH MAY ALSO BE PRESENT...WHICH COULD
SERVE AS A TRIGGER FOR SHOWERS/TSTORMS A FEW HOURS AHEAD OF THE
FRONT. OTHERWISE...WOULD EXPECT A QUIETER START TO THE DAY BEFORE
THE FRONT BEGINS TO APPROACH AND CONVECTION PICKS UP FOR THE
AFTERNOON AND EVENING. OVERALL...EXPECTING A GOOD COVERAGE OF
SHOWERS/TSTORMS BY AFTERNOON/EVENING AND HAVE KEPT POPS IN THE
LIKELY CATEGORY. TEMPERATURES TOMORROW WILL AGAIN BE TRICKY WITH
CLOUD COVER AND CONVECTION...BUT WITH H850 TEMPS BETWEEN 14-16C WILL
KEEP MAX TEMPS WELL INTO THE 70S (NEAR 80 FAR SOUTHEAST MI).

MUCH LIKE TODAY...WILL HAVE TO SEE HOW MUCH INSTABILITY CAN BE
GENERATED FOR SEVERE POTENTIAL. MODELS SHOW CLOUD COVER CURRENTLY
ASSOCIATED WITH CONVECTION OVER ARKANSAS AND MISSOURI LIFTING UP
INTO MICHIGAN DURING THE EARLY MORNING HOURS...CUTTING BACK ON EARLY
DAY INSOLATION. MID-LEVEL LAPSE RATES BY AFTERNOON LOOK LESS STEEP
THAN TODAY...AND MAY ONLY SEE ABOUT 500-1000 J/KG OF SB CAPE BY THE
TIME THE FRONT BEGINS TO WORK THROUGH. STILL...WITH STRONG UPRIGHT
LIFT PROVIDED BY THE FRONT...FGEN...AND RIGHT ENTRANCE REGION
FORCING ALOFT COULD ALLOW A FEW SEVERE STORMS TO DEVELOP (HAIL/WIND
THREAT). MOST ACTIVITY SHOULD CLEAR THE AREA BY AROUND 10 PM AS THE
SURFACE FRONT PUSHES EAST...TAKING ON A NORTHEAST TO SOUTHWEST
ORIENTATION FROM SOUTHERN CANADA DOWN THROUGH SOUTHWEST ARKANSAS.

SOUTHERN STREAM ENERGY MOVING TOWARDS OHIO ON WEDNESDAY THEN LOOKS
TO PHASE WITH ENERGY DIVING DOWN INTO THE MIDWEST FROM NORTHERN
CANADA...RESULTING IN THE FORMATION OF A BROAD CLOSED UPPER LOW OVER
THE GREAT LAKES BY EARLY THURSDAY. AS THE SOUTHERN STREAM ENERGY
LIFTS UP TOWARDS THE OHIO VALLEY...THE PORTION OF THE FRONTAL
BOUNDARY OVER ARKANSAS WILL LIFT UP INTO MICHIGAN EARLY WEDNESDAY
THROUGH WEDNESDAY NIGHT. THIS SHOULD PROVIDE A GOOD CHANCE OF RAIN
FOR SOUTHEAST MICHIGAN...ALTHOUGH THE WESTWARD EXTENT OF THE
PRECIPITATION SHIELD IS STILL A LITTLE UNCERTAIN. MAIN STORY FOR
WEDNESDAY OVERALL WILL BE COOLER AND WETTER.

THE FORECAST FOR THURSDAY IS STILL NOT AT A FINE RESOLUTION DUE TO
MODEL DISCREPANCIES...BUT THERE IS ENOUGH CONFIDENCE TO BRING POPS
INTO THE HIGH LIKELY CATEGORY. LOW PRESSURE IS STILL PROGGED TO BE
ENHANCED BY RIGHT ENTRANCE DYNAMICS OF A 135KT SOUTH TO NORTH JET IN
THE GREAT LAKES REGION. THE LOW WILL RIDE THE BAROCLINIC ZONE AS
500MB HEIGHTS DROP 12 TO 15 DAM IN 24 HOURS IN MICHIGAN. THE UPPER
LOW WILL BECOME CLOSED AND CUTOFF FROM THE OVERALL FLOW WHICH
INCREASES CONFIDENCE IN THE COOL TEMPERATURE FORECAST. SURFACE HIGH
PRESSURE AND H85 TEMPS NEAR 0C WILL MAKE FOR SOME COOL DAYS AND A
THREAT FOR PATCHY FROST AT NIGHT. AGAIN...DAYTIME MIXING INTO STEEP
LAPSE RATES WILL ALLOW FOR AFTERNOON CU AND ISOLATED SHOWERS DURING
MOST OF THE EXTENDED FORECAST.

&&

.MARINE...

AREAS OF FOG REMAIN POSSIBLE OVER LAKE HURON TONIGHT AND TOMORROW AS
VERY WARM AIR LIFTS UP ACROSS THE COLD WATERS. A LOW PRESSURE SYSTEM
LIFTING NORTHEAST OF THE AREA WILL CONTINUE TO BRING ROUNDS OF
SHOWERS AND THUNDERSTORMS TO THE AREA THROUGH TUESDAY NIGHT. THE
BEST POTENTIAL WILL BE THIS EVENING...AND AGAIN TUESDAY AFTERNOON
AND EVENING. SEVERE WEATHER WILL ALSO BE POSSIBLE BOTH DAYS. WINDS
ARE EXPECTED TO REMAIN UNDER 20 KNOTS AS THEY GRADUALLY VEER FROM A
SOUTHERLY DIRECTION TONIGHT TO THE WEST BEHIND THE COLD FRONT LATE
TOMORROW AFTERNOON AND EVENING.

&&

.AVIATION...ISSUED 149 PM EDT MON MAY 12 2014

//DISCUSSION...

PLUME OF DEEPER LOW LEVEL MOISTURE AND WEAK INSTABILITY WILL PROVIDE
SUPPORT FOR ADDITIONAL SHOWER AND THUNDERSTORM DEVELOPMENT ACROSS
LOWER MICHIGAN THROUGH THE EARLY EVENING HOURS.  LATEST RADAR
INDICATES THE GREATER COVERAGE IN THE NEAR TERM WILL EXIST IN THE
VICINITY OF A WARM FRONT ALONG THE FNT/MBS CORRIDOR.  HIGHER DEGREE
OF UNCERTAINTY YET IN BOTH COVERAGE AND TIMING TOWARD THE
SOUTH...THIS CORRIDOR DISPLACED SLIGHTLY FROM THE BETTER MID LEVEL
INSTABILITY.  SOME AREAS OF STRATUS MAY EMERGE IN THE VICINITY OF
THE WARM FRONT AS MOISTURE POOLS ALONG THE BOUNDARY...A PERIOD OF
MVFR CIGS NOT OUT OF THE QUESTION THIS EVENING.

FOR DTW...MAIN CORRIDOR OF THUNDERSTORMS WILL REMAIN NORTH OF THE
TERMINAL PER LATEST RADAR THROUGH 19Z. GREATEST WINDOW FOR
THUNDERSTORM ACTIVITY REMAINS IN THE 20Z TO 23Z PERIOD.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN THUNDERSTORMS LATE THIS AFTERNOON AND
EVENING...LOW CONFIDENCE IN TIMING.

* HIGH CONFIDENCE ON CEILINGS AT OR BELOW 5000 FT THIS AFTERNOON AND
EVENING...MEDIUM CONFIDENCE TONIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

SHORT TERM...MR
LONG TERM....HLO/MM
MARINE.......HLO
AVIATION.....MR

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
405 AM EDT MON MAY 12 2014

MIZ047>049-053>055-060>063-068>070-075-076-082-083-130815-
MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER-
ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE-
405 AM EDT MON MAY 12 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE OF SEVERE WEATHER THIS AFTERNOON AND
EVENING AS A MOIST AND UNSTABLE AIRMASS CONTINUES TO MOVE INTO THE
AREA BEHIND A WARM FRONT. DAMAGING WIND GUSTS TO 60 MPH AND HAIL
TO AROUND ONE INCH IN DIAMETER ARE POSSIBLE...ALONG WITH ISOLATED
BRIEF TORNADOES. IN ADDITION...HEAVY RAINFALL IS LIKELY WITH THE
STRONGEST STORMS...WHICH MAY RESULT IN LOCALIZED FLOODING. STORM
MOTION WILL BE EAST AT 25 MPH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ISOLATED SEVERE STORMS ARE POSSIBLE TUESDAY AFTERNOON AND EARLY
TUESDAY EVENING AS COLD FRONT MOVES THROUGH THE AREA.

.SPOTTER INFORMATION STATEMENT...
DISPATCHERS PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY...
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-130815-
ST. CLAIR RIVER-DETROIT RIVER-LAKE ST. CLAIR-
MICHIGAN WATERS OF LAKE ERIE FROM DETROIT RIVER TO NORTH CAPE MI-
LAKE HURON FROM 5NM EAST OF MACKINAC BRIDGE TO PRESQUE ISLE LT
BEYOND 5 NM OFF SHORE-
LAKE HURON FROM PRESQUE ISLE LIGHT TO STURGEON POINT MI BEYOND 5NM
OFF SHORE-
LAKE HURON FROM STURGEON POINT TO ALABASTER MI BEYOND 5NM OFF SHORE-
OUTER SAGINAW BAY SW OF ALABASTER TO PORT AUSTIN MI TO INNER SAGINAW
BAY-INNER SAGINAW BAY SW OF POINT AU GRES TO BAY PORT MI-
PORT AUSTIN TO HARBOR BEACH MI-HARBOR BEACH TO PORT SANILAC MI-
PORT SANILAC TO PORT HURON MI-
LAKE HURON FROM PORT AUSTIN TO HARBOR BEACH BEYOND 5NM OFF SHORE-
LAKE HURON FROM HARBOR BEACH TO PORT SANILAC BEYOND 5NM OFF SHORE-
LAKE HURON FROM PORT SANILAC TO PORT HURON BEYOND 5NM OFF SHORE-
405 AM EDT MON MAY 12 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE ERIE...LAKE
HURON AND LAKE ST CLAIR.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE OF SEVERE WEATHER THIS AFTERNOON AND
EVENING AS A MOIST AND UNSTABLE AIRMASS CONTINUES TO MOVE INTO THE
AREA BEHIND A WARM FRONT. WIND GUSTS TO 50 KNOTS AND HAIL TO AROUND ONE
INCH IN DIAMETER ARE POSSIBLE. STORM MOTION WILL BE EAST AT 25
MPH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ISOLATED SEVERE STORMS ARE POSSIBLE TUESDAY AFTERNOON AND EARLY
TUESDAY EVENING AS COLD FRONT MOVES THROUGH THE AREA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

SF

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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