000
FXUS63 KDTX 121126
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
726 AM EDT SUN MAY 12 2013


.AVIATION...

//DISCUSSION...

COLD CYCLONIC FLOW WILL LEAD TO ABUNDANT STRATOCU DEVELOPMENT THIS
MORNING...WITH CIGS AROUND 3000 FEET. CIGS WILL GRADUALLY LIFT TO
LOW VFR THIS AFTERNOON AS THE MIXED LAYER DEPTH
INCREASES...PROMOTING WESTERLY WIND GUSTS AROUND 25 KNOTS. STEEP LOW
LEVEL LAPSE RATES WILL LEAD TO SCATTERED SHOWERS...BUT LIMITED
COVERAGE AND SHORT DURATION. HIGHEST CONCENTRATION LOOKS TO BE
ACROSS NORTHERN TAF SITES OF MBS/FNT...WHERE EVEN NONE ACCUMULATING
SNOW SHOWERS MAY OCCUR.

THE LOSS OF DAYTIME HEATING SUNDAY EVENING WILL BRING MOSTLY CLEAR
SKIES AND WINDS AROUND 10 KNOTS BACK TO THE TAF SITES.

//DTW THRESHOLD THREATS...

* MEDIUM TO HIGH CONFIDENCE IN CIGS BELOW 5000 FEET THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND GUSTS AROUND 25 KNOTS FROM 290-310 DEGREES
  THIS AFTERNOON

&&

.PREV DISCUSSION...ISSUED 346 AM EDT SUN MAY 12 2013

SHORT TERM... TODAY AND TONIGHT

LARGE UPPER LEVEL LOW CENTERED JUST NORTH OF THE GREAT LAKES REGION
IS PUMPING COLD AIR INTO LOWER MICHIGAN...AS 00Z GRB RAOB REVEALED
AN 850 MB TEMP OF -4 C...WHILE INL CAME IN AT -7 C.

THESE UPSTREAM OBS MATCH UP WELL WITH THE ADVERTISED 850 MB TEMPS OF
-5 TO -7 C TODAY (SUPPORTIVE OF MAXES HOLDING IN THE 40S TO AROUND
50 DEGREES)...AND SHOULD SEE SUFFICIENT LOW LEVEL LAPSE RATES
COUPLED WITH COLD CYCLONIC FLOW AND LAKE ENHANCEMENT TO PRODUCE
SCATTERED SHOWERS TODAY. THAT INCLUDES RAIN AND PROBABLY EVEN SOME
SNOW FLAKES/GRAUPEL MIXED IN AS WELL...AS 1000-850 MB THICKNESSES
PROGGED AT 1296 M OR COLDER ALONG AND NORTH OF M-59...WITH SURFACE
WET BULB TEMPS IN THE MID 30S. IN ADDITION...IT WILL BE A BREEZY
DAY...AS 925-850 MB LAYER LOOKS TO BE SOLID 30 KNOTS THROUGH THE
DAY. THE PRESSURE GRADIENT/WINDS WILL BE WEAKENING TONIGHT...COUPLED
WITH THE LOSS OF PREDOMINATELY DIURNAL CU FIELD...SETTING US UP FOR
A SUB FREEZING NIGHT...AS LATEST MAV/MET GUIDANCE SUPPORTS INHERITED
MIN GRID... UPPER 20S TO LOWER 30S...WHICH IS RECORD TERRITORY FOR
MAY 13TH. HERE ARE THE RECORD LOWS FOR THE DATE...WITH FLINT HAVING
THE BEST CHANCE AT REACHING OR BREAKING.

MBS...26 DEGREES (1946)
FNT...28 DEGREES (1946)
DTW...30 DEGREES (1971)

FREEZE WARNING HAS BEEN ISSUED.

LONG TERM...MONDAY THROUGH SATURDAY

WEAK SURFACE RIDGING SLIDING THROUGH WILL PROVIDE BENIGN CONDITIONS
FOR MONDAY.  SLOW DEPARTURE OF THE PREVALENT MID LEVEL TROUGH AND
LOWER HEIGHT FIELD WILL TEMPER THE DIURNAL TEMPERATURE RESPONSE.
FAIR AMOUNT OF INSOLATION WILL ASSIST THE PROCESS...BUT A BRIEF
EXPANSION IN DIURNAL CU COVERAGE IS LIKELY FOR MIDDAY WITHIN THE
TRAILING SHEAR AXIS/CYCLONIC FLOW.  A MODESTLY MIXED PROFILE WITH
850 MB TEMPERATURES RESIDING IN THE -2C RANGE WILL YIELD HIGHS OF
LOWER TO MIDDLE 50S.

THE HIGH AMPLITUDE WESTERN RIDGE/EASTERN TROUGH LONGWAVE
CONFIGURATION MARKING CONDITIONS THIS WEEKEND WILL TURN MORE
PROGRESSIVE NEXT WEEK. THE UPSTREAM MEAN RIDGE AXIS WILL TEND
TO DAMPEN AND ELONGATE MORE WEST TO EAST BENEATH EMERGING LOWER
AMPLITUDE WESTERLIES TAKING HOLD OVER THE NORTHERN CONUS/SOUTHERN
CANADA.  THIS WILL PROVIDE A MORE AGGRESSIVE RISE IN THE UPPER
HEIGHT FIELD ACROSS THE GREAT LAKES THROUGH THE TUESDAY AND
WEDNESDAY PERIODS.  A CORRESPONDING DEEPENING OF THE SOUTHWEST
GRADIENT WILL ALLOW THE EMERGING WARM FRONTAL ZONE ALONG THE RIDGE
INTERFACE TO WORK THROUGH SE MICHIGAN TUESDAY AND TUESDAY NIGHT.
THIN SLIVER OF BETTER 850-925 MB THETA-E/MOISTURE ADVECTION TIED TO
THE WAA PROCESS WILL PROVIDE A LOW CHANCE FOR PRECIPITATION THROUGH
THIS TIME...ALTHOUGH MORE IDEAL FORCING WILL RESIDE TO THE NORTH AND
THE OVERALL MOISTURE QUALITY IS LACKING.  TEMPERATURES ON TUESDAY
DICTATED ON OVERALL COVERAGE OF PCPN/CLOUDS...MODERATING THERMAL
COLUMN OTHERWISE SUPPORTIVE OF HIGHS IN THE 60S.

FALLING HEIGHTS EXTENDING SOUTH OF A STRONGER MID LEVEL WAVE
SHIFTING THROUGH THE US/CANADIAN BORDER WILL SEND A COLD FRONT INTO
LOWER MICHIGAN LATE WEDNESDAY AND WEDNESDAY NIGHT.  FRONTAL TIMING
APPEARS DELAYED ENOUGH TO ALLOW INTRUDING WARM SECTOR AIRMASS TO
FULLY WORK INTO THE REGION ON WEDNESDAY.  GIVEN THE RELATIVE
STRENGTH OF THE WARM ADVECTIVE COMPONENT...LOOKING AT HIGHS MAKING A
RUN INTO THE UPPER 70S/LOWER 80S.  FRONTAL PASSAGE WILL PRESENT THE
NEXT OPPORTUNITY FOR CONVECTIVE DEVELOPMENT WITHIN THAT LATE
WEDNESDAY TO WEDNESDAY NIGHT WINDOW.  HOWEVER PROSPECTS FOR BETTER
COVERAGE MAY BE LIMITED GIVEN THE EXISTING WARM MID LEVEL
TEMPERATURES/GOOD CAPPING INVERSION.  THIS CONTINUES TO SUPPORT JUST
A GENERAL CHANCE POP THROUGH THIS TIME.

MARINE...

A SECONDARY COLD FRONT EMITTING FROM LOW PRESSURE JUST NORTH OF
GEORGIAN BAY WILL SWING THROUGH NORTH TWO THIRDS OF LAKE HURON THIS
MORNING...ALLOWING FOR NORTHWEST GALES DURING THE DAY...ALONG WITH
SNOW SHOWERS AS UNSEASONABLY COLD AIR MOVES OVER THE MILDER WATERS
OF LAKE HURON. THIS WILL PRODUCE UNSTABLE CONDITIONS CONDUCIVE TO
HIGHER WIND GUSTS AND LARGER WAVES. FARTHER SOUTH...WESTERLY WINDS
WILL EASILY GUST TO 30 KNOTS AS WELL...INCLUDING AS FAR SOUTH AS
LAKE ERIE. HIGH PRESSURE WILL BUILD INTO THE AREA TONIGHT INTO
MONDAY BRINGING MUCH IMPROVED MARINE CONDITIONS INTO TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZE WARNING...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055-MIZ060-
     MIZ061-MIZ062-MIZ063-MIZ068-MIZ069-MIZ070-MIZ075-MIZ076-MIZ082-
     MIZ083...FROM MIDNIGHT MONDAY TO 8 AM MONDAY.

LAKE HURON...
     GALE WARNING...LHZ361-LHZ362-LHZ363-LHZ421-LHZ422-LHZ441-
     LHZ462...UNTIL 8 PM SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
     HURON...UNTIL 10 PM SUNDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 10 PM SUNDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL 10 PM SUNDAY.

&&

$$

AVIATION.....SF
SHORT TERM...SF
LONG TERM....MR
MARINE.......SF

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