Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 120513
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
113 AM EDT SAT APR 12 2014


.AVIATION...

//DISCUSSION...

THE SHORTWAVE TROUGH AND ENHANCED MIDLEVEL MOISTURE HAS QUICKLY
MOVED EAST OF LOWER MICHIGAN. THERMAL FORCING WITH THIS FEATURE WAS
WEAK...SO NEUTRAL TEMPERATURE ADVECTION IS NOW EXPECTED FOR THE
REMAINDER OF THE NIGHT. QUIET CONDITIONS ARE EXPECTED TO HOLD INTO
THE AFTERNOON HOURS ON SATURDAY. A DEVELOPING WARM FRONT AND SURGE
OF MOISTURE INTO THE REGION DURING THE LATE AFTERNOON HOURS WILL
BRING THE NEXT CHANCE OF SHOWERS AND THUNDERSTORMS.

//DTW THRESHOLD THREATS...

* NONE

&&

.PREV DISCUSSION...ISSUED 323 PM EDT FRI APR 11 2014

SHORT TERM...TONIGHT

A WEAK FRONTAL SYSTEM AND MID LEVEL TROUGH WILL SLIDE THROUGH THE
NORTHERN GREAT LAKES TONIGHT. CURRENT MODEL RUNS ARE SHOWING A
SIGNIFICANT LOW LEVEL DRY LAYER ACROSS MOST OF SOUTHEAST MICHIGAN.
THIS WILL RESULT IN VERY LITTLE MOISTURE AND PRECIPITATION MAKING IT
TO THE GROUND AS THE SYSTEM MOVES ACROSS THE REGION. THE BEST CHANCE
FOR ANY LOCATION TO SEE RAIN WILL BE IN THE EXTREME NORTHERN
COUNTIES WHERE THE LOW LEVEL DRY LAYER IS A BIT WEAKER.
OTHERWISE...A FAIRLY QUIET OVERNIGHT PERIOD ACROSS THE CWA. EXPECT
CLOUDS TO INCREASE THROUGH EARLY EVENING AS THE FRONT APPROACHES
WITH TEMPERATURES DROPPING DOWN INTO THE MID 30S TO LOW 40S.

LONG TERM...SATURDAY THROUGH FRIDAY

STRONG HEIGHT FALL CENTER NOW SEEN ON WATER VAPOR SHIFTING INTO
BRITISH COLUMBIA WILL ANCHOR THE STEADY AMPLIFICATION OF THE MEAN
LONGWAVE PATTERN TOWARD PREDOMINANT CENTRAL CONUS TROUGHING RIGHT
THROUGH EARLY NEXT WEEK.  HEIGHTS WILL BUILD ACCORDINGLY DOWNSTREAM
THROUGH THE WEEKEND, THE NET RESULT BEING A FIRM PLACEMENT OF A WELL
DEFINED LOW LEVEL BAROCLINIC ZONE WITHIN THE DEEPENING MID LEVEL
SOUTHWEST FLOW EXTENDING FROM THE MID MS VALLEY INTO THE GREAT
LAKES.  THE OVERALL PATTERN EVOLUTION SETS UP A POTENTIALLY ACTIVE
PERIOD FOR SE MICHIGAN...PARTICULARLY ACROSS THE NORTH WHERE THE
CLOSER PROXIMITY TO AN ENERGETIC FRONTAL ZONE WILL OPEN THE DOOR FOR
THE POSSIBILITY OF MULTIPLE EPISODES OF RAINFALL WITH AN
ACCOMPANYING HIGH QPF/FLOODING CONCERN.

WARM AIR/THETA-E ADVECTION WILL INCREASE IN EARNEST UPSTREAM TONIGHT
AND SATURDAY IN STRENGTHENING LOW LEVEL SOUTHWEST FLOW.  THIS
PROCESS WILL WORK THE WARM FRONTAL SLOPE INTO SE MICHIGAN ON
SATURDAY.  SOME PESKY CIRRUS MAY CUT INTO THE DEGREE OF INSOLATION,
BUT OTHERWISE LOOKING AT A WELL MIXED LOW LEVEL ENVIRONMENT THROUGH
850 MB.  SOME RETENTION OF A LOW LEVEL EASTERLY COMPONENT WILL
CONTAIN THE TEMPERATURES RESPONSE SLIGHTLY ALONG THE IMMEDIATE
SHORELINE LOCALES /LOW-MID 60S/, ELSEWHERE HIGHS CLOSING IN ON 70
DEGREES.  INITIAL PERIOD OF STRONG MID LEVEL ISENTROPIC ASCENT
APPEARS TO LARGELY TRANSLATE BY TO THE NORTHWEST LATE SATURDAY
AFTERNOON AND EVENING, BUT MAY PROVIDE A GLANCING PERIOD OF LIGHT
SHOWERS FOR THE TRI-CITIES/NORTHERN THUMB.  THE MAIN THETA-E PLUME
WILL THEN FILL EAST-NORTHEAST AND ACROSS ALL AREAS SATURDAY NIGHT.
THIS PROCESS MAY BE ENHANCED BY ONE OR MORE MINOR PERTURBATIONS
SHEARING OFF FROM THE CUT OFF LOW CURRENTLY MEANDERING OFF THE
CALIFORNIA COAST.  THE NET INCREASE IN ASCENT AND DIMINISHING MID
LEVEL STABILITY WILL SUPPORT A ROUND OF SHOWERS, WITH A FEW EMBEDDED
ELEVATED THUNDERSTORMS CERTAINLY PLAUSIBLE.  THE TRI-CITIES/NORTHERN
THUMB WILL BE MORE FAVORABLY POSITIONED FOR A PERIOD OF MODERATE
RAIN AS ANY AUGMENTATION VIA LOW LEVEL JET FORCING WORKING OVER THE
CONTRACTING FRONTAL BOUNDARY WILL TEND TO FOCUS THROUGH THIS
CORRIDOR.

FRONTAL BOUNDARY WILL REMAIN IN THE VICINITY OF CENTRAL LOWER
MICHIGAN INTO SUNDAY, BUT ADDITIONAL SUPPLEMENTAL FORCING BECOMES
LESS CERTAIN THROUGH THIS PERIOD.  ADDITIONAL WEAK ILL-DEFINED
SHORTWAVE ENERGY WORKING OVER THE FRONT COULD CERTAINTY SPARK
ADDITIONAL LIGHT SHOWERS /MAINLY NORTH OF M-59/ DURING THE DAY.
HOWEVER THE DEGREE OF HEIGHT FALLS UPSTREAM MAY TEND TO REORIENT THE
MAIN PROPAGATION VECTOR JUST TO THE NORTH/WEST.  THIS WOULD PROVIDE
A RENEWED PERIOD OF WARM AIR ADVECTION, EFFECTIVELY NUDGING THE
FRONT NORTH OF THE FORECAST AREA AT LEAST TEMPORARILY THROUGH SUNDAY
EVENING/NIGHT.  AT THE VERY LEAST, THIS POINTS TOWARD ANOTHER MILDER
DAY ACROSS A GOOD MAJORITY OF SOUTHEAST MICHIGAN ON SUNDAY...THE
DEGREE OF CIRRUS DEBRIS BEING THE MAIN LIMITING FACTOR TO AN
OTHERWISE FAVORABLE SETUP FOR HIGHS TO PUSH LOWER 70S.

THE MOST ACTIVE PERIOD NOW APPEARS TO LARGELY CENTER ON LATE
SUNDAY NIGHT INTO MONDAY, WITHIN AN ENVIRONMENT CONDUCIVE FOR
SUSTAINED STRONG LOW TO MID LEVEL FRONTAL FORCING AS THE BOUNDARY
ONLY SLOWLY SAGS BACK SOUTHEASTWARD AND ACROSS THE REGION. THIS
FORCING WILL BE AUGMENTED BY THE ARRIVAL OF THE AFOREMENTIONED
CENTRAL PACIFIC CLOSED LOW AS AN OPEN WAVE AND FAVORABLE RIGHT
ENTRANCE UPPER JET FORCING. HIGH QPE POTENTIAL GIVEN THE ELEVATED
PWAT VALUES AND DEGREE OF FORCING. POTENTIAL FOR A LONGER
RESIDENCE TIME AND/OR MULTIPLE EPISODES WILL PLACE A LARGER FOCUS
AGAIN ON THE TRI-CITIES AND NORTHERN THUMB FOR FLOODING ISSUES
SHOULD THE MORE BULLISH SOLUTIONS OF 2 TO 3 INCHES AS SUGGESTED BY
THE ECMWF/GFS HOLD TO FORM. WHILE CONFIDENCE CONTINUES TO GROW ON
A WIDESPREAD RAINFALL EVENT, FORECAST SENSITIVITY TO FRONTAL
POSITIONING/MOVEMENT AND LONGEVITY LEAVES PLENTY OF UNCERTAINTY
YET IN THE PROPER PLACEMENT AND MAGNITUDE OF THE HIGHEST QPF AXIS.
WILL CONTINUE TO HIGHLIGHT THE RISK FOR FLOODING IN THE HWO.

AS THE LOW AND ASSOCIATED COLD FRONT PUSH AWAY FROM THE AREA MONDAY
NIGHT...MUCH COOLER AIR WILL CONTINUE TO OVERTAKE THE AREA.
NORTHWESTERLY FLOW WILL ONCE AGAIN USHER IN BELOW NORMAL
TEMPERATURES WITH LOWS DROPPING BELOW FREEZING AND HIGHS ONLY
REACHING INTO THE 40S BOTH TUESDAY AND WEDNESDAY.  THERE MAY BE A
CHANCE FOR LINGERING SNOW SHOWERS DURING THE OVERNIGHT HOURS MONDAY
INTO EARLY TUESDAY.  GOOD NEWS IS THAT TEMPS DO REBOUND TOWARDS THE
END OF THE WEEK.  BEHIND THE DEPARTING COLD FRONT MONDAY
NIGHT...UPPER LEVEL ZONAL FLOW AND SURFACE HIGH PRESSURE WILL TAKE
OVER AND ARE EXPECTED TO BRING QUIETER CONDITIONS FOR THE MIDDLE OF
THE WEEK BEFORE ANOTHER CHANCE OF PRECIPITATION MOVES IN.

MARINE...

A MODEST EASTERLY WIND WILL SHIFT TO SOUTHERLY ON SATURDAY AS WARM
FRONT LIFTS INTO THE REGION.  THIS ACTIVE FRONTAL BOUNDARY WILL
PROVIDE THE FOCUS FOR ROUNDS OF SHOWERS AND THUNDERSTORMS FROM LATE
SATURDAY INTO MONDAY.  MODERATE SOUTH TO SOUTHWEST WINDS WILL HOLD
SOUTH OF THIS FRONTAL BOUNDARY THROUGH THE LATTER HALF OF THE
WEEKEND.  NORTHWEST WINDS WILL EMERGE AS THE FRONT SAGS SOUTHEAST
MONDAY AND MONDAY NIGHT.

&&

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

&&

$$

AVIATION.....99
SHORT TERM...RK
LONG TERM....MR/SS
MARINE.......MR


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