Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 260503
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1203 AM EST THU FEB 26 2015

.AVIATION...

EXISTING WEAK SURFACE RIDGING WILL SUSTAIN A DRY LOW LEVEL
ENVIRONMENT EARLY THIS MORNING.  THIS WILL MAINTAIN VFR CONDITIONS
UNDER A THICKER CANOPY OF MID CLOUD.  THE DETROIT CORRIDOR REMAINS
IN LINE TO SEE A PERIOD OF LIGHT SNOW DEVELOPMENT MID AND LATE
MORNING HOURS...PONTIAC RESIDING ALONG THE NORTHERN PERIPHERY OF
THIS MOISTURE.  THIS WILL RESULT IN A PREDOMINANT PERIOD OF MVFR
CONDITIONS AT THESE LOCALES...WITH A NARROW WINDOW FOR A TEMPO
WORTHY IFR MENTION DURING THE PEAK.   A MODEST INCREASE IN THE
NORTHEAST GRADIENT WILL COMMENCE AT THE SAME TIME.

FOR DTW...POTENTIAL FOR LIGHT SNOWFALL WILL INCREASE AFTER 10Z-11Z.
PERIOD OF IFR MOST LIKELY CENTERED 12Z-15Z...WITH SNOWFALL THEN
TAPERING OFF 16Z-18Z.  ACCUMULATION LESS THAN HALF AN INCH.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILING BELOW 5000 FT LATE TONIGHT THROUGH THURSDAY
  MORNING.

&&

.PREV DISCUSSION...ISSUED 355 PM EST WED FEB 25 2015

SHORT TERM...TONIGHT

POTENT SHORTWAVE ENERGY CONSOLIDATED IN THE BASE OF THE LONGER WAVE
TROUGH ROTATING ACROSS THE UPPER MIDWEST/GREAT LAKES IS FEASTING
UPON ABUNDANT BAROCLINICITY AND A SIGNIFICANT MOISTURE RESERVOIR
OVER IOWA. 850-700MB LAYER AVERAGE SPECIFIC HUMIDITY OF 3+ J/KG WILL
CONTINUE TO STRING OUT WITHIN THE LOW-LEVEL FRONTAL ZONE AND REMAIN
WELL SOUTH OF THE AREA. THIS WILL EFFECTIVELY LEAVE SOUTHEAST
MICHIGAN IN PRIME LOCATION TO RECEIVE SOME LOW RATIO LEFT-OVERS
OFFERED BY THE 500MB FRONT/LEAD EDGE OF THE PV ANOMALY...WHICH IS
NOTED ON THE NATIONAL RADAR MOSAIC AS DEFINING THE FAR NORTHERN EDGE
OF THE PRECIP SHIELD OVER SOUTHERN MN AND CENTRAL WISCONSIN.
SPECIFIC HUMIDITY OF 1-1.25 G/KG WILL WORK EAST INTO THE CWA AFTER
MIDNIGHT. INCREASING LARGE SCALE ASCENT AS THE UPPER TROUGH BECOMES
LESS POSITIVELY TILTED WILL ENCOURAGE CONTINUED EASTWARD MIGRATION
OF UPSTREAM LIGHT REFLECTIVITY SOUTH OF I-69. VERY LITTLE POTENTIAL
FOR ANYTHING MORE THAN A TENTH OF INCH...ESPECIALLY WITH DRY MID-
LEVEL AIR EXPECTED TO PRODUCE A PERIOD OF VIRGA. HOWEVER, THE
COMPACT SHORTWAVE NOTED OVER WESTERN KANSAS THIS AFTERNOON WILL
BECOME ENTRAINED INTO THE LARGER SCALE FLOW AND SHEAR ACROSS THE
SOUTHERN CWA LATE TONIGHT/EARLY THURSDAY MORNING. THIS SHOULD
PROVIDE SOME ENHANCEMENT TO THE FORCING FIELD AND THE POTENTIAL FOR
UP TO A HALF INCH OF ACCUMULATION MAINLY SOUTH OF I-94 ENDING BY
AROUND 16Z.

NORTHEAST GRADIENT WILL BUILD INTO THE AREA AS THE PARENT UPPER
CIRCULATION PASSES WELL SOUTH. LIGHT WIND COMBINED WITH ABUNDANT
CLOUDS WILL INHIBIT DECOUPLING, BUT ADVECTION ALONE WILL BE
SUFFICIENT TO PRODUCE LOWS RANGING FROM AROUND -3F IN THE THUMB TO 7
TO 10 ABOVE NEAR THE OHIO BORDER. WIND CHILL VALUES MAY HOVER NEAR
ADVISORY CRITERIA IN THE THUMB, MAINLY HURON COUNTY, FOR A FEW HOURS
LATE , BUT THE MARGINAL SCENARIO AND POOR SPATIAL FOOTPRINT PRECLUDE
ADVISORY ISSUANCE. MOST LOCATIONS WILL SEE WIND CHILLS -5 TO -10.

LONG TERM...THURSDAY THROUGH TUESDAY

THE LONGWAVE PATTERN WILL UNDERGO SOME CHANGES THIS WEEKEND AND
BEYOND BUT NOT UNTIL THE PERSISTENT UPPER LEVEL TROUGH PRODUCES A
COUPLE MORE NIGHTS OF SUB ZERO TEMPERATURES. THE NEXT ARCTIC FRONT
DROPPING THROUGH THE REGION ON THURSDAY WILL USHER IN A STRONG SFC
RIDGE +1040MB INTO THE NORTHERN PLAINS THAT WILL SLOWLY DRIFT
EASTWARD ALONG THE OHIO RIVER THROUGH SATURDAY. THE UPPER LEVEL
TROUGH WILL EXPAND WEST ACROSS MUCH OF THE CONUS BY FRIDAY WHICH
RESULTS IN THE NEXT TROUGH SETTING UP OVER THE WEST COAST. THIS
POSITIVELY TILTED TROUGH STRUGGLES TO MAINTAIN DOMINANCE AS POLAR
JET ENERGY CONTINUES TO TRACK THROUGH CANADA. AS IT GETS REINFORCED
EARLY NEXT WEEK BY ENERGY DIVING DOWN THE WEST COAST...SOUTHWESTERLY
FLOW DEVELOPS ACROSS THE MID MISSISSIPPI VALLEY AND INTO THE
SOUTHERN GREAT LAKES. THIS WILL ENCOURAGE A WARMING TREND NEXT WEEK.

BACK TO THE HERE AND NOW...HIGH PRESSURE AND VERY DRY AIR WILL MOVE
OVER THE AREA ON THURSDAY BEHIND THE ARCTIC FRONT. A THERMAL TROUGH
WILL DROP OVER SOUTHERN MI LATE THURSDAY WITH 850MB TEMPS AROUND -
20C. THIS IS NOT NEARLY AS COLD OF AN AIRMASS AS WE HAVE SEEN OF
LATE BUT WITH THE GLACIAL SNOWPACK IN PLACE WE SHOULD STILL DROP
INTO THE NEGATIVE VALUES FOR LOW TEMPS ONCE AGAIN. LOOKS LIKE
THURSDAY NIGHT LOW TEMPS WILL MAKE A RUN AT -10F ACROSS THE
AREA...BUT LIGHT WINDS UNDER THE DECREASING GRADIENT...IN ADDITION
TO CLOUD COVER FROM THE EXITING CLIPPER...WILL KEEP THE WIND CHILLS
ABOVE ADVISORY CRITERIA /-15F/. THURSDAY MAX TEMPS WILL ALSO HAVE A
CHANCE AT HITTING RECORD LOWS AS THE FRONT WILL DROP THROUGH EARLY
ENOUGH IN THE DAY TO PREVENT DIURNAL HEATING. RECORDS FOR
DTW/FNT/MBS ARE LISTED BELOW.

FRIDAY WILL FEATURE DECREASING CLOUDS AS THE HIGH BUILDS MORE FIRMLY
IN PLACE ACROSS SOUTHERN MI. THE THERMAL TROUGH WILL BE WEAKENING
AND TAKING INTO ACCOUNT CLEARING SKIES AND WEAK SW FLOW DEVELOPING
ON THE NW QUADRANT OF THE HIGH...MAX TEMPS WILL BE ABLE TO RISE A
BIT INTO THE MID TEENS. LOW TEMPS FRIDAY NIGHT WILL STILL FALL INTO
THE NEGATIVE VALUES WITH GOOD COOLING SETUP...BUT RISING HEIGHTS AND
SW FLOW WILL KEEP TEMPS IN THE NEGATIVE SINGLE DIGITS. THE
DIFFERENCE WILL BE SLIGHTLY HIGHER WINDS WHICH WILL CAUSE WIND CHILL
VALUES TO DIP TO NEAR ADVISORY CRITERIA.

RECORDS LOW MAX TEMPS (LOWEST HIGHS) FOR FEB 26
DETROIT AREA:  9 (1900)
FLINT AREA:    9 (1963)
SAGINAW:      11 (1963)

RECORD LOWS FOR FEB 27
DETROIT AREA: -4  (1934)
FLINT AREA:   -14 (1994)
SAGINAW:      -8  (1934)

AS HIGH PRESSURE SHIFTS OFF TO THE EAST SATURDAY...UPPER LEVEL ZONAL
FLOW WILL BE REPLACED BY AN APPROACHING TROUGH DIGGING DOWN FROM THE
NORTH.  THIS WILL SET THE STAGE FOR INCREASING SNOW CHANCES AS A
WAVE MOVES ACROSS THE SOUTHERN GREAT LAKES REGION.  THIS QUICK
HITTING SYSTEM WILL MOVE EAST WITH HIGH PRESSURE BUILDING IN ON
MONDAY.  TEMPS ARE FINALLY STARTING TO WARM EVER SO SLIGHTLY THIS
WEEKEND INTO NEXT WEEK...WITH HIGHS POTENTIALLY REACHING CLOSE TO
THE 30 DEGREE MARK.

MARINE...

SURFACE HIGH PRESSURE WILL BEGIN BUILDING INTO THE GREAT LAKES
TONIGHT FROM THE NORTHWEST TONIGHT AS A CLIPPER TRACKS THROUGH THE
SOUTHERN GREAT LAKES. THIS HIGH PRESSURE WILL PERSIST OVER THE
REGION THROUGH SATURDAY BRINGING LIGHT WINDS TO THE REGION. ARCTIC
AIR WILL REMAIN IN PLACE WITH THE RIDGE UNTIL THE NEXT LOW PRESSURE
SYSTEM TARGETS THE REGION ON SUNDAY.

&&

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

$$

AVIATION.....MR
SHORT TERM...JVC
LONG TERM....DRK/SS
MARINE.......DRK

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


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