Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 150752
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
352 AM EDT TUE APR 15 2014

.SHORT TERM... TODAY AND TONIGHT

THE TRANSITION FROM RAIN TO SNOW WAS COMPLETE BY MIDNIGHT OVER ALL
OF SE MICHIGAN. THE QUESTION NOW BECOMES HOW MUCH ACCUMULATION WILL
OCCUR WITH THE REMAINING MOISTURE IN THE SYSTEM WITHIN STRONG AND
WELL ORGANIZED MESOSCALE FORCING. SATELLITE IMAGERY AND MODEL
ANALYSIS FIELDS INDICATE A CLASSIC SET UP OF FRONTOGENETICAL FORCING
IN PROGRESS OVER SE MICHIGAN SUPPORTED BY A SW-NE ORIENTED 150 KNOT
UPPER JET MAX. THE RESULTING AGEOSTROPHIC CIRCULATION INITIALLY
ACTIVATED THE MID TO UPPER LEVELS OF THE FRONTAL ZONE WITH A BAND OF
SNOW OVER WESTERN AND NORTHERN LOWER MICHIGAN THAT PRODUCED 1 TO 3
INCHES OF ACCUMULATION. RADAR TRENDS SINCE MIDNIGHT HAVE SHOWN THIS
SHIFTED EASTWARD AS A RESULTANT COMBINATION OF LARGE SCALE
PROGRESSION OF THE FRONTAL ZONE AND A TENDENCY FOR LIFT TO MIGRATE
TOWARD LOWER ALTITUDES WHERE SPECIFIC HUMIDITY IS IN THE 3-4 G/KG
RANGE. MODEL CROSS SECTIONS INDICATE THE LIFT OCCURRING IN AN
UNSTABLE PROFILE BETWEEN 700 AND 400 MB WHERE THETA-E IS FOLDED
THROUGH MULTIPLE LEVELS ALLOWING THE FRONTAL CIRCULATION TO MODULATE
A MATURE BAND OF SNOW DURING THE EARLY MORNING HOURS. LOCAL OFFICE
OBSERVATIONS ILLUSTRATE THE EFFECTIVENESS OF THE BAND WITH 1 INCH
PER HOUR RATES OF BIG AGGREGATES BETWEEN MIDNIGHT AND 2 AM LIKELY
REPRESENTATIVE ALONG THE HIGHER TERRAIN UP INTO SANILAC COUNTY AND
SETTING UP SOLID 3 INCH TOTALS WITH A FEW 4 INCH REPORTS POSSIBLE.
LOCATIONS TO THE NORTH TOWARD THE TRI CITIES WILL BE LIMITED BY
DURATION TO ABOUT AN INCH OF ACCUMULATION. FLINT AND THE NORTHERN
THUMB WILL BE CLOSER TO THE MATURE PART OF THE BAND FOR THE REST OF
THE EVENT FOR 1 TO 2 INCH TOTALS. THE DTW AREA TO THE OHIO BORDER
STARTED OUT WITH LOWER RATIOS AT FIRST, DUE TO WARMER SURFACE
TEMPERATURE, BUT WILL NOT BE TOO FAR BEHIND THE HIGHER TERRAIN AREAS
IN ACCUMULATION AS THE PRIMARY BANDS AFFECT THAT AREA THROUGH
SUNRISE. SOLID 2 TO 3 INCH TOTALS ARE EXPECTED THERE BEFORE THE
PATTERN EXITS EASTWARD BY 8 AM OR SO.

THE REST OF THE DAY WILL BE DOMINATED BY STRONG COLD ADVECTION THAT
WILL BE ABLE TO RESIST MID APRIL SURFACE HEATING ENOUGH TO LIMIT MAX
TEMPS THE UPPER 30S. MODEL 850 MB TEMPERATURES SETTLING INTO THE -13
TO -16C RANGE BY LATE AFTERNOON IS A STRONG ENDORSEMENT ON THE COLD
NATURE OF THE AIR MASS. BOUNDARY LAYER MOISTURE AND INSTABILITY WILL
KEEP PLENTY OF CLOUDS STIRRED UP WHICH WILL FURTHER LIMIT
TEMPERATURES. THERE MAY BE A FEW FLURRIES AS WELL, ALTHOUGH MODEL
SOUNDINGS SHOW THE AIR TO BE ON THE DRY SIDE BELOW CLOUD BASE. THE
MAIN TAKEAWAY IS THAT THE COLD AFTERNOON TEMPERATURES WILL HAVE
READINGS WELL POSITIONED TO MAKE A RUN AT RECORD LOWS TONIGHT. A
SHORT PERIOD OF IDEAL RADIATIONAL COOLING IS EXPECTED TO OCCUR
AROUND MIDNIGHT AFTER VERY LITTLE MELTING OF THE NEW SNOW COVER
DURING THE DAY COMBINED WITH THE DISSIPATION OF LOWER CLOUDS AND
DIMINISHING WIND. EXPECT MIN TEMPS IN THE TEENS TO LOWER 20S BEFORE
HIGH CLOUDS THICKEN AND THE WIND BACKS TO SOUTHWEST TOWARD SUNRISE
WEDNESDAY. SEE CLIMATE SECTION BELOW FOR STATS.

&&

.LONG TERM...

NOT MUCH OF A WARMUP EXPECTED DURING THE EXTENDED PERIOD...WITH EVEN
A LOW CHANCE FOR ADDITIONAL SNOW FRIDAY NIGHT (SEE 00Z GFS).

UPPER LEVEL WAVE/TROUGH CURRENTLY MOVING ONSHORE OF SOUTHERN BRITISH
COLUMBIA/WASHINGTON WILL SWING THROUGH THE NORTHERN PLAINS WEDNESDAY
AND INTO THE WESTERN GREAT LAKES THURSDAY MORNING. TIGHT BAROCLINIC
ZONE WILL RESIDE OVER THE GREAT LAKES REGION...BUT MID LEVEL
FORCING/FGEN LOOKS TO BE RESIDING NORTH OF SOUTHEAST MICHIGAN. A
DRAMATIC WEAKENING TREND LOOKS TO BE TAKING PLACE DURING THURSDAY AS
SYSTEM ENCOUNTERS REMNANT UPPER LEVEL CONFLUENT FLOW FROM DEPARTING
VORTEX OVER HUDSON BAY.

POTENT PV ANOMALY RETROGRADING THROUGH CENTRAL CANADA DURING THE MID
WEEK PERIOD WILL BE KEY PLAYER AS WE END THE WORK WEEK...WITH
CANADIAN/GFS/EURO ALL SHOWING SUBSTANTIAL TIMING ISSUES...ALONG WITH
THE ISSUES DEALING WITH THE INTERACTION OF THE SOUTHERN ENERGY
COMING OUT OF THE FOUR CORNERS REGION. GFS INDICATING THE OPTIMAL
INTERACTION/PHASING...AND THUS WOULD SUPPORT RAIN CHANGING OVER TO
WET SNOW FRIDAY NIGHT. 00Z EURO/CANADIAN BOTH KEEPING A BIT MORE
WAVE SEPARATION...AND THUS MORE PROGRESSIVE AND NON-PHASED
SOLUTIONS.

&&

.MARINE...

NORTHWEST WINDS OF 20 TO 30 KNOTS TODAY WILL BE COMMON AS COLD
AIRMASS WILL BE IN PLACE. GUSTS COULD EVEN BRIEFLY REACH GALES OVER
THE OPEN WATERS OF LAKE HURON DURING THE AFTERNOON. SIGNIFICANT WAVE
HEIGHTS WILL BUILD TO 7 FEET OR HIGHER OVER THE OPEN WATERS OF
CENTRAL LAKE HURON AND WILL BE IN EXCESS OF 4 FEET ALONG THE EXPOSED
NEARSHORE WATERS OF THE THUMB. THIS IN COMBINATION WITH FREQUENT
GUSTS OF 25 KNOTS SUPPORTS CONTINUANCE OF THE SMALL CRAFT ADVISORIES
FOR LAKE HURON. WINDS AND WAVES WILL QUICKLY SUBSIDE WITH THE
ARRIVAL OF HIGH PRESSURE TONIGHT. THIS HIGH WILL SLOWLY SLIDE EAST
ON WEDNESDAY...LEADING TO INCREASING SOUTHEAST WINDS INTO WEDNESDAY
NIGHT...BUT STILL REMAINING BELOW 30 KNOTS.

&&

.CLIMATE...

SNOWIEST WINTER SEASON (NOT INCLUDING NEW SNOW TODAY)

CITY       2013-2014        RECORD        TO TIE RECORD

FLINT       82.6"      82.9" (1974-75)         0.3"
DETROIT     91.7"      93.6" (1880-81)         1.9"

RECORD LOW MAX TEMPERATURE FOR APRIL 15:

DTW 36 (1904)
FNT 35 (1944)
MBS 33 (1944)

RECORD MINS FOR APRIL 16:

DTW 17 (1875)
FNT 21 (1935)
MBS 21 (1935)


&&

.AVIATION...ISSUED 1253 AM EDT TUE APR 15 2014

//DISCUSSION...

THE COLD AIR HAS PUSHED SOUTHEAST ALL THE WAY THROUGH DETROIT
COMPLETING THE CHANGEOVER FROM RAIN TO SNOW. IFR CIGS AND VSBYS HAVE
SET IN AND MAY DIP INTO LIFR DURING THE HEAVIEST SNOWFALL. SNOW WILL
TAPER OFF AROUND 10Z WITH IMPROVING CONDITIONS QUICKLY FOLLOWING AS
HIGH PRESSURE BUILDS IN. NORTHWEST WINDS WILL PREVAIL THROUGH THE
FORECAST AND SPEEDS WILL STAY ELEVATED...AROUND 10 TO 15 KNOTS THE
REST OF THE NIGHT WITH A TIGHT PRESSURE GRADIENT IN PLACE. GUSTY
WINDS WILL AGAIN DEVELOP THIS AFTERNOON AS WE MIX BACK UP TO AROUND
750MB. THE AFOREMENTIONED HIGH WILL ALLOW WINDS TO RELAX BELOW 10
KNOTS TUESDAY NIGHT.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CIGS BELOW 5000 FEET THROUGH THIS MORNING.

* HIGH CONFIDENCE PRECIPITATION TYPE WILL BE SNOW TONIGHT.

* LOW CONFIDENCE VISIBILITY WILL FALL BELOW 1/2SM EARLY THIS
MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING OUTER SAGINAW BAY...UNTIL MIDNIGHT WEDNESDAY.

LAKE ST CLAIR...NONE.

MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...BT
LONG TERM....SF
MARINE.......SF
CLIMATE......BT/SF
AVIATION.....DRK


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








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