Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 150147
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
947 PM EDT MON APR 14 2014

.UPDATE...
WE HAVE TO AREAS OF PRECIPITATION HEADING INTO THE AREA. A 700MB
FGEN BAND WORKING EAST THROUGH SW MI AND A SHORTWAVE TRACKING
NORTH FROM TENNESSEE. THE FGEN BAND IS DRIFTING EAST BUT THE
FORCING AND MOISTURE ARE SHEARING NE INTO NORTHERN MI AWAY FROM
THE AREA. REPORT FROM GRR HAD 1.5 INCHES OF SNOW THUS FAR IN
NEWAYGO CO. WITH QPF LESSENING AS IT
APPROACHES AND LOTS OF STANDING WATER TO ABSORB THE SNOW...MIDLAND/BAY/SAGINAW
SHOULD MISS OUT ON THESE TOTALS BUT UP TO AN INCH STILL SEEMS
REASONABLE. THE OTHER AREA OF INTEREST WILL AFFECT THE EASTERN
PORTION OF THE CWA OVERNIGHT. TEMPS ARE STILL ABOVE FREEZING AND
FALLING BUT THIS WILL YIELD A FEW HOURS OF LIGHT RAIN OR MIXED
PRECIP BEFORE THE CHANGEOVER. HIGHRES MODELS STILL COMING IN WITH
AROUND 0.3-0.4 INCHES OF QPF WHICH HAS BEEN PRETTY CONSISTENT.
THERE IS A CONVECTIVE NATURE TO THE STORM WITH A FEW LIGHTNING
STRIKES OCCURRING. WHETHER WE HAVE LIGHTNING OR NOT
HERE...CONVECTION WILL HELP WITH INCREASING RATES FOR A FEW HOURS
IF IT LASTS INTO SE MI...MOST LIKELY BETWEEN 05-09Z. STILL AGREE
WITH AROUND 1-3 INCHES OF SNOW BY TUESDAY MORNING FOR LOCATIONS
EAST OF A LINE FROM BAD AXE TO FLINT TO ADRIAN.

&&

.AVIATION...ISSUED 759 PM EDT MON APR 14 2014

//DISCUSSION...

THE NEXT LOW PRESSURE SYSTEM IS SURGING NORTH FROM THE LOWER
MISSISSIPPI VALLEY. THIS WILL BRING A PERIOD OF SNOW TO THE REGION
STARTING AROUND 03Z AND TAPERING OFF AROUND 10Z TUESDAY MORNING.
MODELS CONTINUE TO ADVERTISE HIGHER RATES FOR SEVERAL HOURS AS GOOD
FORCING ALOFT ADVECTS OVER THE REGION. THIS WILL RESULT IN IFR/LIFR
CONDITIONS WITH ACCUMULATIONS UP TO A FEW INCHES BY MORNING. WINDS
WILL STAY SLIGHTLY ELEVATED...AROUND 12 KNOTS...THROUGH THE NIGHT AS
PRESSURE GRADIENT TIGHTEN OVER THE STATE. GUSTS WILL REACH NEAR 25
KNOTS TOMORROW AFTERNOON BEFORE HIGH PRESSURE BUILDS IN ALLOW THEM
TO RELAX.

FOR DTW...CONFIDENCE IS HIGH IN A BURST OF MODERATE TO HEAVY
SNOWFALL TONIGHT. THE OVERALL POTENTIAL FOR ACCUMULATION ON PAVED
SURFACES REMAINS UNKNOWN.

//DTW THRESHOLD THREATS...

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

* HIGH CONFIDENCE PRECIPITATION TYPE WILL BE SNOW TONIGHT.

&&

.PREV DISCUSSION...ISSUED 321 PM EDT MON APR 14 2014

SHORT TERM...THROUGH THIS EVENING

SURFACE LOW PRESSURE AT 990 MB HAS ROCKETED NORTHEASTWARD TO FAR
WESTERN QUEBEC. INITIAL LOW LEVEL COLD AIR ADVECTION IS UNDERWAY IN
THE WAKE OF THE COLD FRONT...WITH A HIGH AMOUNT OF STABILITY HAVING
DEVELOPED IN THE 2-4 KFT AGL LAYER. THIS STABILITY HAS DAMPENED THE
WIND RESPONSE WITH WINDSPEEDS NOW IN THE 15 TO 30 MPH RANGE. EXPECT
THIS TO LARGELY HOLD NOW INTO THE EARLY EVENING HOURS. THE SURFACE
TEMPERATURE RESPONSE HAS BEEN NOTEWORTHY...READINGS OUTSIDE NOW 20
DEGREES COOLER THAN HIGHS ACHIEVED THIS MORNING.

LONG TERM...

FLOW AROUND THE SOUTHERN PERIPHERY OF THE CENTRAL U.S. TROUGH WILL
BECOME INCREASINGLY CONSOLIDATED OVER THE NEXT SEVERAL HOURS AS THE
SOUTHERN STREAM SHORTWAVE OVER THE LOWER GREAT PLAINS BECOMES
INCREASINGLY SHEARED AND ABSORBED INTO THE PREVAILING SOUTHWEST
FLOW. AS THIS OCCURS, THE UPPER TROUGH WILL TRANSITION TO A MORE
NEUTRAL TILT AND THE MASS GRADIENT WILL STRENGTHEN CONSIDERABLY,
ELICITING AN IMPRESSIVE JET RESPONSE. THIS JETLET WILL PROPAGATE
RAPIDLY NORTHEAST, TRAVERSING THE GREAT LAKES 03-09Z. AT THE SAME
TIME, STRONG COLD ADVECTION WILL BE ONGOING AND DEEPENING WITH TIME
IN THE LOW-LEVELS IN THE WAKE OF THIS AFTERNOON`S SURFACE COLD
FRONT. THE H7 PORTION OF THE FRONTAL SLOPE, ALREADY SHOWING SIGNS OF
LIFE FROM SE KANSAS INTO NW ILLINOIS WILL REMAIN ACTIVE AS IT SLIDES
EAST WITH THE MAIN UPPER TROUGH, BRINGING LIGHT TO MODERATE SNOW TO
NORTHWESTERN PORTIONS OF THE AREA.

MEANWHILE, EXTREMELY LOW STATIC STABILITY COMBINED WITH POTENTIAL
FOR UPRIGHT INSTABILITY WILL STRONGLY FAVOR A LOWER PORTION OF THE
FRONTAL SLOPE BECOMING ACTIVE AS FORCING ASSOCIATED WITH THE
AFOREMENTIONED JET RACES INTO THE AREA FROM THE SOUTHWEST. THE BIG
QUESTION THEN BECOMES EXACT PLACEMENT AND JUST HOW QUICKLY THE
COLUMN COOLS, ESPECIALLY FOR SOUTHEASTERN AREAS, INCLUDING METRO
DETROIT. SYNOPTICALLY, ALL LOCATIONS SHOULD CHANGE TO SNOW BY 05Z,
WITH THE METRO AREA CHANGING OVER LAST. THIS EXPECTATION IS
COMPLICATED, HOWEVER, BY THE FACT THAT POTENTIALLY VERY STRONG
ASCENT WILL AID IN COOLING THE COLUMN AND MAY ALLOW AN EARLIER
CHANGEOVER DURING THE HEAVIEST PRECIPITATION. IN ADDITION, THE
POTENTIAL FOR CONVECTION INTRODUCES BOTH THE POTENTIAL FOR
OVERACHIEVING FROM THE METRO AREA SOUTHWARD AS WELL AS THE POTENTIAL
FOR THE RESULTANT LATENT HEATING TO WARM THE COLUMN ABOVE FREEZING.
UNFORTUNATELY, IT APPEARS THAT EVALUATION OF THE EXACT NATURE OF
PRECIP OVER THE AFOREMENTIONED AREA WILL HAVE TO BE AN ONGOING
PROCESSES THIS EVENING. WILL THEREFORE FAVOR A MIDDLE-OF-THE-ROAD
FORECAST FOR ACCUMS TO ALLOW FOR LATER REFINEMENTS EITHER UP OR DOWN.

AS FOR FORECAST AMOUNTS, WEAKER FORCING AND A WET GROUND/STANDING
WATER WILL LIMIT SNOW RATIOS INVOF THE SAGINAW VALLEY. ELSEWHERE,
FAVORABLE NOCTURNAL TIMING, DRIER GROUND, AND HIGHER SNOWFALL RATES
WILL FAVOR SOMETHING CLOSER TO 12:1. GENERALLY EXPECTING AMOUNTS TO
RANGE FROM AROUND AN INCH IN THE SAGINAW VALLEY TO 3 INCHES FROM THE
METRO AREA SOUTH. COULD CERTAINLY SEE SNOWFALL RATES ON THE ORDER OF
AN INCH PER HOUR ACCOMPANIED BY THUNDER ON A LOCAL BASIS. FOLLOWED
AN ARW/NMM BLEND FOR QPF AMOUNTS DUE TO GENERAL CONSENSUS WITH
LARGER SCALE MODELS AND THEIR SIMILAR HANDING OF FINE SCALE
FEATURES, PARTICULARLY INVOF THE METROPOLITIAN AREA. THE FORECAST IN
ITS CURRENT FORM CALLS FOR BREAKING THE ALL-TIME RECORDS FOR
SNOWIEST WINTER SEASON AT BOTH DETROIT AND FLINT (SEE CLIMATE
SECTION).

COLD AIR CHARACTERIZED BY H85 TEMPS AROUND -13C WILL BE FIRMLY
ENTRENCHED FOR THE BALANCE OF THE DAY ON TUESDAY. DAYTIME HEATING
WILL SUPPORT AN EXPANSION OF BOUNDARY LAYER CLOUD COVER AND
SUPERSATURATION SUPPORTIVE OF FLURRIES OR SNOW SHOWERS. BUILDING
HIGH PRESSURE AND REBOUNDING HEIGHTS ALOFT WILL FAVOR CLEARING AND
COLD TEMPERATURES ON TUESDAY NIGHT. TEMPERATURES WILL REBOUND A
SOLID 10 DEGREES BY WEDNESDAY UNDER SHORTWAVE RIDGING AND AND A
DEVELOPING SOUTHEAST GRADIENT IN ADVANCE OF LOW PRESSURE OVER THE
UPPER MS VALLEY.

THE WEEKEND WILL FEATURE TURBULENT UPPER LEVEL FLOW WITH TWO
UPPER LEVEL WAVES TRAVERSING THE EASTER 2/3 OF THE CONUS. THIS
WILL BRING SEVERAL BOUTS OF LIGHT RAIN SHOWERS OVER THE WEEKEND.
TEMPERATURES WILL HOVER JUST UNDER THE CLIMO NORMS FOR THE PERIOD.
HIGH PRESSURE SHOULD DRY THINGS OUT FOR EARLY NEXT WEEK.

MARINE...

MODERATE TO FRESH NORTHWEST WINDS WILL BECOME INCREASINGLY GUSTY AS
COLD AIR POURS INTO THE AREA TONIGHT INTO TUESDAY. GUSTS WILL
APPROACH NEAR GALES AT TIMES 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 SUBSIDE WITH THE ARRIVAL OF
HIGH PRESSURE ON TUESDAY NIGHT.

CLIMATE...

SNOWIEST WINTER SEASON

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 HIGH TEMPERATURE FOR APRIL 15:
DTW 36 (1904)
FNT 35 (1944)
MBS 33 (1944)

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING OUTER SAGINAW BAY...UNTIL 4 PM TUESDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

UPDATE.......DRK
AVIATION.....DRK
SHORT TERM...CB
LONG TERM....JVC/MM
MARINE.......JVC
CLIMATE......JVC
CLIMATE......DRK


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






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