Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 021726
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1226 PM EST MON MAR 2 2015


.AVIATION...

CLEAR SKIES AND VFR WILL PERSIST THROUGH TONIGHT BENEATH THE CENTER
OF HIGH PRESSURE. NORTHWEST WINDS AROUND 10 KNOTS WILL SLACKEN THIS
EVENING AND BECOME LIGHT TO VARIABLE BEFORE TURNING MORE DECIDEDLY
SOUTHEAST TOWARD MORNING. STRONG WARM ADVECTION WILL FOSTER
WIDESPREAD PRECIPITATION SPREADING INTO SOUTHEAST MICHIGAN AROUND
15Z. RAPID EROSION OF DRY LAYER WILL FAVOR QUICK REDUCTION OF
CEILING TO LOW MVFR. LIGHT SNOW WILL BRIEFLY INCREASE IN INTENSITY
ALONG THE LEAD EDGE LEADING TO A LIMITED PERIOD OF IFR VSBY AND
LIGHT ACCUMULATIONS.

FOR DTW...DRY AIR WILL INITIALLY IMPEDE PROGRESS OF SNOW. CIGS NOT
EXPECTED TO FALL TO 5KFT UNTIL AROUND 12Z. APPROX START TIME FOR
SNOW IS 14-15Z. A PERIOD OF IFR VSBY IN MODERATE SNOW IS POSSIBLE
SHORTLY AFTER ONSET BUT DURATION WILL BE SHORT. PRECIP WILL
GRADUALLY BECOME LESS ORGANIZED AS RISING TEMPERATURES FORCE A
CHANGE TO RAIN. IN THE INTERIM, A PERIOD OF FZRA OR SLEET IS
POSSIBLE 17Z-20Z BUT CONFIDENCE IS LOW ATTM. EVENTUAL TRANSITION TO
DRIZZLE/BR APPEARS LIKELY LATE TUESDAY AFTERNOON AS DEWPOINTS RISE
WELL INTO THE 30S.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5KFT AFTER 12Z TUESDAY

* MEDIUM IN VISIBILITY BELOW 1/2 MILE IN FOG AFTER 21Z TUESDAY

* HIGH IN SNOW AS DOMINANT PTYPE THROUGH 17Z / FZRA OR SLEET 17Z-20Z
  / RA OR DZ AFTER 20Z

&&

.PREV DISCUSSION...ISSUED 350 AM EST MON MAR 2 2015

SHORT TERM...TODAY AND TONIGHT

A GLANCING BLOW OF COLDER AIR WILL PUSH A WEAK FRONTAL BOUNDARY
SOUTH INTO THE AREA WITH SCATTERED LIGHT SNOW SHOWERS ENDING EARLY
THIS MORNING AS THIS BOUNDARY SHIFTS TO THE OHIO VALLEY AND WASHES
OUT. WITH THE BULK OF THE COLD AIR WITH THIS SYSTEM PUSHING TO THE
EAST FROM THE NORTHERN GREAT LAKES INTO QUEBEC WITH TIME...THE AREA
WILL ACTUALLY HAVE NEUTRAL TEMPERATURE ADVECTION EARLY TODAY WHICH
WILL TRANSITION TO WEAK WARM AIR ADVECTION LATE TODAY INTO TONIGHT.
TEMPERATURES WILL CLIMB INTO THE MID/UPPER 20S IN MOST LOCATIONS AND
LIKELY AROUND 30 IN PARTS OF METRO DETROIT AS NORTHWEST FLOW WILL
DOWNSLOPE INTO MUCH OF AREA AND WARM THE AREA A FEW EXTRACT DEGREES
LOCALLY.

ELEVATED WARM AIR ADVECTION WILL INCREASE LATE TONIGHT AS LOW
PRESSURE APPROACHES FROM THE SOUTHWEST. AS MOISTURE INCREASES WITH
THE ENCROACHMENT OF THIS SYSTEM...EXPECT A FEW LIGHT SNOW SHOWERS TO
BUILD INTO THE AREA LATE TONIGHT...BASICALLY TOWARDS DAWN. MINIMUM
TEMPERATURES WILL BOTTOM OUT IN THE 10 TO 15 DEGREE RANGE LATE THIS
EVENING BEFORE AN INCREASING SOUTHEASTERLY FLOW LEADS TO SLOWLY
RISING TEMPERATURES OVERNIGHT WITH TEMPERATURES APPROACHING 20 IN
SOME LOCATIONS BY DAYBREAK.

LONG TERM...TUESDAY THROUGH SUNDAY

THE MAIN FORECAST CONCERN IN THE LONG TERM CONTINUES TO BE THE STORM
SYSTEM ON TUESDAY AND TUESDAY NIGHT AND THE RESULTANT PTYPE
EVOLUTION WITH THIS SYSTEM. FAIRLY QUIET STRETCH OF WEATHER FROM
WEDNESDAY INTO THE WEEKEND WITH THE MAIN STORY THERE BEING THE
INCREASING CHANCE OF A WARMING TREND.

FIRST WE WILL LOOK AT THE TUESDAY SYSTEM. A DEEP WEST COAST TROUGH
WILL RELEASE AND WORK ITS WAY ACROSS THE CONUS THE FRONT HALF OF THE
WEEK...BUT WILL DEVELOP A STRONG POSITIVE TILT IN THE PROCESS. THIS
WILL ALLOW THE NEXT POLAR JET WAVE DROPPING THROUGH CANADA TO
REDIRECT THE JET THROUGH CANADA WHILE PINCHING OFF THE BASE OF THE
TROUGH INTO A PSEUDO CUTOFF UPPER LOW...MORE OF AN OPEN WAVE. THE
RESULTANT SETUP IS ONE OF DEEP SOUTHWESTERLY FLOW THROUGH THE
CENTRAL CONUS WITH VERY STRONG JET AMPLIFICATION OVER THE GREAT
LAKES WITH A WAVE EJECTING OUT OF THE BASE OF THE TROUGH PHASING
WITH AN ARCTIC WAVE DROPPING THROUGH CANADA OVER THE MACKINAC
STRAITS. OVERALL MODELS HAVE BEEN PRETTY CONSISTENT WITH THE
SETUP...PRESENTING US WITH A MIXED BAG OF WINTER PTYPES AS A WARM
FRONT LIFTS INTO THE REGION ALLOWING THE WARM SECTOR TO BRUSH SE MI.
TYPICAL MODEL SHIFTS IN TIMING AND LOCATION ARE PRESENT LEADING TO
SMALL ADJUSTMENTS IN THE FORECAST. THE NAM AND GFS ARE FURTHER NORTH
WITH THE SYSTEM AS IS THE GEMREG BUT THIS MODEL FEATURES THE
SOUTHERN SFC LOW BECOMING AN OPEN TROUGH AS IT TRACKS THROUGH THE
REGION. ECMWF SEEMS TO BE A DECENT COMPROMISE AS IT DOES ADVERTISE A
WEAKER SOUTHERN SFC LOW GETTING INGESTED INTO THE STRONGER NORTHERN
LOW. THE JET FLARES UP OVERHEAD BECOMING +150 KNOTS WITH THE JET
AXIS THROUGH MID MI...WHICH ENCOURAGES THE ORGANIZATION FURTHER
NORTH. DEEP LAYER ISENTROPIC ASCENT ON THE WARM FRONT BRINGS IN VERY
GOOD MOISTURE TO THE COLUMN...WITH SPECIFIC HUMIDITIES OF 3 G/KG UP
TO NEARLY 500MB WITH VALUES NEAR 5 G/KG FROM ABOUT 700-900MB.
LEADING THETA E GRADIENT LOOKS TO LIFT INTO THE REGION BETWEEN 12-
15Z ON TUESDAY...WITH THE MOISTURE RIDGE PASSING THROUGH BETWEEN 18-
00Z. THE THERMAL PROFILE IS THE GUIDING FORCE AS TO HOW THE SYSTEM
PLAYS OUT THOUGH. EARLY IN THE AFTERNOON THE STRONG WAA ALOFT RAISES
TEMPS ABOVE 0C AROUND 750-850MB...EXPANDING DOWN TO THE SFC TOWARD
00Z WED. THIS WILL RESULT IN SNOW AT THE ONSET AFTER 12Z CHANGING TO
PELLETS/SLEET IN THE EARLY AFTERNOON...FREEZING RAIN BRIEFLY...THEN
LIKELY ALL RAIN BY 00Z ACROSS THE SOUTH. FURTHER NORTH THE THERMAL
PROFILE...THOUGH A BIT WARMER THEN PREVIOUS RUNS...CONTINUES TO
SUGGEST PTYPES WILL REMAIN MORE OF THE FROZEN VARIETY. A DRY SLOT
WILL MOVE IN QUICKLY AFTER 00Z LIMITING MOISTURE TO THE LOWEST PART
OF THE COLUMN WHICH COULD RESULT IN A PERIOD OF DRIZZLE BEFORE THE
COLD FRONT...AND LATER ARCTIC FRONT BRING BACK COLDER TEMPS AND A
CHANGEOVER TO LIGHT SNOW.

TOTAL QPF FOR THE SYSTEM LOOKS TO BE AROUND 0.3 INCHES. SNOWFALL
FROM THE FRONT END OF THE END LOOKS TO MAX OUT ACROSS THE NORTH WITH
AROUND 3 INCHES...WITH DOWN CLOSER TO AN INCH ACROSS THE SOUTHERN
COUNTIES. THERE REMAINS A CHANCE AN ENHANCED FRONTAL BAND ACROSS THE
NORTH COULD LEAD TO HIGH AMOUNTS BUT THIS SEEMS MOST LIKELY AT THIS
TIME. ANY FREEZING RAIN SHOULD BE LIGHT AS THE BEST MOISTURE WILL BE
THROUGH AT THAT POINT AND SOUNDINGS ADVERTISE A LONGER DURATION OF
PURE RAIN WITH SFC TEMPS RISING CLOSE TO 40F. THIS HAS LEAD TO
SLIGHTLY LOWER SNOW TOTALS FROM ABOUT M59 SOUTHWARD. CONTINUED
REFINEMENT TO PTYPE AND SNOW AMOUNTS AS THE SYSTEM BECOMES HANDLED
BY MORE HIRES MODELS.

BEYOND THE STORM...THE NEXT ARCTIC FRONT ON WEDNESDAY WILL BRING THE
RETURN OF LOW TEMPS NEAR ZERO WEDNESDAY AND THURSDAY NIGHTS. HIGHS
ON THURSDAY WILL ONLY REACH THE MID TEENS. BUT AFTER THAT...RIDGING
LOOKS TO BUILD EASTWARD WITH HEIGHTS ON THE RISE ACROSS THE GREAT
LAKES THROUGH THE WEEKEND. TEMPS WILL REMAIN BELOW NORMAL BUT AT
LEAST HIGHS WILL BE TAKING A RUN INTO THE LOW/MID 30S. MAINLY HIGH
PRESSURE WILL LEAD TO A QUITE STRETCH OF WEATHER DURING THIS TIME.

MARINE...

A COLD FRONT WILL GRAZE THE NORTHERN PORTIONS OF LAKE HURON TODAY
AND BRING A FRESH NORTHWEST BREEZE WITH GUSTS TO 30 KNOTS POSSIBLE
LATE MORNING AS COLD AND MARGINALLY UNSTABLE CONDITIONS DEVELOP.
HIGH PRESSURE WILL THEN BUILD INTO THE AREA FROM THE WEST WITH
NEARLY CALM CONDITIONS TAKING HOLD TONIGHT BEFORE MODERATE SOUTHERLY
WINDS EXPAND INTO THE REGION IN ADVANCE OF THE NEXT STORM SYSTEM DUE
INTO THE AREA BY TUESDAY. THE NEXT ARCTIC COLD FRONT WILL DROP DOWN
THROUGH THE REGION ON WEDNESDAY BRINGING COLD AND UNSTABLE AIR TO
THE GREAT LAKES. THIS MAY RESULT IN AN EXTENDED PERIOD OF GUSTY
WINDS REACHING NEAR 25 KNOTS.

&&

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

$$

AVIATION.....JVC
SHORT TERM...DG
LONG TERM....DRK
MARINE.......DRK


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


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