Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1201 AM EDT MON MAR 30 2015


.AVIATION...

GENERALLY MVFR STRATUS WILL PERSIST TONIGHT EVEN AS -SHRASN SHIFT TO 
THE EAST WITH PASSAGE OF TROUGH AXIS. THESE LOWER CLOUDS WILL BREAK 
UP MONDAY MONDAY INTO AFTERNOON...THEN RETURN LATE MONDAY NIGHT AS 
LIGHT RAIN SPREADS INTO AREA WITH NEXT LOW PRESSURE SYSTEM. GUSTY 
WINDS WILL EASE OVERNIGHT...BUT STILL EXPECT SOME GUSTS TO 25 KNOTS 
FROM THE SSW. MIXING ON MONDAY WILL BRING WESTERLY GUSTS OF THE SAME.

FOR DTW...MVFR CIGS OVERNIGHT WITH SSW WIND GUSTS EASING OVERNIGHT. 
GUSTS TO 25 KNOTS WILL BE POSSIBLE AGAIN BY MIDDAY MONDAY AS THE 
BOUNDARY LAYER MIXES WITH THE CLEARING OF LOW LEVEL CLOUDS.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS AOB 5000 FEET OVERNIGHT INTO EARLY MONDAY.

* LOW IN WIND GUSTS TO 25 KNOTS FROM 270-280 DEGREES 18Z-00Z MONDAY.

&&

.PREV DISCUSSION...ISSUED 402 PM EDT SUN MAR 29 2015 

SHORT TERM...THIS AFTERNOON AND TONIGHT

A LINE OF PRECIPITATION AHEAD OF AN IMPRESSIVE SHORTWAVE IS 
CURRENTLY PUSHING IN FROM WESTERN MICHIGAN TOWARDS THE CWA THIS 
AFTERNOON. A SURFACE TROUGH WILL TRACK THROUGH ALONG WITH THIS LINE 
OF PRECIPITATION...TURNING SOUTHERLY WINDS TO THE SOUTHWEST THIS 
EVENING. UPSTREAM OBSERVATIONS SHOW A MIX OF RAIN...SNOW AND EVEN 
SOME SLEET AS TEMPERATURES CRASH WITH WET BULBING GIVEN THE VERY DRY 
LOWER LEVELS. THE BRIGHTER UPSTREAM RETURNS ON RADAR ARE INDICATIVE 
OF THIS AFOREMENTIONED SLEET WITH SOME VERTICAL MOTION ASSOCIATED 
WITH THE VIGOROUS SHORTWAVE TRACKING THROUGH THE GREAT LAKES. THE 
THREAT FOR SLEET IS EXPECTED TO END AFTER THE INITIAL LINE TRACKS 
THROUGH AND THE SHORTWAVE AND ENHANCED VERTICAL MOTION HEAD EAST. 
THE SHORT AND INTERMITTENT NATURE OF THE SLEET PRECLUDES THE 
ISSUANCE OF ANY HEADLINES WITH THIS INITIAL LINE OF ACTIVITY.

BEHIND THE MAIN TROUGH AND SHORTWAVE THE MAIN COLD FRONT WILL THEN 
TRACK EAST DURING THE EVENING HOURS...CONTINUING THE CHANCE FOR 
RAIN AND SNOW AS THE UPPER COLUMN COOLS BUT SURFACE TEMPERATURES 
STAY ABOVE FREEZING. ONCE THE MAIN COLD FRONT TRACKS EAST 
PRECIPITATION WILL COME TO AN END BY 06Z. ALTHOUGH DRIZZLE WILL 
STILL BE A THREAT AFTER 06Z...DRY AIR ADVECTION WILL WORK AGAINST 
THIS LATE TONIGHT. OVERALL NOT MUCH FROZEN PRECIPITATION IS EXPECTED 
TO ACCUMULATE GIVEN SURFACE TEMPERATURES ARE EXPECTED TO REMAIN 
ABOVE FREEZING WITH LIQUID MIXING IN WITH FROZEN PRECIPITATION FOR 
THE BALANCE OF THE EVENT.

LONG TERM...

THE UPPER TROUGH WILL EXIT EAST BY EARLY TOMORROW...ALLOWING FLAT 
RIDGING TO BRIEFLY OVERTAKE THE AREA BEFORE THE NEXT UPPER WAVE 
EJECTING OUT OF BRITISH COLUMBIA DROPS DOWN THROUGH THE GREAT LAKES 
MONDAY NIGHT AND TUESDAY.

LAPSE RATES WILL STEEPEN TOMORROW AS COLDER AIR ALOFT ARRIVES BEHIND 
THE FRONT AND SURFACE HEATING TAKES PLACE DURING THE DAY. A WELL-
MIXED AND DEEPENING BOUNDARY LAYER WILL PROVIDE BREEZY CONDITIONS 
FROM THE WEST-NORTHWEST...WITH GUSTS TO 35 MPH POSSIBLE THROUGH THE 
AFTERNOON. RIDGING WILL THEN PROVIDE LIGHTER WINDS FOR THE EVENING 
AND OVERNIGHT. SOME SUNSHINE AND A BETTER START TO THE DAY WITH MINS 
ONLY IN THE 30S WILL PROVIDE WARMER TEMPERATURES...WITH MOS VALUES 
FROM THE LOW TO UPPER 40S LOOKING REASONABLE FOR MONDAY AFTERNOON.

UPPER WAVE WILL THEN TRACK THROUGH THE SOUTHERN GREAT LAKES IN THE 
EVENING AND OVERNIGHT...WITH PREFERENCE IN TRACK GIVEN TO THE 
STRONGER CONSENSUS OF THE EURO/GFS. NAM STILL LOOKS TOO AGGRESSIVE IN 
DEEPENING THE SYSTEM. ELEVATED PORTION OF THE FRONT THAT WILL DROP 
THROUGH TONIGHT LOOKS TO REMAIN OVER MICHIGAN AS THIS UPPER WAVE 
APPROACHES. EXPECTING TO SEE A NICE FGEN RESPONSE AS THE MID-LEVEL 
WAVE AND SURFACE LOW TRACK ACROSS THE SOUTHERN GREAT LAKES...WITH 
THE LOW CENTER EXPECTED TO PASS ALONG/JUST SOUTH OF THE MICHIGAN 
BORDER. THE FGEN COMBINED WITH MID-LEVEL PVA AND SOME FORCING FROM 
AN UPPER JET WILL WORK WITH 3 G/KG (AVERAGE) OF SPECIFIC HUMIDITY 
ACROSS THE AREA TO GENERATE PRECIPITATION...MAINLY SOUTH OF A LINE 
FROM SAGINAW TO PORT HURON. PRECIPITATION TYPE IS A LITTLE 
TRICKIER...WITH DRY AIR PRECEDING THE SYSTEM IN THE LOWEST LEVELS 
PROMOTING WET BULB EFFECTS. WENT WITH THERMAL FIELDS SIMILAR TO THE 
GFS...BUT DID HEDGE THE FORECAST SLIGHTLY WARMER BASED ON THE EURO. 
THE NAM WAS NOT USED. THIS KEEPS A RAIN/SNOW MIX IN THE 
FORECAST...WITH THE BEST CHANCE FOR SNOW STILL NORTH OF FLINT. THIS 
IS WHERE PRECIPITATION AMOUNTS ALSO TAPER OFF HOWEVER...AND DUE TO 
THE SLIGHT SHIFT IN TRACK...FORECAST AMOUNTS DO NOT EXCEED AN INCH.

COLDER AIR FILTERING INTO THE AREA BEHIND LOW PRESSURE WILL FIGHT 
DIURNAL HEATING ON TUESDAY. MUCH LOWER DEWPOINTS WILL ALSO 
ARRIVE...KEEPING A CHANCE FOR RAIN SHOWERS TO MIX WITH SNOW (WET-
BULB EFFECTS) DESPITE MAX TEMPERATURES IN THE UPPER 30S AND LOW 40S.

HIGH PRESSURE WILL BE IN PLACE FOR WEDNESDAY RESULTING IN DRY 
CONDITIONS AND CALM WINDS ACROSS SOUTHEAST MICHIGAN. WARM AIR 
ADVECTION WILL ALLOW WARMER TEMPERATURES TO FILTER INTO THE REGION 
WITH HIGHS ON WEDNESDAY IN THE UPPER 40S AND LOW 50S. WARMER 
TEMPERATURES WILL CONTINUE INTO THURSDAY /HIGHS IN THE MID 60S FOR 
MOST LOCATIONS/ HOWEVER...THE NEXT WEATHER SYSTEM ARRIVES THURSDAY. 
THIS LOW PRESSURE SYSTEM TRACKING ACROSS THE NORTHERN GREAT LAKES 
WILL DRAG A COLD FRONT ACROSS LOWER MICHIGAN. WITH TEMPERATURES WELL 
ABOVE FREEZING...PRECIP WILL REMAIN ALL RAIN. TIMING ON THIS SYSTEM 
IS A BIT UNCERTAIN THOUGH AND WILL HAVE TO BE FINE TUNED AS THE WEEK 
PROGRESSES. DRY WEATHER RETURNS FOR FRIDAY AND SATURDAY AS WEAK HIGH 
PRESSURE TRIES TO BUILD INTO THE REGION. RAIN POSSIBLY RETURNS FOR 
SATURDAY NIGHT AS A WEAK LOW PRESSURE SYSTEM SLIDES JUST NORTH AND 
EAST OF SOUTHEAST MICHIGAN.

MARINE...

A GALE WARNING IS NOW IN EFFECT FOR ALL OF LAKE HURON WITH UPSTREAM 
OBSERVATIONS OVER LAKE MICHIGAN SUPPORTING MOSTLY GUSTS TO GALE 
FORCE AS OF 300 PM. THE WARNING REMAINS IN EFFECT INTO TONIGHT FOR 
ALL OF THE LAKE AS SOUTHERLY WINDS CONTINUE TO INCREASE AHEAD OF A 
LOW PRESSURE SYSTEM TRACKING ACROSS ONTARIO. THE WARNING WILL THEN 
REMAIN IN EFFECT FOR THE NORTHERN THIRD OF LAKE HURON OVERNIGHT AND 
THROUGH MONDAY AFTERNOON AS WINDS FLIP TO THE NORTHWEST. COLDER AIR 
SPILLING INTO THE AREA WILL ALLOW STRONGER WIND GUSTS TO MIX DOWN TO 
THE SURFACE...CONTINUING THE THREAT FOR GALES OVER THE NORTHERN 
PORTION OF THE LAKE AND ALLOWING GUSTS TO REACH ABOUT 30 KNOTS FOR 
THE SOUTHERN TWO-THIRDS OF LAKE HURON.

FURTHER TO THE SOUTH...A SMALL CRAFT ADVISORY IS NOW IN EFFECT FOR 
LAKE ST CLAIR AND WESTERN LAKE ERIE...WITH GUSTS TO 30 KNOTS 
EXPECTED THIS EVENING. 

BRIEF RIDGING WILL THEN ALLOW FOR LIGHTER WINDS ACROSS ALL OF THE 
CENTRAL GREAT LAKES MONDAY EVENING BEFORE THE NEXT LOW PRESSURE 
SYSTEM TRACKS ACROSS THE AREA MONDAY NIGHT AND TUESDAY. THIS SYSTEM 
DOES NOT LOOK TO PRODUCE STRONG WINDS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 6 PM EDT THIS EVENING FOR LHZ361-362.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....99
SHORT TERM...KURIMSKI
LONG TERM....HLO/RK
MARINE.......HLO


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

National Weather Service Glossary of Abbreviations