389  
FXUS63 KDTX 171101  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
601 AM EST WED JAN 17 2018  
 
   
AVIATION
 
 
LAKE STRATUS WILL BRING MVFR TO LOWER VFR CEILINGS TODAY WITH A  
TREND TO LESS COVERAGE MID/LATE AFTERNOON. GRADIENT FLOW WILL  
INCREASE AND BRING WIND GUSTS TO 20+ KNOTS LATE IN THE DAY. IN FACT,  
HIGHEST GUSTS, 25 KNOTS, LOOK TO OCCUR DURING THE EVENING INTO PARTS  
OF THE OVERNIGHT.  
 
/DTW THRESHOLD PROBABILITIES...  
 
* HIGH FOR CIGS AOB 5KFT THIS MORNING, MEDIUM THIS AFTERNOON, LOW  
TONIGHT.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 240 AM EST WED JAN 17 2018  
 
DISCUSSION...  
 
NEAR TERM / TODAY THROUGH TONIGHT  
 
AS OF 240 AM EST...UPPER-LEVEL TROUGH CONTINUES TO OPEN UP AND  
BECOME MORE PROGRESSIVE WITH TIME AS IT CONTINUES ITS EXIT EAST OF  
THE REGION EARLY THIS MORNING. INCREASING SUBSIDENCE HAS ALLOWED FOR  
A FEW PATCHES OF CLEARING IN THE CLOUD COVER, WITH TEMPERATURES  
PLUMMETING INTO THE LOWER SINGLE DIGITS TO A FEW DEGREES BELOW ZERO  
IN THESE AREAS DUE TO THE FRESH SNOWPACK. WHERE CLOUDS HAVE LINGERED  
THROUGH THE NIGHT, TEMPERATURES HAVE BEEN A FEW DEGREES WARMER  
SOLIDLY IN THE SINGLE DIGITS. WOULD NOT BE SURPRISED IF LOW  
TEMPERATURES BOTTOM OUT NEAR OR SLIGHTLY BELOW ZERO FOR MOST AREAS  
AROUND DAYBREAK, SO WILL GO ON THE COLDER SIDE OF GUIDANCE.  
 
BEHIND THE DEPARTING TROUGH, UPPER-LEVEL HEIGHTS WILL CONTINUE TO  
BUILD THROUGH TODAY AND INTO TONIGHT AS SURFACE HIGH PRESSURE RIDGES  
IN FROM THE SOUTHWEST. THIS PATTERN WILL RESULT IN MAINLY DRY  
CONDITIONS THROUGH THE NEAR TERM PERIOD. THE EXCEPTION WILL BE  
SPORADIC BRIEF FLURRIES AS A RELEASE OF LAKE MOISTURE DOWNSTREAM OF  
LAKE MICHIGAN PLAGUES THE REGION WITH MOSTLY CLOUDY STRATUS/STRATOCU  
THROUGHOUT THE DAY. THE LOW-LEVEL FLOW WILL BACK TO THE  
WEST/SOUTHWEST AND BECOME INCREASINGLY GUSTY AS THE DAY PROGRESSES  
DUE TO A TIGHTENING PRESSURE GRADIENT BETWEEN THE HIGH TO THE SOUTH  
AND LOW PRESSURE TRACKING UP NEAR HUDSON'S BAY. WIND GUSTS OF 20-30  
MPH WILL BE COMMON ESPECIALLY DURING THE AFTERNOON AND EVENING, WITH  
OCCASIONAL GUSTS OF 30-40 MPH IN THE SAGINAW VALLEY AND NORTHERN  
THUMB REGIONS. HIGH TEMPERATURES WILL REACH INTO THE MID 20S. WITH  
THE GUSTY WINDS IN PLACE, IT WILL FEEL MUCH COLDER WITH WIND CHILLS  
IN THE SINGLE DIGITS.  
 
DRIER AIR WILL FILTER IN TONIGHT ALLOWING FOR GRADUALLY CLEARING  
SKIES. CONTINUED GUSTY WINDS WILL LIMIT LOW TEMPERATURES TONIGHT,  
WITH LOWS ONLY FALLING INTO THE MID AND UPPER TEENS WITH A FEW  
READINGS NEAR 20.  
 
SHORT TERM / THURSDAY THROUGH FRIDAY NIGHT  
 
QUIET AND DRY WEATHER CONTINUES THROUGH THE SHORT TERM PERIOD WITH  
DRY NORTHWEST FLOW ALOFT AND FLAT UPPER-LEVEL RIDGING. LAKE  
AGGREGATE MOISTURE IN THE LOW-LEVELS WILL CONTINUE TO LEAD TO  
PERIODS OF MOSTLY CLOUDY SKIES, ESPECIALLY NORTH OF THE DETROIT  
METRO. SURFACE HIGH PRESSURE SETTLING ACROSS THE SOUTHEAST STATES  
WILL RESULT IN SOUTHWESTERLY BREEZY RETURN FLOW SETTING UP ACROSS  
THE REGION, ADVECTING IN A MODERATING AIRMASS WITH TIME AS  
TEMPERATURES RISE INTO THE MID AND UPPER 30S. NORTHERN STREAM  
SHORTWAVE ENERGY WILL DIVE SOUTHEAST ACROSS THE NORTHERN GREAT LAKES  
THURSDAY INTO THURSDAY NIGHT WITH LITTLE FANFARE AS THIS SYSTEM WILL  
BE QUITE MOISTURE-STARVED.  
 
LONG TERM / SATURDAY THROUGH TUESDAY  
 
LONG RANGE GUIDANCE CONTINUES TO BE IN FAIRLY GOOD AGREEMENT WITH AN  
INCREASINGLY UNSETTLED WEATHER PATTERN TAKING SHAPE FOR THE WEEKEND  
AND INTO EARLY NEXT WEEK. VIGOROUS PACIFIC ENERGY MOVING INTO THE  
INTERMOUNTAIN WEST WILL CARVE OUT A DEEPENING LONGWAVE TROUGH THAT  
WILL INDUCE LEE CYCLOGENESIS OVER THE CENTRAL PLAINS FRIDAY INTO  
SATURDAY. THIS LOW PRESSURE SYSTEM WILL DEEPEN AS IT TRACKS  
NORTHEASTWARD INTO THE GREAT LAKES REGION, WITH GOOD CONSENSUS THAT  
THE LOW WILL TRACK NORTHWEST OF SOUTHEAST MICHIGAN. THIS TRACK WILL  
RESULT IN THE REGION BEING PLACED IN THE WARM SECTOR AHEAD OF THE  
SYSTEM, WHICH WILL FEATURE SOUTHWESTERLY FLOW ADVECTING IN MILDER  
AND MORE MOIST AIR AS TEMPERATURES RISE INTO THE 40S. A TIGHTENING  
PRESSURE GRADIENT BETWEEN THE APPROACHING LOW AND LINGERING HIGH  
PRESSURE ANCHORED OVER THE SOUTHEAST CONUS WILL ALSO LEAD TO A  
PERIOD OF GUSTY WINDS AS WELL.  
 
THERE REMAINS SOME TIMING DIFFERENCES IN THE LONG RANGE GUIDANCE AS  
TO THE BEGINNING OF INCREASING RAIN CHANCES, SO WILL TAKE A  
CONSENSUS BLEND WHICH FAVORS INCREASING CHANCES FOR DRIZZLE/LIGHT  
RAIN SHOWERS LATE SATURDAY NIGHT AND INTO SUNDAY, WITH MORE STEADY  
RAIN SUNDAY NIGHT AND INTO MONDAY. TIMING WILL BE REFINED AS WE GET  
CLOSER TO THE EVENT, BUT THE WEEKEND AND INTO EARLY NEXT WEEK WILL  
GENERALLY FEATURE CLOUDY, MILD, BUT DAMP CONDITIONS.  
 
MARINE...  
 
THE GALE WARNING WILL CONTINUE FOR WEDNESDAY AND WEDNESDAY EVENING  
AS STRONG AND UNSTABLE SOUTHWEST FLOW DEVELOPS WITHIN STRENGTHENING  
PRESSURE GRADIENT BETWEEN ARCTIC HIGH PRESSURE TO THE SOUTH AND LOW  
PRESSURE TRAVERSING THE SOUTHERN SHORES OF HUDSON BAY. GUSTS TO AT  
LEAST MARGINAL GALES ARE PROBABLE OVER A GOOD PORTION OF LAKE HURON,  
INCLUDING SAGINAW BAY AND THE NORTHERN NEARSHORE WATERS. GUSTS TO 40  
KNOT GALES ARE ANTICIPATED OVER THE CENTRAL OPEN WATERS. EPISODES OF  
FRESH TO STRONG SOUTHWEST FLOW WILL BE COMMON FOR THE REMAINDER OF  
THE WEEK, BUT GUST POTENTIAL WILL DIMINISH DUE TO AN INCREASINGLY  
WARM STABLE FETCH.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...GALE WARNING FROM 10 AM THIS MORNING TO 4 AM EST THURSDAY FOR  
LHZ363-441-462.  
 
GALE WARNING FROM 10 AM THIS MORNING TO 10 PM EST THIS EVENING FOR  
LHZ362-421.  
 
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
AVIATION.....MR  
DISCUSSION...IRL  
MARINE.......DG  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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