058  
FXUS63 KDTX 271748  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
1248 PM EST THU FEB 27 2020  
   
AVIATION
 
 
WEST TO NORTHWEST WIND GUSTING NEAR 35 KNOTS IS THE PRIMARY AVIATION  
WEATHER ELEMENT FOR THE AFTERNOON. THESE CONDITIONS EASE UP DURING  
THE EVENING WITH FEWER GUSTS AND/OR GUSTS UNDER 20 KNOTS AFTER  
MIDNIGHT SHORT OF FULL DECOUPLING. COLDER AIR MOVING IN ON THIS WIND  
PATTERN IS ACTIVATING SNOW SHOWERS FROM LAKE MICHIGAN THE STRONGEST  
OF WHICH PRODUCE A VERY BRIEF IFR REDUCTION WITH MVFR MORE LIKELY AT  
ANY ONE TERMINAL SITE. ANY BOOST OF INTENSITY PROVIDED BY LATE  
FEBRUARY DAYTIME WARMING IS COMPENSATED FOR BY A TREND TOWARD  
CELLULAR/SCATTERED COVERAGE WITH LOW PREDICTABILITY ON TIMING AND  
LOCATION. EXPECT A DECREASE IN COVERAGE OF STRATOCU TONIGHT IN  
BETWEEN STREAMERS OF LAKE EFFECT CLOUDS AND SNOW SHOWERS. THE WIND  
DIRECTION FROM 270-300 SUGGESTS GREATER COVERAGE ALONG AND SOUTH OF  
I-96/94 POSSIBLY BRUSHING DTW THROUGH SUNRISE FRIDAY. A REBOUND IN  
WIND GUSTS OCCURS ACROSS THE AREA AS DAYTIME WARMING INCREASES FRIDAY  
MORNING.  
 
FOR DTW... WIND AVERAGING A 300 DIRECTION CONTINUES TO CAUSE  
CROSSWIND THRESHOLD CONCERNS WITH GUSTS NEAR 35 KNOTS UNTIL EASING  
BACK TOWARD SUNSET. AFTER THAT, EXPECT SKY CONDITION TO VARY WIDELY  
FROM CLEAR TO BROKEN VFR BELOW 5000 FT TO POSSIBLY MVFR AT TIMES DUE  
TO STREAMERS OF LAKE EFFECT CLOUDS AND SNOW SHOWERS. OVERALL,  
COVERAGE IS EXPECTED TO BE GREATER SOUTH OF THE I-94 CORRIDOR THROUGH  
FRIDAY MORNING.  
 
DTW THRESHOLD PROBABILITIES...  
 
* HIGH FOR CEILING 5000 FT OR LESS TODAY. MODERATE TONIGHT.  
 
* HIGH FOR REACHING CROSSWIND THRESHOLD THIS AFTERNOON.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 308 AM EST THU FEB 27 2020  
 
DISCUSSION...  
 
DEFORMATION SNOW IS DISINTEGRATING AS THE WINTER STORM INTENSIFIES  
AND LIFTS THROUGH THE LOWER GREAT LAKES THIS MORNING - NO ADDITIONAL  
ACCUMULATION. 12-06Z STORM TOTAL SNOW ENDED UP AROUND 4 INCHES WHICH  
WAS ON TOP OF THE 1-2 THAT FELL THE PREVIOUS NIGHT. GUSTS UP TO 30  
MPH CONTINUE TO CAUSE AREAS OF BLOWING SNOW IN RURAL AND OPEN OPEN  
AREAS.  
 
MID-LEVEL THERMAL TROUGH CHARACTERIZED BY 850MB TEMPERATURES AROUND  
-16C NOW BEING USHERED INTO THE AREA BY THE CRISP PV ANOMALY NOTED  
ON WATER VAPOR IMAGERY OVER LAKES SUPERIOR AND MICHIGAN AND  
EXTENDING INTO THE OHIO VALLEY THIS MORNING. AS PGF ASSOCIATED WITH  
THE DEEPENING CYCLONE OVER EASTERN ONTARIO/QUEBEC STEADILY  
INCREASES, LAPSE RATES WITHIN WELL-MIXED WNW FLOW WILL SUPPORT GUSTS  
UP TO 35 MPH THROUGH TODAY WITH HIGHER GUSTS POSSIBLE OVER  
NORTHEASTERN ZONES. THIS WILL BE THE CASE THROUGH FRIDAY AS LARGE  
SCALE CONDITIONS REMAIN GOVERNED BY THE DEVELOPING CLOSED  
CIRCULATION OVER THE NE SECTOR OF THE US. DEEP LAYER CYCLONIC FLOW  
AND OVERLAKE INSTABILITY WILL BE SUFFICIENT THROUGHOUT THIS TIME TO  
SUPPORT PERIODS OF SNOW SHOWERS AND FLURRIES, PARTICULARLY AS  
FORECAST SOUNDINGS INDICATE THE 3KFT DEEP DGZ WILL REMAIN ENTIRELY  
WITHIN THE THE SURFACE-BASED CONVECTIVE LAYER. EVEN SO, THE  
POTENTIAL FOR ORGANIZED SNOW SHOWERS/SQUALL TYPE OF ACTIVITY APPEARS  
QUITE LIMITED AT THIS TIME. DIURNAL INSTABILITY THIS TIME OF YEAR IS  
GENERALLY MORE SUPPORTIVE OF CELLULAR CONVECTION ESPECIALLY GIVEN  
THE MUSHY INVERSION ATOP THE MOIST LAYER. BOUNDARY LAYER CONVERGENCE  
WITHIN WNW FLOW AT THE SURFACE WILL ALSO BE MINIMAL, THOUGH THE  
OCCASIONAL WAVE OF MID-LEVEL FORCING MAY SUPPORT PERIODS OF MORE  
ORGANIZED ACTIVITY, ESPECIALLY AT NIGHT. THE GREATEST SIGNAL FOR  
IMPACTFUL SNOW SHOWERS IS 00-06Z TONIGHT IN THE CLIMATOLOGICAL  
CORRIDOR BETWEEN I-94 AND M59. HOWEVER, EXPECTATIONS ARE LOW AT THIS  
TIME.  
 
THE MEANINGFUL CHANGE TO THE FORECAST FOR TODAY THROUGH TONIGHT  
WAS TO RAISE POPS. GIVEN FAVORABLE SUPERSATURATION OF THE DGZ WITHIN  
THE BOUNDARY LAYER AND CONTRIBUTIONS TO THE MOISTURE FIELD FROM THE  
GREAT LAKES OCCURING AGAINST A BACKDROP OF PERSISTENT CYCLONIC FLOW,  
POPS WERE RAISED TO HIGH CHC/LIKELY THROUGH TONIGHT. LITTLE/NO  
ACCUMULATION IS FORECAST AT THIS TIME. ENVIRONMENT WILL BE  
ESSENTIALLY UNCHANGED ON FRIDAY, THOUGH VEERING BOUNDARY LAYER FLOW  
AND SUBSIDENCE BEHIND FRIDAY NIGHT'S WAVE WILL DAMPEN SNOW SHOWER  
POTENTIAL FOR A TIME. PROBABLE RETURN OF SNOW SHOWERS OR FLURRIES BY  
FRIDAY AFTN AS THE SAME PROCESSES OF A SATURATED, COLD BOUNDARY  
LAYER WILL STILL BE AT WORK.  
 
BIG MOMENTUM PUSH INTO THE WESTERN US LATE THIS WEEKEND INTO EARLY  
NEXT WEEK FROM BOTH THE PACIFIC AND SUBTROPICAL JETS. THIS WILL VERY  
QUICKLY FORCE BUILDING HEIGHTS INTO THE GREAT LAKES REGION DURING  
THE LATTER HALF OF THE WEEKEND. RAPIDLY MODIFYING THERMAL PROFILE  
WILL SEE 850MB TEMPERATURES WARM BY 15-18C DURING THE SATURDAY-  
SUNDAY NIGHT TIME FRAME REACHING LOW SINGLE DIGITS MONDAY MORNING.  
HIGHS DURING THIS TIME RISE INTO THE 30S SATURDAY, 40S SUNDAY, AND  
50S BY MONDAY  
 
MARINE...  
 
NORTHWEST WINDS RAMP UP THIS MORNING AS COLD ADVECTION KICKS IN WITH  
LOW PRESSURE DEEPENING OVER THE EASTERN GREAT LAKES AND TRACKING  
NORTHWARD INTO QUEBEC TODAY. STEEPENING LOW-LEVEL LAPSE RATES AND A  
STRONG GRADIENT ACROSS THE REGION WILL LEAD TO HIGH LIKELIHOOD FOR  
GALE FORCE GUSTS AND POSSIBLY A FEW HOURS OF SUSTAINED GALES ACROSS  
LAKE HURON TODAY INTO TONIGHT. INCREASING OVER-LAKE INSTABILITY  
BRINGS THE POTENTIAL FOR SNOW SQUALLS TODAY WHILE THE GALES AND WAVE  
ACTION ON THE ORDER OF 10-12+ FEET OVER CENTRAL LAKE HURON LEAD TO  
HEAVY FREEZING SPRAY CONCERNS. SMALL CRAFT ADVISORY CONDITIONS DUE  
TO GUSTS ON THE ORDER OF 30 KT WILL PREVAIL FOR INNER SAGINAW BAY,  
LAKE ST. CLAIR, AND WESTERN LAKE ERIE. NORTHWEST TO WEST WINDS  
WEAKEN GRADUALLY OVER THE COURSE OF FRIDAY WITH A PERSISTENT  
PRESSURE GRADIENT IN PLACE DUE TO HIGH PRESSURE BUILDING INTO THE  
MIDWEST. SNOW SHOWERS WILL CONTINUE TO BE LIKELY ACROSS LAKE HURON  
ON FRIDAY.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...LAKESHORE FLOOD ADVISORY UNTIL 10 AM EST FRIDAY FOR MIZ049.  
 
LAKE HURON...HEAVY FREEZING SPRAY WARNING UNTIL 10 AM EST FRIDAY FOR LHZ361>363-  
462>464.  
 
GALE WARNING UNTIL 10 AM EST FRIDAY FOR LHZ361>363-421-441>443-  
462>464.  
 
SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LHZ422.  
 
LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LCZ460.  
 
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LEZ444.  
 
LOW WATER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR LEZ444.  
 

 
 

 
 
AVIATION.....BT  
DISCUSSION...JVC  
MARINE.......JVC  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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