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
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