Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 121041 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 541 AM EST FRI FEB 12 2016 .AVIATION... VFR CEILINGS LOOK TO BE IN PLACE FOR MOST OF THE TAF PERIOD. HOWEVER...A STRONG ARCTIC FRONT MOVING THROUGH DURING THE AFTERNOON HOURS WILL TRIGGER SNOW SHOWERS...LIKELY CAUSING VISIBILITIES TO DIP INTO IFR...WITH LIGHT ACCUMULATIONS EXPECTED (LESS THAN ONE INCH). IN ADDITION...NORTHWEST WINDS WILL INCREASE BEHIND THE FRONTAL PASSAGE...GUSTING TO 25 KNOTS OR GREATER LATE THIS AFTERNOON INTO THE EVENING. THE POST FRONTAL ENVIRONMENT MAY SUPPORT SOME HEAVIER BUT MORE LOCALIZED SNOW SHOWERS/SQUALLS DURING THROUGH THE EVENING. LOW CONFIDENCE SCENARIO AT THIS STAGE GIVEN THE DIFFICULTY IN DEFINING BOTH TIMING AND DURATION...BUT QUICK/BRIEF DISRUPTIONS OF VISIBILITY /LIFR-IFR/ WILL BE POSSIBLE. FOR DTW... MID CLOUDS LOWERING WITH PERIOD OF SNOW SHOWERS THIS AFTERNOON AS A STRONG ARCTIC FRONT SLIPS THROUGH. ACCUMULATION PROJECTIONS CURRENTLY AT A HALF INCH OR LESS. INCREASING NORTHWEST WINDS /300-310 DEG/ BEHIND THIS FRONT LATE AFTERNOON INTO THIS EVENING...WITH GUSTS PEAKING OUT BETWEEN 25-30 KNOT RANGE DURING THIS TIME. POSSIBLE HEAVIER SNOW SHOWERS/SQUALLS COULD BRING ABRUPT VISIBILITY REDUCTIONS DOWN TO IFR-LIFR...BUT HIGH UNCERTAINTY YET IN POSSIBLE TIMING/COVERAGE. DRY NATURE OF THE ARCTIC AIRMASS MAY PROMOTE SKIES PARTIALLY CLEARING OUT SOONER THAN FORECASTED (9Z)...BUT RENEWED VFR CU UP IS THEN FAVORED DURING SATURDAY. //DTW THRESHOLD PROBABILITIES... * LOW FOR CEILING AOB 5KFT THIS MORNING MORNING...HIGH THIS AFTERNOON...THEN LOW TO MEDIUM CONFIDENCE TONIGHT INTO TOMORROW. * LOW TO REACH CROSSWIND THRESHOLDS FROM 300-310 DEGREES LATE FRIDAY AFTERNOON AND EVENING /21Z-03Z/ * HIGH FOR PTYPE AS SNOW. && .PREV DISCUSSION...ISSUED 306 AM EST FRI FEB 12 2016 DISCUSSION... THE STRONGEST ARCTIC FRONT OF THE SEASON...WITH H85 TEMPERATURES OF -25F OR LOWER...IS STILL SLATED TO MOVE THROUGH THE AREA LATE THIS AFTERNOON WITH THE ARCTIC AIRMASS THEN DEEPENING INTO SATURDAY AS THE ARCTIC HIGH PRESSURE CENTERED SHIFT EASTWARD OVER THE CENTRAL GREAT LAKES. WHILE SNOW SHOWERS WILL BE SOMEWHAT LIMITED WITH THIS FRONT IN TERMS OF DURATION AND COVERAGE...STILL EXPECT NUMEROUS SNOW SHOWERS ALONG AND BEHIND THIS FRONT...WITH LOCAL ACCUMULATIONS ON THE ORDER OF HALF AN INCH POSSIBLE. THE MORE NOTABLE ASPECT OF THIS SYSTEM WILL BE DANGEROUSLY COLD WIND CHILL READINGS TONIGHT INTO SATURDAY MORNING...ESPECIALLY OVER THE THUMB REGION WHERE NORTHWEST FLOW WILL BE ENHANCED AFTER TRAVELING ACROSS A LARGELY FROZEN SAGINAW BAY. IN ADDITION...LOW TEMPERATURES WILL BE COLDER...ZERO TO -5F...DUE TO THE POSITION OF THE ARCTIC AIR MASS AND ALSO DUE TO SLIGHTLY BETTER RADIATIONAL COOLING WITH SOME BREAKS IN THE CLOUDS AS LAKE EFFECT BANDS WILL ALIGN NNW TO SSE...AND FOCUS FROM I-75 WESTWARD. WIND CHILL READINGS OVER THE THUMB WILL HOVER AROUND -20F FROM LATE THIS EVENING INTO SATURDAY MORNING WITH READINGS CLOSER TO -10F TO THE WEST AND SOUTH OF THE ADVISORY AREA. WILL RUN THE ADVISORY FROM 03Z-16Z TO ENCOMPASSES THE PERIOD WHERE -15F TO -20F WIND CHILL READINGS AREA EXPECTED TO BE COMMON. THIS ARCTIC AIRMASS WILL BE RELATIVELY SHORT LIVED AND PEAK ON SATURDAY WITH HIGH TEMPERATURES CLIMBING ONLY INTO THE UPPER SINGLE DIGITS OVER THE THUMB TO PERHAPS 15F DETROIT SOUTH. SCATTERED SNOW SHOWERS WILL PERSIST AT TIMES TONIGHT INTO SUNDAY AS THE BITTERLY COLD NORTHWEST FLOW PRODUCES AN ABUNDANCE OF LAKE EFFECT SNOW BANDS/SHOWERS. THE NEXT DECENT CHANCE OF WIDESPREAD LIGHT SNOW WILL COME SUNDAY NIGHT INTO MONDAY AS A CLIPPER LOW PRESSURE SYSTEM SWEEPS INTO THE SOUTHERN GREAT LAKES AROUND THE BASE OF THE SLOWLY EXITING ARCTIC AIR. BY EARLY NEXT WEEK...SOUTHERN STREAM ENERGY IS EXPECTED TO PROGRESS INTO THE CONUS FROM THE CENTRAL PACIFIC OCEAN...WITH A NORTHERN STREAM SHORTWAVE DROPPING FROM THE VICINITY OF ALASKA INTO SOUTH CENTRAL CANADA DURING THE SAME TIME FRAME. MEDIUM RANGE MODELS ALL SUGGEST A DECENT PHASING OF THESE STREAMS BY THE TUESDAY/WEDNESDAY TIME FRAME. WHILE THE RESULTANT STORM SYSTEM WILL MOST LIKELY BRUSH THE AREA TO THE SOUTHEAST...AS A LARGE MAJORITY OF MODELS/ENSEMBLES SUGGEST...TIMING OF THE TWO MAIN SHORTWAVES...AND THE EVENTUAL INTERACTION OF THEM...WILL NEED TO BE MONITORED CLOSELY OVER THE NEXT SEVERAL DAYS...AND ESPECIALLY BY LATE THIS WEEKEND WHEN THEY ARE BETTER SAMPLED. THE UPPER LEVEL PATTERN APPEARS TO BECOME RATHER PROGRESSIVE IN THE WAKE OF THIS EARLY/MID WEEK SYSTEM...WITH TEMPERATURES MODERATING FURTHER BY THE END OF NEXT WEEK AS UPPER LEVEL RIDGING BUILDS EAST INTO THE AREA. MARINE... AN ARCTIC FRONT SLIDING THROUGH THE CENTRAL GREAT LAKES THIS AFTERNOON AND EVENING WILL PRODUCE SNOW SQUALLS...AS STRONG WINDS ALOFT AND FRIGID AIR GLIDING OVER THE WARMER LAKE WATERS WILL CREATE UNSTABLE CONDITIONS...ALLOWING GALE FORCE WINDS TO DEVELOP OVER THE OPEN WATERS OF LAKE HURON. HIGH-END GALE FORCE GUSTS TO 45 KNOTS ARE EXPECTED BY EVENING...LASTING INTO THE EARLY OVERNIGHT HOURS. WINDS WILL SUBSIDE BELOW GALE FORCE SATURDAY MORNING...THEN DECREASE FURTHER THROUGH THE DAY AND FINALLY BECOME LIGHT SATURDAY NIGHT AS HIGH PRESSURE SETTLES INTO THE AREA. THE GALE FORCE WINDS COMBINED WITH LARGE WAVES AND FRIGID AIR WILL ALSO CREATE AREAS OF HEAVY FREEZING SPRAY. A HEAVY FREEZING SPRAY WARNING IS IN EFFECT FOR ALL OF LAKE HURON LATE FRIDAY AFTERNOON THROUGH FRIDAY NIGHT...LASTING THROUGH SATURDAY FOR THE SOUTHERN BASIN OF THE LAKE. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...WIND CHILL ADVISORY FROM 10 PM THIS EVENING TO 11 AM EST SATURDAY FOR MIZ049-054-055-062-063. LAKE HURON...HEAVY FREEZING SPRAY WARNING FROM 1 PM THIS AFTERNOON TO 10 PM EST SATURDAY FOR LHZ363-462>464. GALE WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR LHZ363-421-441>443-462>464. HEAVY FREEZING SPRAY WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR LHZ421-441>443. HEAVY FREEZING SPRAY WARNING FROM 1 PM THIS AFTERNOON TO 4 AM EST SATURDAY FOR LHZ361-362. GALE WARNING FROM 1 PM THIS AFTERNOON TO 4 AM EST SATURDAY FOR LHZ361-362. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....DG DISCUSSION...DG MARINE.......SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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