Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 080455 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1155 PM EST SUN FEB 7 2016 .AVIATION... AREA OF STRATUS AROUND 3500 FEET WILL WORK THROUGH TERMINALS EARLY IN THE FORECAST...ESPECIALLY MBS/FNT. SSW FLOW WILL VEER TO SW ON MONDAY AS SHORTWAVE A DISTURBANCE PIVOTS INTO THE AREA...BRINGING ADDITIONAL STRATUS...LOWER VFR/MVFR. COLDER AIR WILL THEN GRADUALLY FUNNEL INTO AREA MIDDAY MONDAY INTO MONDAY EVENING ON W/WNW FLOW WITH AN INCREASING CHANCE OF -SHRASNS AND THEN JUST -SHSNS. THIS ACTIVITY WILL BE RATHER LIGHT AND SHOULD NOT IMPACT TERMINALS TOO MUCH. AT DTW...GENERALLY EXPECT CIGS ABOVE 5KFT OVERNIGHT AS CURRENT AREA OF STRATUS IN THE 3500-5000 FOOT RANGE LIFTS NORTH OF TERMINALS. ADDITIONAL MVFR STRATUS WILL BE POSSIBLE MONDAY MORNING WITH AT LEAST BKN CIGS HOVERING IN THE 3000-5000 FOOT RANGE PERSISTING THRU THE DAY AS SHORTWAVE DIGS INTO THE CENTRAL GREAT LAKES. //DTW THRESHOLD PROBABILITIES... * LOW FOR CIGS AOB 5KFT OVERNIGHT...MEDIUM ON MONDAY. && .PREV DISCUSSION...ISSUED 349 PM EST SUN FEB 7 2016 DISCUSSION... THE AMPLIFICATION AND EVENTUAL BROADENING OF AN UPPER LEVEL TROUGH OVER SOUTHEASTERN MICHIGAN IS RESULTING IN A VERY CHALLENGING FORECAST FOR THE EARLY WEEK PERIOD. SPECIFICALLY...THERE IS LOW PREDICTABILITY IN THE INTEGRITY AND TIMING OF INDIVIDUAL SHORTWAVE ENERGY THAT WILL BE HARBORED WITHIN THE UPPER LEVEL TROUGH AXIS. DISTINCT UPPER LEVEL ABSOLUTE VORTICITY CENTERS ARE DIGGING SOUTHEASTWARD OUT OF THE NORTHERN PLAINS THIS AFTERNOON. FORECAST DATA SUPPORTS THE LEAD EDGE OR GRADIENT OF THE PARENT PV ANOMALY TO PUSH ACROSS LAKE MICHIGAN AND TO IMPINGE UPON WESTERN LOWER MICHIGAN PRIOR TO 00Z THIS EVENING. MODELS ARE STRONGLY IN FAVOR OF A RELATIVELY MESSY JET EVOLUTION DURING THE NEXT 6-12 HOURS WHERE A DISORGANIZED UPPER LEVEL JET STREAM ELEMENT WILL RAPIDLY BECOME ANTICYCLONIC IN CURVATURE AND BECOME PHASED WITHIN THE ENTRANCE REGION OF THE MUCH MORE DOMINANT NE U.S. JET BRANCH. THE NET RESULT IS FOR SOME DECENT TO STRONG RIGHT ENTRANCE REGION DYNAMICS DEVELOPING OVER SOUTHEASTERN MICHIGAN. WHAT IS LIKELY MORE FAVORABLE FROM A DYNAMICAL STANDPOINT IS THE CONVERGENCE BOUNDARY/FRONT THAT WILL BECOME SHARPER THIS EVENING ALONG THE PV GRADIENT WHERE FORCING WILL BE MAXIMIZED DUE TO THE MASS ADJUSTMENT CAUSED BY THE TROPOPAUSE FOLD ARRIVAL. NUMERICAL OUTPUT SUPPORTS A CORRIDOR OF LIGHT RAIN SHOWER DEVELOPMENT (WARM SFC TEMPERATURES) OVER MUCH OF SOUTHEASTERN MICHIGAN BETWEEN 01-04Z. PRETTY INCONSEQUENTIAL...WITH VERY LIGHT QPF AMOUNTS OF A COUPLE HUNDREDTHS OF QPF OR LESS. THE LOW PREDICTABILITY THEN BEGINS IN EARNEST ALREADY LATE TONIGHT AS INTRA-INTER MODEL CONTINUITY HAS BEEN EXTREMELY POOR WITH REGARDS TO AMOUNT OF LOW LEVEL MOISTURE THAT WILL SATURATE/DEVELOP OVER THE EXTREME SOUTHEASTERN SECTIONS OF THE CWA...NEAR DETROIT RIVER/LAKE ST CLAIR. EARLIER DETERMINISTIC AND HIRES SOLUTIONS SHOWED AN INCREASING LOW LEVEL MOISTURE PLUME AND PRECIPITATION DURING THE 10- 12Z TIMEFRAME ACROSS SECTIONS OF SOUTH CENTRAL LOWER MICHIGAN AND OVER THE FAR WESTERN LAKE ERIE BASIN. THE NEW 07.12Z ITERATIONS OF THESE SAME MODELS ARRIVED AND BACKED WAY OFF. PREFERENCE SIDES WITH A DRIER SOLUTION FOR THE MONDAY MORNING COMMUTE TIME FOR A COUPLE OF REASONS...1. THERE IS NO LOW LEVEL JET FEATURE DRIVING ADVECTION...2. LOW LEVEL SATURATION WHILE BEING AIDED BY RIGHT ENTRANCE REGION DYNAMICS ALOFT IS STILL LIKELY DEPENDENT ON A GOOD AMOUNT OF PRECIPITATION/HYDROMETEOR PRODUCTION THIS EVENING. THE NAM IS SHOWING A MINIMUM CORRIDOR OF 850-700MB SPECIFIC HUMIDITY DIRECTLY IN PLACE AT 12Z MONDAY. THE MODEL SOLUTIONS NOW SUPPORT THE CORRIDOR OF LIGHT PRECIPITATIONPROGRESSING EAST OF LOWER MICHIGAN FOR THE MONDAY PERIOD SETTING UP WHAT SHOULD BE FAIRLY WIDESPREAD DRY CONDITIONS. WHILE A CLASSIC MIDLEVEL DRY SLOT IS NOT RESOLVED FOR MONDAY...THERE IS A GOOD AMOUNT OF DRY AIR ENTRAINED WITHIN THE MIDLEVEL TROUGH AXIS. ADDITIONALLY...MODEL DATA SUPPORTS NEUTRAL TO ISENTROPIC DOWNGLIDE OVER SOUTHEASTERN MICHIGAN. CARRYING A LOW CHANCE FOR SNOW SHOWERS IN MANY AREAS. THE ONE ITEM TO WATCH FOR IS SOME POSSIBLE CONVECTIVE SHOWER DEVELOPMENT ALONG A SECONDARY COLD FRONT/GRADIENT FEATURE THAT WILL PUSH INTO THE FAR WESTERN CWA/SAGINAW VALLEY BETWEEN 21- 24Z MONDAY. NO TANGIBLE HEIGHT RISES WILL SUPPORT VERY LITTLE COLD ADVECTION ON MONDAY. PREFERENCE SIDES WITH WARMER TEMPERATURES IN THE UPPER 30S TO NEAR 40 DEGREES. THE MODEL TREND TODAY HAS BEEN FOR MORE OF A SOUTHWARD SOLUTION WITH THE MAIN VORTICITY ENERGY WITHIN THE TROUGH AXIS BY TUESDAY. THIS SUGGESTS POSSIBLY MORE OF AN EASTWARD LEAK TO THE SURFACE LOW/REFLECTION THAN WHAT WAS EARLIER ADVERTISED. THE BEST CVA WOULD SHIFT SOUTH AND EAST OF THE CWA WHICH WOULD TAKE THE MAIN DYNAMICAL SUPPORT FOR PRECIPITATION WITH IT. WHAT REMAINS OVER SOUTHEASTERN MICHIGAN IS MORE IN THE WAY OF NORTHWESTERLY FLOW WHICH IS A DRY ONE FOR THE AREA. THE LAKE EFFECT POTENTIAL STILL REMAINS FOR TUESDAY AND WEDNESDAY WITH VERY COLD TEMPERATURES OF -12 TO -20C 850MB EXPANDING ACROSS THE AREA. THE ONE ITEM OF PARTICULAR INTEREST IS A POTENTIAL LAKE AGGREGATE TROUGH WHICH COULD LEAD TO A GOOD POTENTIAL FOR SHOVEL-ABLE SNOWS OVER PORTIONS OF THE THUMB...PRIMARILY ON WEDNESDAY. THERE IS GROWING CONFIDENCE THAT WE WILL SEE SOME OF THE COLDEST AIR OF THE SEASON SO FAR LATE NEXT WEEK INTO NEXT WEEKEND. 12Z GFS/GEFS MEAN/ECMWF CONTINUE TO HIGHLIGHT -15 TO -20C 850 MB TEMPS WED/THU. POTENTIAL FOR EVEN COLDER AIR NEXT WEEKEND WITH THE ARCTIC CLOSED LOW SWEEPING INTO SOUTHEAST CANADA. STILL SOME UNCERTAINTY WITH THE MAGNITUDE OF COLD AIR AS IT LOOKS TO BE A GLANCING BLOW WITH THE HEART OF THE COLD AIR OVER THE NORTHEAST US...BUT EVEN A GLANCING BLOW WOULD LIKELY PUT 850 MB TEMPS NEAR -20 TO -25C WHICH WOULD BE THE COLDEST AIRMASS SO FAR THIS WINTER. LAKE EFFECT SNOW SHOWER ACTIVITY WILL BE AROUND...ESPECIALLY WEDNESDAY...BUT LIKELY ON A DIMINISHING TREND INTO THE END OF THE WEEK AS COLDER...DRIER NW FLOW SETS UP. MARINE... MODERATE SOUTH-SOUTHWEST OF 15 TO 25 KNOTS WINDS WILL CONTINUE INTO THIS EVENING BEFORE DIMINISHING CONSIDERABLY TONIGHT INTO TUESDAY AS EXPANSIVE LOW PRESSURE SETTLES ACROSS THE GREAT LAKES. WINDS WILL BACK TO NORTHWESTERLY BY LATE TUESDAY INTO WEDNESDAY AND INCREASE AS LOW PRESSURE DEPARTS DURING THE MIDWEEK PERIOD. GUSTS OF 25 TO 30 KNOTS ARE ANTICIPATED OVER SOUTHERN LAKE HURON...ALONG WITH SNOW SQUALLS...AS MUCH COLDER FILTERS INTO THE GREAT LAKES REGION OVER THE UPCOMING WEEK. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....DG DISCUSSION...CB/DT MARINE.......SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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