Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 021915 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 315 PM EDT TUE SEP 2 2014 .SHORT TERM...THROUGH TONIGHT CURRENT OBSERVATIONS STILL HAVE THE SURFACE COLD FRONT SITUATED ROUGHLY ALONG A LINE FROM PORT HURON DOWN THROUGH ANN ARBOR. THIS HAS BEEN THE FOCUS FOR RAIN AND THUNDERSTORMS TODAY AND WILL CONTINUE TO BE THE CASE THROUGH THE EARLY EVENING. LATEST SATELLITE AND RADAR AS OF 3PM SHOW SHOWERS FINALLY DIMINISHING. AREAS NORTH OF THE BOUNDARY HAVE AND WILL REMAIN DRY THROUGH THE OVERNIGHT HOURS. ONCE THE FRONT SETTLES OFF TO THE EAST...RAIN/THUNDERSTORM CHANCES OVER THE SOUTHERN CWA WILL END. VERY FEW CHANGES WERE MADE TO THE GOING FORECAST WITH THE ONLY CHANGE BEING TO UP POPS SLIGHTLY ACROSS THE SOUTH THROUGH 21Z. HIGH PRESSURE WILL SLOWLY TAKE OVER THIS EVENING AND EXTEND THROUGH THE OVERNIGHT HOURS. DRIER AIR HAS ALREADY BEGUN FILTERING INTO THE NORTHERN HALF OF THE CWA WHERE DEWPOINTS ARE IN THE MIDDLE TO UPPER 50S. THIS TREND IS EXPECTED TO CONTINUE WHILE SLOWLY SCOURING OUT ANY LOW LEVEL LINGERING CLOUDS OVERNIGHT. A WAS DISCUSSED IN THE PREVIOUS DISCUSSION...A FEW AREAS OF SHALLOW GROUND FOG MAY BE POSSIBLE ACROSS NORTHERN AREAS EARLY WEDNESDAY MORNING A LITTLE MOISTURE REMAINS IN THE BOUNDARY LAYER. LOWS OVERNIGHT WILL BE COOLER THAN THE PREVIOUS NIGHT WITH LOWS RANGING FROM THE LOWER 60S OVER THE DETROIT METRO AREA TO THE UPPER 50S TO THE NORTH. && .LONG TERM... DRY WEATHER AND INCREASING TEMPS ARE ON TAP FOR WEDNESDAY THROUGH THURSDAY AS HEIGHTS BUILD AND SWLY FLOW INCREASES AHEAD OF THE WAVE DIGGING INTO THE PACNW THIS AFTERNOON. THIS WAVE WILL SHEAR ACROSS SOUTHERN CANADA, REACHING JAMES BAY BY FRIDAY. AS IT DOES SO, A RESPECTABLE LOW-LEVEL JET RESPONSE IS FORECAST TO EMERGE UPSTREAM SUPPORTING EPISODES OF CONVECTION OVER THE UPPER MS VALLEY. FLOW WILL ONLY SLOWLY BACK TO SOUTHERLY ON WEDNESDAY WITH LITTLE AIRMASS CHANGE COMPARED TO TODAY. HOWEVER, WITH GREATER INSOLATION EXPECTED AS TODAY`S COLD FRONT PROGRESSES EAST, TEMPERATURES SHOULD MODERATE A FEW DEGREES TO AROUND 80F. WARM ADVECTION THROUGH THE COLUMN WILL TAKE HOLD ON THURSDAY AS DEEP LAYER SWLY FLOW INCREASES AHEAD OF THE RAPIDLY APPROACHING PAC NW WAVE. CONVECTION WILL REMAIN TIED TO THE UPSTREAM THETA-E AXIS/LOW-LEVEL JET. WHILE IT IS NOT OUT OF THE QUESTION THAT NOCTURNAL REMNANT ACTIVITY APPROACHES THE AREA LATE WED NIGHT OR THURSDAY MORNING, MUCH PREFER TO LET THE COARSE RESOLUTION MODELS HANDLE THE SYNOPTIC SCALE AND WILL DEFER TO HIGH RES ARW/WRF FOR SPECIFICS. AS EXPECTED, THE HIGH RES GUIDANCE DOES NOT ALLOW ANY SUCH REMNANTS TO REACH THE CWA AND KEEPS CONVECTION TIED TO UPSTREAM FORECING. AS SUCH, PREFER TO SEE THE WHITE`S OF ITS EYES SO TO SPEAK BEFORE CLUTTERING THE GRIDS WITH POPS. THE FORECAST IS THEREFORE DRY THROUGH THURSDAY. INSTEAD, THURSDAY WILL LIKELY BE CHARACTERIZED BY A FAIR AMOUNT OF CONVECTIVE DEBRIS EARLY, INCREASING DEWPOINTS, AND H85 TEMPERATURES RISING INTO THE UPPER TEENS. PER EXPECTATION FOR NO/MINIMAL PRECIP, MAINTAINED FORECAST HIGHS ON THE WARMER SIDE OF GUIDANCE. TSTORM CHANCES WILL INCREASE LATE THURSDAY NIGHT AS VEERING LLJ AXIS MIGRATES TOWARD THE AREA. SHOWERS AND THUNDERSTORMS REMAIN LIKELY FRIDAY AS A COLD FRONT MOVES THROUGH THE REGION WITH MOIST AND UNSTABLE AIR PRECEDING THE FRONT. THERE REMAINS A DECENT DENSITY GRADIENT IN PLACE AND ISOLATED SEVERE WIND GUSTS REMAIN POSSIBLE. COOL HIGH PRESSURE WILL FILL IN BEHIND THE FRONT FOR SEVERAL DAYS AS TEMPERATURES TREND SEVERAL DEGREES COOLER THAN NORMAL. && .MARINE... LIGHT WINDS WILL GIVE WAY TO A MODERATE SOUTHERLY BREEZE THURSDAY INTO FRIDAY AS A COLD FRONT APPROACHES THE AREA. STABLE WARM SOUTHERLY FLOW WILL KEEP WIND GUSTS TO A MINIMUM. THERE IS A LOW CHANCE FOR THUNDERSTORMS ACROSS NORTHERN LAKE HURON ON THURSDAY...WITH INCREASING CHANCES FOR ALL THE WATERS THURSDAY NIGHT THROUGH FRIDAY NIGHT. && .AVIATION...ISSUED 118 PM EDT TUE SEP 2 2014 //DISCUSSION... SURFACE COLD FRONT IS EVER SO SLOWLY SAGGING OFF TO THE EAST...HOWEVER WITH THE SLOW EXIT RAIN WILL EXIST THROUGH THE AFTERNOON FOR LOCATIONS SOUTH OF PTK. ONCE THE FRONT DOES SHIFT OUT OF THE AREA THIS EVENING...HIGH PRESSURE BUILDS IN OVERNIGHT AND WILL REMAIN IN PLACE THROUGH THE TAF CYCLE. WINDS WILL REMAIN LIGHT AND GENERALLY OUT OF THE WEST/SOUTHWEST. FOG WAS MENTIONED IN THE PREVIOUS DISCUSSION AND THE LATEST MODEL SOUNDINGS STILL SHOW LOW FOG POTENTIAL EARLY WEDNESDAY MORNING WITH SOME GROUND FOG POSSIBLE ESPECIALLY FOR NORTHERN AREAS. FOR DTW...CHANCES FOR RAIN WILL CONTINUE THROUGH THE AFTERNOON WITH A LOW POTENTIAL FOR A THUNDERSTORM. WINDS WILL GENERALLY REMAIN OUT OF THE WEST EVEN AS THE FRONTAL BOUNDARY SLIDES EAST THIS AFTERNOON. //DTW THRESHOLD THREATS... * LOW CONFIDENCE/POTENTIAL FOR A THUNDERSTORM THROUGH THE AFTERNOON. * HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH THE EARLY EVENING. * MEDIUM CONFIDENCE IN CEILINGS ABOVE 5000 FEET OVERNIGHT. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...SS LONG TERM....JVC/MM MARINE.......JVC AVIATION.....SS YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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