Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 231757 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1257 PM EST SUN NOV 23 2014 .AVIATION... //DISCUSSION... A BRIEF PERIOD OF LIGHT RAIN MAY HOLD TOGETHER AT MBS SHORTLY AFTER 18Z...BUT THE REST OF THE TERMINALS WILL BE DRY FOR THE BULK OF THE AFTERNOON BEFORE A SURGE OF RAIN MOVES IN FROM THE OHIO VALLEY. THE PATTERN OF RAIN...ALONG WITH THE SURFACE LOW AND WARM FRONT DEVELOPING TOWARD THE SOUTH END OF LAKE MICHIGAN...WILL PRODUCE IFR/LIFR CONDITIONS ACROSS ALL LOCATIONS DURING MID TO LATE EVENING. SE WIND AVERAGING 15 KNOTS WILL MAKE IT DIFFICULT FOR LESS THAN IFR VISIBILITY RESTRICTION BUT LIFR CEILING WILL BE A HIGH CONFIDENCE FORECAST GIVEN THE MATURE WARM FRONT APPROACHING WITH THE PRIMARY LOW PRESSURE CENTER. NORTHWEST TO SOUTHEAST POSITIONING OF THE FRONT FAVORS SIMILAR ONSET TIMING THROUGH THE TERMINAL CORRIDOR FOLLOWED BY A PROGRESSION OF THE WARM SECTOR MONDAY MORNING WITHIN A FEW HOURS FROM SOUTH TO NORTH OVER THE REGION. THE EXCEPTION TO THIS MAY BE WITH THE ONSET OF STRONG SOUTHWEST FLOW AT MBS WHERE THE SURFACE FRONT/TROUGH WILL LINGER FOR A LONGER PERIOD THROUGH THE MORNING. WARM SECTOR WIND GUSTS NEAR 30 KNOTS WILL LIKELY EXCEED 40 KNOTS FROM THE SOUTHWEST UPON PASSAGE OF A STRONG COLD FRONT MONDAY AFTERNOON. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILING BELOW 5000 FEET TONIGHT THROUGH MONDAY. * HIGH CONFIDENCE IN RAIN AS PRECIPITATION TYPE && .PREV DISCUSSION...ISSUED 1050 AM EST SUN NOV 23 2014 UPDATE... A WEAK WING OF MID LEVEL ISENTROPIC ASCENT WILL RUN ITS COURSE THROUGH THE LATE MORNING AND EARLY AFTERNOON IN FAVOR OF A BREAK IN COVERAGE FOR A FEW HOURS DURING MID AFTERNOON. THE BREAK WILL OCCUR WHILE THE NEXT MOISTURE SURGE QUICKLY RELOADS AND MOVES NORTHWARD FROM THE TENNESSEE VALLEY. INCOMING MODEL DATA POINTS TO THE BREAK FILLING IN RAPIDLY DURING LATE AFTERNOON INTO EARLY EVENING AS THE CENTRAL GULF COAST UPPER LOW MOVES INTO WESTERN KENTUCKY. THE LOW WILL BE PRECEDED BY A STRONG AND DEEP SURGE OF GULF MOISTURE TRANSPORT SURFACE THROUGH 700 MB ENSURING RENEWED WIDESPREAD COVERAGE OF RAIN SHOWERS TOWARD SUNSET THROUGH TONIGHT. THE NEXT FORECAST UPDATE WILL REFLECT LESS COVERAGE OF SHOWERS DURING THE FIRST HALF OF THE AFTERNOON BUT MAINTAIN A TREND TOWARD CATEGORICAL PROBS LATE IN THE DAY. PREV DISCUSSION...ISSUED 320 AM EST SUN NOV 23 2014 SHORT TERM... TODAY AND TONIGHT COPIOUS AMOUNT OF UPPER LEVEL ENERGY/PV WORKING THROUGH THE ROCKIES THIS MORNING. MOISTURE LADEN UPPER LEVEL WAVE OVER EASTERN TEXAS ALREADY BECOMING ABSORBED/CAPTURED WITHIN THE STRENGTHENING SOUTHWEST FLOW OVER THE CENTRAL CONUS. IMPRESSIVE 12 HR HEIGHT FALL CENTER (-18 DAM) WILL MOVE OVER WESTERN OHIO VALLEY BY 12Z MONDAY...SUPPORTING GOOD CYCLOGENESIS MOVING INTO THE CENTRAL GREAT LAKES. THIS WILL ASSURE A SOAKING RAIN TONIGHT...WITH STRONG LOW LEVEL JET/GOOD OVERRUNNING SET UP/LARGE SCALE ASCENT...AND 850 MB DEW PTS OF 7-8 C TO WORK WITH. RAINFALL TOTALS AROUND 1 INCH WILL LIKELY BE COMMON. A QUICK LOOK AT 6 HR FLOOD GUIDANCE SHOWS 2 INCH THRESHOLDS...AND DO THINK THE GROUND WILL THAW OUT ENOUGH TODAY TO BE ABLE TO HANDLE THIS RAINFALL...AND NOT PLANNING ON ISSUING A FLOOD WATCH DESPITE THE 3+ STANDARD ANOMALY WITH RESPECT TO PW VALES. A MILD START TO THE DAY...AS TEMPERATURE ARE CURRENTLY IN THE MID 40S TO AROUND 50 DEGREES. HOWEVER...WITH THE SURFACE/NEAR SURFACE WINDS BACKING OUT OF THE SOUTHEAST TODAY...WOULD NOT EXPECT MUCH MORE OF A RISE (LOWER 50S)...WITH TEMPS HOVERING IN THE UPPER 40S TO LOWER 50S TONIGHT WITH RENEWED SURGE OF WARM AIR ARRIVING. LONG TERM... MONDAY THROUGH SATURDAY DYNAMIC MID LEVEL WAVE LOCKED ONTO THE EXIT REGION OF AN ACTIVE UPPER JET OF NORTH PACIFIC ORIGIN WILL QUICKLY LIFT INTO THE GREAT LAKES ON MONDAY...IMMEDIATELY BEHIND THE LEAD SYSTEM WORKING THROUGH TONIGHT. SOME DEGREE OF INTERACTION BETWEEN THESE PV FEATURES AND ATTENDANT UPPER JET COUPLING WILL RESULT IN A STEADY STRENGTHENING OF THE ASSOCIATED SURFACE LOW TRACKING FROM SOUTHERN LAKE MICHIGAN TO JUST NORTH OF THE STRAITS THROUGH MONDAY. THERE REMAINS SOME VARIABILITY YET WITHIN THE 00Z MODEL GUIDANCE IN TERMS OF BOTH THE STRENGTH AND FORWARD MOMENTUM OF THE KEY LOW LEVEL FEATURES HEADING INTO MONDAY. HOWEVER THE GUIDANCE ENVELOP CONTINUES TO CONTRACT WITH EACH PROGRESSIVE MODEL CYCLE...LENDING INCREASING CONFIDENCE IN THE DETAILS THROUGH THIS TIME. BRIEF WINDOW OF DEEPER PRE-FRONTAL SOUTHWEST FLOW IN PLACE MONDAY MORNING...TEMPERATURES LIKELY PEAKING IN THE LOWER 50S DURING THIS TIME. BRIEF SUBSIDENCE SUGGESTS A SMALL PAUSE IN SHOWER DEVELOPMENT MID MORNING...BEFORE THE INBOUND MID LEVEL WAVE WORKS ACROSS LATE MORNING/EARLY AFTERNOON. STRONG SIGNAL OF FRONTAL CONVERGENCE TUCKED BENEATH FAVORABLE UPPER JET DYNAMICS AND A PERIOD OF GOOD CVA POINTS TO AN INCREASE IN SHOWER COVERAGE THROUGH THIS TIME. DIMINISHING STABILITY THROUGH THE COLUMN COULD YIELD A FEW RUMBLES OF THUNDER AS WELL. MAIN FORECAST ELEMENT OF INTEREST REMAINS THE WIND POTENTIAL AS STRONG COLD AIR ADVECTION ENSUES FROM MID AFTERNOON INTO THE EVENING HOURS. STRONG POST-FRONTAL SOUTHWEST GRADIENT TAKES HOLD DURING THIS TIME...SUSTAINED SPEEDS INCREASING INTO THE 25 MPH RANGE. GUST POTENTIAL WILL CAPITALIZE ON A PERIOD OF STRONG 280-285K ISENTROPIC DESCENT AND AT LEAST WEAK MIXING POTENTIAL AS LAPSE RATES STEEPEN WITH THE ADVECTIVE PROCESS. RECENT GUIDANCE MAINTAINS WIND SPEEDS IN THE 40 KNOT RANGE AT 925 MB. THIS WOULD INDICATE GUSTS CLOSE TO OR AT A LOW END ADVISORY /40 TO 45 MPH/...GREATEST GUSTS CENTERED 21Z-02Z. AGGRESSIVE COLD AIR ADVECTION BRINGS TEMPERATURES BACK INTO THE 30S BY EARLY EVENING...A PLUMMETING FREEZING LEVEL REINTRODUCING THE POTENTIAL FOR SNOW SHOWERS TO MIX IN DURING THIS TIME. MODEST LAKE MICHIGAN RESPONSE INITIALLY /LAKE INDUCED EQUILIBRIUM LEVELS BELOW 5000 FT/ WITH THE STRENGTH OF THE WIND FIELD LIKELY CONTRIBUTING TO A LACK OF BETTER DOWNSTREAM ORGANIZATION. THE MAIN SHORTWAVE ANCHORING THE PRIMARY HEIGHT FALL AXIS WILL SETTLE THROUGH OVERNIGHT...WHICH MAY HELP AUGMENT THE MOISTURE FLUX IN GENERATING SOME LIGHT SHOWERS WITH MINOR ACCUMULATION. LOW TEMPERATURES BOTTOM OUT WITHIN THE 25 TO 30 DEGREE RANGE. EXTENDED STRETCH OF BELOW NORMAL TEMPERATURES STARTING TUESDAY... LINGERING LOW LEVEL THERMAL TROUGH /-12C AT 850 MB/ AND PLENTY OF CLOUD COVER ENSURING HIGHS ARRIVE WITHIN A COUPLE DEGREE OF FREEZING. LOW LEVEL FLOW VEERS TO A WESTERLY COMPONENT DURING THE DAY...A MORE FAVORABLE TRAJECTORY FOR GREATER DOWNSTREAM ADVANCEMENT OF THE LAKE MICHIGAN MOISTURE PLUME AND SOME LOCALIZED CONVERGENCE. THIS WILL MAINTAIN A CHANCE FOR SNOW SHOWERS THROUGH THE DIURNAL HEATING CYCLE. DRY AND COLD INTO WEDNESDAY UNDER LOWER AMPLITUDE RIDGING. CLIPPER SYSTEM ON TRACK TO LIFT ACROSS THE GREAT LAKES WEDNESDAY NIGHT AND EARLY THURSDAY. MODEST MOISTURE RECOVERY IMMEDIATELY IN ADVANCE OF THIS SYSTEM WOULD SUPPORT A LIGHT ACCUMULATING SNOWFALL AS THE COMPACT MID LEVEL DYNAMICS SWEEP ACROSS DURING THIS TIME. DAYTIME HIGHS IN THE LOWER 30S BOTH WEDNESDAY AND THURSDAY. MARINE... MODERATE SOUTHERLY WINDS WILL REMAIN IN PLACE TODAY AND TONIGHT AS STRENGTHENING LOW PRESSURE LIFTS INTO THE GREAT LAKES. THE ARRIVAL OF WARMER AIR IN ADVANCE OF THIS SYSTEM WILL CONTAIN THE GUST POTENTIAL...WITH WINDS GENERALLY AT 15 TO 25 KNOTS THROUGH THIS PERIOD. THE LOW PRESSURE SYSTEM WILL LIFT ACROSS THE WESTERN AND NORTHERN GREAT LAKES THROUGH MONDAY...SENDING A STRONG COLD FRONT ACROSS THE AREA MONDAY AFTERNOON. GALE FORCE WINDS LOOK LIKELY BEHIND THE COLD FRONT MONDAY AND MONDAY NIGHT AS A TIGHT PRESSURE GRADIENT DEVELOPS AND MUCH COLDER AIR RUSHES INTO THE AREA...WITH GUSTS POTENTIAL IN EXCESS OF 45 KNOTS. THERE IS STILL SOME UNCERTAINTY WITH HOW MUCH THIS SYSTEM WILL DEEPEN AND THE EXACT TRACK IT WILL TAKE ACROSS THE GREAT LAKES. FURTHER ADJUSTMENT TO THE FORECAST IS POSSIBLE. IF THE SYSTEM DEEPENS FURTHER THAN CURRENTLY ANTICIPATED...STORM FORCE WIND GUSTS COULD DEVELOP OVER PORTIONS OF LAKE HURON. THOSE WITH INTERESTS IN THE GREAT LAKES MONDAY AND MONDAY NIGHT SHOULD FOLLOW CHANGES IN THE FORECAST CLOSELY. A STORM WATCH IS NOW IN EFFECT FOR CENTRAL LAKE HURON...WHILE A GALE WATCH REMAINS IN EFFECT MONDAY AND MONDAY NIGHT FOR ALL OTHER MARINE AREAS. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LHZ361- 421-422-441>443-462>464. STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LHZ362- 363. LAKE ST CLAIR...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LCZ460. MICHIGAN WATERS OF LAKE ERIE...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LEZ444. && $$ AVIATION.....BT UPDATE.......BT SHORT TERM...SF LONG TERM....MR MARINE.......MR YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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