Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221131
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
731 AM EDT WED APR 22 2015


.AVIATION...

LARGE LOW PRESSURE SYSTEM OVER THE REGION WILL PRODUCE ANOTHER DAY
OF GUSTY WINDS AND RAIN/SNOW SHOWERS. COLDER AIR ALOFT WILL RESULT
IN MORE SNOW SHOWERS TODAY BUT WARMING SFC TEMPERATURES WILL RESULT
IN RAIN/SNOW MIX THIS AFTERNOON. COVERAGE OF SHOWERS IS QUESTIONABLE
SO WILL TEMPO THIS FIRST BATCH MOVING THROUGH ABOUT 12-14Z AND
AMEND FOR AFTERNOON COVERAGE LATER. CEILINGS WILL VARY THROUGH THE
DAY WITH PRIMARILY VFR CONDITIONS...BUT DIPPING TO MVFR WITHIN
PASSING SHOWERS. DAYTIME HEATING WILL AGAIN PROMOTE DEEP MIXING
WHICH WILL PRODUCE STRONG WIND GUSTS TODAY. THOUGH NOT AS HIGH AS
YESTERDAY DUE TO WEAKER FLOW ALOFT...WE SHOULD SEE NORTHWEST WINDS
GUSTING TO 30 KNOTS THIS AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT TODAY. LOW CONFIDENCE
  TONIGHT.

* HIGH CONFIDENCE IN SNOW THIS MORNING...MIXING WITH RAIN THIS
  AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 320 AM EDT WED APR 22 2015

SHORT TERM...TODAY AND TONIGHT

ANOTHER DAY WITH THE UPPER LEVEL LOW SLOWLY DRIFTING EASTWARD OVER
THE GREAT LAKES. THE LOW IS SEVERAL DAYS OVER AND PAST ITS PRIME
THUS IT WILL SLOWLY BE FILLING IN THROUGH THE DAY.
REGARDLESS...THERE IS STILL PLENTY OF COLD AIR THROUGHOUT THE COLUMN
WHICH WILL AGAIN LEAD TO VERY STEEP LL LAPSE RATES WITH MIXING
DEPTHS JUST 50-100MB LOWER THAN TUESDAY...AROUND 800MB. THE COLD
POOL AT 500MB HAS SHIFTED NE OF THE AREA BUT THE THERMAL TROUGH IN
THE LOWER LAYERS WILL LINGER INTO TONIGHT BEHIND A WEAK COLD
FRONT/TROUGH DROPPING THOUGH SE MI THIS AFTERNOON. 850/700 TEMPS
WILL STILL BE -7/-17C THIS AFTERNOON WITH 850MB TEMPS FALLING
OVERNIGHT BEHIND THE TROUGH AXIS BELOW -11C.

MODELS UNDER FORECAST THE LL JET TUESDAY BY A GOOD 10 KNOTS PEAKING
AROUND 65 KNOTS AT 650MB WITH WINDS >=50 KNOTS DOWN TO 775MB. THIS
ALLOWED SFC WINDS TO PEAK CLOSE TO 50 MPH ALONG AND SOUTH OF 696
CORRIDOR. WILL AGAIN SEE GUSTY CONDITIONS TODAY AS WE STILL HAVE
COLD CYCLONIC FLOW OVER THE REGION WITH A DEEP LAYER OF NW FLOW
AVERAGING 30-40 KNOTS. THEY DO ALL AGREE THAT WITH THE SLIGHT
WEAKENING OF THE TROUGH AND THE STRONG CORE OF LL JET WINDS SHIFTING
SE WHICH WILL LIMIT THE GUST POTENTIAL BUT WE SHOULD STILL SEE A
BREEZY DAY WITH GUSTS IN THE 30-40MPH RANGE.

AS FOR PRECIP...THE DRY AIR AT THE SFC WILL LEAD TO WET BULB
TEMPERATURES AT OR BELOW ZERO THIS AFTERNOON. CAA HAS COOLED MOST OF
THE SOUNDING BELOW ZERO WITH THE BULK OF THE UNSTABLE LAYER THROUGH
THE DGZ WHICH WILL LEAD TO SNOW GROWTH WITHIN PASSING SHOWERS. WITH
SFC TEMPS HAVING BEEN ABOVE FREEZING FOR SO LONG AND HIGH TEMPS
TOMORROW IN THE LOW 40S...THIS WILL LIKELY LEAD TO ANY LIGHT
SNOWFALL QUICKLY MELTING AFTER THE SHOWER PASSES.

LASTLY...MIN TEMPS TONIGHT WILL FALL BELOW FREEZING FOR MOST
LOCATIONS AS THE LOW LEVEL THERMAL TROUGH GETS REINFORCEMENT FROM
THE NORTH/NORTHWEST FLOW BEHIND THE COLD FRONT IN THE AFTERNOON.

LONG TERM...

EXTENDED PERIOD OF DRY WEATHER IN THE OFFING AS SEVERAL DAYS OF
HEIGHT RISES OVER THE GREAT LAKES COMMENCES WITH THE DEPARTURE OF
THE LINGERING CLOSED LOW AND DIGGING HEIGHTS OVER THE ROCKIES.

PRESSURE GRADIENT WILL REMAIN ELEVATED ON THURSDAY AS LOWER MICHIGAN
REMAINS ENTRENCHED IN BROAD DEEP LAYER MOIST CYCLONIC FLOW. MID-
LEVEL COLD POOL AND APRIL INSOLATION WILL COMBINE AGAIN TO PRODUCE A
DEEP BOUNDARY LAYER SUPPORTIVE OF WIDESPREAD STRATOCU AND WIND GUSTS
TO 25 MPH. THERMAL TROUGH CHARACTERIZED BY H85 TEMPERATURES OF -11C
TO BEGIN THE DAY AND HIGH CLOUD FRACTION WILL LIMIT TEMPERATURES TO
THE MID 40S...SLIGHTLY HIGHER THAN THOSE EXPECTED FOR TODAY GIVEN
THE POTENTIAL FOR AFTN BREAKUP OF CLOUDS AS THE THERMAL TROUGH AND
DEEPER MOISTURE LIFT NORTHEAST. DEPARTURE OF THE UPPER LOW TO
NORTHERN NEW ENGLAND WILL ALLOW THE GRADIENT TO WEAKEN CONSIDERABLY
RELATIVE TO RECENT NIGHTS. DECOUPLING MAY STRUGGLE AT FIRST GIVEN
H10 GEOSTROPHIC WIND PROGS AROUND 15 KTS FOR MUCH OF THE NIGHT, BUT
SHOULD OCCUR EVENTUALLY AS SKIES CLEAR. NO ARGUMENTS WITH 00Z
GUIDANCE IN THE MID/UPPER 20S BY FRIDAY MORNING.

SUBSIDENCE WILL INCREASE THROUGH THE COLUMN AS HEIGHTS BUILD IN
ADVANCE OF EJECTING 4-CORNERS ENERGY ON FRIDAY. THE REBOUNDING
THERMAL FIELD WILL APPROACH 0C AT 850MB BY LATE FRIDAY. WITH A
SIGNIFICANTLY DRIER COLUMN IN PLACE, EXPECT MOSTLY SUNNY SKIES FOR
THE FIRST TIME IN SEVERAL DAYS. NW WINDS WILL GUST NO HIGHER THAN 15
MPH AND HIGH TEMPERATURES WILL REACH 50 TO 55 ACROSS SE MICHIGAN.

A LOW POTENTIAL FOR SHOWERS WILL EXIST ACROSS THE SOUTH LATE FRIDAY
NIGHT OR SATURDAY AS AFOREMENTIONED 4-CORNERS WAVE TRACKS ACROSS THE
OHIO VALLEY, BUT WITH HIGH PRESSURE AUGMENTED BY LAKE INFLUENCES IN
PLACE AND FORCING DISPLACED TO THE SOUTH, HAVE DOUBTS ABOUT
POTENTIAL. ATTM...NO WELL-DEFINED OR NOTEWORTHY POTENTIAL WORTH
MENTIONING FOR THE NEXT 7 DAYS. ACTIVE NORTHERN BRANCH WILL HELP
CONTAIN HIGH TEMPERATURES TO THE COOL SIDE OF NORMAL...50S...INTO
NEXT WEEK.

MARINE...

MODERATE TO FRESH WESTERLY FLOW WILL GUST AS HIGH AS 30
KNOTS...ESPECIALLY OVER LAKES ERIE AND SAINT CLAIR...TODAY AS THE
PRESSURE GRADIENT OVER AREA WATERS REMAINS RATHER STRONG. SMALL
CRAFT ADVISORIES ARE IN EFFECT FOR THE BALANCE OF THE DAY FOR ALL
NEARSHORE WATERS. NEAR GALES ARE LIKELY OVER THE NORTHERN THIRD OF
LAKE HURON THROUGH LATE TONIGHT. ALTHOUGH AN ISOLATED GALE FORCE
GUST IS POSSIBLE...GALES ARE NOT ANTICIPATED. SIMILAR CONDITIONS
WILL REDEVELOP ON THURSDAY AND ANOTHER ROUND OF SMALL CRAFT
ADVISORIES MAY BE NEEDED. THE PRESSURE GRADIENT WILL GRADUALLY
WEAKEN THURSDAY NIGHT THROUGH THE WEEKEND ALLOWING WINDS TO DIMINISH
CONSIDERABLY DURING THIS TIME.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THURSDAY FOR LHZ441.

     SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LHZ421-422-
     442-443.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LEZ444.

&&

$$

AVIATION.....DRK
SHORT TERM...DRK
LONG TERM....JVC
MARINE.......JVC


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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