Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 230357
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1157 PM EDT WED APR 22 2015

.AVIATION...

EXTENSIVE CLOUD COVER WILL REMAIN IN PLACE THROUGH TONIGHT UNDER
CONTINUED COLD MOIST WESTERLY FLOW.  CEILINGS PREDOMINATELY CENTERED
WITHIN THE 4000 TO 7000 FT RANGE.  COVERAGE MAY TEND TO THIN DURING
THE EARLY MORNING PERIOD...BEFORE RENEWED DIURNAL EXPANSION AFTER
14Z THURSDAY.  GUST POTENTIAL ON THURSDAY IN THE 20 TO 25 KNOT RANGE
OUT OF NORTHWEST.

FOR DTW...UPSTREAM OBSERVATIONS CONTINUE TO SUGGEST CEILINGS
PREDOMINATELY HOLDING ABOVE 5000 FT THROUGH DAYBREAK.  EXPANSION IN
LOWER VFR DIURNAL STRATOCUMULUS EXPECTED AFTER 14Z.

//DTW THRESHOLD PROBABILITIES...

* LOW CONFIDENCE IN CEILINGS AT OR BELOW 5000 FT TONIGHT. MEDIUM
  CONFIDENCE THURSDAY.

&&

.PREV DISCUSSION...ISSUED 359 PM EDT WED APR 22 2015

SHORT TERM...THROUGH TONIGHT

BROAD UPPER LOW OVER CENTRAL ONTARIO WILL SLIDE SOUTHEAST ALONG THE
ONTARIO/QUEBEC BORDER TONIGHT...FILLING IN A LITTLE AS IT DOES. THIS
WILL ALLOW ONE MORE SHORTWAVE TO TRACK ACROSS NORTHERN MICHIGAN AND
LAKE HURON THIS EVENING...PER RECENT MODEL SOLUTIONS AND WATER VAPOR
IMAGERY. THE PASSAGE OF THE SHORTWAVE IN COMBINATION WITH MOIST
CYCLONIC FLOW AND COOL AIR ALOFT (WHICH IS PROVIDING STEEP LAPSE
RATES THROUGH ABOUT 800MB) WILL KEEP THE THREAT FOR SHOWERS AROUND
INTO THIS EVENING. BEST COVERAGE WILL BE CLOSEST TO THE SHORTWAVE
AND COLD POCKET OF AIR...ACROSS THE SAGINAW VALLEY AND THUMB...THEN
TAPER AS YOU HEAD TOWARDS THE OHIO BORDER. LITTLE TO NO ACCUMULATION
IS EXPECTED...AND WITH ROAD TEMPERATURES ABOVE FREEZING (MOSTLY IN
THE 40S) NOT ANTICIPATING ANY ISSUES OUTSIDE OF BRIEF LOWERED
VISIBILITIES IN QUICK BURSTS. WINDS WILL ALSO DECREASE THIS EVENING
AS THE MIXED LAYER SHRINKS. UNTIL THEN HOWEVER...GUSTS TO 35 MPH
WILL STILL BE POSSIBLE.

CLOUD COVER FORECAST WILL BE THE MOST CHALLENGING ELEMENT OVERNIGHT.
TEMPERATURES IN THE MID-LEVELS WILL WARM TONIGHT AS THE UPPER LOW
SHIFTS AWAY FROM THE AREA. THIS AND THE LOSS OF DIURNAL HEATING WILL
WEAKEN THE INVERSION JUST ENOUGH TO INTRODUCE SOME UNCERTAINTY INTO
THE FORECAST FOR SOUTHERN LOWER MICHIGAN. WILL MAINTAIN A MOSTLY
CLOUDY FORECAST FOR MOST OF THE AREA...BUT THINK WE COULD SEE SOME
BREAKS LATE SOUTH OF M-59. TEMPERATURES WILL REMAIN COLD GIVEN
CURRENT TEMPS MOSTLY IN THE 30S. CLOUD COVER SHOULD HELP INSULATE US
TONIGHT...AND EXPECTING MIN TEMPS IN THE UPPER 20S TO NEAR 30.

LONG TERM...

CYCLONIC UPPER FLOW REMAINS IN PLACE FOR MUCH OF THURSDAY. DIURNAL
MIXING EXPECTED TO LEAD TO A HEALTHY COVERAGE OF STRATOCU AGAIN
TOMORROW WITH THE H85 THERMAL TROUGH IN PLACE /TEMPS OF -6 TO -10C
AT 18Z/. GOOD PRESSURE GRADIENT BETWEEN NEARLY-STATIONARY SURFACE
LOW OVER MAINE AND HIGH PRESSURE BUILDING INTO THE UPPER MISSISSIPPI
VALLEY SHOULD LEAD TO NWLY WINDS GUSTING TO AROUND 25 KT. WITH STEEP
LOW-LEVEL LAPSE RATES COULD SEE A FLURRY/SPRINKLE DURING THE
AFTERNOON HOURS...THOUGH LOWER MIXING DEPTHS AND LESS MOISTURE IN
THE DGZ COMPARED WITH TODAY WILL LIMIT COVERAGE RELATIVE TO TODAY. A
WEST-TO-EAST CLEARING TREND IS EXPECTED IN THE LATE AFTERNOON/EARLY
EVENING HOURS AS HEIGHT RISES BEGIN IN EARNEST...HOWEVER IT WILL
LIKELY BE TOO LATE TO HAVE MUCH OF AN IMPACT ON HIGH TEMPS. IN
ALL...EXPECT A SIMILAR DAY TO TODAY ALTHOUGH A COUPLE DEGREES WARMER
AND WITH LESS SNOW SHOWERS.

CHALLENGE FOR THURSDAY NIGHT WILL BE LOW TEMPERATURES WITH CLEARING
SKIES LEADING TO THE POTENTIAL FOR TEMPS TO GET QUITE COLD. LIMITING
FACTOR MAY BE THE GRADIENT AS H10 GEOSTROPHIC WINDS LOOK TO REMAIN
AOA 10 KT FOR AT LEAST THE EARLY PART OF THE OVERNIGHT
HOURS...ESPECIALLY OVER THE THUMB...SO FULL DECOUPLING MAY NOT BE
REALIZED. HAVE TRIED TO WORK THIS IDEA INTO LOW TEMP FORECAST WITH
LOWEST TEMPS ALONG AND WEST OF US 23/I-75...POSSIBLY APPROACHING
RECORD TERRITORY. RECORD VALUES FOR APRIL 24TH:

FLINT...25 (1996)
SAGINAW...25 (1918)
DETROIT...27 (1892)

HIGH PRESSURE REMAINS IN CONTROL FRIDAY AND WITH NEAR-FULL
INSOLATION AND CONTINUED RELAXATION OF THE GRIP OF THE LOW-LEVEL
THERMAL TROUGH...EXPECTING HIGH TEMPS IN THE LOWER 50S. LIGHT WINDS
TURNING NE WILL KEEP THINGS COOLER IN THE THUMB AND ESPECIALLY ALONG
THE LAKE HURON SHORELINE...LOW TO MID-40S EXPECTED. ANOTHER COLD
NIGHT EXPECTED FRIDAY NIGHT...THOUGH INCREASING CLOUDS FROM ENERGY
MOVING ACROSS THE CENTRAL PLAINS SHOULD LIMIT THE TEMP DROP ACROSS
SOUTHERN PORTIONS OF THE AREA.

THE UPCOMING WEEKEND IS EXPECTED TO BE MAINLY DRY WITH TEMPERATURES
FINALLY REBOUNDING BACK INTO THE UPPER 50S BY THE END OF THE
FORECAST PERIOD.  THE ONLY MINOR CONCERN AT THIS POINT IS THE
POTENTIAL SYSTEM THAT WILL BE MOVING SOUTH OF THE AREA ON SATURDAY.
SOME MODELS ARE SHOWING POTENTIAL FOR THE VERY NORTHERN EDGE OF THAT
SYSTEM COMING UP INTO EXTREME SOUTHERN PARTS OF THE CWA.  A POSITIVE
NOTE IN THE EXTENDED IS THAT TEMPERATURES DO FINALLY START TO
WARM...ESPECIALLY COMPARED TO THE COOLER TEMPS THAT HAVE HELD OVER
THE AREA THIS WEEK.

MARINE...

A STRONG PRESSURE GRADIENT WILL CONTINUE OVER THE WATERS TONIGHT AND
INTO EARLY TOMORROW. GUSTS WILL APPROACH GALE FORCE EARLY TONIGHT
OVER THE NORTHERN THIRD OF LAKE HURON...BUT SHOULD BE INFREQUENT
ENOUGH TO ABSTAIN FROM ISSUING A GALE WARNING. SMALL CRAFT
ADVISORIES REMAIN IN EFFECT THROUGH THIS EVENING FOR THE NEARSHORE
WATERS. AN INCREASE IN THE PRESSURE GRADIENT TONIGHT WILL ALLOW FOR
THE ZONES FROM PORT AUSTIN TO PORT SANILAC TO CONTINUE THE SMALL
CRAFT ADVISORY INTO THURSDAY. WINDS WILL DIMINISH ACROSS THE
NEARSHORE WATERS THURSDAY AFTERNOON WHILE STILL REMAINING ELEVATED
OVER NORTHERN PORTIONS OF THE OPEN WATERS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THURSDAY FOR LHZ441-442.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....MR
SHORT TERM...HLO
LONG TERM....DT/SS
MARINE.......DT


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


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