Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 171713
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
113 PM EDT THU APR 17 2014


.AVIATION...

//DISCUSSION...

VFR CONDITIONS WILL PERSIST INTO LATE TONIGHT AS DRY SOUTHEAST FLOW
CONTINUES ACROSS SOUTHEAST MICHIGAN. A WEAK LOW LIFTING INTO ONTARIO
WILL THEN DRAG A COLD FRONT THROUGH THE AREA LATE TONIGHT INTO
FRIDAY MORNING, BRINGING ROUND OF LIGHT SHOWERS CAPABLE OF A BRIEF
RESTRICTION TO MVFR VSBY AND LOW VFR CEILING. WINDS WILL REMAIN ON
THE LIGHTER SIDE BUT WILL SHIFT TO NORTHWEST BEHIND THE FRONT.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5KFT

&&

.PREV DISCUSSION...ISSUED 353 AM EDT THU APR 17 2014

SHORT TERM... TODAY AND TONIGHT

EARLY MORNING OBSERVATIONS INDICATE THE DAY STARTING OUT WITH
TEMPERATURES IN THE 30S...MILD COMPARED TO RECENT DAYS...BUT WITH A
STEADY SOUTHEAST WIND ADDING A CHILL TO THE AIR. THE WIND AND BROKEN
HIGH CLOUD COVERAGE WILL BE THE ONLY EVIDENCE OF THE LOW PRESSURE
SYSTEM MOVING INTO WISCONSIN DURING THE MORNING WHICH WILL WEAKEN
WHILE MOVING TOWARD THE STRAITS AREA TODAY. THE MAIN CHALLENGE IN
THE FORECAST WILL BE THE DETERMINATION OF MAX TEMPS WITHIN LOW LEVEL
THICKNESS WARMING BUT WITH CONSIDERABLE HIGH CLOUD COVER AND A
LINGERING EASTERLY COMPONENT IN THE SURFACE WIND. THE WEAKENING
TREND IN THE WISCONSIN LOW WILL BE FORCED WITH GOOD CONFIDENCE BY
LARGER SCALE UPPER LEVEL HEIGHT FALLS OVER THE PLAINS ASSOCIATED
WITH THE NEXT SYSTEM. THE RESULTING WEAKER SURFACE GRADIENT FLOW
OVER LOWER MICHIGAN WILL PRESERVE THE EASTERLY COMPONENT IN THE WIND
FIELD WHICH STRONGLY SUPPORTS THE COOL END OF THE TEMPERATURE
GUIDANCE SPECTRUM. EXPECT MAX TEMPS TO REACH THE UPPER 50S
INTERIOR...LOWER TO MID 50S CLOSER TO THE LAKES...AND READINGS
OPTIMISTICALLY FORECAST TO REACH THE MID 40S NEAR THE LAKE HURON
SHORELINE LATE IN THE DAY.

THE SHORT WAVE OVER THE SOUTHERN PLAINS DURING THE MORNING...
COMBINED WITH THE NEXT SURGE OF UPPER LEVEL JET ENERGY THROUGH THE
ROCKIES...WILL LEAD TO NEARLY FULL LATITUDE THROUGH DEVELOPMENT OVER
THE CENTRAL STATES BY TONIGHT. THE RESULTING INCREASED SOUTHWEST
FLOW ALOFT AS THE UPPER JET MOVES OVERHEAD WILL HELP STRENGTHEN THE
FRONTAL ZONE TRAILING THE STRAITS SYSTEM OVER LOWER MICHIGAN. MODEL
CROSS SECTIONS THROUGH THE FRONTAL ZONE INDICATE INSTABILITY WITHIN
THE LOW LEVEL THETA-E RIDGE WITH ADEQUATE MOISTURE SUPPLY. GIVEN THE
WARM NATURE OF THE SYSTEM...SPECIFIC HUMIDITY OF 3-4 G/KG AND 850 MB
DEWPOINT STRUGGLING TO RISE ABOVE 1-2C IS JUST OK AND SUGGESTS A
HIGH POP/LOW QPF SCENARIO. THE MODEST MOISTURE SUPPLY DEPICTED BY
THE MODELS LOOKS GOOD IN LIGHT OF SURFACE HIGH PRESSURE SPRAWLED
OVER THE ENTIRE ATLANTIC AND GULF COASTS FORCING SLOW DEVELOPMENT OF
GULF MODIFIED RETURN FLOW IN THE LOW LEVELS. THE INHERITED LIKELY
POP FORECAST FOR TONIGHT WILL BE MAINTAINED BUT NUDGED FARTHER BACK
IN TIME TO ALLOW FOR SATURATION OF THE LOW LEVELS BY MIDNIGHT.
EXPECT TEMPERATURES TO REMAIN EASILY ABOVE FREEZING THROUGH THE
NIGHT. MIN TEMPS IN THE UPPER 30S TO LOWER 40S LOOK GOOD BY SUNRISE
FRIDAY.

LONG TERM...

PROGRESSIVE PATTERN WITH STORM TRACK PREDOMINATELY NORTH OF THE
REGION DURING THE EXTENDED PERIOD...SETTING US FOR WARMER
TEMPERATURES.

UPPER LEVEL TROUGH TO SWING THROUGH THE CENTRAL GREAT LAKES DURING
FRIDAY...WITH SURFACE COLD FRONT LIKELY CLEARING THE STATE AROUND
NOON...PER LATEST TRENDS. THIS FASTER TIMING....AND DISPLACEMENT
WITH THE SOUTHERN STREAM/MOISTURE DOES NOT GIVE ONE A LOT OF
CONFIDENCE IN SHOWERS...AND CERTAINLY NOT DURING THE AFTERNOON HOURS
WHERE WE WILL CUT BACK DRAMATICALLY ON POPS. STRONGLY CONFLUENT
UPPER LEVEL NORTHWEST FLOW FRIDAY EVENING/NIGHT WILL LEAD TO GOOD
SUBSIDENCE AND SURFACE HIGH BUILDING IN...LEADING TO ANOTHER COLD
NIGHT ACROSS SOUTHEAST MICHIGAN. THUMB REGION LOOKS TO BE DROPPING
INTO THE 20S WITH LOWER 30S ELSEWHERE...PER LATEST GUIDANCE.

UPPER LEVEL RIDGE AND SPRAWLING HIGH PRESSURE WILL DOMINATE DURING
SATURDAY. LIGHT EAST-SOUTHEAST FLOW DEVELOPING WILL ATTEMPT TO LIMIT
THE TEMPERATURE CLIMB...BUT TEMPS SHOULD BE ABLE TO SNEAK INTO THE
LOW TO MID 50S WITH MID APRIL INSOLATION.

500 MB LOW EXITING MONTANA AND TRACKING NORTHEAST...INTO ONTARIO ON
SUNDAY. MINIMAL HEIGHT FALLS OVER THE SOUTHERN GREAT LAKES
REGION...AND COLD FRONT WILL BECOME NEARLY PARALLEL TO THE MEAN
FLOW...WHICH SHOULD ALLOW FOR A NICE DAY ON SUNDAY (LOW CHANCE OF
RAIN SHOWERS FAR NORTH)...AS SOUTHWEST FLOW ADVECTS MILDER AIR INTO
THE REGION. 850 MB TEMPS RISE INTO THE HIGH SINGLE NUMBERS. MAXES
CLIMBING WELL INTO THE 60S ARE EXPECTED...WITH 70 DEGREES WITHIN
REACH ACROSS SOUTHERN AREAS IF SKIES END UP MOSTLY SUNNY.

MARINE...

A WEAKENING LOW APPROACHING THE CENTRAL GREAT LAKES TODAY WILL
DISSIPATE TONIGHT...BUT COLD FRONT WILL PRODUCE A FEW SHOWERS AS IT
TRACKS THROUGH THE REGION FRIDAY MORNING. SOUTHEAST WINDS OF 15 TO
20 KNOTS WILL BECOME LIGHT WESTERLY POST FRONTAL. SPRAWLING HIGH
PRESSURE WILL THEN BUILD INTO THE AREA LATE FRIDAY INTO
SATURDAY...LEADING TO LIGHT WINDS. SOUTHERLY WINDS WILL PICK UP FOR
THE SECOND HALF OF THE WEEKEND...BUT REMAINING UNDER 20 KNOTS ACROSS
MOST AREAS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....JVC
SHORT TERM...BT
LONG TERM....SF
MARINE.......SF


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






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