Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 160352
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1152 PM EDT WED APR 15 2015


.AVIATION...

VERY DRY LOW LEVEL AIR ASSOCIATED WITH HIGH PRESSURE DEPARTING TO
THE EAST WILL KEEP CLEAR SKIES BELOW 10K FEET AT THE TERMINALS
THROUGH DAYBREAK. AN INFLUX OF MOISTURE WILL ARRIVE FROM THE
SOUTHWEST THIS MORNING AND IS ASSOCIATED WITH THE PASSAGE OF A WEAK
UPPER LEVEL DISTURBANCE LIFTING UP FROM THE OH/MS VALLEY. THIS WILL
LEAD TO A STEADY DECREASE IN CEILINGS HEIGHTS DURING THE COURSE OF
THE DAY ON THURS AND A CHANCE OF LIGHT RAIN IN THE AFTERNOON.

FOR DTW...THE 00Z MODEL GUIDANCE WITH SOME SUPPORT OF UPSTREAM
OBSERVATIONS SUGGEST CEILINGS WILL DROP TO 5K FT LATE IN THE
MORNING.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS DROPPING AT OR BELOW 5000 FT AFTER 14Z THURSDAY.

&&

.PREV DISCUSSION...ISSUED 330 PM EDT WED APR 15 2015

SHORT TERM...THROUGH TONIGHT

SPLIT UPPER FLOW IN PLACE WITH JET MAX OVER HUDSON BAY TOPPING A
RIDGE AXIS AND WEAKER SOUTHERLY BRANCH ALONG THE GULF COAST. SURFACE
ANTICYCLONE CENTERED OVER EASTERN ONTARIO DOWNSTREAM OF THE UPPER
RIDGE MAINTAINING EASTERLY FLOW OVER SE MI TODAY. MUCH OF THE COLUMN
IS VERY DRY AS SEEN ON 12Z DTX SOUNDING...THE EXCEPTION BEING HIGH
CLOUDS WHICH ARE MORE PREVALENT OVER SOUTHERN PORTIONS OF THE LOCAL
AREA. DIURNAL MIXING HAS ALLOWED TEMPS TO REACH THE LOW 60S WITH
DEWPOINTS PLUMMETING INTO THE TEENS EARLIER...THOUGH THEY HAVE COME
UP SOMEWHAT LATELY. EXPECT WINDS AROUND 10 KT WITH OCCASIONAL GUSTS
NEAR 18 KT FOR THE NEXT FEW HOURS BEFORE DIURNAL MIXING CEASES.

MOISTURE ADVECTION EXPECTED TO INCREASE TONIGHT AS SHORTWAVE OVER
THE MID-MISSISSIPPI VALLEY TRACKS NORTHEASTWARD. THIS WILL ALLOW
THICKENING HIGH CLOUDS LATE TONIGHT. MOISTURE ADVECTION AT LOW/MID
LEVELS WILL BE SLOWER TO DEVELOP WITH REMNANT EASTERLY WIND
COMPONENT IN PLACE AND DRY ANTECEDENT AIRMASS. DEEPER MOISTURE WILL
PREFERENTIALLY STREAM INTO WESTERN PORTIONS OF THE STATE...SLOWLY
WORKING BACK EASTWARD TOWARD 12Z. THIS SUPPORTS A MOSTLY DRY
FORECAST OVERNIGHT...THOUGH KEPT LOW CHANCE POPS AFTER 10Z FOR
EXTREME SOUTHWESTERN CWA. MAINTENANCE OF THE PRESSURE GRADIENT ALONG
WITH THICKENING CLOUD CANOPY SUPPORTS LOWS IN THE UPPER 30S TO LOWER
40S...COOLEST ACROSS THE THUMB.

LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY

BROAD UPPER WAVE STRETCHING FROM THE DAKOTAS DOWN INTO ARKANSAS WILL
LIFT ACROSS MICHIGAN TOMORROW. THIS WILL PROVIDE A FOCUS FOR SHOWERS
AS THE MID-LEVEL WAVE APPROACHES AND ISENTROPIC ASCENT INCREASES
(BEST AT 290K) ALONG A WEAK BUT ELEVATED WARM FRONT. A VERY DRY
AIRMASS WILL PRECEDE THE ARRIVAL OF THIS WAVE...WITH 12Z KDTX RAOB
FROM THIS MORNING SHOWING A PW OF ONLY 0.15 INCHES. DRY AIRMASS WILL
NEED TO BE OVERCOME BEFORE PRECIPITATION REACHES THE GROUND...BUT
THIS SHOULD OCCUR FAIRLY QUICKLY AS 30-40KT LOW-LEVEL JET HELPS
USHER MOISTURE INTO THE AREA. NAM MODEL SHOWS FAIRLY QUICK AND
HEALTHY THETA-E ADVECTION LATE TONIGHT AND EARLY TOMORROW...AND H850
DEWPOINTS ARE STILL PROGGED ON THE MODELS TO REACH BETWEEN 6-8C BY
AFTERNOON. EXPECT TO SEE NUMEROUS SHOWERS DURING THE AFTERNOON AND
EVENING...BEFORE DRIER AIR AND SUBSIDENCE MOVE IN ON THE BACK SIDE
OF THE SYSTEM. CHANCES FOR THUNDER LOOK TOO LOW TO INCLUDE A MENTION
ON THE LATEST NAM/GFS...WITH MODEL CROSS-SECTIONS SHOWING LITTLE TO
NO CONVECTIVE INSTABILITY AND LAPSE RATES ON FORECAST SOUNDINGS
LOOKING PRETTY MEAGER. CLOUDS AND MOISTURE WILL HOLD TEMPERATURES
BACK TOMORROW...WITH HIGHS ONLY EXPECTED TO REACH THE UPPER 50S TO
LOW 60S.

DRY WEATHER IS EXPECTED ON FRIDAY AS HIGH PRESSURE EXPANDS BACK INTO
THE AREA. NORTHERN STREAM ENERGY DROPPING THROUGH ONTARIO WILL SEND
A SURFACE LOW PRESSURE TOWARDS HUDSON BAY WHILE DROPPING A COLD
FRONT DOWN THROUGH ONTARIO AND INTO THE NORTHERN GREAT LAKES. AS THE
FRONT APPROACHES...WARMER AIR WILL LIFT BACK UP INTO LOWER MICHIGAN.
THE COMBINATION OF H850 TEMPS OF 8-9C AND BETTER MIXING (STEEPER
LAPSE RATES WITH THE WARMER LOW-LEVEL AIR) WILL SEND MAX
TEMPERATURES BACK UPWARDS...MAKING A RUN AT 70 ACROSS MUCH OF
SOUTHEAST MICHIGAN. COOLER TEMPS CAN BE EXPECTED NEAR THE LAKESHORES
HOWEVER.

THIS UPCOMING WEEKEND WILL START OFF DRY AS SOUTHEAST MICHIGAN IS
POSITIONED BETWEEN TWO WAVES...ONE TO THE NORTH AND ONE THAT WILL BE
FORMING OVER THE SOUTHERN PLAINS.  UPPER LEVEL RIDGING WILL HELP TO
KEEP THE AREA DRY ON SATURDAY BEFORE CHANCES FOR PRECIPITATION
INCREASE COME SUNDAY.  UNSETTLED WEATHER THEN TAKES OVER FOR THE
BEGINNING OF NEXT WEEK AS THE UPPER LEVEL TROUGH SWINGS ACROSS THE
GREAT LAKES REGION.  TEMPERATURES BEGIN TO COOL OFF A TINY BIT NEXT
WEEK WITH HIGHS RESTING IN THE 50S.

MARINE...

EAST TO NORTHEAST FLOW WILL BE A LITTLE GUSTY LATE THIS AFTERNOON
AND EVENING OVER SOUTHERN LAKE HURON AND SAGINAW BAY. WINDS AND
WAVES ARE EXPECTED TO REMAIN UNDER SMALL CRAFT ADVISORY CRITERIA
HOWEVER...AND WINDS ARE EXPECTED TO WEAKEN OVERNIGHT AS THE CENTER
OF HIGH PRESSURE SLIDES FROM THE NORTHERN GREAT LAKES DOWN TO THE
EAST COAST. FAIRLY LIGHT WINDS ARE EXPECTED THURSDAY INTO
FRIDAY...EVEN AS A WEAK UPPER LEVEL DISTURBANCE LIFTS UP ACROSS THE
AREA AND ANOTHER LOW PRESSURE SYSTEM TRACKS ACROSS NORTHERN ONTARIO.
AN ADDITIONAL AREA OF LOW PRESSURE TRACKING THROUGH ONTARIO WILL
DROP A COLD FRONT DOWN INTO THE AREA BY FRIDAY NIGHT. THIS WILL
ALLOW WINDS TO INCREASE FROM THE WEST-NORTHWEST...ESPECIALLY OVER
NORTHERN AND CENTRAL LAKE HURON WHERE WIND GUSTS MAY REACH 25 TO 30
KNOTS.

&&

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

$$

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


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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