Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 181919
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
319 PM EDT FRI APR 18 2014

.SHORT TERM... TODAY AND TONIGHT

A WEAK LOW PRESSURE SYSTEM THAT TRACKED THROUGH NORTHERN MI THURSDAY
IS FORCING A WEAK COLD FRONT THROUGH SE MI AT PRESS TIME. LOOKING
ALOFT...HEIGHTS ARE LOWERING AS A MID LEVEL TROUGH WORKS EASTWARD
WITH A LOBE OF VORTICITY PIVOTING THROUGH LOWER MI. THE TROUGH IS
FRACTURING IN THE SENSE THAT AN UPPER LOW THAT HAS BEEN CLINGING TO
THE BASE OF THE TROUGH FINALLY CUTS OFF OVER THE DEEP SOUTH. A
SHORTWAVE SEEN ON WATER VAPOR OVER THE PLAINS IS SHEARING APART AS
IT LIFTS OVER THE AREA LEADING TO A MIDLEVEL CLOUD FIELD. MODELS
CONTINUE TO ADVERTISE AN UPTICK IN FRONTOGENESIS RIGHT OVER SE MI
THIS MORNING FROM ABOUT 09-12Z AS THE 500MB HEIGHT FALL MAXIMUM
FLARES UP OVER THE AREA INDUCING THE JET TO STRENGTHEN WITH THE
RIGHT ENTRANCE REGION ALSO OVER THE AREA. SO MODEL WISE THE UPPER
LEVELS LOOK FAVORABLE FOR SOME PRECIP THIS MORNING WITH SOME AIDE IN
THE LOW LEVEL FGEN. A BIG DOWNFALL TO THE SYSTEM WILL BE WITH
MOISTURE. THE DTX 00Z SOUNDING SHOWS ONLY A HALF INCH OF PWAT IN THE
COLUMN WITH A DEEP LAYER OF DRY AIR UP TO ABOUT 9KFT. MODELS ARE
RIGHT ON TRACK WITH THIS AND DO UP THE PWATS TO AROUND .7 DURING THE
FROPA. UPSTREAM OBS ARE GOOD FOR SHOWING THE VERY SCATTERED NATURE
OF THE PRECIP THUS FAR WITH A FEW OBS SHOWING LIGHT RAIN OR DRIZZLE
WITH CIGS LOWERING FROM 10KFT TO AROUND 6500FT WITH THE PRECIP. THE
STRUGGLES WITH DRY BL AIR SHOULD CONTINUE AND HAVE BEEN THUS FAR AS
RADAR RETURNS HAVE BEEN SHOWING UP FOR HOURS WITH NOTHING TO SHOW
FOR IT. BUT AS MENTIONED...THE MODELS SHOW THE STRONGEST FORCING
DEVELOPING RIGHT OVER HEAD AS THE UPPER LEVEL PLAYERS COME TOGETHER
SO WILL CONTINUE A BAND OF CHANCE POP WORKING THROUGH THE AREA
DURING THE MORNING HOURS. QPF WILL REMAIN LOW DUE TO THE LACK OF
MOISTURE PRESENT TO WORK WITH.

THE REST OF THE DAY WILL SHOW AN IMPROVING TREND AS RIDGING WILL
QUICKLY FILL IN BEHIND THE FRONT. THE LONGWAVE PATTERN IS LOW
AMPLITUDE LEADING TO ONLY A SMALL DROP OFF IN TEMPERATURES BEHIND
THE FRONT. THE SFC HIGH WILL PASS TO THE NORTH SO WE SHOULD KEEP A
SEMBLANCE OF EASTERLY FLOW AS WINDS RELAX OVERNIGHT. SKIES WILL
ALSO BE CLEARING WHICH WILL FAVOR SOME RADIATIVE COOLING PROCESSES.
DEWPOINTS WILL ONLY FALL INTO THE UPPER 20S TO LOW 30S WHICH WILL
CAP OFF THE TEMPERATURE DROP OVERNIGHT.

&&

.LONG TERM...SATURDAY THROUGH NEXT FRIDAY

STRONG SURFACE HIGH PRESSURE WILL EXPAND INTO THE NORTHERN AND
CENTRAL GREAT LAKES BY TOMORROW MORNING. THIS WILL KEEP DRY AND
QUIET WEATHER OVER THE AREA. TEMPERATURES HOWEVER WILL RUN BELOW
NORMAL AS A STRONG SUBSIDENCE INVERSION CONFINES MIXING HEIGHTS TO
NEAR/BELOW 4500 FEET AND EASTERLY FLOW DEVELOPS OFF THE COLD WATERS
OF THE GREAT LAKES. WITH GOOD INSOLATION EXPECTED...HIGHS IN THE
LOW/MID 50S STILL LOOK REASONABLE...WITH COOLER READINGS NEAR THE
LAKESHORES.

THE HIGH WILL SHIFT EAST LATE SATURDAY NIGHT INTO SUNDAY AS THE
UPPER WAVE NOW NEAR THE MONTANA/ALBERTA BORDER BEGINS TO TRACK
ACROSS NORTHERN ONTARIO. THE PASSAGE OF THIS SYSTEM WILL DROP A COLD
FRONT ACROSS NORTHERN MICHIGAN AND LAKE HURON LATE SATURDAY NIGHT
INTO SUNDAY...WITH THE FRONT REMAINING QUASI-STATIONARY ON SUNDAY AS
MOISTURE BEGINS TO RIDE OVER IT AND RIGHT ENTRANCE REGION FORCING
FROM A JET STREAK BECOMES POSITIONED OVERHEAD. IT LOOKS AS IF
PRECIPITATION THROUGH LATE SUNDAY SHOULD REMAIN MOSTLY TO OUR
NORTH...WITH JUST A FEW SHOWERS POTENTIALLY BRUSHING THE SAGINAW
VALLEY AND NORTHERN THUMB. A SECOND LOW PRESSURE SYSTEM WILL THEN
LIFT UP INTO THE SOUTHERN GREAT LAKES FROM THE CENTRAL PLAINS ON
MONDAY...AHEAD OF A PIECE OF UPPER ENERGY THAT WILL BREAK OFF THE
UPPER LOW NOW PUSHING TOWARDS THE WEST COAST. AS THE LOW TRACKS
THROUGH THE AREA...IT WILL PULL MOISTURE UP INTO SOUTHEAST
MICHIGAN...BEFORE DRAWING THE FRONT HOLDING OVER NORTHERN MICHIGAN
SOUTHWARD. THIS SHOULD ALL PROVIDE A GOOD CHANCE FOR RAIN SHOWERS
MONDAY AND MONDAY NIGHT. THERE REMAIN SOME MODEL DIFFERENCES WITH
THE TIMING OF THE FRONTAL BOUNDARY...AND WILL CONTINUE TO FAVOR THE
MORE CONSISTENT CONSENSUS OF THE GFS/EURO/GEM INSTEAD OF THE FASTER
NAM WHICH IS AN OUTLIER WITH THE WAY IT HANDLES BOTH LOW PRESSURE
SYSTEMS EARLY NEXT WEEK. TEMPERATURES WILL REBOUND AHEAD OF BOTH
THESE SYSTEMS...FIRST WITH THE PASSAGE OF A WARM FRONT LATE SATURDAY
NIGHT AND THEN WITH WARM AIR ADVECTION CONTINUING ON SUNDAY AND
AGAIN MONDAY AS THE SECOND LOW APPROACHES. HIGH LOOK TO PUSH INTO
THE 60S TO NEAR 70 BOTH AFTERNOONS.

LOW PRESSURE EXITS TO THE EAST NORTHEAST BY TUESDAY BRINGING IN A
DRY NORTHERLY FLOW THROUGH WEDNESDAY NIGHT. A LOW PRESSURE SYSTEM
SETTING UP OVER THE NORTHERN PLAINS IS EXPECTED TO USHER IN ANOTHER
CHANCE OF RAIN SHOWERS FOR THURSDAY AND FRIDAY...WITH HIGH PRESSURE
RETURNING FOR SATURDAY.

&&

.MARINE...

WINDS WILL CONTINUE TO GUST UP TO 25 KNOTS OVER NORTHERN AND CENTRAL
LAKE HURON INTO THIS EVENING AS COOLER AIR FILTERS INTO THE REGION
BEHIND A COLD FRONT. STRONG HIGH PRESSURE CENTERED OVER ONTARIO WILL
THEN EXPAND INTO THE NORTHERN AND CENTRAL GREAT LAKES TONIGHT
THROUGH SATURDAY NIGHT...BRINGING MORE TRANQUIL WEATHER. TWO LOW
PRESSURE SYSTEMS WILL THEN PASS NEAR THE AREA INTO EARLY NEXT WEEK.
THE FIRST WILL TRACK ACROSS ONTARIO ON SUNDAY...DROPPING A COLD
FRONT DOWN INTO LAKE HURON. THE FRONT WILL REMAIN QUASI-STATIONARY
OVER THIS AREA UNTIL ANOTHER LOW PRESSURE SYSTEM DRAWS IT SOUTHWARD
MONDAY AND MONDAY NIGHT. STRONGER NORTH WINDS ARE THEN POSSIBLE
ACROSS THE AREA LATE MONDAY NIGHT INTO TUESDAY BEHIND THE FRONT.

&&

.AVIATION...ISSUED 147 PM EDT FRI APR 18 2014

//DISCUSSION...

GOOD COVERAGE OF CU HAS SPRUNG UP IN THE WAKE OF THIS MORNING/S
FRONTAL PASSAGE. AFTER AREAS OF MVFR AND EVEN A FEW IFR CEILINGS
THIS MORNING...EXPECT VFR CEILINGS WITH A RISING TREND THE
REMAINDER OF THE DAY. WINDS WILL SHIFT TO NORTH/NORTHEASTERLY
LATER THIS EVENING DUE TO A COMBINATION OF BACKDOOR COLD FRONT AND
LAKE EFFECTS. OTHER ISSUE OF CONCERN IS THE POTENTIAL FOR FOG OR
LOW STRATUS OVERNIGHT. TRAJECTORIES OFF LAKE HURON COMBINED WITH
MOIST GROUND FROM THIS MORNING/S RAINFALL COULD LEAD TO SOME LOW
LEVEL MOISTURE...WITH NAM FORECAST SOUNDINGS SHOWING SOME MOISTURE
BEING TRAPPED BELOW AN INVERSION. CONFIDENCE WAS NOT HIGH ENOUGH
TO INCLUDE IN THE TAFS AT THIS TIME...BUT THIS WOULD BE MOST
LIKELY OVER PTK/FNT IF IT WERE TO DEVELOP.

FOR DTW...SCT/BKN SUB-5000 FT CLOUDS SHOULD CONTINUE THIS
AFTERNOON INTO EARLY EVENING...BUT CEILINGS WILL UNDERGO A RISING
TREND. A WIND SHIFT TO NORTH/NORTHEASTERLY IS EXPECTED AROUND 00Z.

//DTW THRESHOLD THREATS...

* MODERATE CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH 00Z.

&&

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

&&

$$

SHORT TERM...DT
LONG TERM....HLO/DE
MARINE.......HLO
AVIATION.....DT


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




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