Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231626
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1126 AM EST FRI JAN 23 2015

.UPDATE...

12Z DTX RAOB SHOWED A LAYER OF MOISTURE TRAPPED BENEATH A SHARP
INVERSION AT 1600 FEET. ABOVE THIS LAYER...THERE EXISTED A DEEP
LAYER OF VERY DRY AIR. A WEAK TROUGH DROPPING THROUGH CANADA HAS
BROUGHT AN INCREASE IN MIXING THIS AFTERNOON...CHIPPING INTO THE
DRY LAYER POSITIONED ABOVE THE INVERSION AND ALLOWING FOR SOME
CLEARING ACROSS THE THUMB. SOME UNCERTAINTY DOES EXIST AS TO HOW
FAR SOUTH AND WEST THE CLEARING WILL OCCUR HOWEVER...AS MODELS
STRUGGLE TO RESOLVE THE AMOUNT OF LOW-LEVEL MOISTURE. WILL BE
UPDATING THE SKY COVER FORECAST ACCORDINGLY BASED ON SATELLITE
TRENDS. MAX TEMPS FOR TODAY WERE ALSO NUDGED UPWARDS DUE TO THE
CLEARING AND AS MIXING HAS BEEN A LITTLE STRONGER THAN MODELS
PREVIOUSLY HINTED AT.

&&

.AVIATION...ISSUED 546 AM EST FRI JAN 23 2015

MOISTURE ADVECTION FROM THE SOUTHWEST HAS ALLOWED MVFR STRATUS TO
SURGE BACK INTO SOUTHEAST MICHIGAN DURING THE PREDAWN HOURS.
SATELLITE VIEW REVEALS EXTENSIVE COVERAGE EXTENDING WELL UPSTREAM.
THE COMBINATION OF A STRENGTHENING LOW-LEVEL INVERSION AND A
PERSISTENCE OF SOUTHWEST FLOW, EXPECT STRATUS TO PERSIST FOR MUCH,
IF NOT ALL, OF THE DAY. DIMINISHED MIXING POTENTIAL SHOULD PREVENT
MUCH IN THE WAY OF WIND GUSTS. EXPECT SW WINDS AROUND 10 KTS INTO
TONIGHT. A FEW SNOW SHOWERS WILL BE POSSIBLE LATE TONIGHT WITH
LITTLE TO NO DETERIORATION IN CONDITIONS EXPECTED AS A WEAK SURFACE
TROUGH SETTLES INTO THE AREA.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE IN CEILINGS BELOW 5KFT

&&

.PREV DISCUSSION...ISSUED 333 AM EST FRI JAN 23 2015

SHORT TERM...TODAY AND TONIGHT

WIDESPREAD STRATUS IS ENTRENCHED AROUND THE NORTHERN PERIPHERY OF
ELONGATED HIGH PRESSURE POSITIONED DRAPED ACROSS THE MIDWEST THIS
MORNING. SOUTHWEST FLOW AROUND THE SURFACE HIGH HAS ALLOWED CLOUDS
TO MAKE GRADUAL INROADS INTO THE CWA DURING THE PREDAWN HOURS, A
TREND WHICH IS FORECAST CONTINUE THROUGH THE MORNING. STRENGTHENING
SOUTHWEST GRADIENT IN ADVANCE OF THE SHORTWAVE DIGGING INTO MANITOBA
THIS MORNING WILL NOT ONLY PROMOTE CONTINUED MOISTURE ADVECTION, BUT
ALSO A STRENGTHENING TEMPERATURE INVERSION THAT WILL PREVENT MUCH IN
THE WAY OF MIXING. THEREFORE, MOVED FORWARD WITH A MORE AGGRESSIVE
CLOUD COVER FORECAST AND DROPPED FORECAST HIGH TEMPERATURES A FEW
DEGREES ACCORDINGLY.

AFOREMENTIONED MANITOBA SHORTWAVE WILL RUN INTO A ROAD BLOCK TODAY
IN THE FORM OF THE DEVELOPING EAST COAST CYCLONE. WHATEVER PORTION
OF THE WAVE DOESN`T GET SHEARED EAST TOWARD THE CANADIAN MARITIMES
WILL QUICKLY PASS WEST AND THEN SOUTH OF THE AREA WITHIN THE
DEEPENING LONGWAVE TROUGH. THE ORPHANED COLD FRONT WILL EASE THROUGH
THE AREA COINCIDENT WITH THE UPPER TROUGH AXIS, BUT WITH LITTLE IN
THE WAY OF ORGANIZED FORCING, THE FRONTAL CIRCULATION WILL BE
WEAKENING AND SUPPORT NOTHING MORE THAN A PARTIAL COVERAGE OF SNOW
SHOWERS WITHIN THE LOW-LEVEL CONVERGENT AXIS. LOW CHC POPS REMAIN
APPROPRIATE.

LONG TERM...SATURDAY THROUGH THURSDAY

SOUTHERN STREAM STORM SYSTEM WILL SKIRT THE AREA TO THE SOUTH AND
SOUTHEAST SATURDAY AS NORTHERN STREAM COMPONENT LAGS THIS MORE
SIGNIFICANT WAVE AND DELAYS PHASING OF THE NORTHERN AND SOUTHERN
STREAMS UNTIL THE RESULTANT SYSTEM IS LIFTING UP THE NEW ENGLAND
COAST. THIS WILL LIMIT THE CHANCE OF SNOW SATURDAY TO SCATTERED
LIGHT SNOW SHOWERS OR FLURRIES AS A WEAK COLD FRONT ASSOCIATED WITH
THE NORTHERN STREAM SHORTWAVE SINKS THROUGH THE AREA.

THIS FRONTAL BOUNDARY WILL HANG UP OVER THE NORTHERN OHIO VALLEY AND
SOUTHERN GREAT LAKES AS A VIGOROUS SHORTWAVE TRACKS INTO THE AREA BY
SUNDAY. THIS FEATURE IS NOTED ON WATER VAPOR OFF THE COAST OF
BRITISH COLUMBIA EARLY THIS MORNING. WITH SOME SAMPLING OF THIS
DISTURBANCE DURING THE 00Z CYCLE...THE OVERALL POSITION ONCE IT
REACHES THE CENTRAL GREAT LAKES AS SHIFTED SLIGHTLY SOUTHWARD. WILL
MAKE MINOR ADJUSTMENTS TO PRECIPITATION AMOUNTS AND CHANCES...BUT
ALLOW FOR A MORE THOROUGHLY SAMPLING DURING THE 12Z CYCLE TO CONFIRM
ANY MAJOR SOUTHWARD SHIFT. FOR NOW...SNOW STILL APPEARS LIKELY
ACROSS THE SOUTHERN HALF OF THE CWA WHERE A COUPLE OF INCHES OF
ACCUMULATION WILL BE POSSIBLE SUNDAY. PRECIPITATION CHANCES APPEAR
TO TAPER OFF RATHER QUICKLY ALONG THE NORTHERN EDGE OF THE CWA.

ONCE THIS SYSTEM PASSES THE AREA...MUCH COLDER AIR SPILLS BACK INTO
THE REGION AS EASTERN CONUS UPPER TROUGH EXPANDS TO COVER MUCH OF
THE NATION EAST OF THE MISSISSIPPI AND BRINGS SEVERAL DAYS WORTH OF
ARCTIC AIR SOUTH INTO THE REGION. AFTER HIGHS IN THE 30-35F DEGREE
RANGE OVER THE WEEKEND...EXPECT TEMPERATURES AOB 20F FOR HIGHS ON
MONDAY AND TUESDAY. THIS UPPER TROUGH IS EXPECTED TO BE RELATIVELY
PROGRESSIVE AND AS IT SHIFTS EAST OVER THE ATLANTIC OCEAN...HEIGHTS
WILL RISE AND TEMPERATURES WILL REBOUND BACK INTO THE 30S BY THE END
OF THE FORECAST PERIOD. ANY SNOW BEYOND SUNDAY IS EXPECTED TO BE
MINIMAL WITH LITTLE MORE THAN A PASSING FLURRY EXPECTED NEXT WEEK
ATTM.

MARINE...

LOW PRESSURE TRACKING THROUGH CENTRAL CANADA WILL REACH NORTHERN
QUEBEC BY AFTERNOON. THIS SYSTEM WILL DROP A WEAK COLD FRONT INTO
THE REGION LATE TONIGHT INTO SATURDAY MORNING. EXPECT A TIGHTENING
PRESSURE GRADIENT BETWEEN THIS FRONT AND AN EXITING SURFACE HIGH.

THIS WILL ALLOW SOUTHWEST WINDS TO STRENGTHEN OVER CENTRAL AND
NORTHERN LAKE HURON. WHILE SUSTAINED WINDS WILL LIKELY REACH 25
KNOTS OR SO OVER THE OPEN WATERS...WARM AIR ALOFT AND A STEEP LOW
LEVEL INVERSION WILL PREVENT CONSISTENT STRONGER GUSTS FROM REACHING
THE SURFACE. WILL MAINTAIN GUSTS AOB 30 KNOTS FOR THIS FORECAST OVER
NORTHERN AND CENTRAL LAKE HURON AS ANY GUSTS TO GALE FORCE SHOULD BE
LIMITED IN DURATION AND SCOPE.

EXTENSIVE ICE COVER IN THE LAKE HURON NEARSHORE ZONES WILL PREVENT
WAVE DEVELOPMENT. WITH THE OFFSHORE FLOW LIMITED TO 25 KNOTS...A
SMALL CRAFT ADVISORY WILL NOT BE NEEDED AT THIS TIME. COLD NORTHWEST
FLOW WILL MAINTAIN ELEVATED WINDS THIS WEEKEND. HOWEVER...GUSTS
SHOULD REMAIN BELOW GALE FORCE.

&&

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

$$

UPDATE.......HLO
AVIATION.....JVC
SHORT TERM...JVC
LONG TERM....DG
MARINE.......DG


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