Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280123
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
923 PM EDT MON OCT 27 2014

.UPDATE...

AFTER A BRIEF LULL FROM THE EARLY EVENING SCT SHOWER
ACTIVITY...ANOTHER AREA OF SHOWERS /WITH SOME EMBEDDED THUNDER/ IS
GRADUALLY LIFTING INTO SRN MI FROM INDIANA. THESE SHOWERS ARE
LOCATED WITHIN A MID LEVEL THETA E PLUME WHICH WILL OVERSPREAD SE
MI DURING THE COURSE OF THE NIGHT. ISENTROPIC ASCENT WITHIN THIS
MOISTURE PLUME AMIDST UPPER LEVEL DIFFLUENT FLOW WILL LEAD TO AN
INCREASE IN SHOWER COVERAGE DURING THE NIGHT...GENERALLY IN LINE
WITH THE CURRENT FORECAST. MID LEVEL LAPSE RATES /PER 00Z DTX
SOUNDING/...REMAIN STEEP SO A FEW EMBEDDED THUNDERSTORMS WILL ALSO
REMAIN POSSIBLE. THE MILD OVERNIGHT MIN TEMP FORECAST STILL LOOKS
GOOD AS THE SFC WARM FRONT /NOW DRAPED ACROSS THE SAGINAW VALLEY
AND THUMB/ WILL LIFT NORTH OVER THE NEXT FEW HOURS LEAVING VERY
MILD SSW FLOW IN PLACE ACROSS THE FORECAST AREA. SO IN
SHORT...MINIMAL FORECAST ADJUSTMENTS WILL BE MADE TO THE CURRENT
FORECAST.

&&

.AVIATION...ISSUED 642 PM EDT MON OCT 27 2014

//DISCUSSION...

WARM FRONT STILL DRAPED ACROSS THE CWA...AND IS SPARKING OFF SOME
ELEVATED SHOWERS. THIS THREAT WILL BE EAST OF THE TAF CORRIDOR BY
ISSUANCE TIME...AND VSBYS HAVE NOT BEEN REDUCED MUCH IN THESE
SHOWERS. CIGS WILL SLOWLY LOWER AS MOISTURE AXIS CONTINUES TO SURGE
NORTHEAST INTO MICHIGAN. NUMEROUS SHOWERS WILL SPREAD ACROSS THE
AREA TUESDAY AHEAD OF THE COLD FRONT...BUT UPSTREAM OBS AND LACK OF
MOISTURE DEPTH PRECLUDE MENTION OF ANYTHING WORSE THAN MVFR.

FOR DTW...EXPECT FROPA IN THE 17-18Z TIME FRAME WITH WINDS TURNING
TOWARD 240-260 DEGREES. THIS APPROACHES CROSS WIND THRESHOLD BUT
SPEEDS SHOULD STAY UNDER 25KT...MITIGATING THAT THREAT.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FT TUESDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 538 PM EDT MON OCT 27 2014

UPDATE...

A REGION OF DEEP LAYER MOISTURE CONVERGENCE IN THE VICINITY OF A
SFC WARM FRONT AND STEEP MID LEVEL LAPSE RATES HAS RESULTED IN AN
EXPANDING REGION OF SHOWERS AND SOME THUNDERSTORMS NOW MOVING INTO
THE WESTERN HALF OF THE FORECAST AREA. THIS MOISTURE CONVERGENCE
SHOULD TRANSLATE EAST ACROSS THE AREA THIS EVENING AND WILL
SUPPORT AN INCREASE TO THE COVERAGE OF SHOWERS AND THUNDERSTORMS
IN THE EVENING FORECAST.

&&

.PREV DISCUSSION...ISSUED 351 PM EDT MON OCT 27 2014

SHORT TERM...THROUGH TONIGHT

A DEEPENING UPPER LEVEL TROUGH IS TRACKING THROUGH THE NORTHERN
PLAINS AND WILL REACH THE WESTERN GREAT LAKES TONIGHT. ASSOCIATED
WITH THIS TROUGH IS A LOW PRESSURE SYSTEM WHICH CURRENTLY RESIDES
OVER NE IA. THE WARM FRONT EXTENDED OUT OF THE LOW IS CURRENTLY
DRAPED ACROSS SOUTHERN MI ON ITS WAY NORTH. ISENTROPIC ASCENT AHEAD
OF THE FRONT HAS ALREADY LIFTED NORTH OF THE AREA WHICH HAS TAKEN
THE SHOWERS AND THUNDERSTORMS ALONG WITH IT. THE WARM SECTOR IS NOW
LIFTING THROUGH SE MI AND IS WELL CAPPED RESULTING IN MOSTLY CLEAR
SKIES. THE COLD FRONT WILL NOT TRAVERSE THE AREA UNTIL TUESDAY BUT A
SOUTHERN STREAM WAVE WILL LIFT NE AHEAD OF THE COLD FRONT TONIGHT
WITH THE NOSE OF A DEEPER PLUME OF THETA E SURGING INTO AREA LIFTING
AROUND 03-06Z. THIS WILL WARRANT THE INTRODUCTION OF POPS AGAIN AS
IT IS COUPLED WITH A DECENT BAND OF ENHANCED LIFT ON THE 310K
SURFACE. AS THE NIGHT PROGRESSES...ADDITIONAL FORCING FROM THE COLD
FRONT WILL START BEING FELT OVER OUR WESTERN COUNTIES WARRANTING
LIKELY POPS FOR THEM.

THE CLEARING SKIES AND GUSTY SW FLOW HAVE ALLOWED TEMPS TO CLIMB
TOWARD 70 DEGREES FOR MANY LOCATIONS. WITH THE WARM SECTOR IN PLACE
THROUGH THE NIGHT... DEWPOINTS SOLIDLY IN THE 50S CURRENTLY LIFTING
INTO THE REGION...AND WINDS STAYING ELEVATED OVERNIGHT...LOW TEMPS
WILL BE QUITE MILD IN THE UPPER 50S TO NEAR 60.

LONG TERM...TUESDAY THROUGH SUNDAY

CLOSED LOW WILL BE IN THE PROCESS OF MOVING NORTHEAST TOWARDS THE
HUDSON BAY ON TUESDAY.  THE COLD FRONT ASSOCIATED WITH THE LOW WILL
MOVE THOUGH THE AREA DURING THE LATER MORNING/EARLY AFTERNOON HOURS.
DUE TO THE TIMING OF THE FRONT AND CLOUD COVER...INSTABILITY LOOKS
TO REMAIN LOW RESULTING IN KEEPING THUNDERSTORMS AT BAY WHICH WAS
STATED IN THE PREVIOUS DISCUSSION.  THERE ARE BETTER MID LEVEL LAPSE
RATES OVER THE NORTHERN CWA WITH PWATS VALUES SHOWING JUST ABOVE ONE
INCH. 12Z MODELS HAVE BEEN PRETTY CONSISTENT WITH THE 00Z MODEL RUNS
CONCERNING THE TIMING OF THE SURFACE FRONT BETWEEN 18-21Z AND LOOKS
TO BE COMPLETELY OUT OF THE AREA BY 00Z THURSDAY.

THE MAIN CONCERN WITH THE PASSAGE OF THE FRONT WILL COME AFTER AS
CAA BEHIND THE FRONT KICKS IN WITH POSSIBLE GUSTS AROUND 35-40 MPH
ESPECIALLY ACROSS THE SAGINAW VALLEY.  ONE ISSUE IS THAT MODELS ARE
NOT HANDLING THE WINDS VERY WELL AND CURRENTLY ARE UNDERESTIMATING
THE STRENGTH WHICH HAS BEEN SEEN COMPARING THE LATEST MODEL RUNS TO
CURRENT CONDITIONS THIS AFTERNOON. THE WARMEST PART OF THE EXTENDED
WILL COME JUST BEFORE THE PASSAGE OF THE COLD FRONT TUESDAY BEFORE
TEMPS DROP LATER IN THE DAY.  UPPER LEVEL TROUGH AND A WEAK
SHORTWAVE MOVING THROUGH NORTHERN LOWER ON WEDNESDAY WILL HELP TO
KEEP THE POTENTIAL FOR LAKE EFFECT SHOWER ACTIVITY IN THE FORECAST.
UPPER LEVEL TROUGH WILL MOVE ACROSS THE GREAT LAKES DURING THE DAY
ON WEDNESDAY BEFORE UPPER LEVEL RIDGING TAKES IT PLACE DURING THE
OVERNIGHT HOURS WITH DRY CONDITIONS TAKING OVER.

THURSDAY NIGHT INTO FRIDAY...A MID LEVEL WAVE AND VORT MAX WILL DIVE
SOUTHEAST INTO THE GREAT LAKES. THIS SYSTEM WILL USHER IN VERY COLD
AIR AND PRECIPITATION IN THE FORM OF COLD RAIN MIXING IN WITH SNOW.
TEMPERATURES WILL BE 10 DEGREES COLDER THAN NORMS...AND BRISK WINDS
BEHIND THE SURFACE LOW WILL BRING APPARENT TEMPS DOWN TO THE UPPER
20S FOR HALLOWEEN. HIGH PRESSURE WILL FILL IN FOR THE WEEKEND...BUT
THE COLD AIRMASS REMAINS IN PLACE AS TEMPS ARE STEADILY 10 DEGREES
BELOW CLIMO.

MARINE...

SOUTHERLY FLOW WILL INCREASE THROUGH TUESDAY AS A COLD FRONT
ADVANCES TOWARDS THE AREA.  THIS FRONT WILL BRING SHOWERS AND
EMBEDDED THUNDERSTORMS TUESDAY MORNING BEFORE EXITING THE AREA
TUESDAY AFTERNOON.  SOUTHERLY WINDS WILL VEER TO THE WEST/SOUTHWEST
BEHIND THE FRONT WITH WINDS GUSTING AROUND 25 KNOTS.  EVEN COLDER
AIR IS FORECASTED TO ARRIVE ON FRIDAY BEHIND AN ARCTIC FRONT...AND
SUBSEQUENTLY WINDS WILL LIKELY BE STRONGER AS WELL...WITH GUSTS TO
AT LEAST 30 KNOTS OVER THE OPEN WATER OF LAKE HURON.

&&

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

$$

UPDATE.......SC
AVIATION.....MM
SHORT TERM...DRK
LONG TERM....SS/MM
MARINE.......SS


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



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