Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 150759
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
359 AM EDT MON SEP 15 2014

.SHORT TERM... TODAY AND TONIGHT

SOUTHEAST MICHIGAN FIRMLY POSITIONED THIS MORNING ALONG THE SOUTHERN
PERIPHERY OF NORTHERN STREAM MID LEVEL TROUGHING...AND AT THE
WESTERN EDGE OF SLOWLY EXITING SURFACE RIDGING.  LINGERING INFLUENCE
OF THE EXISTING RIDGING AXIS AND ATTENDANT PLUME OF DEEPER AMBIENT
DRY AIR WILL REMAIN A PREVALENT FEATURE THROUGH THE FIRST HALF OF
THE DAY...PARTICULARLY SOUTH OF THE I-69 CORRIDOR WHERE SOME EARLY
DAY SUN IS LIKELY PER RECENT SATELLITE TRENDS.  TO THE NORTH...A
LEAD SHORTWAVE AND ATTENDANT 100 KNOT UPPER JET STREAK BENDING
ACROSS NORTHERN LOWER WILL CONTRIBUTE TO A MORE PROGRESSIVE ONSET
OF THICKER/INCREASING CLOUD COVER.  ASSOCIATED FRONTAL ZONE TIED TO
THE LOWERING HEIGHT FIELD WILL STRENGHTEN THROUGH THE MID LEVELS AS
THIS PROCESS UNFOLDS...THE FRONTAL ZONE SHIFTING INTO THE SAGINAW
VALLEY/THUMB BY MIDDAY.  THIS WILL RESULT IN AN INCREASING CHANCE
FOR SHOWER DEVELOPMENT INITIALLY ALONG THIS CORRIDOR.

STRONGER FORCING WILL AWAIT THE ARRIVAL OF THE INBOUND COMPACT WAVE
NOW DIGGING ACROSS THE DAKOTAS.  SOLID CORRIDOR OF CVA TIED TO THIS
SYSTEM WILL TRANSLATE ACROSS SE MICHIGAN 21Z-03Z LATE TODAY.  WEAK
LOW LEVEL CYCLOGENESIS UPSTREAM WILL INITIATE A PERIOD OF STRONGER
THETA-E ADVECTION COINCIDENT WITH THIS TIMING.  THIS IN COMBINATION
WITH THE HIGH DEGREE OF MID LEVEL ASCENT EXPECTED IN THE PRESENCE
OF FAVORABLE ENTRANCE UPPER JET SUPPORT WILL LEAD TO THE EXPANSION
IN SHOWER COVERAGE OVER THE AREA DURING THIS TIME. HIGH END POPS
REMAIN IN ORDER FOR THIS TIME WINDOW. SUFFICIENT STABILITY THROUGH
THE COLUMN WILL CONTINUE TO PRECLUDE A MENTION OF THUNDER TODAY.

LIGHT PRE-FRONTAL SOUTHWEST FLOW WILL CONTRIBUTE SLIGHTLY TOWARD
MODERATING THE EXISTING AIRMASS...WITH THE BOTH THE TIMING AND
EXTENT OF CLOUD COVER APPLYING A COUNTER TO THIS RESPONSE.  OVERALL
A MODESTLY MIXED PROFILE INTO A 900 MB LAYER CARRYING 7-9C TEMPS
CONTINUES TO SUPPORT A HIGH DISTRIBUTION RANGING FROM MID 60S
SOUTH TO AROUND 60 NORTH.

STEADY POST FRONTAL LOW LEVEL COLD AIR ADVECTION ENSUES THROUGH THE
LATTER HALF OF TONIGHT.  CONTINUED MOIST RH FIELDS AS THIS PROCESS
UNFOLDS SUGGESTS THE CLEARING OF THE RESIDUAL LOW STRATUS WILL TAKE
SOME TIME...LIKELY UNTIL CLOSER TO DAYBREAK ACROSS THE SOUTH. LOWS
TONIGHT WITHIN THE LOWER TO MIDDLE 40S RANGE.

&&

.LONG TERM...TUESDAY THROUGH SUNDAY

THE WEEK AHEAD WILL BE DOMINATED BY FAST NORTHWESTERLY FLOW ALOFT
WITH GENERAL RIDGING AT THE SURFACE. SOUTHEASTERN MICHIGAN CAN
EXPECT AN EXTENDED DURATION OF BELOW NORMAL TEMPERATURES WITH HIGHS
EACH DAY REGISTERING IN THE 60S. A VERY STABLE MIDDLE TROPOSPHERE IS
PROGGED ACCORDING TO FCST BUFFER SOUNDINGS WHICH WILL MAKE IT
DIFFICULT FOR THE COLUMN TO SUPPORT PRECIPITATION GIVEN VERY DRY
AUTUMN SFC DEWPOINTS. THE ONE EXCEPTION MAY BE ALONG A SHALLOW
SURFACE FRONT THAT WILL SLIP INTO THE NORTHERN GREAT LAKES DURING
THE MIDDLE OF THE WEEK...POSSIBLY DROPPING INTO THE SAGINAW BAY
REGION FOR WEDNESDAY AFTERNOON. ATTM...THE MODELS ARE FORECASTING A
SHALLOW LAYER OF SATURATED UNSTABLE LAPSE RATES THAT IS GOOD FOR A
LOW CHANCE POPS ACROSS THE NORTHERN CWA. THE FRONT IS EXPECTED TO
WASH OUT...LEADING TO A CONTINUATION OF QUIET AND VERY COMFORTABLE
WEATHER FOR THURSDAY AND FRIDAY.

TUESDAY...THE ONE QUESTION IS WHAT SORT OF SKY FRACTION WILL EXIST
IN THE WAKE OF THE MONDAY NIGHT SYSTEM. THE COLUMN IS AGAIN SHOWING
A DEVELOPING INVERSION BETWEEN 7-12Z WITH A BASE AT ROUGHLY 6 KFT
AGL. THIS IS REMINISCENT TO THE SUNDAY MORNING CASE WITH THE MODELS
AT THIS VANTAGE POINT SHOWING NO SATURATION OR HIGH MOISTURE
CONTENT. BUT AS WE WITNESSED...THAT ALL CHANGED AS TIME APPROACHED
ZERO. WILL SIDE WITH THE DATA THAT IS AVAILABLE...AND WILL BE LIGHT
ON CLOUD COVER FOR TUESDAY. HIGH TEMPERATURES ARE EXPECTED TO REACH
THE LOWER TO MIDDLE 60S...OR APPROXIMATELY 10 DEGREES BELOW NORMAL.

&&

.MARINE...

SURFACE RIDGING WILL RETREAT OUT OF THE CENTRAL GREAT LAKES
TODAY...ALLOWING FOR A VERY WEAK SURFACE TROUGH AND FRONTAL SYSTEM
TO ADVANCE INTO THE REGION FOR TONIGHT. THE TROUGH WILL BE VERY FAST
MOVING AND WILL NOT PROVIDE MUCH SUPPORT IN DEVELOPING A STRONG
FRONTAL BOUNDARY. THEREFORE...SURFACE WINDS WILL ONLY INCREASE
MODESTLY OUT OF THE NORTH TONIGHT DUE TO A WEAK PRESSURE GRADIENT.
HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE WEST FOR MUCH OF
THE WORK WEEK...WITH ONLY BENIGN WIND AND WAVES FOR THE TIME OF YEAR
EXPECTED THROUGH FRIDAY.

&&

.AVIATION...ISSUED 1138 PM EDT SUN SEP 14 2014

//DISCUSSION...

VFR AND LIGHT WINDS WILL PERSIST INTO MONDAY MORNING. SHOWERS
ASSOCIATED WITH A FRONTAL BOUNDARY WILL SAG SOUTH TOWARD KMBS
THROUGH THE MORNING. PARTIAL COVERAGE OF LIGHT SHOWERS THROUGH EARLY
AFTERNOON WILL GIVE WAY TO INCREASING COVERAGE AND INTENSITY 18-21Z.
APPROX 5 HOUR PERIOD OF RAINFALL WILL THEN BRING A PERIOD OF MVFR
MAINLY AFTER 21Z FOLLOWED BY THE POTENTIAL DEVELOPMENT OF A LOW
MVFR/HIGH IFR CEILING AS CAA ENSUES IN ITS WAKE. DRY ADVECTION
SHOULD HELP CLEAR LINGERING CLOUD DEBRIS BY LATE MONDAY NIGHT.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5KFT MONDAY AFTERNOON

&&

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

&&

$$

SHORT TERM...MR
LONG TERM....CB
MARINE.......CB
AVIATION.....JVC


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




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