Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDTX 212315
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
615 PM EST FRI NOV 21 2014


.AVIATION...

//DISCUSSION...

HIGH PRESSURE WILL SHIFT TOWARDS THE EAST COAST TONIGHT...ALLOWING
CLOUDS TO SPREAD INTO THE AREA FROM THE WEST. A WARM
FRONT...INITIALLY ELEVATED...WILL THEN LIFT UP INTO LOWER MICHIGAN
LATE TONIGHT AND SATURDAY. THIS WILL ALLOW A WARMER LAYER OF AIR TO
SETTLE IN OVER SUB-FREEZING AIR AT THE SURFACE...POTENTIALLY LEADING
TO FREEZING RAIN AND SLEET AS MOISTURE AND LIFT ARRIVE WITH THE
FRONT. A PERIOD OF FREEZING RAIN OR SLEET WILL BE POSSIBLE BEFORE 14-
16Z BEFORE STRONGER WARM AIR ADVECTION COMMENCES AND PRECIPITATION
CHANGES TO ALL RAIN. THE FRONT WILL ALSO ALLOW CEILINGS TO FALL TO
MVFR...WITH POSSIBLY A DROP TO IFR MID-MORNING SATURDAY.

IN ADDITION...THE LOW-LEVEL JET WILL NOSE INTO THE AREA LATE TONIGHT
AND REMAIN OVERHEAD ON SATURDAY...RESULTING IN A STRONG CORE OF 40-
50 KT WINDS ABOVE 1500 FEET. LOW-LEVEL WIND SHEAR IS EXPECTED AFTER
08Z AT ALL OF THE TAF SITES.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS FALLING BELOW 5000 FEET AFTER 09Z
  SATURDAY.

* MEDIUM CONFIDENCE WITH AT LEAST A LITTLE FREEZING RAIN AT ONSET OF
  PRECIPITATION BETWEEN 08Z-13Z SATURDAY. HIGH CONFIDENCE
  PRECIPITATION WILL THEN CHANGE TO RAIN DURING THE MID-MORNING.

&&

.PREV DISCUSSION...ISSUED 328 PM EST FRI NOV 21 2014

SHORT TERM...THROUGH LATE TONIGHT

STRONG HIGH PRESSURE CENTERED OVER THE OHIO VALLEY AND AN UPPER
RIDGE OVER THE WESTERN GREAT LAKES HAVE PROVIDED QUIET CONDITIONS
AND MOSTLY CLEAR SKIES OVER SOUTHEAST MICHIGAN TODAY AS THEY HAVE
WORKED TO QUELL LAKE EFFECT PROCESSES. THE QUIET WEATHER IS EXPECTED
TO CONTINUE THROUGH MOST OF THE NIGHT...ALTHOUGH WE WILL SEE SOME
HIGHER CLOUDS MOVING IN AHEAD OF THE NEXT SYSTEM. TEMPERATURES WILL
DROP PRETTY QUICKLY INTO THE MID TEENS TO NEAR 20 THIS EVENING WITH
CLEAR SKIES AND FRESH SNOW OFF-SETTING 5 TO 10 MPH SOUTHWEST WINDS.
THESE WILL ACTUALLY BE OUR MINS FOR THE NIGHT...AS WARMER AIR BEGINS
TO ADVECT IN OVERNIGHT. MORE DETAILS ON THE WARM FRONT AND WEATHER
EXPECTED ALONG WITH IT (AFTER ABOUT 4 AM) FOLLOW IN THE LONG TERM
DISCUSSION.

LONG TERM...

RETURN FLOW IS UNDERWAY OVER THE EASTERN PLAINS AS HEIGHT FALLS AND
SOUTHERLY FLOW LEADING THE POTENT WAVE DIGGING INTO THE BAJA
OVERSPREAD EASTERN TX, OK, AND KS. THE ASSOCIATED THETA-E RIDGE IS
BEING DRAWN NORTHWARD AND IS NOTED ON VISIBLE SATELLITE IMAGERY AS
WIDESPREAD LOW CLOUDS BENEATH THE DEVELOPING INVERSION SPANNING AN
EVER-INCREASING COVERAGE OF THE MIDWEST. MEANWHILE, A SHORTWAVE
NOTED OVER THE WESTERN HIGH PLAINS THIS AFTERNOON IS IN THE PROCESS
OF LIFTING TO THE NORTHEAST IN ADVANCE OF NORTHERN STREAM SHORTWAVE
TROUGH. THIS WAVE WILL ZIP ACROSS THE GREAT LAKES LATE TONIGHT INTO
EARLY SATURDAY MORNING BRINGING WITH IT A QUICK HIT OF ISENTROPIC
ASCENT/PV ADVECTION AND AND A QUICKLY DEVELOPING LOW-LEVEL JET
RESPONSE. WITH ARCTIC AIR FIRMLY IN PLACE AT THE SURFACE AND WARM
ADVECTION ONGOING ALOFT, CONFIDENCE IN AT LEAST A BROKEN COVERAGE OF
FREEZING SHOWERS 09Z-14Z HAS INCREASED. MODEL CONSENSUS IS THAT WARM
ADVECTIVE SHOWERS WILL NOT BE PARTICULARLY WELL ORGANIZED EXCEPT
THOSE IMMEDIATELY SUPPORTED BY THE DEEPER ASCENT ASSOCIATED WITH THE
PV ANOMALY ITSELF. CURRENT INDICATIONS ARE THAT THIS WILL BE ACROSS
THE FAR NORTH OF THE CWA, WHERE QPF IS A TENTH OF AN INCH OR SO AND
A FREEZING RAIN ADVISORY IS NOW IN EFFECT. WITH ROADS DRYING OUT
TODAY/TONIGHT THINKING IS THAT THERE IS SUFFICIENT POTENTIAL FOR A
BRIEF DISRUPTION TO TRAVEL TO WARRANT ADVISORY ISSUANCE. THERE IS
SOME POTENTIAL FOR A SECONDARY PEAK IN FREEZING RAIN COVERAGE
ASSOCIATED WITH THE THE STRENGTHENING LOW-LEVEL WIND FIELD MAINLY
SOUTH OF DETROIT WHICH WILL WARRANT MONITORING AS THE SCENARIO
UNFOLDS.

THETA-E GRADIENT WILL BECOME INCREASINGLY ZONALLY ORIENTED AS THE
UPPER FLOW FLATTENS OUT SATURDAY INTO SATURDAY NIGHT. PERIODS OF
INCREASED WARM ADVECTION SUPPORT A BLANKET CHC POP. IT IS DIFFICULT
TO ARGUE GOING HIGHER GIVEN THE LACK OF FOCUSED FORCING, BUT CAN
ENVISION A SCENARIO INVOLVING SCATTERED COVERAGE OF SHOWERS INVOF
THE BAROCLINIC ZONE ON SATURDAY, ESPECIALLY AS A WEAKER NORTHERN
STREAM WAVE TRACKS BY DURING THE EVENING. DRIZZLE IS ALSO A
POSSIBILITY ONCE MID-LEVEL MOISTURE IS SCOURED OUT SATURDAY
AFTERNOON. EITHER WAY, SHOULD BE A DREARY AND DAMPISH DAY ALBEIT
WARMER WITH NORMAL TEMPERATURES IN THE 40S.

A POTENT SHEAR MAX WITH ORIGINS IN THE STRONG EAST PAC JET WILL THEN
QUICKLY RACE SOUTHEAST INTO THE TX PANHANDLE BY 12Z SUNDAY CAUSING
THE STRONG PV ANOMALY PRESENTLY DIGGING INTO THE BAJA TO EJECT
NORTHEAST AND ROLL BACK TOWARD THE STRAITS AS SIGNIFICANT LARGE
SCALE HEIGHT FALLS ENVELOP THE CENTRAL UNITED STATES. THE CURVED
UPPER JET THAT DEVELOPS IN RESPONSE TO THE INCREASING HEIGHT
GRADIENT WILL PLACE SOUTHEAST MICHIGAN UNDER VERY STRONG RIGHT
ENTRANCE DYNAMICS & UPPER DIVERGENCE SIMULTANEOUS WITH THE MAXIMUM
IN PV ADVECTION ARRIVING FROM THE SOUTH. THE SURFACE LOW IS PROGGED
TO PASS OVER OR JUST WEST OF THE AREA, CARRYING WITH IT AN
IMPRESSIVELY DEEP LAYER AXIS OF DEFORMATION FLOW. WITH PWATS OF 1.1"
APPROACHING 2 SIGMA TERRITORY FOR LATE NOVEMBER, A WIDESPREAD HALF
TO INCH OF RAIN IN ABOUT 9 HOURS SHOULD NOT BE HARD TO COME BY.
BUMPED POPS UP ANOTHER NOTCH AND RAMPED UP QPF ACCORDINGLY.

LOW PRESSURE TRACKING ACROSS THE GREAT LAKES ON EARLY MONDAY STILL
APPEARS TO START AS MODERATE RAIN...WITH A GRADUAL TRANSITION TO
RAIN/SNOW MIX AND THEN SNOW ON THE BACK SIDE OF THE LOW. NWP STILL
NOT CONVERGENT ON ONE OUTPUT...BUT BELIEVE THIS HIGH POP EVENT WILL
BRING ANOTHER REGIME CHANGE TO BELOW NORMAL THROUGH THE WEEK. MID
LEVEL FLOW REMAINS IN A DOMINANT TROUGH PATTER THROUGH THE EXTENDED
WITH ANY FURTHER IMPULSES ACROSS THE AREA RESULTING IN SNOW SHOWERS.
THIS PATTERN WILL BE FAVORABLE FOR 1-2 CLIPPER SYSTEMS TO DROP A FEW
INCHES OF SNOW TO THE REGION OVER THE NEXT 7 DAYS.

MARINE...

STRONG HIGH PRESSURE WILL SHIFT FROM THE OHIO VALLEY TO THE EAST
COAST TONIGHT...WHILE A LOW PRESSURE SYSTEM DROPS THROUGH NORTHERN
ONTARIO. STRONG SOUTHWEST FLOW WILL DEVELOP OVER THE CENTRAL GREAT
LAKES LATE THIS EVENING THROUGH EARLY SATURDAY AS THE AREA BECOMES
SITUATED BETWEEN THESE TWO FEATURES. ALTHOUGH WARMER AIR WILL BE
STREAMING INTO THE AREA LATE TONIGHT ALONG A WARM FRONT...THE AIR
WILL STILL REMAIN COLDER THAN THE WATER SURFACE...AND ALLOW GUSTS
FROM A STRONG CORE OF WINDS ALOFT TO MIX DOWN TO THE WATER SURFACE.
GALE FORCE WINDS ARE EXPECTED TO DEVELOP OVER MUCH OF LAKE
HURON...INCLUDING OUTER SAGINAW BAY WHERE WINDS WILL GET AN EXTRA
BOOST FROM FUNNELING BETWEEN THE LAND AREAS. WIND SPEEDS WILL
DECREASE ON SATURDAY AS LOW PRESSURE LIFTS INTO QUEBEC AND THE AREA
OF HIGH PRESSURE PUSHES OFF THE EAST COAST.

ANOTHER LOW PRESSURE SYSTEM WILL LIFT ACROSS THE AREA SUNDAY INTO
MONDAY. THIS WILL BRING ANOTHER ROUND OF STRONG SOUTHERLY WINDS TO
THE GREAT LAKES.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY FROM 4 AM TO 9 AM EST SATURDAY FOR
     MIZ047>049-053>055.

LAKE HURON...GALE WARNING UNTIL 11 AM EST SATURDAY FOR LHZ362-363-421-462-463.

     SMALL CRAFT ADVISORY UNTIL 4 PM EST SATURDAY FOR LHZ441-442.

     SMALL CRAFT ADVISORY UNTIL 11 AM EST SATURDAY FOR LHZ422.

     SMALL CRAFT ADVISORY UNTIL 9 PM EST THIS EVENING FOR LHZ421.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....KURIMSKI
SHORT TERM...HLO
LONG TERM....JVC/MM
MARINE.......HLO


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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.