FXUS63 KDTX 151102
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
602 AM EST TUE DEC 15 2009
.AVIATION...
ARCTIC AIR WILL ADVANCE ACROSS SOUTHEAST MICHIGAN TODAY. THE
ASSOCIATED DRY AIR ADVECTION WILL BEGIN TO LIFT CEILINGS FROM LOW
END MVFR/IFR UP TO MVFR BY AFTERNOON. THE CLOUDS WILL THEN BEGIN TO
SCATTER OUT TOWARD 00Z WITH CONTINUED LOW LEVEL DRY AIR ADVECTION.
WINDS WILL BACK MORE WESTERLY BY AFTERNOON. MODEL SOUNDINGS INDICATE
MIXING DEPTHS WILL BE SUPPORTIVE OF WIND GUSTS AROUND 20 KNOTS
THROUGH MUCH OF THE AFTERNOON.
&&
.PREV DISCUSSION...ISSUED 358 AM EST TUE DEC 15 2009
SHORT TERM...TODAY
WATER VAPOR IMAGERY SHOWS A MID LEVEL TROUGH EXTENDING FROM
NORTHWESTERN ONTARIO THROUGH MINNESOTA. THIS TROUGH IS FORECAST TO
SLIDE ACROSS THE GREAT LAKES REGION THIS AFTERNOON...WHICH WILL
ADVECT THE ARCTIC AIRMASS UPSTREAM ACROSS THE STATE TODAY. TEMPS ARE
CURRENTLY IN THE 30S ACROSS SE MI...BUT WILL SLOWLY FALL INTO THE
LOW TO MID 20S BY EVENING AS 850MB TEMPS FALL TO -14 TO -16 C.
THE LATEST SURFACE ANALYSIS SHOWS A TROUGH AXIS EXTENDING ACROSS THE
THUMB REGION...WITH WINDS ACROSS HURON COUNTY NOW OUT OF THE NORTH.
EXETER ONT RADAR SUGGESTS SOME RETURNS IMPACTING HURON COUNTY. MODEL
SOUNDINGS /WITH SUPPORT OF THE 00Z APX SOUNDING/ ARE NOT SUPPORTIVE
OF DEEP CONVECTION OVER LAKE HURON THROUGH 09Z. AS OF 07Z...BOUNDARY
LAYER TEMPS ACROSS THE THUMB REGION ARE STILL TOO WARM TO SUPPORT
SNOW. COLD AIR ADVECTION WILL HOWEVER DEEPEN CONVECTIVE DEPTHS
TOWARD 12Z AND INDUCE ENOUGH COOLING IN THE BOUNDARY LAYER TO
SUPPORT ALL SNOW. A REGION OF ENHANCED MID LEVEL MOISTURE AND LIFT
NOW RESPONSIBLE FOR THE WIDESPREAD LIGHT SNOW/FLURRIES ACROSS
NORTHERN AND CENTRAL LOWER MI WILL ADVANCE ACROSS LAKE HURON BETWEEN
09Z AND 12Z. THIS WILL CERTAINLY ENHANCE LAKE EFFECT POTENTIAL
ACROSS THE THUMB TOWARD DAYBREAK. THE LOW LEVEL WIND FIELD HOWEVER
IS FORECAST TO BACK MORE TO THE NORTHWEST BY 15Z...FOCUSING THE BEST
CONVERGENCE OFFSHORE. GIVEN THIS SHORT WINDOW OF OPPORTUNITY...PLAN
TO KEEP SNOW ACCUMULATIONS LESS THAN AN INCH ACROSS THE THUMB.
AFTER SOME DISRUPTIONS FROM A MESO SCALE VORTEX OVER SOUTHERN LAKE
MICHIGAN...A FAIRLY WELL ORGANIZED NORTH-SOUTH LAKE BAND HAS
DEVELOPED OVER THE WESTERN PART OF THE LAKE. AS THE WINDS BACK MORE
WEST-NORTHWESTERLY DURING THE COURSE OF THE DAY...RESIDUAL LAKE
EFFECT SNOW SHOWERS WILL MAKE THEIR WAY INTO SE MI. LAKE MODIFIED
SOUNDINGS HOWEVER ONLY SHOW EQUILIBRIUM LEVELS REACHING 6K FEET DUE
TO THE SHALLOW ARCTIC AIR ADVANCING INTO THE REGION. DESPITE THIS
LIMITING FACTOR...LARGE SCALE ASCENT ASSOCIATED WITH APPROACHING MID
LEVEL WAVE IN COMBINATION WITH THE MODEST LAKE INSTABILITY WILL BE
ENOUGH TO MAINTAIN SCATTERED SNOW SHOWERS THROUGH THE DAY.
LONG TERM...TONIGHT THROUGH MONDAY
UPPER LEVEL TROUGH AXIS WILL PASS EAST OF THE STATE BY WEDNESDAY
LEAVING A NORTH TO NORTHWEST FLOW OVER THE REGION FOR THE REMAINDER
OF THE LONG TERM FORECAST. THIS PATTERN WILL FEATURE BELOW NORMAL
TEMPERATURES AND PRECIPITATION AS WEAK SHORTWAVES MOVING OUT OF
CANADA WILL LACK MOISTURE. THE EXCEPTION TO THIS MAY BE ACROSS THE
THUMB AS THE POLAR VORTEX OVER EASTERN CANADA PIVOTS WESTWARD INTO
THE CENTRAL GREAT LAKES AND PROVIDES ENOUGH MOISTURE FOR LAKE EFFECT
SNOW SHOWERS TO DEVELOP BY SUNDAY OR MONDAY.
STRONG HIGH PRESSURE WILL SLOWLY BUILD EAST INTO THE GREAT LAKES
REGION THROUGH WEDNESDAY. MODEL SOUNDINGS SHOW PARTLY TO MOSTLY
CLOUDY SKIES HANGING ON THROUGH THIS TIME AS LOW LEVEL MOISTURE
GETS TRAPPED BENEATH A STRENGTHENING INVERSION. THE PRESSURE
GRADIENT WILL KEEP WINDS UP AROUND 10 MPH TONIGHT BUT THE COOL
AIRMASS WILL STILL SUPPORT LOWS DROPPING SOLIDLY INTO THE TEENS.
TEMPERATURES WILL ONLY REBOUND INTO THE 20S ON WEDNESDAY WHICH
WILL SET THE STAGE FOR A VERY CHILLY NIGHT ON WEDNESDAY NIGHT AS
LOW CLOUDS FINALLY SCATTER OUT AND WINDS DROP TO NEAR CALM FOR
INTERIOR AREAS. WILL UNDER-CUT GUIDANCE BY A COUPLE DEGREES ON
WEDNESDAY NIGHT WITH THE EXPECTATION THAT SIZABLE BREAKS IN THE
CLOUDS WILL DEVELOP AND ALLOW SOME RURAL LOCATIONS TO CREEP INTO
THE SINGLE DIGITS. DRY AND COOL AND CONDITIONS WILL CONTINUE
THROUGH FRIDAY WITH A MIX OF SUN AND CLOUDS AS SHORTWAVES MOVING
THROUGH THE FLOW ALOFT BRING OCCASIONAL MID AND HIGH CLOUDS.
BY THIS WEEKEND...MODELS DEPICT THE POLAR VORTEX OVER EASTERN
CANADA RETROGRADING TO THE WEST AND HELPING TO RE-ESTABLISH THE
LONGWAVE TROUGH OVER THE EASTERN UNITED STATES. THE NWP SUITE IS
LACKING CONSISTENCY REGARDING THE TIMING AND WESTWARD EXTENT OF
THIS FEATURE WITH THE GFS SHOWING A FAVORABLE SET UP FOR LAKE
EFFECT SNOW WITH DEEP NORTHERLY FLOW SETTING UP OFF LAKE HURON ON
SUNDAY. SOME OF THE OTHER MODEL SOLUTIONS ARE NOT AS FAVORABLE AT
THAT TIME AND WILL JUST CARRY A CHANCE OF SNOW INTO NEXT WEEK. WE
WILL ALSO CONTINUE TO MONITOR THE INTERACTION OF THE POLAR VORTEX
WITH ENERGY MOVING IN FROM THE PACIFIC OCEAN ON THE NOSE OF A
STRONG UPPER LEVEL JET. CYCLOGENESIS IS FORECAST TO OCCUR AS THIS
FEATURE ROUNDS THE BASE OF THE TROUGH NEAR THE GULF BEFORE
TRACKING UP THE EAST COAST. THERE IS SOME POTENTIAL FOR THIS TRACK
TO SHIFT WESTWARD BUT IS UNLIKELY TO COME FAR ENOUGH WEST TO
IMPACT SOUTHEAST MICHIGAN AS WE WILL BE DEEPLY ENTRENCHED IN THE
COLD AIR AND REMOVED FROM THE STORM TRACK.
MARINE...
WINDS AND WAVES WILL INCREASE ACROSS LAKE HURON TODAY AS ARCTIC AIR
INFILTRATES THE REGION. THIS ARCTIC AIR WILL ARRIVE IN ADVANCE OF
STRONG HIGH PRESSURE SLIDING INTO THE UPPER MISSISSIPPI RIVER
VALLEY. THE HIGH WILL BECOME CENTERED OVER THE REGION TOWARD THE END
OF THE WEEK...ALLOWING THE WINDS AND WAVES TO DECREASE.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
FROM PORT AUSTIN TO HARBOR BEACH...UNTIL 4 PM WEDNESDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
HURON...UNTIL 4 AM WEDNESDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....SC
SHORT TERM...SC
LONG TERM....KEC
MARINE.......SC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
