FXUS63 KDTX 041725
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1225 PM EST FRI DEC 4 2009
.AVIATION...
WITH THE COLD AIR ALOFT...STRATOCUMULUS IS EXPECTED TO FILL THIS
AFTERNOON ACROSS MUCH OF THE AREA (STILL EXPECTING AN MVFR CEILING
TO DEVELOP ACROSS THE SOUTH). PRECIPITATION TODAY HAS HAD GREATER
SUPPORT ACROSS THE FAR NORTHERN CWA AND SHOULD CONTINUE TO FAVOR
THAT AREA...CARRIED A TEMPO AT KMBS/KFNT FOR -SHSN/DRY SOUTHERN
TAF SITES. SURFACE HIGH PRESSURE WILL SQUEEZE ACROSS THE OHIO
RIVER VALLEY THIS AFTERNOON AND TONIGHT. THIS WILL KEEP A TIGHT
WESTERLY GRADIENT IN PLACE...WITH 10-15 KNOTS THIS
AFTERNOON...WITH EASING WINDS OVERNIGHT. THE SOUTHERN FORECAST
AREA WILL EXPERIENCE SURFACE RIDGING AND A CLEARING OF SKIES.
DEEPER CYCLONIC FLOW AND PRECONDITIONING OFF OF LAKE MICHIGAN
SHOULD RESULT IN A SOLID MVFR DECK OVERNIGHT AT KMBS. SURFACE
HIGH PRESSURE AND WARMING TEMPERATURES TOMORROW WILL DEVELOP A
SCT040 FOR MOST OF THE AREA.
&&
.PREV DISCUSSION...ISSUED 1139 AM EST FRI DEC 4 2009
UPDATE...
ISSUED AN UPDATE FOR LATEST RADAR AND PRECIPITATION TRENDS. THE
LAKE EFFECT ACTIVITY STREAMING OFF OF LAKE MICHIGAN AFTER SUNRISE
WAS ABLE TO LOCK INTO A POSITIONING DOWNSTREAM NEAR/ALONG M 57. AN
EMBEDDED CYCLONIC VORT...CARRYING GREATER LOW LEVEL
CONVERGENCE...BROKE OFF AND ALLOWED FOR THE RECENT ENHANCED
SNOWFALL RATES. PEERING AT WV IMAGERY OVERNIGHT SUGGESTS THIS VORT
TO BE NEAR THE CENTER OF THE MUCH LARGER U/L PV ANOMALY EXITING
LOWER MICHIGAN TO THE NORTHEAST. HAVE TAKEN MULTIPLE REPORTS THIS
MORNING THAT A GENERAL 1 TO 3 INCHES ACCUMULATED IN A VERY NARROW
BAND ALONG M 57. RECENT HIRES WRF RUNS HANDILY REPRESENTED THIS
SCENARIO.
VIRTUALLY ALL OF THE MODEL GUIDANCE FOR THIS AFTERNOON
IS PROGGING THE CONVECTIVE SNOWS TO TRANSITION TO CELLULAR
ORGANIZATION (HINTS OF THIS ALREADY OCCURRING IN KGRR/KDTX RADAR).
STILL EXPECT THE CELLULAR CONVECTION TO IMPACT ALONG AND
IMMEDIATELY NORTH OF THE I 69 CORRIDOR WITH NO EXPECTED SHIFT IN
THE LOW LEVEL WIND FIELD/CURRENT SURFACE OBSERVATIONS VAGUELY
SUGGEST SOME CONFLUENCE IN THAT VICINITY. WITH STEEP 900-775MB
LAPSE RATES FEEL SNOWFALL RATES WILL CONTINUE TO BRIEFLY DROP TO A
MILE OR LESS AT TIMES. EACH OF THE BURSTS WILL BE CAPABLE OF
DROPPING A QUICK HALF INCH...WITH ADDITIONAL ACCUMULATIONS TODAY
OF AROUND AN INCH. FARTHER SOUTH...THE AIRMASS IS NOT
PRECONDITIONED FROM LAKE MICHIGAN. DAYTIME HEATING WILL RESULT IN
AN INCREASE IN CLOUD COVER...BUT SHALLOW CONVECTIVE DEPTHS WILL
KEEP ANY FORECASTED ACTIVITY AT THE ISOLATED CATEGORY. ACROSS THE
TIP OF THE THUMB/NEAR PORT AUSTIN...WATCHING A BAND THAT IS
REMAINING JUST OFFSHORE. THERE IS THE POTENTIAL FOR THIS BAND TO
BRUSH AGAINST THE SHORELINE AREAS THIS AFTERNOON AND HAVE CARRIED
ACCUMULATIONS OF 1 TO 2 INCHES. TWEAKED A DEGREE OR TWO OFF OF
AFTERNOON HIGHS...WITH LOWER TO MIDDLE 30S EXPECTED.
PREV DISCUSSION...ISSUED 404 AM EST FRI DEC 4 2009
SHORT TERM...TODAY
LAKE EFFECT SNOW BANDS CONTINUE TO MOVE INTO SOUTHEASTERN MICHIGAN
EARLY THIS MORNING. DESPITE THE LAKE EFFECT SNOW...THE BANDS
THEMSELVES HAVE BEEN TRANSIENT ENOUGH TO NOT DUMP A LOT OF SNOW IN
ANY ONE LOCATION. WHILE THE LAKE EFFECT OVERNIGHT WAS MORE BANDED
WITH EMBEDDED VORTICES...DTX HI-RES RUNS INDICATE LAKE EFFECT THIS
MORNING WILL BE MORE CELLULAR...FURTHER LIMITING THE POSSIBILITY OF
SIGNIFICANT ACCUMULATIONS. ALL MODELS ARE IN GOOD AGREEMENT THAT THE
BEST SNOW CHANCES THIS MORNING WILL BE ALONG AND NORTH OF INTERSTATE
69...HOWEVER WITH LESS ORGANIZED LES BANDS MAKING THEIR WAY INTO THE
CWA WILL LOWER POPS TO 60 ACROSS THESE LOCATIONS.
THIS AFTERNOON 850 MB AND 925 MB WINDS TURN FROM WESTERLY TO
SOUTHWESTERLY. THIS SLIGHT TURN IN THE WINDS AT THESE LEVELS SHOULD
SIGNIFICANTLY LIMIT THE LAKE EFFECT POTENTIAL ACROSS SOUTHEASTERN
MICHIGAN DURING THE AFTERNOON HOURS. WITH THE LESS FAVORABLE WIND
DIRECTION AND MODEL AGREEMENT IN MUCH LOWER AMOUNTS OF QPF...WILL
LOWER POPS INTO THE CHANCY CATEGORY AS A FEW STRAY LES SHOWERS MAY
MAKE THEIR WAY INTO THE CWA BUT NOT AMOUNT TO MUCH IN THE WAY OF
ACCUMULATION.
A CONTINUED TIGHT PRESSURE GRADIENT WILL LEAD TO BRISK CONDITIONS
TODAY AS CLOUDY SKIES AND COLD TEMPERATURES ALOFT LIMIT HIGH
TEMPERATURES. HIGHS TODAY SHOULD STAY IN THE 30S...WITH LITTLE IN
THE WAY OF DIURNAL VARIATION FROM THIS MORNINGS LOWS WITH CONTINUED
COLD AIR ADVECTION AT 925 AND 850 MB.
LONG TERM...TONIGHT THROUGH THURSDAY
LONGWAVE TROUGHING WILL KEEP AN OVERALL COOL AND ACTIVE PATTERN OVER
THE GREAT LAKES THROUGH THE END OF NEXT WEEK...WITH TWO STORMS
SYSTEMS TO KEEP AN EYE ON.
SURFACE RIDGING WILL EXTEND INTO LOWER MICHIGAN TONIGHT AND SUNDAY.
EXPECT THE WEATHER TO REMAIN COOL...WITH LAKE EFFECT SHOWERS
GRADUALLY LIFTING NORTHWARD AND TAPERING OFF AS WINDS ACROSS LAKE
MICHIGAN GRADUALLY TAKE ON MORE OF A SOUTHERLY COMPONENT (BECOMING
SOUTHWEST OVERALL)...AND MOISTURE DEPTH BEGINS TO WANE. SHORTWAVE
ENERGY EJECTING OUT OF THE TROUGH CURRENTLY OVER THE PACIFIC
NORTHWEST WILL ZIP ACROSS THE CENTRAL ROCKIES BEFORE LIFTING UP INTO
THE SOUTHERN GREAT LAKES ON MONDAY. MODELS ARE IN GOOD AGREEMENT
WITH THE ASSOCIATED SURFACE LOW TRACKING ACROSS MICHIGAN...ALTHOUGH
THERE IS SOME VARIATION WITH REGARD TO WHERE IN MICHIGAN THAT WILL
BE. 00Z GFS/EURO/NAM HAVE SHIFTED THE TRACK SOUTHWARD ACROSS SOUTH
CENTRAL MICHIGAN...WITH BEST DEFORMATION NOW LIFTING ACROSS CENTRAL
MICHIGAN. WITH COLD AIR ALREADY ENTRENCHED OVER THE REGION PRECEDING
THE SYSTEM...EXPECT ALL PRECIPITATION TO BE SNOW. FAST SPEED SHOULD
LIMIT SNOW AMOUNTS...WITH THE TRI-CITIES AND THUMB NOW LOOKING TO
SEE THE MOST ACCUMULATION...CURRENTLY PROGGED AT 1-2 INCHES PER
LATEST GFS/EURO FORECAST TRACK. WILL KEEP AN EYE ON THIS LITTLE
SYSTEM AS VERTICALLY STACKED DYNAMICS (COLD FRONT...LEFT EXIT
REGION) WILL PACK A QUICK PUNCH THAT COULD COINCIDE WITH THE MORNING
COMMUTE.
SURFACE HIGH PRESSURE LOOKS TO BUILD IN BEHIND THE SYSTEM MONDAY
NIGHT...HOWEVER COLD AIR ADVECTION OVER THE GREAT LAKES WILL ALLOW
LIGHT LAKE EFFECT SNOW SHOWERS TO LINGER. VERY LIGHT WINDS SHOULD BE
PRESENT OVERHEAD BY TUESDAY...AND HAVE KEPT THE INHERITED DRY
FORECAST AS THIS SHOULD ALLOW THE THREAT FOR LAKE EFFECT TO END.
A MORE POTENT STORM SYSTEM IS LOOKING TO TAKE AIM AT THE GREAT LAKES
AROUND WEDNESDAY PER RECENT GFS/EURO RUNS. UPPER WAVE OVER THE
PACIFIC NORTHWEST WILL DROP DOWN THE WEST COAST AND INTO THE DESERT
SOUTHWEST AS ADDITIONAL ENERGY FEEDS INTO THE SYSTEM FROM THE NORTH.
THIS WILL ALLOW A FAIRLY STRONG SURFACE LOW PRESSURE SYSTEM TO SPIN
UP AND CONTINUE TO DEEPEN AS IT LIFTS THROUGH THE CENTRAL PLAINS ON
TUESDAY. MODELS SHOW THIS WILL ALL BE MET BY PRETTY IMPRESSIVE JET
DYNAMICS AND A MOISTURE SURGE FROM THE GULF BY THE TIME IT REACHES
THE GREAT LAKES. MODELS SUPPORT SNOW INITIALLY ON TUESDAY NIGHT AS
THE SYSTEM APPROACHES...WITH STRONG EASTERLY FLOW FEEDING INTO THE
NORTH SIDE OF THE SYSTEM AND PROVIDING SOME ENHANCEMENT OFF LAKES
ERIE AND HURON. LAST FEW RUNS OF THE GFS AND EURO TAKE THE SURFACE
LOW CENTER EITHER DIRECTLY OVER US OR NORTH OF US...ALLOWING WARM
AIR TO SURGE INTO THE REGION ON WEDNESDAY. HAVE ADDED A CHANCE OF
RAIN TO THE FORECAST FOR WEDNESDAY IN ADDITION TO THE SNOW...AND
WILL WATCH THE TRACK CAREFULLY AS THIS SYSTEM LOOKS LIKE IT WILL
GENERATE QUITE A BIT OF PRECIPITATION. STRONG FROPA WILL ALLOW
PRECIPITATION TO CHANGE BACK TO SNOW WEDNESDAY NIGHT...HOWEVER
PRECIPITATION RATES SHOULD COME DOWN BEHIND THE FRONT. THIS SYSTEM
CERTAINLY BEARS WATCHING AS IT HAS THE POTENTIAL TO PRODUCT
ACCUMULATING SNOWFALL.
MARINE...
HIGH PRESSURE BUILDING IN ACROSS THE NORTHERN OHIO VALLEY WILL TURN
WINDS SOUTHWESTERLY AS AN INCREASED PRESSURE GRADIENT CAUSES WIND
GUSTS OF 20 TO 25 KNOTS TODAY. ALTHOUGH WINDS WILL MOSTLY BE
OFFSHORE...THERE WILL BE ENOUGH OF A FETCH ACROSS SAGINAW BAY AND
THE TIP OF THE THUMB FOR WAVES TO REACH 4 TO 7 FEET LATER TODAY AND
TONIGHT. WITH WIND AND WAVE CONDITIONS WILL ISSUE SMALL CRAFT
ADVISORIES FOR THESE AREAS TODAY AND TONIGHT. THE HIGH WILL CAUSE
THE PRESSURE GRADIENT TO SLACKEN TONIGHT...HOWEVER WAVES WILL STILL
REMAIN HIGH ACROSS SAGINAW BAY AND THE TIP OF THE THUMB FOR A GOOD
PORTION OF THE NIGHT. WINDS AND WAVES WILL SUBSIDE BELOW SMALL CRAFT
ADVISORY CRITERIA DURING THE WEEKEND.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL 10 PM FRIDAY.
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
FROM PORT AUSTIN TO HARBOR BEACH...UNTIL 4 AM SATURDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....CB
UPDATE.......CB
SHORT TERM...KURIMSKI
LONG TERM....HLO
MARINE.......KURIMSKI
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
