FXUS63 KAPX 282326
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
627 PM EST SAT NOV 28 2009
.SYNOPSIS.../ISSUED AT 348 PM/
THE EFFECTS OF HIGH PRESSURE WILL FADE TONIGHT...AS A LOW PRESSURE
SYSTEM DEVELOPS OVER THE LWR GREAT LAKES SUNDAY. THIS WILL BRING A
WINTRY MIX OF LIGHT PRECIP TO PARTS OF NORTHERN MI. BEHIND THIS
SYSTEM...TEMPERATURES WILL AVERAGE COLDER THAN NORMAL NEXT WEEK.
THIS WILL RESULT IN INCREASING PROBABILITIES FOR ACCUMULATING LAKE
EFFECT SNOW...WITH THE FIRST EVENT SUNDAY NIGHT THRU MONDAY NIGHT. A
BRIEF INTERRUPTION IS EXPECTED TUE WITH THE NEXT CHANCE COMING WED
THRU FRI.
JH
&&
.SHORT TERM.../ISSUED AT 348 PM/...TONIGHT
LOW AMPLITUDE MID LEVEL RIDGING AND WEDGE OF DRY AIR SLIPPING ACROSS
THE MIDWEST/WESTERN GREAT LAKES THIS AFTERNOON...PROVIDING
RELATIVELY QUIET WEATHER TO THE REGION. AT THE SFC...LOOSELY
ORGANIZED AREA OF LOW PRESSURE AND/OR SEMBLANCE OF A SFC FRONT
EXTENDS FROM THE U.P. ACROSS WISCONSIN AND INTO THE CENTRAL PLAINS.
NO PRECIP OR SIGNIFICANT CLOUD COVER ASSOCIATED WITH THIS
FEATURE...OTHER THAN SOME WARM ADVECTION MID AND HIGH CLOUDS NORTH
OF THE FRONT DRIFTING ACROSS THE UPPER MIDWEST/NRN MICHIGAN.
MEANWHILE...HAVE BEEN TRACKING AND ADJUSTING SKY GRIDS FOR LAKE
INDUCED CLOUD COVER AND SOME SEMBLANCE OF A LAKE BAND THAT HAS BEEN
MIGRATING UP THE LAKE MICHIGAN SHORELINE INTO THE STRAITS AND UPPER
MICHIGAN. CLOUD COVER HAD EXPANDED INLAND JUST A BIT EARLIER IN THE
DAY...ALTHOUGH IT HAS BEEN MIXING OUT/THINNING TO SOME EXTENT DURING
THE LAST FEW HOURS.
TONIGHT...LOW AMPLITUDE RIDGE AND AN OVERALL DRY AIRMASS SLIDING
THROUGH THE REGION WILL REMAIN THE DOMINATE PLAYER. BIGGEST FORECAST
HEADACHE WILL CONTINUE TO BE CLOUD COVER. IN THE NEAR TERM...HAVE
TWEAKED SKY GRIDS TO ACCOUNT FOR AFOREMENTIONED LAKE CLOUD COVER
INTO THE EVENING HOURS...ESSENTIALLY PUSHING THE BULK OF LAKE CLOUD
COVER INTO THE STRAITS/TIP OF THE MITT.
THEN...AFOREMENTIONED WEAK SFC FRONT/TROUGH EXPECTED TO SLIP THROUGH
NRN MICHIGAN DURING THE EVENING TURNING WINDS INTO THE NW. NO PRECIP
ANTICIPATED. HOWEVER...NAM/GFS RH FORECASTS CONTINUE TO SUGGEST A
FAIRLY SHALLOW LOW CLOUD LAYER (BLO 2K FEET) DEVELOPING SOUTHWARD
TONIGHT AS A SLIGHTLY COOLER AIRMASS OVERSPREADS THE REGION. NO EASY
ANSWER...BUT THIS IDEA DOES MAKES SENSE GIVEN THE PATTERN/TIME OF
YEAR...ETC. SO... WILL HAVE ALL AREAS TURNING CLOUDY LATER THIS
EVENING AND OVERNIGHT ACCORDINGLY. AS FAR AS THE INHERITED
DRIZZLE/FREEZING DRIZZLE IDEA. FORECAST LOW SATURATED LAYER LOOKS
PRETTY SHALLOW PARTICULARLY ON GFS SOUNDINGS...AND NOT ENOUGH TO
SUPPORT A SUBSTANTIAL DRIZZLE THREAT. SUPPOSE A FEW SPITS ARE
POSSIBLE BUT NOT ENOUGH TO WARRANT LEAVING IT IN THE FORECAST.
ADAM
&&
.LONG TERM.../ISSUED AT 348 PM/...SUNDAY AND BEYOND
SUNDAY/SUNDAY NIGHT...THE NEXT SYSTEM MOVES IN WITH THE CHANCE OF
RAIN IN N LOWER AS THE TEMPERATURES ARE AROUND 40 EARLY IN THE
AFTERNOON. THE 500 MB TROUGH IS MOVING INTO UPPER MICHIGAN WITH THE
SFC LOW OVER US, ACCORDING THE GFS. THE NAM HAS LESS QPF, DUE TO THE
SFC TROUGH BEING EAST OF THE FORECAST AREA. TEMPERATURES DO START TO
COOL LATE IN THE AFTERNOON AND EARLY IN THE EVENING AS THE LOW GOES
TO THE EAST. SO THE RAIN/SNOW MIX IN E UPPER AND NW LOWER LOOKS TO
BE CHANGING INTO THE ALL SNOW AND THEN IN NE LOWER BY THE LATE
EVENING. WINDS CONTINUE TO BE NW OVERNIGHT AND WITH THE MOISTURE IN
THE 850-700 MB LAYER AROUND 70% AND THE TEMPERATURES NEAR -10C WILL
EXPECT LES FORMING.
MONDAY...LES LOOKS TO BE LIKELY FOR THE DAY AS THE 850 MB
TEMPERATURES DROP TO AROUND -10C WITH A PROFILE THAT IS MOSTLY BELOW
FREEZING. INSTABILITY WOULD BE PRETTY AVAILABLE WITH THE DELTA TS
AROUND 13 TO 15C. MOISTURE LOOKS TO BE AROUND 70-80% IN THE 850-700
MB LAYER SO SCATTERED SNOW BANDS LOOK LIKE THEY WILL BE IN THE
REGION. WITH NW FLOW DOMINANT IN THE MORNING AND WNW IN THE
AFTERNOON.
MONDAY NIGHT...THE WINDS WILL CONTINUE TO BACK TO THE WEST AND 850
MB TEMPERATURES WILL BEGIN TO RISE. SO THE CHANCES OF SNOW WILL
BEGIN TO FALL OVERNIGHT, BUT THERE WILL BE A DECENT SHOT OF W FLOW
TO WSW FLOW ALONG THE LAKE MICHIGAN SHORELINE.
TUESDAY...THE HIGH PRESSURE BUILDS INTO THE OHIO VALLEY WITH A SFC
RIDGE INTO THE UPPER MISSISSIPPI VALLEY. THERE IS A SFC TROUGH THAT
IS MOVING THROUGH THE UPPER LAKES AROUND 12Z. THERE IS A DISCREPANCY
BETWEEN THE FORECAST MODELS WITH THE WIND DIRECTIONS INITIALLY. THE
NAM GOES SW EARLIER THAN THE GFS SO THE SNOW COULD WIND UP SOONER IF
THE NAM IS RIGHT. OTHERWISE, BY 00Z THE SNOW WILL BE ISOLATED TO THE
NW LOWER SHORELINE AND THEN STOP AS THE 850-700 MB DRY AIR MOVES IN
AND THE 850 MB TEMPERATURES WARM TO AT LEAST 0C. WITH THE WATER
TEMPERATURES AROUND +8C THE DELTA TS WILL BE WELL BELOW THE MAGIC
13C. OVERNIGHT, THE 500 MB RIDGE AND THE SFC RIDGE ARE IN THE
REGION. IT LOOKS LIKE THE GFS WANTS TO CREATE PRECIPITATION
OVERNIGHT WITH A WEAK FRONT, BUT THINK THAT IT A BIT OVERBLOWN.
EXTENDED (WEDNESDAY THROUGH SATURDAY)...WEDNESDAY, AN ALBERTA
CLIPPER SYSTEM MOVES INTO W LAKE SUPERIOR. LOOKS DRY ON THE FRONT
END WITH THE 850 MB TEMPERATURES ABOVE 0C. THIS WILL KEEP THE
PRECIPITATION OUT AT THE BEGINNING. ONCE THE FRONT GOES THROUGH, THE
DOMINANT PRECIPITATION WILL BE SNOW AS THE COLD AIR SPILLS INTO THE
REGION QUICKLY. THURSDAY, MODELS ARE TRENDING TOWARD A SCENARIO OF
THE CLIPPER PHASING AND BEING ABSORBED INTO THE EAST COAST SYSTEM.
PLENTY OF COLD AIR WITH THE 850 MB TEMPERATURES DROPPING ON THE GFS
ENSEMBLE AND ECMWF MODELS TO COOLER THAN -10C. SO EXPECTING PLENTY
OF INSTABILITY FOR LES. FRIDAY AND SATURDAY, HPC/ECMWF/GFS ENSEMBLE
ALL SHOW WHAT LOOKS LIKE A LAKE AGGREGATE TROUGH THAT HANGS OVER THE
WESTERN LAKES FOR A COUPLE OF DAYS, WITH 700 MB MOISTURE OF 70%.
THIS MAY BE IF THIS HOLDS OUT A SIGNIFICANT EARLY SEASON SNOW FALL.
JSL
&&
.MARINE.../ISSUED AT 348 PM/
MAIN CONCERN FOR THE MARINE PACKAGE WILL BE ON SUNDAY AFTERNOON WITH
THE COLD FRONT PASSING THROUGH THE REGION. THE COLD AIR ADVECTION
WILL ALLOW FOR HIGHER NW WINDS WHICH WILL BRING AT MOST SMALL CRAFT
ADVISORIES. THERE IS A SMALL CHANCE THAT THE WINDS WILL GUST TO GALE
FORCE, BUT AT THIS POINT IT LOOKS MORE LIKELY THAT IT WILL BE SCA
CONDITIONS.
JSL
&&
.AVIATION.../ISSUED AT 627 PM/...VALID FOR 00Z TAFS
AS A TROF OF LOW PRESSURE WORKS INTO THE REGION...MVFR CIGS WILL
GRADUALLY FROM NORTHERN LAKE MI AND EXTREME NORTHERN LOWER MI. ALL
SITES WILL SEE MVFR CIGS BY THE EARLY OVERNIGHT HOURS...AND THOSE
SHOULD PERSIST THRU SUNDAY. AS COOLER AIR SLOWLY FILTERS IN...
SHOWERS (MAINLY SNOW) WILL DEVELOP SUNDAY AFTERNOON. IFR VSBYS
POSSIBLE AT TIMES.
JZ
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.
&&
$$
