FXUS63 KAPX 150453
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1150 PM EST MON DEC 14 2009
.SYNOPSIS.../ISSUED AT 408 PM/
LOW PRESSURE MOVING AWAY FROM THE UPPER GREAT LAKES THIS EVENING
WILL PULL COLDER AIR BACK INTO THE REGION FOR THE MIDDLE PART OF
THIS WEEK. THIS WILL SET THE STAGE FOR LAKE EFFECT AND LAKE
ENHANCED SNOW SHOWERS FOR TUESDAY AND INTO THE DAY WEDNESDAY.
ACCUMULATING SNOWS ARE EXPECTED IN THE TYPICAL NORTHWEST FLOW
SNOWBELTS DOWNWIND OF LAKES SUPERIOR AND MICHIGAN TUESDAY AND
TUESDAY NIGHT.
&&
.SHORT TERM.../ISSUED AT 1018 PM/...OVERNIGHT
DEPARTING SURFACE LOW HAS REACHED LAKE ONTARIO LATE THIS EVENING...
WHILE A CLOSED 500 MB LOW IS SWINGING SE OUT OF S CENTRAL CANADA
TOWARD THE ARROWHEAD OF MINNESOTA. IN BETWEEN...NRN MICHIGAN
CONTINUES TO SEE SOME LIGHT SYNOPTICALLY DRIVEN SNOW AS A SECONDARY
VORT MAX SLIDES THRU THE REGION. RADAR REFLECTIVITIES AND SNOWFALL
ESTIMATES HAVE BEEN GENERALLY OVERDONE THIS EVENING AS SURFACE OBS
HAVE REPORTED VSBYS WITHIN THE LIGHT SNOW NO LESS THAN 3 SM.
UPSTREAM RADARS SHOW SOME LIGHT SYNOPTIC SNOW STILL TO COME OVER
THE NEXT FEW HOURS BEFORE COLDER AIR SWEEPS INTO THE REGION BEHIND
THIS SHORT WAVE AND ACTIVATES THE LAKES. HAVE MODIFIED FORECAST TO
INCREASE POPS FOR THE NEXT SEVERAL HOURS AS THIS SHORT WAVE MOVES
THRU. HAVE ALSO INCREASED SNOW AMOUNTS JUST A BIT OVERNIGHT TO
ACCOUNT FOR ADDITIONAL SYNOPTIC SNOWS OVER THE NEXT FEW HOURS. STILL
EXPECT NORTHERLY FLOW LAKE EFFECT WILL BEGIN TO KICK IN VERY LATE
TONIGHT. LAST FEW FRAMES FROM KMQT RADAR IS ALREADY SHOWING SOME
SIGNS OF INITIATION OF LAKE CONTRIBUTION TO SNOWFALL.
&&
.LONG TERM.../ISSUED AT 408 PM/...TUESDAY AND BEYOND
AFTER A FAIRLY ACTIVE WEATHER PATTERN OVER THE LAST SEVERAL
DAYS...IT LOOKS LIKE WE WILL FINALLY CATCH A BREAK BUT NOT BEFORE
ONE MORE BOUT WITH LAKE EFFECT LATER TONIGHT INTO TUESDAY NIGHT OR
WEDNESDAY. THE MAIN LONG TERM FORECAST CONCERNS REVOLVE AROUND
SNOWFALL ACCUMULATIONS AND POSSIBLE HEADLINES TUESDAY THEN POPS
AND EXTENT OF LAKE EFFECT THEREAFTER.
TUESDAY...MEAN LOW LEVEL FLOW LOCKS INTO THE WEST NORTHWEST. 850 MB
TEMPERATURES STEADILY FALL INTO THE NEGATIVE MIDDLE TO UPPER
TEENS THROUGH THE DAY INCREASING OVER LAKE INSTABILITY. LIFT FROM
A SHORT WAVE CURRENTLY EVIDENT ON WATER VAPOR LOOP ACROSS
NORTHWEST NORTH DAKOTA WILL PUSH INVERSION HEIGHTS INTO THE 7000
FOOT RANGE TO START THE DAY BEFORE FALLING OFF TO ABOUT 4000 FEET
BY 16/00Z AS WE TRANSITION INTO A MORE PURE LES SITUATION.
THEREFORE...EXPECT A FEW INCHES OF SNOW IN THE SNOWBELTS OF
NORTHWEST LOWER AND EASTERN UPPER IN THE MORNING WITH ACTIVITY
LIKELY SHOWING A DOWNWARD TREND IN THE AFTERNOON (MOISTURE FIELDS
SHOW MEAN 850-700 MB RH FALLING FROM ABOUT 75 PERCENT AT 12Z TO
JUST 45 PERCENT AT 00Z). EXPECT ACCUMULATIONS OF 2 TO 4 INCHES
WITH POSSIBLE LOCALLY HIGHER AMOUNTS POSSIBLE WHICH IS BORDERLINE
FOR AN ADVISORY (WILL LET MIDSHIFT MAKE THE CALL ON THIS ONE).
HIGHS MAINLY IN THE 20S.
TUESDAY NIGHT INTO WEDNESDAY...INCREASING HOSTILE ENVIRONMENT FOR
LAKE EFFECT AS RIDGING AT THE SURFACE AND ALOFT BUILD IN ALONG WITH
LOTS OF DRY AIR (MEAN 850-700 MB RH FALLING FROM AROUND 50 PERCENT
IN THE EVENING TO A PALTRY 25 PERCENT OR SO OVERNIGHT INTO WEDNESDAY
MORNING BEFORE A BIT OF A REBOUND WEDNESDAY AFTERNOON).
THEREFORE...IF WE ARE ABLE TO SUSTAIN ACTIVITY AT ALL...IT WILL HAVE
TO BE PURE LAKE EFFECT AS WE WILL BE VOID OF ANY SYNOPTIC MOISTURE.
INVERSION HEIGHTS ARE SHOWN TO BE SUPPRESSED TO ABOUT 3000 FEET OR
SO AS THE DRIER AIR AND SUBSIDENCE LIKELY TAKE ITS TOLL ON INTENSITY
SO WILL DECREASE POPS TO LIKELY ACROSS FAVORED WNW FLOW AREAS
OVERNIGHT. THEN CONTINUE WITH JUST CHANCE POPS ON WEDNESDAY. AN INCH
OR TWO OF ACCUMULATION SHOULD BE THE TOP END. LOWS RANGING FROM THE
MIDDLE SINGLE DIGITS TO THE MIDDLE TEENS. HIGHS ONLY IN THE UPPER
TEENS TO THE LOWER 20S.
WEDNESDAY NIGHT THROUGH FRIDAY...MORE GENERAL RIDGING AT THE SURFACE
AND ALOFT. SO DESPITE CONTINUED ADEQUATE OVER LAKE
INSTABILITY...ABUNDANCE OF DRY AIR SHOULD LIMIT ACTIVITY. HINTS OF A
WEAK SHORT WAVE OR TWO MOVING THROUGH THE FLOW BUT THEY DO NOT
LOOK TO DO A WHOLE LOT. LOWS RANGING FROM THE MIDDLE SINGLE DIGITS
TO MIDDLE TEENS. HIGHS IN THE LOWER TO MIDDLE 20S.
SATURDAY THROUGH MONDAY...EXTENDED MODELS ARE IN GENERAL AGREEMENT
WITH A WEST TO NORTHWEST FLOW ALOFT THROUGH THIS PERIOD ALONG WITH A
RETROGRADING TROUGH THAT MOVES SLOWLY SOUTHWEST ACROSS THE REGION.
THEREFORE...WILL KEEP THE FORECAST GENERAL WITH CHANCE POPS FOR SNOW
SHOWERS. TEMPERATURES REMAINING AT OR SLIGHTLY BELOW CLIMATOLOGY.
SULLIVAN
&&
.MARINE.../ISSUED AT 408 PM/
COLD AIR WILL SURGE INTO NORTHERN MICHIGAN TONIGHT AND
TUESDAY...SETTING THE STAGE FOR MORE UNSETTLED CONDITIONS ON THE
GREAT LAKES THROUGH MIDWEEK. WITH THIS SAID...ANOTHER PERIOD OF
SMALL CRAFT CONDITIONS WILL DEVELOP LATE THIS EVENING AND CONTINUE
THROUGH AT LEAST WEDNESDAY MORNING. WIND GUSTS UP TO 30 KNOTS ARE
POSSIBLE ALONG WITH CHOPPY WAVES.
KAS
&&
.AVIATION.../ISSUED AT 1150 PM/...VALID FOR 06Z TAFS
MVFR TO AT TIMES IFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 HOURS
AS AREAS OF LIGHT SNOW GRADUALLY TRANSITION TO LAKE EFFECT SNOW
SHOWERS OVERNIGHT. LAKE EFFECT SNOW SHOWERS WILL PERSIST THRU
TUESDAY...TARGETING NW FLOW AREAS FOR THE BEST CHANCE OF
ACCUMULATING SNOW. SNOW SHOWERS WILL DIMINISH TUESDAY EVENING AS MID
LEVEL DRY AIR FILTERS INTO THE REGION AND INVERSION HEIGHTS STEADILY
LOWER.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LMZ323-341-342-
344>346.
LH...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LHZ345>349.
LS...SMALL CRAFT ADVISORY UNTIL 7 AM EST WEDNESDAY FOR LSZ321-322.
&&
$$
