FXUS63 KAPX 220510
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1210 AM EST TUE DEC 22 2009
.SYNOPSIS.../ISSUED AT 347 PM/
AN ALBERTA CLIPPER CROSSING THE UPPER GREAT LAKES THIS EVENING
WILL BRING SNOW TO A GOOD PORTION OF THE STATE TONIGHT...BEFORE
EXITING TO THE EAST AND ALLOWING HIGH PRESSURE TO BUILD INTO THE
REGION FOR THE MIDWEEK PERIOD. ALL EYES WILL THEN TURN TO A STORM
SYSTEM FORECAST TO DEVELOP OVER THE SOUTHERN PLAINS WEDNESDAY...
AND LIFT NORTHEAST TOWARD MICHIGAN BY CHRISTMAS DAY. ALTHOUGH THIS
MAY CHANGE...INITIAL INDICATIONS ARE THAT A MIX OF RAIN AND SNOW
WILL FALL ACROSS NORTHERN MICHIGAN THURSDAY NIGHT INTO CHRISTMAS
DAY...THEN CHANGING BACK TO ALL SNOW SHOWERS BY CHRISTMAS NIGHT.
JPB
&&
.SHORT TERM.../ISSUED AT 1005 PM/...TONIGHT
THE WEATHER WEENIE IN ME IS SCREAMING OUT OUT "CHECK OUT THAT
MESOLOW ON NORTHERN LAKE MICHIGAN!". TEXTBOOK MESO-VORT DEVELOPMENT
TOOK SHAPE LATE THIS AFTN/EVENING WITHIN SLACK BOUNDARY LAYER FLOW
REGIME...INCREASINGLY DOMINATED BY LATE AFTN LAND BREEZE DEVELOPMENT
OUT INTO NORTHERN LAKE MICHIGAN...AND SUPPLEMENTED BY PRE-EXISTING
TROUGH AXIS LAID OUT ACRS THAT REGION AS WELL. CERTAINLY ONE OF THE
MOST IMPRESSIVE-LOOKING LAKE-INDUCED VORTICES THIS FCSTR HAS SEEN.
THAT SAID...MAIN CONCERN THRU THE OVERNIGHT HOURS IS CENTERED ON
LINGERING SNOW TIMING/PLACEMENT...AS WELL AS DEGREE OF CLEARING TO
TAKE SHAPE (OR NOT) LATER TONIGHT. AS EXPECTED PER RADAR TRENDS AND
NAM/RUC13 SHORT TERM GUIDANCE...SYNOPTIC SNOW TAKING A BIT OF A HIT
THE PAST FEW HOURS AS MID LEVEL MOISTURE/850-700MB -DIVQ DEPARTING
EAST (NOTE RAPIDLY DIMINISHING RADAR TRENDS ACRS THE NORTH)...WITH
FOCUS PURELY ON THE MESOSCALE THE REMAINDER OF THE NIGHT.
STRENGTHENING LOW LEVEL RIDGE AXIS DRAPED ACRS WESTERN ONTARIO
PROGGED TO SLOWLY DESCEND TOWARD NORTHERN MICHIGAN OVERNIGHT...
SHIFTING LOW LEVEL FLOW TO THE NORTH/NORTHEAST BY 12Z. THIS ALREADY
ONGOING ACRS THE NORTH PER RADAR RETURNS OUT OVR LAKE SUPERIOR FROM
KMQT...AND ANTICIPATE LINGERING LAKE-HELPED CONVECTION ALONG
MESOLOW/LOW LEVEL CONVERGENCE AXIS WILL INCREASINGLY BECOME
DISRUPTED OVR THE NEXT FEW HOURS. WITH THIS IN MIND...HAVE
COMPLETELY REWORKED GOING FCST TO OBVIOUSLY SUPPORT CATEGORICAL POPS
ACRS NORTHWEST LOWER THE NEXT FEW HOURS...TAPERING TO NOTHING NORTH
PER INTRUSION OF DRIER LOW LEVEL AIRMASS ALREADY UNDERWAY (DEWPOINT
7F AT KANJ AT 02Z). PER LOCAL OBS/SPOTTER REPORTS...SNOW HAS BEEN
RATHER FLUFFY IN NATURE (GREAT INVERSION HEIGHTS/CLOUD TOP TEMPS
RUNNING AROUND -17C PER 00Z APX RAOB)...SO WILL CARRY A GENERAL
1-2 INCHES WHERE BEEFIER SNOW SHOWERS ONGOING...LITTLE TO NOTHING
ELSEWHERE.
OTHER THING TO WATCH LATER TONIGHT (SAY AFTER 08Z) WILL BE DEGREE OF
CLEARING TRYING TO WORK IN FROM THE NORTHEAST ON DEVELOPING DRAINAGE
FLOW OUT OF ONTARIO. PLENTY OF CLEAR SKIES NOT THAT FAR AWAY...
THOUGH RATHER HEALTHY LOWERING INVERSION COUPLED WITH PLENTY OF
OVERLAKE INSTABILITY (H85 TEMPS RUNNING -12C OR SO) SUPPORT A
STUBBORN LOSS OF STRATOCU. THAT SAID...EXPECTED LOW LEVEL FLOW HAS A
HISTORY OF CLEARING OUT MUCH OF EASTERN UPR AND INTERIOR OF NORTHERN
LOWER (WITH CLOUDS STRADDLING THE COASTS OF NORTHERN LOWER)...AND
WILL TREND THINGS THIS WAY LATER TONIGHT. TEMPS ALSO TRICKY PENDING
CLEARING...BUT OVERALL GOING NUMBERS LOOK OK AT THIS JUNCTURE
(THOUGH COULD BE MUCH COLDER...AGAIN HEAVILY DEPENDENT ON EVOLUTION
OF CLEARING).
LAWRENCE
&&
.LONG TERM.../ISSUED AT 347 PM/...TUESDAY AND BEYOND
LARGE SCALE PATTERN CONTINUES TO FEATURE STRONG -NAO BLOCKING ACROSS
GREENLAND...WITH MEAN TROUGHING ACROSS CENTRAL CANADA/EASTERN U.S.
MEAN RIDGING LIES ALONG THE WEST COAST OF NORTH AMERICA...ALTHOUGH A
SHORT WAVE TROUGH MOVING THROUGH THE MEAN RIDGE POSITION THIS
AFTERNOON LOOKS TO HAVE INTERESTING IMPLICATIONS ON GREAT LAKES
WEATHER AS CHRISTMAS APPROACHES. THIS ENERGY WILL DROP DOWN THE
FRONT SIDE OF THE MEAN RIDGE WITHIN THE SOUTHERN BRANCH OF A SPLIT
FLOW PATTERN AND ACROSS THE DESERT SOUTHWEST. WHERE THIS FEATURE
BOTTOMS OUT AND BEGINS ITS TURN TO THE NORTH WILL BE THE VEXING
PROBLEM OVER THE COMING FORECAST CYCLES...BUT NOW THAT THE SYSTEM
HAS REACHED THE UPPER AIR NETWORK WE'LL SEE IF WE CAN START TO GET
SOME CONSENSUS ON SYSTEM TRACK. IN THE NEAR TERM... HIGH PRESSURE
RIDGING IN FROM THE NORTHWEST WILL HANG TOUGH INTO THE MIDWEEK
PERIOD AS STORM SYSTEM GETS ORGANIZED OVER THE SOUTHERN PLAINS. SO
OTHER THAN SOME NUISANCE MESOSCALE LAKE ISSUES...FOR THE MOST PART
THE NEXT TWO DAYS LOOK TO BE THE PROVERBIAL CALM BEFORE THE STORM.
TUESDAY...SURFACE RIDGE AXIS FORECAST TO CUT ACROSS MICHIGAN FROM
NORTHWEST ONTARIO...WITH A SHARP LOW LEVEL DEFORMATION ZONE SETTING
UP AND TRYING TO KEEP A BAND OF SNOW ACROSS SOUTHERN LOWER MICHIGAN
AT BAY. PROVIDED THAT IS SUCCESSFUL...ONLY REAL ISSUE FOR TUESDAY
IS EAST/NORTHEAST FLOW OFF LAKE HURON AND SOME FLURRIES OR LIGHT
SNOW SHOWERS...THOUGH EVEN THESE LOOK LIKE THEY SHOULD TREND
DOWNWARD WITH TIME. CLEAR TO PARTLY CLOUDY SKIES WILL BE FORECAST
FOR TUESDAY NIGHT. HIGHS TUESDAY AFTERNOON MOSTLY 20S WITH A FEW
POCKETS OF 30/LOWER 30S ACROSS NORTHERN LOWER...CHILLY TUESDAY NIGHT
ESPECIALLY ACROSS AREAS THAT CLEAR OUT WITH SINGLE DIGITS ABOVE AND
BELOW ZERO LOWS EXPECTED.
WEDNESDAY...HIGH PRESSURE CONTINUES TO HANG ON ACROSS THE UPPER
LAKES...ALONG WITH SHORT WAVE RIDGING IN ADVANCE OF UPPER TROUGH
SLIDING INTO TEXAS. SO LOOKS LIKE A NICE DAY ON TAP MINUS ANY
NUISANCE SC IN EASTERLY FLOW OFF LAKE HURON...WHICH LOOKS TO BE MORE
OF AN ISSUE WEDNESDAY NIGHT AS GUIDANCE SUGGESTING AN INCREASE IN
LOW LEVEL HUMIDITY ADVECTING OUT OF ONTARIO AND ONTO THE LAKE. WILL
INCREASE CLOUDS ACROSS NORTHEAST LOWER FOR WEDNESDAY NIGHT AND ADD
IN A FEW FLURRIES.
EXTENDED FORECAST (THURSDAY THROUGH SUNDAY)...CURRENT INDICATIONS
(AT LEAST AS OF THIS MORNING WHEN THE BULK OF THIS PORTION OF THE
FORECAST WAS PREPARED) REGARDING DEVELOPING STORM SYSTEM IS THAT
SURFACE LOW WILL ORGANIZE/SPIN UP ACROSS TEXAS WEDNESDAY...THEN
SWING NORTHEAST ACROSS UP MISSISSIPPI VALLEY AND INTO THE GREAT
LAKES LATER CHRISTMAS DAY. STILL SOME SPREAD IN THE LONGER RANGE
GUIDANCE REGARDING SYSTEM TRACK...ALONG WITH SOME SUBTLE DIFFERENCES
IN HOW STREAMS INTERACT IN EACH MODEL. 21/00Z OPERATIONAL GFS MADE
UP THE WESTERN EDGE OF THE GUIDANCE ENVELOPE...WHILE GGEM STARTS TO
EMPHASIZE MORE IN THE WAY OF A SECONDARY AREA OF LOW PRESSURE
DEVELOPING EAST OF THE APPALACHIANS. WILL TREND THE FORECAST MORE
TOWARD THE MIDDLE OF THE ROAD ECMWF...INITIAL TRACK FROM CENTRAL
MISSOURI/SOUTHEAST IOWA UP TOWARD CENTRAL UPPER/NORTHERN LAKE
MICHIGAN BY CHRISTMAS EVENING. QUICK LOOK AT THE 21/12Z GFS
TRENDING TOWARD A FARTHER EAST/WEAKER SOLUTION...WHICH HELPS
SOLIDIFY ABOVE THINKING. TRACK OF LOW LEVEL SYSTEM WILL BE CRITICAL
WITH RESPECT TO PRECIPITATION TYPE...BUT WILL ASSUME THAT ENOUGH LOW
LEVEL WARM AIR GETS IN TO BRING A THREAT FOR MIXED PRECIP. SOME OF
THIS MAY BE OFFSET BY EVAPORATIONAL COOLING CONCERNS...AND SURFACE
TEMPERATURES WILL ALSO BE MARGINAL ESPECIALLY ACROSS EASTERN UPPER/
HIGHER TERRAIN OF NORTHERN LOWER. WILL BACK OFF SYNOPTIC PRECIP
COVERAGE A LITTLE ON THURSDAY...FOCUSING MORE OF THURSDAY NIGHT
GOING INTO FRIDAY. THE EXCEPTION WILL BE ACROSS NORTHEAST LOWER AND
EXTREME SOUTHEAST UPPER WITH THE THREAT FOR SOME FLURRIES OR LIGHT
SNOW SHOWERS OFF LAKE HURON.
BASED ON PARTIAL THICKNESSES...FORECAST PRECIP TYPES ACROSS NORTHERN
LOWER FOR THURSDAY NIGHT/CHRISTMAS DAY WILL RUN THE GAMUT...AND PLAN
TO THROW EVERYTHING AND THE KITCHEN SINK AT IT. FORECAST WORDING
ESSENTIALLY LIKELY RAIN OR SNOW/CHANCE FREEZING RAIN AND SLEET
ACROSS NORTHERN LOWER. PREFER NOT TO GO WITH LIKELY WORDING FOUR
DAYS OUT WHEN DEALING WITH FREEZING RAIN/SLEET IN SITUATIONS WHERE
SUBTLETIES IN THERMAL PROFILES WILL MAKE ALL THE DIFFERENCE (I.E.,
FORECAST SCENARIOS THAT ARE NOT AN OBVIOUS ICE STORM SETUP). BY
FRIDAY...WE COULD BE DEALING WITH DRY SLOT ISSUES AND A PERIOD WHERE
MEASURABLE PRECIP SHUTS DOWN TO JUST DRIZZLE (WHICH OF COURSE ALSO
CUTS DOWN ON QPF POTENTIAL)...AND ENSEMBLE MEANS/PROBABILITIES
SUGGEST THAT MOST AREAS WILL BE ABOVE FREEZING FRIDAY AFTERNOON.
SO WILL LEAVE A LOT OF THESE QUESTIONS OPEN ENDED FOR THE TIME
BEING...AND KEEP OPTIONS ON THE TABLE FOR LATER REFINEMENT. WITH
COLDER AIR POTENTIALLY SWEEPING BACK IN FRIDAY NIGHT...WILL BRING
LINGERING PRECIPITATION BACK OVER TO ALL SNOW AND CONTINUE SOME
MENTION OF LIGHT SNOW SHOWERS FOR SATURDAY. HEADING INTO THE START
OF NEXT WEEK...21/00Z GFS TRIES TO BREAK OFF A PIECE OF POLAR VORTEX
AND SHOVE A SUBSTANTIAL PUSH OF COLD AIR INTO THE REGION BY THE
MIDDLE OF NEXT WEEK. NO OTHER PIECE OF GUIDANCE REALLY WANTS TO
PLAY ALONG WITH THIS IDEA AT THIS POINT...BUT THE FORECAST WILL BE
TRENDED TOWARD COLDER WEATHER AND SNOW SHOWERS TO START THE LAST
WEEK OF 2009.
JPB
&&
.MARINE.../ISSUED AT 347 PM/
SURFACE RIDGE AXIS CUTTING ACROSS THE STATE TUESDAY WILL ENSURE JUST
A LIGHT EASTERLY/NORTHEASTERLY FLOW PREVAILS ACROSS THE UPPER LAKES
THROUGH TUESDAY NIGHT. THIS SAME SET UP CONTINUES FOR WEDNESDAY...
WITH WINDS NOT REALLY PICKING UP UNTIL WEDNESDAY NIGHT GOING INTO
CHRISTMAS EVE.
JPB
&&
.AVIATION.../ISSUED AT 1210 AM/...VALID FOR 06Z TAFS
HIGH PRESSURE BUILDING INTO THE REGION WILL PROVIDE IMPROVING
CONDITIONS FOR THE TERMINAL SITES OVER THE NEXT 12 HOURS. LINGERING
LOW END VFR TO LOCALLY MVFR CEILINGS WILL GIVE WAY TO SOLIDLY VFR
CONDITIONS BY MORNING AS MUCH DRIER AIR BACKS INTO THE AREA ON
DEVELOPING NORTH/NORTHEAST FLOW. WINDS WILL REMAIN MAINLY AT OR
BELOW 8 KNOTS THROUGH THE END OF THE TAF PERIOD.
LAWRENCE
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
LS...NONE.
&&
$$
