Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 022152
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
452 PM EST MON MAR 2 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 451 PM EST MON MAR 2 2015

WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW OVER N AMERICA.
FEATURES OF INTEREST FOR THE SHORT TERM FCST ARE A NRN STREAM
SHORTWAVE DROPPING THRU ALBERTA/SASKATCHEWAN AND THE SRN STREAM TROF
OVER CA/NV...IN PARTICULAR THE SHORTWAVE OVER SRN CA/SRN NV WHERE
CONVECTION IS NOTED. THESE TWO WAVES WILL BRING A WIDESPREAD
SYNOPTIC SNOW TO THE AREA TUE. ABUNDANT SUNSHINE HAS BEEN THE RULE
ACROSS THE AREA THIS AFTN UNDER DRY AIR MASS ASSOCIATED WITH SFC
HIGH OVER THE MID MISSISSIPPI VALLEY AND WRN GREAT LAKES REGION.
SUNSHINE WORKING ON THE FORESTED TERRAIN OF UPPER MI HAS RESULTED IN
TEMPS RISING WELL INTO THE 20S OVER MOST OF THE AREA. COOLEST
CONDITIONS (AROUND 20F) ARE OVER THE FAR E...CLOSER TO THE DEPARTING
850MB THERMAL TROF...AND AT MANY LOCATIONS ALONG LAKE SUPERIOR WHERE
LAKE/ICE BREEZE HAS DEVELOPED.

LATEST MODEL RUNS CONTINUE TO SHOW THE 2 AFOREMENTIONED SHORTWAVES
REMAINING UNPHASED AS THEY AFFECT THE AREA TUE. THE SRN WAVE WILL
ACCELERATE OUT OF THE SW INTO THE DOWNSTREAM CONFLUENT FLOW...AND IT
WILL BE THE DRIVER OF THE SNOW THAT SPREADS INTO THE UPPER LAKES. IT
APPEARS 1 MAIN STREAK OF PCPN OR AT LEAST MORE ORGANIZED/HEAVIER
PCPN WILL DEVELOP TONIGHT TO THE SW. THIS PCPN WILL STREAK NE ACROSS
SD INTO CNTRL MN IN ASSOCIATION WITH A COUPLED UPPER JET
STRUCTURE/ENHANCED UPPER DIVERGENCE FROM LEFT EXIT OF 150KT JET
TRANSLATING OUT OF THE SRN ROCKIES AND THE RIGHT ENTRANCE OF 125KT
JET STREAK OVER ND INTO NRN ONTARIO. MORE PCPN WILL BEGIN TO GET
ORGANIZED FARTHER E LATE IN THE NIGHT AS MID LEVEL FRONTOGENESIS AND
BROADER WAA/ISENTROPIC ASCENT BEGIN TO SATURATE DRIER AIR AT THE
LOWER LEVELS. MODELS ARE NEARLY IDENTICAL IN TIMING THE PCPN INTO
WRN AND SRN UPPER MI IN THE 08-12Z TIME FRAME...AND STARTING ACROSS
THE N AND E AROUND OR SHORTLY AFTER 12Z. SO...LITTLE ADJUSTMENT WILL
BE REQUIRED WITH ONSET TIMING. ACCUMULATIONS AROUND ONE HALF INCH
MAY OCCUR ALONG THE WI BORDER BY 12Z.

ON TUE...THE BEST UPPER DIVERGENCE ASSOCIATED WITH A WEAKENING
COUPLED UPPER JET STRUCTURE QUICKLY SHIFTS NE ACROSS NE MN/WRN LAKE
SUPERIOR INTO NRN ONTARIO. MEANWHILE...WAA/ISENTROPIC
ASCENT/FRONTOGENETICALLY FORCED PCPN WILL QUICKLY EXPAND/INCREASE IN
INTENSITY AS AIR MASS SATURATES AND DEEP LAYER FORCING PROVIDED BY
SHORTWAVE ARRIVES. ON THE 285K SFC (ROUGHLY 700-750MB)...MIXING
RATIOS AROUND 2.5G/KG ARE AVBL...SUGGESTING SOMETHING AROUND 3
INCHES OF SNOW FOR 6-9HRS OF ASCENT. HOWEVER...GIVEN THE OTHER
FACTORS AT PLAY...A WIDESPREAD FAIRLY UNIFORM 3-5 INCH SNOW IS
EXPECTED ACROSS THE ENTIRE FCST AREA TUE...WHICH FALLS NICELY INLINE
WITH THE CONSENSUS QPF NUMBERS FROM THE MODELS CONVERTED TO SNOW
USING A 15 TO 1 OR SO SNOW RATIO. WITH SOUTHERLY LOW-LEVEL FLOW UP
LAKE MICHIGAN FOR SEVERAL HRS AND AIR MASS JUST COLD ENOUGH TO
SUPPORT ENHANCEMENT...THERE SHOULD BE SOME BOOST TO SNOW TOTALS
DOWNWIND OF LAKE MICHIGAN THOUGH ICE COVER WILL LIMIT THE
ENHANCEMENT OVER WHAT IT COULD BE. THAT AREA IS MORE LIKELY TO SEE
ACCUMULATIONS CLOSER TO 5 INCHES THAN 3...AND NOT OUT OF THE
QUESTION THAT SOME 6 INCH AMOUNTS COULD OCCUR. FORCING QUICKLY
SHIFTS E TUE AFTN...RESULTING IN SNOW RAPIDLY DIMINISHING W TO E
DURING THE MID AND LATE AFTN HRS. IN FACT...IT MAY END COMPLETELY
OVER PORTIONS OF THE WEST LATE IN THE AFTN. WITH SNOW RATIO LIKELY
UNDER 20 TO 1...THIS SYSTEM WILL ACHIEVE THE WETTER SNOW TYPE ADVY
CRITERIA OF AN AVG SNOWFALL OF AT LEAST 3IN/12HR OVER THE ENTIRE
FCST AREA. SO...ADVY WILL BE HOISTED ACROSS THE BOARD.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 402 PM EST MON MAR 2 2015

AT THE START OF THE LONG TERM PERIOD...UPPER MICHIGAN WILL SEE THE
SYNOPTIC PRECIPITATION QUICKLY COMING TO AN END OVER THE EASTERN
THIRD OF THE CWA. THIS IS DUE TO THE DRY MID LEVEL AIR MOVING OVER
THE AREA BEHIND THE COLD FRONT AND AHEAD OF THE MAIN SHORTWAVE
TROUGH THAT WILL MOVE THROUGH ON TUESDAY. THEN...AS COLDER AIR
SURGES INTO THE AREA...GENERALLY AFTER MIDNIGHT TUESDAY
NIGHT...SHOULD SEE THE POTENTIAL FOR LAKE EFFECT INCREASE FROM WEST
TO EAST. 850MB TEMPS WILL FALL FROM AROUND -11C AT 00Z WEDNESDAY
TO -26C AT 18Z WEDNESDAY...PROVIDING PLENTY OF OVER LAKE
INSTABILITY WHERE THERE IS OPEN WATER. THAT IS THE BIG QUESTION FOR
THE LAKE EFFECT FORECAST. VISIBLE SATELLITE SHOWS SEVERAL LARGER
AREAS OF OPEN WATER AND SLUSH OVER WESTERN...NORTH CENTRAL...AND
SOUTH CENTRAL LAKE SUPERIOR. THOSE AREAS HAVE NOT BEEN REPRESENTED
IN THE MODELS AT THIS POINT...SO I DON/T FEEL THE MODELS ARE
INDICATING THE LAKE EFFECT POTENTIAL IN THE QPF FIELDS.
THUS...HAVE PERFORMED SIGNIFICANT HAND EDITS TO THE GRIDS...BOTH IN
RAISING POPS AND HIGHLIGHTING AREAS DOWNWIND OF THE CURRENT OPEN
WATER AREAS. WITH THE STRONG WEST TO WEST-NORTHWEST WINDS TUESDAY
NIGHT INTO WEDNESDAY...THOSE AREAS OF OPEN WATER WILL LIKELY EXPAND
AND MOVE...SO THAT DOES INCREASE THE UNCERTAINTY OF THE LAKE EFFECT
SOME...BUT EVEN WITH THE COLD AIR...THINK THE WINDS WILL LIMIT THE
ICE COVER EXPANDING AT LEAST THROUGH WEDNESDAY. WHILE THE LAKE
EFFECT WON/T BE TOO STRONG INITIALLY TUESDAY NIGHT...THE CLOUD WILL
BE WITHIN THE DGZ AND LEAD TO A FLUFFY INCH OR SO OF ACCUMULATION.
THEN ON WEDNESDAY...INVERSION HEIGHTS WILL RISE TO 7-9KFT AS A
SHORTWAVE MOVES THROUGH AND SUPPORT MODERATE TO POTENTIALLY EVEN
LOCALLY HEAVY SNOWFALL. WITH THE COLD AIR BEING IN PLACE ON
WEDNESDAY...SNOWFLAKE SIZE SHOULD BE SMALL AND KEEP ACCUMULATIONS
IN THE COUPLE INCH RANGE FOR THE WEST-NORTHWEST WIND AREAS DOWNWIND
OF THE OPEN WATER. IN ADDITION...RECENT SNOWFALL AND THE STRONG
WINDS WILL LIKELY LEAD TO PATCHY/AREAS OF BLOWING SNOW...ESPECIALLY
OVER THE KEWEENAW AND NEAR LAKE SUPERIOR EAST OF MARQUETTE. WHEN
COMBINED WITH THE FINE FLAKED LAKE EFFECT SNOW...THIS WILL LEAD TO
VISIBILITIES BEING REDUCED BELOW 1 MILE AND IN THE STRONGER BANDS
LIKELY BELOW 1/2MI. FORTUNATELY...WITH WINDS MORE OUT OF THE WEST TO
WEST-NORTHWEST...THE IMPACT FOR AREAS EAST OF MARQUETTE WILL BE
FOCUSED MORE IN THE AREAS TO THE EAST OF MUNISING AND GENERALLY LESS
POPULATED AREAS.

HIGH PRESSURE RIDGE WILL BEGIN TO MOVE INTO THE AREA WEDNESDAY
NIGHT...DECREASING WINDS AND INCREASING SUBSIDENCE (LOWERING
INVERSION HEIGHTS). A WEAK SURFACE TROUGH MOVING OVER EASTERN LAKE
SUPERIOR AROUND MIDNIGHT WILL SHIFT WINDS MORE TO THE NORTHWEST FOR
A BRIEF PERIOD OF TIME BEFORE BACKING BACK TO THE WEST BY THURSDAY
AFTERNOON. WILL SHOW A GRADUALLY DECREASING TREND TO THE POPS FOR
THAT TIME PERIOD WHILE FOLLOWING THE WIND DIRECTIONS.

SHOULD SEE TEMPERATURES MODERATING BOTH ALOFT AND AT THE SURFACE
FRIDAY THROUGH THE WEEKEND AS 500MB FLOW BEGINS TO TURN A LITTLE
MORE WEST-NORTHWESTERLY. THIS SHOULD LEAD TO TEMPERATURES WARMING
TOWARDS MORE NORMAL VALUES FOR THIS TIME OF YEAR (INTO THE LOWER
30S). BUT THE CONFIDENCE ON PRECIPITATION OCCURRENCE IS LOW DUE TO
DIFFERENCES IN THE WAY THE MODELS HANDLE A COUPLE WAVES COMING ON
SHORE IN NORTHERN BRITISH COLUMBIA. THE 12Z GFS/GEM SLIDE THE WAVES
SOUTHEAST THROUGH THE AREA LATE FRIDAY NIGHT INTO SATURDAY...WITH
ANOTHER ONE ARRIVING ON SUNDAY. MEANWHILE...THE 12Z ECMWF SHOWS THE
WAVES BECOMING SEPARATED AND SPLITTING THE CWA THROUGH THE WEEKEND.
EITHER WAY WITH THE LIMITED DEEP MOISTURE...WOULDN/T EXPECT MUCH
MORE THAN LIGHT PRECIP ACCUMULATION THROUGH THE WEEKEND AND WILL
ONLY MENTION SLIGHT CHANCES.

A STRONGER SHORTWAVE LOOKS TO MOVE THROUGH THE AREA SUNDAY NIGHT
INTO MONDAY...LIKELY PULLING IN THE LAST SURGE OF COLD AIR FOR A
WHILE THROUGH THE AREA. EXPECT THERE TO BE SOME PRECIP ASSOCIATED
WITH THE SHORTWAVE...BUT THEN WITH WINDS TURNING NORTHERLY BETWEEN
THE DEPARTING SURFACE TROUGH AND A HIGH IN THE DAKOTAS...SHOULD SEE
A PERIOD OF LAKE EFFECT IN THE NORMAL SNOW BELTS. WITH THE FAVORABLE
850MB TEMPS (AROUND -14 TO -18C MONDAY)...WILL TREND POPS UP TO
MID/HIGH END CHANCES FOR NOW UNTIL WE ARE ABLE TO GET A BETTER
HANDLE ON THE ICE SITUATION ON LAKE SUPERIOR.

BEHIND THIS WAVE...GFS/ECMWF DETERMINISTIC AND ENSEMBLE MEMBERS ARE
SHOWING THE RIDGE THAT HAS BEEN PERSISTENT OVER THE WESTERN CONUS
AND ALASKA FOR THE LAST MONTH TO SHIFT EAST INTO THE CENTRAL CONUS
AROUND THE MIDDLE OF NEXT WEEK. THIS WILL LEAD TO TEMPERATURES
WARMING TO ABOVE NORMAL VALUES AND START MELTING SOME OF THE
SNOWPACK.
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1240 PM EST MON MAR 2 2015

VFR CONDITIONS WILL PREVAIL AT KIWD/KCMX/KSAW THIS AFTN/EVENING
UNDER DRY AIR MASS ASSOCIATED WITH HIGH PRES MOVING FROM THE MID
MISSISSIPPI VALLEY TO THE MID ATLANTIC STATES. LATE TONIGHT...SW
FLOW BTWN THE HIGH AND AN APPROACHING LOW PRES TROF WILL BRING A
RAPID INCREASE IN MOISTURE WHICH WILL LEAD TO SNOW DEVELOPMENT. AS
THE SNOW SPREADS NE...MVFR CONDITIONS SHOULD DEVELOP AT KIWD AROUND
09Z AND AT KCMX/KSAW AROUND 12Z. BY MID TO LATE MORNING...ALL
TERMINALS SHOULD SEE IFR CONDITIONS.
&&

.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 451 PM EST MON MAR 2 2015

GENERALLY LIGHT WINDS CURRENTLY ACROSS LAKE SUPERIOR WILL BECOME S
AND RAMP UP TONIGHT AND TUE TO 15-25KT IN ADVANCE OF AN APPROACHING
LO PRES TROF. ONCE THE TROF PASSES TO THE E TUE NIGHT...TIGHTENING
PRES GRADIENT AND STRONG COLD AIR ADVECTION AHEAD OF ARCTIC HIGH
PRES MOVING INTO THE NORTHERN PLAINS WILL LIKELY BRING A PERIOD OF
NW GALES INTO WED...MAINLY ACROSS CNTRL AND ERN LAKE SUPERIOR. AFTER
WED...NO GALE FORCE WINDS ARE EXPECTED THRU THE REMAINDER OF THE
WEEK. LATEST OFFICIAL ICE CONCENTRATION ON LAKE SUPERIOR IS AROUND
94 PCT. EVEN WITH STRONG WINDS AT TIMES THIS WEEK...THE HIGHER ICE
COVERAGE SHOULD PERSIST AS TEMPERATURES STAY BELOW FREEZING.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  WINTER WEATHER ADVISORY FROM 7 AM EST /6 AM CST/ TO 7 PM EST /6
     PM CST/ TUESDAY FOR MIZ001>007-009>014-084-085.

LAKE SUPERIOR...
  GALE WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY EVENING FOR
     LSZ264>267.

LAKE MICHIGAN...
NONE.
&&

$$

SHORT TERM...ROLFSON
LONG TERM...SRF
AVIATION...ROLFSON
MARINE...ROLFSON


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