Issued by NWS Marquette, MI
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000
FXUS63 KMQT 150538
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
140 AM EDT FRI MAY 15 2009
UPDATED FOR 06Z AVIATION DISCUSSION
.SHORT TERM (TONIGHT AND FRIDAY)...
A ZONAL FLOW HAS SET UP ALOFT...WITH WEAK RIDING POISED TO MOVE OVER
THE CWA LATE FRIDAY MORNING...IN ADVANCE OF THE SFC LOW/UPPER TROUGH
DEEPENING OVER MANITOBA LATE IN THE DAY FRIDAY. WINDS WILL CONTINUE
TO WEAKEN AS THE SURFACE HIGH MOVES OVERHEAD EARLY THIS EVENING...OR
AT LEAST THE RIDGE FROM THE MAIN HIGH OVER THE OHIO VALLEY.
ANY LINGERING CLOUDS SHOULD QUICKLY DISSIPATE BY 02Z AS HIGH
PRESSURE NOSES INTO THE FORECAST AREA. PW VALUES WILL BOTTOM OUT
BETWEEN 00Z AND 06Z AROUND 0.3 INCHES...ROUGHLY 40 TO 50 PERCENT OF
NORMAL. A MID DECK SHOULD ALSO SLIDE IN FROM THE WSW AFTER 06Z.
WILL KEEP AN EYE UPSTREAM TO THE CURRENT MID TO HIGH CLOUDS OVER
SOUTHERN SASKATCHEWAN...AND THEIR QUICK EASTWARD PROGRESSION. THESE
ADDITIONAL CLOUDS...IF THEY DEVELOP...WILL KEEP TEMPERATURES FROM
BOTTOMING OUT TOO LOW...AND NEAR 40 DEGREES FAR WEST NEAR IWD AND
SOUTH NEAR MNM. HAVE OPTED TO TAKE PATCHY FROST OUT FOR
NOW...THOUGH IT MAY NEED TO BE ADDED IN ONCE AGAIN IN THE CLEAR SKY
LINGERS LONGER THAN ANTICIPATED.
EXPECT SSE WINDS TO BE ON THE INCREASE FROM MID MORNING FRIDAY ON AS
THE SURFACE LOW MOVES FROM THE EASTERN DAKOTAS TO WESTERN LAKE
SUPERIOR BY THE CLOSE OF BUSINESS FRIDAY. A SLIGHTLY MORE WRAPPED
UP SYSTEM FRIDAY AFTERNOON LOOKS TO KEEP CENTRAL AND EASTERN UPPER
MICHIGAN DRY THROUGH 00Z SATURDAY.
&&
.LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)...
LONG TERM PERIOD BEGINS WITH UPPER TROUGH DIGGING OVER THE NRN
PLAINS AND ELONGATED SFC LOW OVER NRN MN. THIS SFC LOW WILL TRACK NE
AND INTENSIFY AS IT REACHES JAMES BAY BY 00Z SUN. NAM/GFS/ECMWF/GEM
ARE FAIRLY CONSISTENT WITH THE POSITIONING OF THE LOW BY 00Z
SUN...BUT THE INTENSITY VARIES. THE STRONGEST RUNS ARE THE 00Z
ECMWF/GEM AND THE 12 Z NAM AROUND 993MB...WITH THE 12Z GFS RUN
AROUND 998MB WHICH IS A LITTLE STRONGER THAN PAST RUNS. SINCE THERE
IS PRETTY GOOD AGREEMENT...HAVE DECIDED TO GO WITH A BLEND OF THE
12Z NAM AND 00Z ECMWF FOR THE FRI NIGHT THROUGH 00Z SUN PERIOD.
UPPER WAVE ROTATES NE AROUND THE TROUGH AND CLOSER TO THE LOW ON FRI
NIGHT...BRINGING BEST QPF ACROSS THE NW PART OF THE LK SUPERIOR.
OCCLUDED FRONT LOOKS TO MOVE FROM W TO E ACROSS THE AREA ON FRI
NIGHT...AS BEST WARM/COLD FRONT FORCING AND PCPN MOVES ACROSS SE WI
AND CENTRAL LOWER MI. OVERALL...MODERATE ISENTROPIC
ASCENT...H850-500 Q-VECTOR CONV...AND A MOIST ATMO SHOULD PRODUCE
AROUND A QUARTER INCH OF PCPN ACROSS THE CWA AS THE FRONT MOVES
THROUGH. THEREFORE...LIKELY POPS SEEM REASONABLE AND WILL ONLY MAKE
MINOR TWEAKS TO THE TIMING. INSTABILITY IS STILL LACKING...WITH
LITTLE TO NO SFC/ELEV CAPE AND H850-500 LR/S AROUND 5.5C/KM...SO
WILL CONTINUE JUST THE SLIGHT CHANCE OF THUNDER. DRY SLOT BEHIND THE
FRONT MOVES ACROSS THE CWA FROM W TO E STARTING FRI EVENING...WHICH
SEEMS A LITTLE FASTER THAN YESTERDAYS RUNS...SO HAVE DIMINISHED POPS
OVER THE W AFTER MIDNIGHT AND TRIED TO ADD A LITTLE MORE TIMING TO
THE POPS. THIS SHOULD BRING SOME BREAKS IN THE CLOUDS FOR LATE FRI
NIGHT AND INTO SAT MORNING...BEFORE LLVL MOISTURE ROTATING AROUND
THE LOW SWEEPS ACROSS MOST OF THE CWA ON SAT AND THE UPPER TROUGH
ROTATES THROUGH. VERY STRONG SURGE OF COLD AIR IS STILL SHOWN ON THE
LATEST GFS/NAM RUNS...WITH H850 TEMPS DROPPING TO -7C BY 18Z SAT.
THIS SHOULD KEEP THE WRN HALF OF UPPER MI 10-15 DEGREES BELOW NORMAL
DURING THE AFTN...WITH TEMPS STRUGGLING TO REACH THE LOW 40S. THAT
COLD H850 AIR AND THE RELATIVELY WARM LK SUP TEMPS...AROUND 2C...MAY
PRODUCE A LITTLE LK ENHANCED PCPN ACROSS THE WRN CWA. THE STRONG
WINDS AND MAINLY LLVL MOISTURE WILL KEEP THE CLOUDS FAIRLY
SHALLOW...BUT THINK THERE WILL BE ENOUGH INSTABILITY OFF THE LK AND
STEEP LLVL LR/S TO PRODUCE SOME ISOLATED SHOWERS DURING THE LATE
MORNING AND AFTN. HAVE ADDED THE SLIGHT CHANCE OF PCPN IN AND
MENTIONED SN IN THE MORN...AS THE COOLING TEMPS BRING THE TOP OF THE
CLOUD DECK INTO THE -10-13C RANGE PER BUFKIT SOUNDINGS. THE
PREVIOUSLY MENTIONED STRONG WINDS SHOULD GUST TO 35 TO 40KTS ALONG
THE KEWEENAW PENINSULA...AS H925-850 WINDS ARE TO 40KTS WITH THE CAA
ALLOWING THOSE WINDS TO COME DOWN. OVERALL...THE FRI NIGHT AND SAT
PERIOD LOOKS TO BE VERY SIMILAR TO LAST NIGHT AND TODAY...BUT WITH
SLIGHTLY COLDER H850 TEMPS.
HIGH PRESSURE SLIDES OUT OF THE NRN PLAINS AND ACROSS THE AREA ON
SAT NIGHT AND SUN...AS AN UPPER RIDGE BUILDS OVER THE WRN 2/3RDS OF
THE CONUS. WITH THE RIDGE BUILDING N OF THE US/CANADA BORDER...A
WEAK LOW DEVELOPS ALONG HUDSON BAY WITH A COLD FRONT STRETCHING SW
TO A DEVELOPING LOW OVER THE NRN ROCKIES BY 12Z MON. SAT NIGHT AND
SUN SHOULD BE COOL BUT NICE WX...AS HIGH PRESSURE DRIFTS ACROSS THE
REGION. HAVE LOWERED SAT NIGHT LOWS INTO THE MID 20S...AS WINDS
GRADUALLY DIMINISH OVERNIGHT AND SKIES CLEAR. ADDED MENTION OF FROST
FOR LOCATIONS LESS THAN 32 DEGREES AND WINDS LESS THAN 10-15KTS LATE
SAT NIGHT. MAIN CONCERN FOR SUN WILL BE DROPPING TD VALUES AS AREA
MIXES INTO DRIER AIR ALOFT. OUR LOCAL MIXED TD TOOL GIVES VALUES IN
THE HIGH SINGLE DIGITS OVER THE INTERIOR WEST HALF OF THE
CWA...WHILE NAM/GFS ML TD/S ARE IN THE TEENS. THUS...HAVE SPLIT THE
DIFF FOR NOW AND MAY NEED TO BE ADJUSTED DOWN ON FUTURE SHIFTS.
AFTER 12Z MON...MODEL DIFFERENCES BEGIN TO APPEAR AND LEADS TO A
LESS CONFIDENT FORECAST. 00Z ECMWF...LIKE THE LAST 2 RUNS...STILL
SHOWS THE RIDGE BREAKING DOWN AND DRIVING THE UPPER TROUGH SE ACROSS
THE GREAT LAKES REGION. THIS CAUSES THE COLD FRONT TO DIVE RIGHT
THROUGH THE AREA ON MON NIGHT...ACROSS THE MID ATLANTIC STATES...AND
OVER THE ATLANTIC BY 00Z THURS. ON THE OTHERHAND...THE 00Z
GFS/UKMET/GEM/GFS ENS AND 12Z GFS ALL STALL THE COLD FRONT SOMEWHERE
AROUND OR N OF THE CWA ON MON NIGHT...AS A LOW DEVELOPS OVER THE NRN
PLAINS. WILL FOLLOW A BLEND OF THE LATTER SOLUTION...DUE TO THE
BETTER AGREEMENT IN THOSE MODELS AND BASED OFF NATIONAL GUIDANCE
FOLLOWING A BLEND OF GFS/ECMWF ENS MEANS. THUS...PCPN CHANCES AND
TEMPS WILL DEPEND ON WHERE THE FRONT ENDS UP STALLING OUT. A FARTHER
N SOLUTION...AS SHOWN ON THE 00/06Z RUNS OF THE GFS...WILL KEEP THE
AREA IN THE WARM SECTOR AS THE WARM FRONT SETS UP NEAR US/CANADA
BORDER. THIS WILL ALLOW SW WINDS TO BRING WARMER TEMPS TO THE AREA
AND KEEP THE PCPN OVER NRN LK SUPERIOR OR SRN CANADA THROUGH THURS.
WHILE THE UKMET/GEM SHOW THE FRONT STALLING RIGHT OVER THE CWA ON
MON NIGHT AND TUES...BEFORE PUSHING TO THE N ON TUES AND INTO WED.
BUMPED TEMPS UP ON MON THROUGH WED PERIOD DUE TO EXPECTED BOUNDARY
PUSHING N...BUT DIDN/T GO AS HIGH AS GFS AND GFS ENS BASED ON THE
UNCERTAINTY. ALSO...PUT LOW CHANCE POPS ACROSS THE NRN HALF OF THE
CWA FOR MON THROUGH TUES NIGHT...WITH THE BEST CHANCES ON MON
NIGHT...AS THE FRONT PUSHES INTO LK SUP AND THEN STALLS.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
VFR CONDITIONS ARE EXPECTED TO PREVAIL TONIGHT THROUGH FRIDAY BUT
EXPECT MID/HIGH CLOUDS TO MOVE IN OVERNIGHT IN ADVANCE OF THE NEXT
SURFACE LOW IN THE NORTHERN PLAINS. A PERIOD OF RAIN SHOWERS IS
EXPECTED AHEAD OF A COLD FRONT MOVING THROUGH THE REGION WHICH MAY
BE ACCOMPANIED BY MVFR CIGS/VSBY.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
LOW PRESSURE NEAR JAMES BAY WILL CONTINUE TO PUSH NORTHEASTWARD INTO
QUEBEC...BRINGING AN END TO OUR GALES TEMPORARILY. HIGH PRESSURE
STRETCHING FROM LAKE SUPERIOR THROUGH THE OHIO VALLEY WILL
STRENGTHEN ACROSS EASTERN ONTARIO AND THE LOWER GREAT LAKES FRIDAY.
THIS WILL ALLOW LOW PRESSURE TO MOVE FROM THE DAKOTAS FRIDAY
MORNING...TO JUST NORTH OF LAKE SUPERIOR BY LATE FRIDAY. EXPECT
SOUTHERLY WINDS TO 30KTS FRIDAY AHEAD OF ANOTHER CHANCE OF GALES
ONCE AGAIN SATURDAY. ON SATURDAY...THE LOW SHOULD SLIDE TO SOUTHERN
JAMES BAY...WHILE HIGH PRESSURE DIVES INTO THE PLAINS STATES. THE
HIGH WILL MOVE OVER THE OHIO VALLEY SUNDAY...AND SLIDE A RIDGE
ACROSS LAKE SUPERIOR. EXPECT THE HIGH TO PUSH TO THE NORTHEASTERN
STATES MONDAY AND TUESDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 7 PM EDT THIS EVENING FOR LSZ244-245-264>267.
GALE WARNING UNTIL 5 PM EDT THIS AFTERNOON FOR LSZ263.
GALE WARNING UNTIL 6 PM EDT THIS EVENING FOR LSZ242-243-246-
249>251.
GALE WARNING UNTIL 4 PM EDT THIS AFTERNOON FOR LSZ247-248.
LAKE MICHIGAN...NONE.
&&
$$
SHORT TERM...KF
LONG TERM...SRF
AVIATION...JLB
MARINE...KF
