AREA FORECAST DISCUSSION
NWS MARQUETTE MI
AFDMQT 445 PM EDT SAT APR 7 2001
...SYNOPTIC HIGH WINDS AND EVENING CONVECTION ARE MAIN CONCERNS...
WV AND IR LOOPS AND 12Z RAOBS TELL STORY OF VERY POTENT NEG TILTED
TROUGH RAKING ACROSS THE UPPER MISSISSIPPI VALLEY AND WRN GREAT
LAKES REGION. WAA PRECIP ASSOCIATED WITH H85 WARM FRONT IS WELL INTO
ONTARIO WITH PRECIP IN CCB/UPR LOW VCNTY SPINNING ACROSS NERN MN INTO
ERN DAKOTAS. SFC LOW CENTER IN VCNTY OF ST CLOUD MN WITH CENTRAL
PRESSURE OF 978MB. NEXT BOUNDARY OF CONCERN FOR UPR MI IS SFC WARM
FRONT WHICH IS ORIENTED FM STC TO RHI ACROSS LK MI TO THE TVC AREA
IN NRN LOWER MI. AS ONE WOULD ANTICIPATE...QUITE A BATTLEGROUND IN
PLACE AS OVR UPR MI TEMPS ARE STRUGGLING INTO THE 40S WITH LOW
STRATUS AND FOG LOCKED IN PLACE...THANKS IN PART TO ERLY FLW OF MUCH
COOLER LK MI AND LK SUPERIOR. IMMEDIATELY SOUTH OF WARM FRONT OVR
NRN WI...TEMPS HAVE SHOT TO 74/46 AT GRB AS VRY STRONG SW FLW (GUSTS
TO 50KT) RAPIDLY DISSIPATED CLOUDS THIS AFTN.
MAIN CONCERNS ARE VERY SHORT TERM SEVERE THREAT PRIMARILY IN FORM OF
HIGH WINDS WITH POSSIBLE HAIL AS INSTABILITY ALONG WARM FRONT COMES
TOGETHER ATTM WITH POTENT H85/H3 JETS AND SURGE OF H85 DWPTS AROUND
12C INTO UPR MI THROUGH 23Z. SMALL HAIL ALSO POSSIBLE WITH ANY
UPDRAFTS WITH H85-H5 LAPSE RATES AROUND 7C/KM AND WBZ HTS AROUND
9KFT OVRHEAD EARLY TONIGHT. GRADIENT WINDS AHEAD OF LOW ALSO MAJOR
CONCERN WITH MANY AREAS SEEING ADVISORY CRITERIA WINDS JUST TO SOUTH
AS TIGHT GRADIENT MOVES OVERHEAD ACCOMPANIED IN UPR LEVELS BY
VIGOROUS SUBSIDENCE AND NVA PER WV LOOP.
AVN HAS BEEN CONSISTENT...BUT TO FAR EAST WITH SFC LOW. WL FOLLOW
ETA GENERALLY AS IT HAS BEST HANDLE ON SHORT TERM SITUATION.
SHORT TERM TONIGHT...LATE MORNING-ERLY AFTN INSOLATION OVR NRN WI
HAS HELPED INCREASE INSTABILITY AS SFC-H85 LAPSE RATES INCREASE TO
7.5C/KM AND SBCAPES RISE TO AROUND 500J/KG. SCATTERED SHOWERS WITH
SOME LIGHTNING STRIKES PER MQT 88D/LDN BUT NOTHING APPROACHING SVR
LEVELS YET AS ONLY UP TO PEA SIZE HAIL HAS BEEN REPORTED BY SPOTTERS.
HOWEVER...1000-H9 CONVERGENCE ASSOCIATED WITH WARM FRONTAL BOUNDARY
SHIFTS NORTHEAST DURING SAME TIME THAT 60 KT H85 JET AND LFQ OF
APPROACHING 120KT JET STREAK AT H3 COINCIDE OVR SC UPR MI...BTWN
21Z-00Z...AIDING IN POSSIBLE DEVELOPMENT OF SVR CONVECTION. AT THE
LEAST...WITH S/SW WINDS IN THE 60-70KT RANGE THRU 10KFT OVR WI PER
ACARS DATA...ANY CONVECTIVE DOWNDRAFTS WILL HAVE POTENTIAL TO
PRODUCE DAMAGING WINDS THIS EVENING. AWAY FM CONVECTIVE THREAT...UPR
LOW AND BULLSEYE OF H5-H3 QVECTOR CONVERGENCE WILL PASS OVR WRN LAKE
SUPERIOR THIS EVENING. DLH 88D SHOWING BROAD AREA OF 0.10"/HR RAINS
OVR ERN MN INTO NW WI. AS THIS AREA OF H5 DIFFLUENCE AND QVECTOR
CONVERGENCE PASSES OVR FA MOST AREAS WL SEE SCT/NUM RAIN
SHOWERS...BUT WITH SI/S ABOVE ZERO AND 1000-850MB LAPSE RATES
FALLING BLO 6C/KM...TT/S DIVING TO BLO 30C BY 00Z...AND K INDICES
AROUND 25C...POSSIBILITY OF THUNDER WL BE ISOLATED OVR WRN/CNTRL
ZONES ALONG LK SUPERIOR.
OVERNIGHT THROUGH SUNDAY...AREA OF H5-H3 QVECTOR CONVERGENCE CROSSES
UPR MI BY 06Z WITH MOST PRECIP ENDING BY MIDNIGHT AS LOW LEVEL
CONVERGENCE IS TO THE EAST. WITH EVENING PRECIPITATION AND MOIST
LOW-LEVELS REMAINING OVRNIGHT...FOG SHOULD DEVELOP QUICKLY OR REMAIN
IN AREAS THAT HAVE SEEN IT ALL DAY...MAINLY OVR WRN HIGHLANDS OVR
THE PENINSULA. DESPITE H7 RH AOA 70 PCT SLIDING NE OUT OF FA BY 12Z
SUN...LINGERING MOISTURE BLO H85 REMAINS. COULD SEE SOME CLEARING
OVR FAR SWRN FA IN AFTN...BUT ELSEWHERE CLOUDS AND FOG WL HANG
TOUGH. TEMPS SIM TO WARMER MAV GUIDANCE...BUT EASILY COULD REMAIN IN
UPR 30S IN THE NRN TIER.
SUNDAY NIGHT AND MONDAY...ETA/AVN ARE MOST AGRESSIVE WITH NEXT
SHRTWV AND BAROCLINIC ZONE THAT REACHES INTO SRN TIER OF ZONES INTO
MONDAY MORNING. ETA H3 DIVERGENCE AND H7 OMEGA FIELDS HINT AT A MCS
TO DEVELOP ALONG BOUNDARY OVR NRN IL AND SRN WI OVRNIGHT...SO THIS
COULD ROB FA OF INITIAL ANTICIPATED MOISTURE. ATTM WL GO WITH LOW
CHANCE POPS OVRNIGHT...BUT THEN HIT WITH HIGH CHANCE/LIKELY POPS
MONDAY AS MAIN BAND OF H5-H3 QVECTOR CONVERGENCE AND SIMBLANCE OF
COUPLED JET STRUCTURE DEVELOPS OVR WRN LAKES REGION.
EXTENDED...MEDIUM RANGE MODELS IN AGREEMENT AS TO GENERAL UPR LEVEL
FLOW THROUGH NEXT WEEKEND. APPEARS AFTER CURRENT NEG TILTED TROUGH
SHOOTS INTO CANADA BY 12Z MON...FLAT RIDGE/SW FLOW DEVELOPS FM
PLAINS SW CONUS INTO SE CANADA. BY 12Z/10 MRF/UKMET/AVN AND MOST
NOTABLY GLOBAL CANADIAN INDICATE SHRTWV TROUGH MOVING OFF PAC COAST
THEN RUNNING INTO MEAN RIDGE TUESDAY. CHANCE OF RAIN STILL LOOKS TO
HOLD...WITH BEST LIKLIHOOD OVR NRN TIER. TEMPORARY BUT SHARP RIDGING
TAKES PLACE WED WITH MODELS THEN SHOWING ANOTHER SHARP NEG TILTED
TROUGH BLASTING OUT OF SW INTO WRN LAKES 4/12-4/13. BOTH ECMWF/UKMET
ARE MOST AGRESSIVE WITH THIS IDEA...WITH CANADIAN WEAKEST AS IT
FAVORS EARLY WEEK TROUGH TO DIG FARTHER SOUTHEAST AIDING IN SLOWING
DOWN OVERALL PATTERN BY ALMOST 2 DAYS COMPARED TO OTHER MODELS AND
ENSEMBLES. MRF SHOWS QUITE A COOL SHOT OF AIR BEHIND EXITING LOW
PRESSURE SAT...BUT DPROG/DT OF H85 TEMPS SUGGEST THAT ECMWF TEMPS
AROUND -4C SEEM MORE REALISTIC. WL GO WITH CHANCE POPS THU-FRI WITH
SYSTEM.
.MQT...HIGH WIND ADVISORY THIS EVENING MIZ010>012.
GALE WARNING LAKE SUPERIOR
GALE WARNING LAKE MICHIGAN NEARSHORE.
JLA