Issued by NWS Grand Rapids, MI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35 36
37
38
39
40
41
42
43
44
45
46
47
48
000 FXUS63 KGRR 270002 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 800 PM EDT SUN OCT 26 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(415 PM EDT SUN OCT 26 2008) THE GREAT LAKES REGION WILL EXPERIENCE THE FIRST TASTE OF WINTER EARLY THIS WEEK AS A SERIES OF COLD FRONTS PASS THROUGH AND BRING PROGRESSIVELY COLDER AIR DOWN FROM CANADA. SCATTERED LAKE EFFECT RAIN SHOWERS WILL BE MIXED WITH SNOW SHOWERS TONIGHT AND MONDAY THEN CHANGE TO MOSTLY SNOW ON MONDAY NIGHT INTO TUESDAY. SOME LIGHT ACCUMULATIONS WILL BE POSSIBLE WEST OF HIGHWAY 131 MONDAY NIGHT. A WARMING TREND WILL BEGIN ON WEDNESDAY. && .SHORT TERM...(415 PM EDT SUN OCT 26 2008) (TODAY THROUGH TUESDAY) THE CORE OF THE STRONGEST WINDS ALOFT /50-55KT AT H8/... AS WELL AS THE STRONGEST COLD ADVECTION /-8C AT H8/... IS PASSING SOUTHWEST OF MICHIGAN THIS AFTERNOON AND EVENING. THUS WIND GUSTS ARE STRUGGLING TO REACH ADVISORY CRITERIA OF 45 MPH (39KTS). HOWEVER HAVE OPTED TO RIDE THE ADVISORY THROUGH IT/S EXPIRATION TIME OF 8 PM SINCE THERE IS CURRENTLY SOME CONVECTION AROUND THAT COULD HELP PRODUCE SOME BRIEF/ISOLATED 45 MPH GUSTS. WILL ALSO CARRY A MENTION OF THUNDER AND POSSIBLE SMALL HAIL IN THE GRIDS THROUGH 00Z AS LIFTED INDICES HOLD AROUND -2 OR SO UNTIL AROUND SUNSET. THE CORE OF THE COLDEST AIR GOES SOUTH OF MI TONIGHT AND A TROUGH OF WARMER H8 AIR /-3C/ PIVOTS DOWN FROM THE NW WITH THE NEXT SHORTWAVE. THIS WILL MAKE IT VERY TOUGH TO TRANSITION THE LAKE EFFECT PCPN TO ALL SNOW TONIGHT WHICH WILL MAKE ACCUMULATIONS UNLIKELY. NAM LOW LEVEL THICKNESS SCHEMES AND SFC TEMP PROGS LOOK A TAD TOO WARM. THIS IS A TREND WHICH BEGAN WITH THE 00Z GUIDANCE AND HAS CONTINUED IN THE 12Z GUIDANCE. THERE IS STILL A STRONG CONCERN HOWEVER THAT OCCASIONAL CHANGEOVERS TO ALL SNOW COULD OCCUR WITHIN THE MORE INTENSE LAKE EFFECT BANDS LATE TONIGHT. SOME OF THOSE BANDS CERTAINLY COULD BE INTENSE SINCE DEEP MOISTURE WILL BE PRESENT WITH VIRTUALLY NO INVERSION ALOFT INDICATED IN THE FCST SOUNDINGS. THUS QUICK COATINGS OF AN INCH OR SO CANNOT BE COMPLETELY RULED OUT TONIGHT AND MONDAY MORNING. LAKE EFFECT BANDS WILL PROBABLY BECOME MORE OPEN CELLULAR BY MONDAY AFTERNOON DUE TO DISRUPTION FROM DIURNAL EFFECTS. THE BEST CHANCE OF ACCUMULATING LAKE EFFECT SNOW WILL BE MONDAY NIGHT AND TUESDAY MORNING. THIS IS WHEN THE COLDEST H8 AIR OF -8C WILL BE IN PLACE BEHIND THE DEPARTING SECONDARY TROUGH. FLOW IS NNW... WHICH WOULD SUPPORT SOME POTENTIAL 1-3 ACCUMULATIONS WEST OF HIGHWAY 131. EXCEPTION WOULD BE THE IMMEDIATE LAKE MI COASTLINE WHERE A MIX WILL LIKELY CONTINUE SINCE THE LK MI WATER TEMP IS 55F. MEANWHILE AREAS ALONG/EAST OF HWY 131 WILL LIKELY CLR OUT MONDAY NIGHT AND HAVE A HARD FREEZE. && .LONG TERM...(415 PM EDT SUN OCT 26 2008) (TUESDAY NIGHT THROUGH SATURDAY) UPPER CYCLONIC FLOW WILL BE EXITING THE CWFA AS THE UPPER JET MIGRATES TO THE EAST AT THE BEGINNING OF THE LONG TERM ON WED MORNING. UPPER RIDGING IS EXPECTED TO BUILD...AND DRY OUT THE AREA FOR A COUPLE OF DAYS ALONG WITH SOME ABOVE NORMAL TEMPERATURES. STRONG UPPER ENERGY DIVING SOUTHEAST OUT OF CANADA WILL SQUEEZE THE UPPER RIDGING TO THE EAST. MODELS ARE COMING INTO AGREEMENT ON THIS HAPPENING IN THE FRI TIME FRAME. MODELS ARE INDICATING THAT LITTLE IF ANY PCPN IS GOING TO BE ASSOCIATED WITH THE FRONT. MOISTURE IS NOT ALL THAT DEEP WITH DIFFERENT LAYERS OF MOISTURE NOT OVERLAPPING WELL. WE WILL MAINTAIN THE DRY FCST FOR NOW WITH NO GOOD JUSTIFICATION ATTM TO INTRODUCE POPS INTO THE FCST. H850 TEMPS ARE EXPECTED TO DROP FROM AROUND +10C OR SO AHEAD OF THE FRONT...TO -6C OR SO BEHIND THE FRONT. THREAT OF LAKE EFFECT SEEMS RATHER LOW EVEN WITH THE COLD AIR DROPPING INTO THE CWFA. THIS IS BECAUSE THE FLOW IS EXPECTED TO BE NORTHEAST AS A RESULT OF THE ORIENTATION OF THE SFC HIGH COMING IN FROM THE NW. THIS RIDGE WILL THEN MOVE OVERHEAD NEXT WEEKEND. && .MARINE...(415 PM EDT SUN OCT 26 2008) MAY BE ABLE TO CANCEL THE GALE WARNING EARLY BUT EVEN SO VERY ROUGH CONDITIONS WILL PERSIST IN LAKE MI INTO TUESDAY AS UNSEASONABLY COLD AIR AND CYCLONIC FLOW AFFECTS THE REGION. WAVE HEIGHTS NEAR 10 FEET SHOULD BEGIN TRENDING DOWN MONDAY NIGHT... BUT REMAIN ABOVE SMALL CRAFT ADVISORY CRITERIA INTO TUESDAY. && .AVIATION...(800 PM EDT SUN OCT 26 2008) THERE IS A BAND OF SHOWERS ON THE THERMAL BOUNDARY THAT SEPARATES AIR NORTH OF I-96 WHICH HAD TEMPERATURES MOSTLY IN THE LOWER 40S AND DEW POINTS IN THE MID 30S FROM AIR SOUTH OF THAT WHICH HAD TEMPERATURES NEAR 50 AND DEW POINTS BELOW FREEZING. THAT BOUNDARY HAS PRODUCED SOME LAKE ENHANCED THUNDERSTORMS NEAR MKG FROM 3 PM THROUGH 8 PM. FREQUENT REPORTS OF 1/4 INCH HAIL WHERE RECEIVED. THIS BOUNDARY WILL DROP SOUTH OVER THE NEXT 3 HOURS REACHING I-94. WITH THE SUN NOW SET... THUNDERSTORMS ARE NO LONGER EXPECTED AS THE SURFACE INSTABILITY IS NO LONGER THERE. STILL... SHOWERS WILL CONTINUE AS THE FRONT DROPS SOUTH WITH TIME. ONCE THAT BOUNDARY IS THROUGH WINDS BECOME MORE NORTHWEST THROUGH A DEEP LAYER. THE AIR BECOMES NEARLY SATURATED THROUGH -20C ISOTHERM AND STAYS THAT WAY THROUGH MONDAY. THUS NORTHWEST FLOW LAKE EFFECT IS EXPECTED. LOCATIONS LIKE MKG AND AZO SHOULD SEE NEARLY CONTINUOUS SHOWERS THROUGH MONDAY AFTERNOON. SINCE THE WET BULB ZERO STAYS ABOVE 2000 FT MOST OF THAT TIME... I DO NOT SEE AN ISSUE WITH SNOW. I IS POSSIBLE TO GET GRAUPEL FROM THE STRONGER SHOWERS BUT I DID NOT FEEL CONFIDENT ENOUGH TO PUT IT IN THE TAFS. LOCATIONS EAST OF MKG AND AZO WILL SEE A PERIOD OF SHOWERS TONIGHT AS THE COLDER AIR MOVES IN BUT AFTER THAT...AFTER MIDNIGHT OR SO PRECIPITATION WILL FOR THE MOST PART END AND THEY WELL HAVE FOR THE MOST PART MVFR CIGS. NORTHWEST WINDS OF 15 TO 25 KNOTS THROUGH MONDAY. && .HYDROLOGY...(415 PM EDT SUN OCT 26 2008) NO HYDRO CONCERNS AS PCPN NEXT 72 HOURS WILL BE GENERALLY SCATTERED IN NATURE WITH QPF AMOUNTS BELOW HALF INCH. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WIND ADVISORY THROUGH 8 PM...ENTIRE CWA. LM...GALE WARNING IN EFFECT ST. JOE TO MANISTEE TODAY THROUGH MONDAY AFTERNOON. && $$ SYNOPSIS: MEADE SHORT TERM: MEADE LONG TERM: NJJ MARINE: MEADE AVIATION: WDM HYDROLOGY: MEADE
