000
FXUS63 KGRR 272033
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 PM EST MON DEC 27 2010
LATEST UPDATE...ALL EXCEPT AVIATION...
.SYNOPSIS...(330 PM EST MON DEC 27 2010)
FAIRLY TRANQUIL WEATHER WILL CONTINUE THROUGH MIDWEEK WITH DRY
CONDITIONS AND SEASONABLE TEMPERATURES. RAIN SHOWERS ARE POSSIBLE
THURSDAY AFTERNOON THROUGH FRIDAY. PRECIPITATION COULD START OUT AS
A PERIOD OF FREEZING DRIZZLE OR LIGHT SNOW THURSDAY MORNING.
THE BEST CHANCE OF RAIN WILL COME FRIDAY NIGHT IN ADVANCE OF THE
APPROACHING COLD FRONT WHICH WILL MOVE THROUGH SATURDAY MORNING.
THERE IS A CHANCE OF SNOW BEHIND THE FRONT SATURDAY AFTERNOON INTO
SUNDAY. TEMPERATURES WILL GRADUALLY WARM INTO THE 40S BY LATE WEEK
BEFORE MUCH COLDER AIR ARRIVES THIS WEEKEND.
&&
.SHORT TERM...(330 PM EST MON DEC 27 2010)
(TONIGHT THROUGH WEDNESDAY NIGHT)
OUR PRIMARY SHORT TERM FCST CHALLENGE IS TO ASSESS POTENTIAL FOR ANY
-SN/FZDZ/-FZRA TOWARD DAYBREAK THURSDAY.
WEAK UPPER RIDGING WILL PRODUCE DRY WX TONIGHT THROUGH TUESDAY WITH
SOME LINGERING LOW CLOUDS AND PARTIAL CLEARING. I AM CONCERNED ABOUT
POTENTIAL FOR PATCHY FOG TO DEVELOP LATE TONIGHT... BUT DID NOT FEEL
CONFIDENT ENOUGH IN THE POTENTIAL TO ADD IT TO THE FCST.
IT WILL BECOME A LITTLE BREEZY TUESDAY AS WSW WINDS RAMP UP TO
AROUND 15 TO 25 MPH AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE
SFC RIDGE OVER THE SOUTH AND LOW OVER HUDSON BAY. DECIDED TO
ADD PATCHY FOG TO THE FCST LATE TUE NIGHT INTO WEDNESDAY MORNING. I
NOTICED 27/15Z SREF GUIDANCE SHOWS FAIRLY HIGH PROBABILITIES FOR SFC
VISBYS TO DROP TO UNDER A MILE IN THAT TIME FRAME ACROSS LWR MI.
SOME OF OUR NUMERICAL GUIDANCE HINTS AT THE POTENTIAL TOO.
TEMPS WILL UNDERGO A SLOW MODERATING TREND TONIGHT THROUGH WEDNESDAY
NIGHT AS WINDS GRADUALLY BACK TO THE WSW TO SW AND EVENTUALLY SOUTH
BY WEDNESDAY. VERY LIGHT WAA PCPN MAY DEVELOP AFTER 06Z THURSDAY AS
MOISTURE STARTS TO RAMP UP IN CONTINUED SOUTHERLY FLOW.
LOW LEVEL CRITICAL THICKNESS TOOLS SUGGEST PCPN TYPE DURING THE
EARLY MORNING HOURS THURSDAY WOULD MOST LIKELY BE LIGHT SNOW.
HOWEVER IT IS NOTED THAT 12Z NAM/GFS FCST SOUNDINGS CERTAINLY SHOW
POTENTIAL FOR FZDZ TOWARD DAYBREAK THURSDAY WITH TEMP PROFILES ABOVE
FREEZING FROM AROUND 1-5 KFT AGL BUT STILL BELOW FREEZING AT/NEAR
THE SFC. MODEL CONSENSUS QPF FROM 06Z-12Z THURSDAY IS VERY LIGHT...
RANGING FROM NO MEASURABLE PCPN TO PERHAPS A COUPLE HUNDREDTHS OF AN
INCH TOWARD DAYBREAK THURSDAY.
&&
.LONG TERM...(330 PM EST MON DEC 27 2010)
(THURSDAY THROUGH MONDAY)
THE MAIN FOCUS WILL CONTINUE TO BE ON THE STORM SYSTEM THAT WILL
IMPACT OUR REGION TOWARD THE END OF THE WEEK. CONFIDENCE IS GROWING
IN THE TIMING OF HEAVIEST PRECIPITATION AS WELL AS FROPA. FIRST OF
ALL...THE FREEZING RAIN POTENTIAL FOR THURSDAY MORNING WILL BE
ADDRESSED.
GFS BUFKIT SOUNDINGS FOR MUCH OF THE CWA SUPPORT AT LEAST A CHANCE
FOR FREEZING RAIN OR FREEZING DRIZZLE THURSDAY MORNING. LOW TO MID
LEVEL SATURATION IS ANTICIPATED IN THE EARLY TO MIDDLE PART OF THE
MORNING. BOTH THE GFS AND ECMWF ARE SIMULATING VERY LIGHT
PRECIPITATION DURING THE MORNING HOURS AS SURFACE TEMPS CLIMB FROM
THE UPPER 20S TO MID 30S BY EARLY AFTERNOON. SO...THE PREVIOUS WX
GRIDS DURING THIS PERIOD LOOKED GREAT AND I LEFT THEM AS THEY WERE.
SHOWERS WILL GRADUALLY INCREASE IN COVERAGE...WITH THE MOST
WIDESPREAD ACTIVITY EXPECTED FRIDAY AND FRIDAY NIGHT. FOG FORMATION
BOTH THURSDAY AND FRIDAY IS LIKELY ESPECIALLY FOR AREAS THAT HAVE
BETTER SNOWPACKS. LI'S JUST AHEAD OF FROPA MAY DIP TO ZERO OR
SLIGHTLY BELOW ZERO. NOT IMPOSSIBLE THAT A FEW RUMBLES OF THUNDER
MAY OCCUR IN THE LINE OF SHOWERS OUT AHEAD OF THE FRONT.
THE LOW TRACK OFF THE GFS IS FURTHER SOUTH AND EAST THAN THE
ECMWF...BUT EITHER SOLUTION WOULD GIVE US FROPA BETWEEN 06Z AND 09Z
SATURDAY. I AM NOT IMPRESSED WITH OUR CHANCES FOR SIGNIFICANT SNOW
SHOWERS EVEN AS THE COLD AIR ADVECTION DRIVES INTO OUR REGION AFTER
THE SYSTEM DEPARTS. THIS IS MAINLY BECAUSE MOISTURE WILL BE SHALLOW
AND OUR WINDOW OF OPPORTUNITY WILL BE BRIEF BEFORE SURFACE RIDGING
BUILDS IN MONDAY. SO...LAKE EFFECT SNOW SHOWERS ARE STILL POSSIBLE
BUT NOTHING HEAVY IT APPEARS AT THIS POINT. EVEN WITH A SHORTWAVE
IMPULSE MOVING THROUGH SUNDAY...MOISTURE DEPTH WILL BE THE
MITIGATING FACTOR. QUIET WEATHER FOLLOWS FOR EARLY NEXT WEEK.
&&
.AVIATION...(1224 PM EST MON DEC 27 2010)
STRATOCUMULUS OFF LAKE MICHIGAN WILL BE PROGRESSING INLAND AS WINDS
BACK MORE WESTERLY THIS AFTERNOON. MUSKEGON WILL BE THE FIRST TO
CLEAR OUT THIS EVENING. RUC13 MODEL IS DOING A NICE JOB SHOWING THE
HIGHER RH IN THE 1500-2500FT LAYER MOVING EASTWARD WITH TIME TODAY.
THIS WILL BRING THE STRATOCUMULUS INTO LAN AND JXN LATER THIS
AFTERNOON. HOWEVER...THE CIGS WILL NOT BE LOW ENOUGH FOR IFR
CONDITIONS. ASIDE FROM A BIT OF A W/WSW BREEZE THROUGH
TOMORROW...CONDITIONS WILL IMPROVE.
&&
.MARINE...(330 PM EST MON DEC 27 2010)
THE SCA CONTINUES IN EFFECT THROUGH TUESDAY WITH WAVE HEIGHTS OF 3
TO 5 FEET TODAY BUILDING TO 4 TO 7 FEET TONIGHT AND UP TO 5 TO 8
FEET TUESDAY.
&&
.HYDROLOGY...(330 PM EST MON DEC 27 2010)
ANY ICE JAM THREAT WILL BE MITIGATED BY WARMING TEMPERATURES MID TO
LATE WEEK. RAIN AND MELTING SNOW LATE THIS WEEK MAY CAUSE
RIVERS/STREAM TO FLUCTUATE BUT FLOODING IS NOT EXPECTED AS QPF IS
UNDER AN INCH.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH TUESDAY AFTERNOON FROM
ST JOSEPH TO MANISTEE.
&&
$$
SYNOPSIS: LAURENS
SHORT TERM: LAURENS
LONG TERM: HOVING
AVIATION: HOVING
MARINE: LAURENS
HYDROLOGY: LAURENS
