677
FXUS63 KGRR 200728
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
328 AM EDT WED OCT 20 2021
LATEST UPDATE...
SYNOPSIS/DISCUSSION/MARINE
SYNOPSIS
ISSUED AT 328 AM EDT WED OCT 20 2021
-SHOWERS AND STORMS LATE WEDNESDAY INTO THURSDAY
-COOLER WEATHER FRIDAY THROUGH MOST OF THE WEEKEND
-CHANCE FOR SIGNIFICANT PRECIPITATION MID NEXT WEEK
DISCUSSION
(TODAY THROUGH NEXT TUESDAY)
ISSUED AT 328 AM EDT WED OCT 20 2021
--SHOWERS AND STORMS LATE WEDNESDAY INTO THURSDAY --
TODAY BEGINS WITH A CRISP CLEAR AUTUMN MORNING DUE TO STRONG
OVERNIGHT RADIATIONAL COOLING. HOWEVER, OVERNIGHT LOWS AS WELL AS
TODAYS HIGH TEMPERATURES, WILL BE ABOVE NORMAL. THE ABOVE NORMAL
TEMPERATURES WILL BE AIDED BY WARM SOUTHWESTERLY FLOW IN THE MID-
LEVELS, ALONG WITH MOIST FLOW AHEAD OF ANY APPROACHING LOW
PRESSURE SYSTEM. THE LATEST NAFES ENSEMBLES ARE SHOWING MEAN
TEMPERATURES ANOMALIES ARE +2 SIGMA, INDICATING A SLIGHTLY
ANOMALOUS SIGNAL.
AHEAD OF THE APPROACHING SYSTEM WILL BE A WEAK LLJ AT ABOUT 35KTS
AT 2KFT. WHILE NOT NECESSARILY STRONG, IT SHOULD PROVIDE ENOUGH
LOW LEVEL MIXING COUPLED WITH THE UNSEASONABLY WARM AIR FOR
AFTERNOON SHOWERS AND STORMS. ONE OF THE LIMITING FACTORS WILL BE
THE TIMING AS THIS SYSTEM WILL REACH THE REGION LATE IN THE DAY
WITH THE STRONGEST PWATS MOVING THROUGH NORTHERN MICHIGAN AND
ARRIVING WELL AFTER SUNSET. SO WHILE STORMS ARE POSSIBLE, THEY
WILL TEND TO BE SCATTERED THROUGH SOUTHWEST MICHIGAN AND WILL LACK
ORGANIZATION AND WILL NOT BE SEVERE. SHOWERS ARE LIKELY, BUT AS
STATED ABOVE, THE STRONGEST MOISTURE WILL BE TO THE NORTH SO
FLOODING IS NOT A CONCERN, ESPECIALLY WITH THE SPEED THAT THESE
SHOWERS/STORMS WILL BE MOVING.
SHOWERS AND STORMS WILL MOVE THROUGH NORTHEAST OVERNIGHT
WEDNESDAY INTO THURSDAY AND AS THEY MOVE THROUGH CENTRAL INTO
EASTERN MICHIGAN, THE MID TO NEAR RANGE MODELS SHOW THE OVERNIGHT
CONVECTION ORGANIZING INTO A COHESIVE LINE TOWARDS THURSDAY
MORNING. WHILE THIS WILL MAINLY EFFECT THE EASTERN HALF OF THE
STATE, ANY LINE OF SHOWERS AND STORMS THAT FORM COULD AFFECT THE
US 127 CORRIDOR INCLUDING LANSING AND JACKSON. AS STATED ABOVE,
NONE OF THIS IS EXPECTED TO BECOME SEVERE.
--COOLER WEATHER FRIDAY THROUGH MOST OF THE WEEKEND
AS THE MID TO UPPER LEVEL LOW TRAVERSES THE GREAT LAKES, IT WILL
BE PULLED INTO A LARGER UPPER LEVEL TROUGH EXTENDING FROM AROUND
HUDSON BAY THROUGH THE MIDWEST. STRONG NORTHERLY FLOW WILL DROP A
COLD FRONT ACROSS MICHIGAN THURSDAY EVENING INTO FRIDAY MORNING.
THE MID RANGE MODELS ARE IN DECENT AGREEMENT THAT COLDER AIR, 0C
TO -2C AT 850MB, WILL ADVECT INTO THE AREA BY 12Z FRIDAY MORNING.
THE STRONG NORTHERLY FLOW ALONG WITH GUSTY WINDS WILL ALLOW FOR A
BLUSTERY DAY ON FRIDAY.
THE COLDEST TEMPERATURES IN THIS PERIOD WILL BE SATURDAY MORNING
WITH PATCHY FROST POSSIBLE SO IF YOU HAVE ANY VEGETATION LEFT IT
WOULD BE A GOOD IDEA TO PROTECT IT. THERE ARE SOME OUTLINING
MODELS ALONG US 10 THAT HAVE THE POTENTIAL FOR SNOW FLURRIES.
HOWEVER, GIVEN THE LACK OF MOISTURE IT IS UNLIKELY AND IF IT DOES
OCCUR WILL NOT AMOUNT TO ANYTHING.
THE COLDER AIR MASS WILL LINGER OVER THE STATE INTO SUNDAY BEFORE
THE NORTHWESTERLY FLOW SHIFTS TO THE EAST SUNDAY AFTERNOON AS THE
UPPER LEVEL TROUGH GIVES WAVE TO ANOTHER SYSTEM MOVE IN FROM THE
CENTRAL US. THAT WILL MODERATE TEMPERATURES AND BRING WARMER AIR
INTO THE REGION LATE SUNDAY INTO THE UPCOMING WORK WEEK. THE
MODEL SOLUTIONS BEGIN TO DIVERGE AS THE GFS HAS A BETTER CHANCE OF
PRECIPITATION SUNDAY. HOWEVER THE EC HAS THE STRONG, DRY EASTERLY
FLOW MAINLY FENDING OFF ANY APPROACHING PRECIPITATION. SO WHILE
PRECIPITATION IS POSSIBLE SUNDAY INTO MONDAY, IT WILL BE
INHIBITED INTO COMING INTO A DRIER AIR MASS AND WILL HAVE CONTEND
WITH DRY AIR ADVECTING INTO IT. THE BEST CHANCE FOR PRECIPITATION
SUNDAY INTO MONDAY WILL BE ALONG THE I-94 CORRIDOR
--CHANCE FOR SIGNIFICANT PRECIPITATION MID NEXT WEEK --
STRONG, DIVERGENT UPPER LEVEL FLOW WILL MOVE ANY PRECIPITATION TO
THE NORTHEAST MONDAY MORNING WITH NORTHWESTERLY FLOW ONCE AGAIN
TAKING THE STAGE INTO TUESDAY. A WEAK UPPER LEVEL RIDGE WILL MOVE
OVER THE AREA BEFORE A DEEPENING LOW WAVE TROUGH DEVELOPS IN THE
MIDWEST AS TRAVERSES THE GREAT LAKES STATES WEDNESDAY INTO
THURSDAY. THERE IS SOME SIGNAL FOR DECENT QPF THOUGH THE BEST
PWATS ARE TO THE NORTH OF THE REGION.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 147 AM EDT WED OCT 20 2021
VFR WEATHER CONTINUES TODAY INTO THE EVENING AS INCOMING
CLOUDINESS HAS HIGH BASES, MOSTLY AT OR ABOVE 10,000 FT. A FEW
SHOWERS ARRIVE LATER IN THE DAY BUT NO APPRECIABLE VSBY
REDUCTIONS ARE EXPECTED AT THIS TIME.
THE RISK FOR THUNDER WITH LOWER CIGS WITH BRIEF VSBYS
RESTRICTIONS RAMPS UP A BIT AFTER 03Z TONIGHT, BUT HAVE EXCLUDED
THAT IN THE TAFS FOR NOW. SHOULD CONFIDENCE IN TIMING AND COVERAGE
OF CONVECTION INCREASE, THUNDER/CBS MAY NEED TO BE ADDED FOR
TONIGHT IN LATER TAF UPDATES.
MARINE
ISSUED AT 328 AM EDT WED OCT 20 2021
WINDS AND WAVES WILL BE LIGHT TODAY, THOUGH THEY WILL INCREASE AS
THE DAY CONTINUES. STRONG NORTHWESTERLY FLOW IS EXPECTED TOMORROW
WITH WINDS INCREASING TO AT LEAST ADVISORY THOUGH IF THE STRONG
FLOW INTENSIFIES ON THURSDAY IT COULD FLIRT WITH GALE CRITERIA.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LM...NONE.
SYNOPSIS...CERU
DISCUSSION...CERU
AVIATION...MEADE
MARINE...CERU
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