Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240817
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
320 AM EST TUE FEB 24 2015

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM

.SYNOPSIS...
ISSUED AT 320 AM EST TUE FEB 24 2015

A LOW PRESSURE SYSTEM MOVING THROUGH THE GREAT LAKES REGION TODAY
WILL BRING WINDY CONDITIONS AND SOME LIGHT SNOW. SOME LIGHT SNOW
SHOWERS WILL LINGER TONIGHT AND ANOTHER ARCTIC AIRMASS WILL MOVE
IN BEHIND THIS SYSTEM FOR MID TO LATE WEEK.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 320 AM EST TUE FEB 24 2015

A LOW PRESSURE SYSTEM AND APPROACHING COLD FRONT WILL CAUSE SNOW
TO DEVELOP FROM NW TO SE ACROSS OUR FCST AREA LATER THIS MORNING
AND AFTERNOON. THE RELATIVELY HIGHER SNOW ACCUMULATIONS ON THE
ORDER OF TWO TO FOUR INCHES WILL OCCUR NW OF KGRR DUE TO LAKE
ENHANCEMENT. ONLY AROUND AN INCH OF SNOW IS ANTICIPATED IN KGRR
WITH LIGHTER AMOUNTS THAN THAT FURTHER SE.

SOUTHWEST WINDS WILL CONTINUE TO RAMP UP TO 20 TO 30 MPH WITH GUSTS
TO 35 MPH AND HIGHER GUSTS AROUND 40 MPH NEAR THE LAKE MI SHORELINE
WHERE STRONG WIND GUSTS ARE ALREADY OCCURRING. THIS WILL RESULT IN
SOME BLOWING AND DRIFTING SNOW.

THE WINTER WX ADVISORY HEADLINE REMAINS IN EFFECT FOR ALL OF OUR
FCST AREA FROM 4 AM THROUGH EARLY THIS EVENING AS THE COMBINATION OF
THE SNOW AND WIND WILL LIKELY RESULT IN SOME HAZARDOUS TRAVEL
CONDITIONS PARTICULARLY NW OF KGRR.

SNOW SHOWERS WILL LINGER INTO THIS EVENING BEFORE HIGH PRESSURE
BUILDS IN TO PRODUCE FAIR BUT COLD WX WEDNESDAY. SUB ZERO MIN TEMPS
ARE EXPECTED ACROSS MOST OF OUR AREA WEDNESDAY NIGHT AS SKIES AT
LEAST PARTIALLY CLEAR AND WITH EXPANSIVE SNOW COVER IN PLACE. MAX
TEMPS THURSDAY WILL STRUGGLE TO REACH 5 TO 10 DEGREES ABOVE ZERO.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 320 AM EST TUE FEB 24 2015

TONIGHT/S MODELS CONTINUE TO INDICATE A SHIFT IN THE UPPER AIR
PATTERN HEADING INTO THE WEEKEND. A PERSISTENT TROUGH THAT HAS
BROUGHT REPEATED BOUTS OF ARCTIC AIR (WHICH WILL HANG ON MUCH OF
THIS WEEK) LIFTS OUT AND IS REPLACED BY SOUTHWEST UPPER FLOW OVER
THE WEEKEND. WARMER AIR MOVES IN ALOFT OVER THE WEEKEND AND INTO
EARLY NEXT WEEK WHICH SHOULD PUSH HIGHS UP INTO THE UPPER 20S TO
AROUND 30 DEGREES. THIS IS STILL BELOW NORMAL...BUT WILL FEEL WARMER
GIVEN THE VERY COLD WEATHER OF THE LAST TWO WEEKS.

REGARDING WEATHER DETAILS...THURSDAY NIGHT THROUGH SATURDAY LOOKS
QUIET AS SURFACE HIGH PRESSURE SLOWLY TRAVERSES THE AREA. COLD AIR
HANGS ON INTO FRIDAY.

THE PATTERN LOOKS BE BECOME MORE ACTIVE AS WE HEAD INTO THE WEEKEND
AND BEYOND IN THE SOUTHWEST FLOW. BOTH THE GFS AND ECMWF CONTINUE TO
INDICATE AN OVERRUNNING SNOW EVENT FOR SATURDAY NIGHT INTO SUNDAY
NIGHT. BOTH ALSO SHOW THE SNOW ASSOCIATED WITH A VERY WEAK TROUGH
AND NO SURFACE REFLECTION. THE UPPER AIR PATTERN INDICATING A WEAK
WAVE BEING SHEARED EAST IN THE SOUTHWEST FLOW WOULD SUPPORT LITTLE
IF ANY SURFACE DEVELOPMENT. THE ECMWF HAS TRENDED JUST A BIT
COLDER...SO WHAT FALLS SHOULD BE SNOW. AT THIS POINT NOT EXPECTING
BIG SNOWS...BUT A 3 TO 6 SWATH IS A POSSIBILITY. CONFIDENCE IN THIS
SNOW OCCURRING IS STILL ON THE LOW SIDE GIVEN ALL THE FACTORS
MENTIONED ABOVE. LOCATION OF THE HEAVIER SWATH IS CURRENTLY ACROSS
THE SOUTHERN HALF OF THE FORECAST AREA...BUT THAT WILL LIKELY CHANGE
WITH TIME GIVEN THE LACK OF SIGNIFICANT FEATURES TO LATCH ON TO.
SURFACE HIGH PRESSURE BUILDS BACK IN FOR MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1122 PM EST MON FEB 23 2015

THE MAIN AVIATION ISSUE OVER THE NEXT 24 HOURS IS THE WINDS.
SOUTHWEST WINDS WILL INCREASE OVERNIGHT TO 15 TO 25 KNOTS AND
AFTER DAYBREAK TO 20 TO 30 KNOTS WITH SOME GUSTS AS HIGH AS 40
KNOTS. THE HIGHEST WINDS APPEAR TO OCCUR BETWEEN 12Z AND 18Z.

THE STRONG WINDS WILL RESULT IN AREAS OF BLOWING SNOW DEVELOPING
BEFORE THE SNOW MOVES IN WHICH COULD LEAD TO REDUCE VSBYS AND
SLICK RUNWAY CONDITIONS FOR THE MORNING RUSH.

THE FALLING SNOW WILL SPREAD INTO THE REGION FROM NORTHWEST TO
SOUTHEAST... REACHING MKG AROUND 15Z AND LAN/JXN AROUND 19Z. THE
HEAVIEST SNOW AND LOWEST VSBYS WILL BE AT MKG AND GRR SO WILL KEEP
PREDOMINATELY IFR VSBYS TUESDAY AFTERNOON AT THESE TWO SITES AND
MOSTLY MVFR VSBYS AT THE OTHER TERMINALS. THERE IS A POTENTIAL
HOWEVER FOR IFR TO DEVELOP AT ALL THE TERMINALS DEPENDING ON THE
EXTENT OF THE BLOWING SNOW.

WINDS DIMINISHING AFTER 00Z WED BUT STILL 10 TO 20 KTS... AND
CIGS/VSBYS REMAINING PREDOMINATELY MVFR. CANT RULE OUT SOME IFR
VSBYS IN SNOW SHOWERS PERSISTING BEYOND 00Z WED BUT WAS NOT
CONFIDENT ENOUGH TO HAVE IN THE TAFS.


&&

.HYDROLOGY...
ISSUED AT 239 PM EST MON FEB 23 2015

WITH NO MAJOR WARM UPS OR RAINFALL HEADED OUR WAY IN THE NEAR
FUTURE...RUNOFF WILL BE LIMITED. SERIOUS ICE JAMS AND FLOODING
CONCERNS ARE UNLIKELY UNTIL A SIGNIFICANT WARM UP AND RAINFALL
OCCUR.  CONSIDERABLE ICE DOES EXIST IN THE RIVERS SO WE WILL NEED
TO MONITOR TRENDS CLOSELY. FOR NOW WITH CONDITIONS STABLE DUE TO
THE ARCTIC AIRMASS IN PLACE...THE RISK IS SOMEWHAT LIMITED FOR
FLOODING.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
     MIZ037>040-043>046-050>052-056>059-064>067-071>074.

LM...NONE.
&&

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...DUKE
AVIATION...MEADE
HYDROLOGY...MJS








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