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000
FXUS63 KGRR 261214
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
714 AM EST THU FEB 26 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EST THU FEB 26 2015

A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER ACROSS FAR
SOUTHERN LOWER MICHIGAN THIS MORNING BEFORE HIGH PRESSURE BUILDS
IN TO PRODUCE FAIR BUT COLD WEATHER LATER TODAY THROUGH SATURDAY.
TEMPERATURES WILL FINALLY UNDERGO A GRADUAL MODERATING TREND
SUNDAY INTO EARLY NEXT WEEK.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 330 AM EST THU FEB 26 2015

KGRR RADAR TRENDS AND A CONSENSUS OF SHORT RANGE GUIDANCE SUGGESTS
THAT A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS
MORNING MAINLY SOUTH OF I-96 WITH VERY LIGHT ACCUMULATIONS OF
UNDER AN INCH.

HIGH PRESSURE WILL BUILD IN LATER TODAY THROUGH SATURDAY TO
PRODUCE FAIR BUT VERY COLD WX. MAX TEMPS TODAY WILL ONLY REACH THE
UPPER SINGLE DIGITS TO MIDDLE TEENS.

WIDESPREAD SUB ZERO MIN TEMPS ARE ANTICIPATED TONIGHT AS SKIES
CLEAR AND WINDS GO CALM AND WITH EXPANSIVE SNOW COVER IN PLACE
ACROSS OUR AREA.

MAX TEMPS FRIDAY WILL ONLY REACH THE TEENS IN SPITE OF A FAIR
AMOUNT OF SUN AFTER THE VERY COLD START TO THE DAY. IT WILL BE
VERY COLD FRIDAY NIGHT AS WELL BUT NOT QUITE AS COLD AS TONIGHT
WITH MIN TEMPS GENERALLY IN THE FIVE BELOW TO FIVE ABOVE ZERO RANGE.

A CONSENSUS OF 00Z TIME HEIGHT RH PROGS SUGGESTS THERE WILL BE
PLENTY OF SUN ON SATURDAY. HOWEVER MAX TEMPS SATURDAY WILL ONLY
REACH THE UPPER TEENS TO LOWER 20S.

WIND SPEEDS TONIGHT WILL BE CALM TO LESS THAN 5 MPH. APPARENT
TEMP READINGS MAY FLIRT WITH -15 ACROSS OUR NORTHERN COUNTIES
DURING THE EARLY MORNING HOURS FRIDAY. HOWEVER GIVEN VERY LITTLE
TO NO WIND OVERNIGHT WIND CHILL ADVISORY CRITERIA WILL LIKELY NOT
BE ATTAINED.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 AM EST THU FEB 26 2015

FELT YESTERDAY AFTERNOON/S LONG TERM DISCUSSION HAD A VERY GOOD
DESCRIPTION AND HANDLE ON THE EXTENDED PERIODS. DID NOT DEVIATE MUCH
FROM THAT THINKING AS THERE WERE NO REAL SURPRISES IN THE EVENING
MODEL RUNS.

THERE ARE STILL TWO MAIN SYSTEMS TO FOCUS ON IN THE LONG TERM...THE
SNOW EVENT FOR LATE SATURDAY NIGHT THROUGH SUNDAY EVENING AND THE
SYSTEM CENTERED ON NEXT TUESDAY.

THE SUNDAY SNOW EVENT HAS BEEN VERY STEADY IN REGARD TO TIMING AND
AMOUNTS. SNOW TOTALS RANGE FROM 1-2 INCHES UP TOWARDS U.S. 10...TO
3-6 INCHES TOWARDS I-94. THE SNOW IS GENERATED VIA UPPER LEVEL
DIVERGENCE ASSOCIATED WITH A STRONG JET STREAK...LOW LEVEL
ISENTROPIC RESPONSE AND A WEAK FRONTAL ZONE. MODELS HAVE BEEN
CONSISTENT WITH AMOUNTS FROM RUN TO RUN AND MODEL TO MODEL...SO
CONFIDENCE IN THE SATURDAY NIGHT THROUGH SUNDAY NIGHT SNOW IS FAIRLY
HIGH.

FOCUS THEN SHIFTS TO A LOW THAT DEVELOPS IN THE LEE OF THE ROCKIES
IN SOUTHEAST COLORADO ON MONDAY. THE LOW MOVES NORTHEAST TOWARDS THE
GREAT LAKES AND SHOULD SPREAD SNOW INTO SOUTHWEST LOWER MICHIGAN
LATE MONDAY NIGHT. A MIXTURE OF PRECIPITATION THEN APPEARS POSSIBLE
TUESDAY AND TUESDAY NIGHT AS A GOOD SOUTHERLY FLOW OF MOISTURE AND
WARMTH IS TAPPED. 850MB TEMPERATURES ARE WARM ENOUGH FOR PLAIN RAIN
TUESDAY EVENING ALONG I-94 WITH BOTH THE GFS AND ECMWF SHOWING +5C.
AT THIS POINT HAVE OPTED TO INCLUDE A SNOW...SLEET AND FREEZING RAIN
MIX TO THE SOUTHERN HALF OF THE FORECAST AREA INCLUDING THE I-96
CORRIDOR.

THE TUESDAY SYSTEM IS STILL A LOW CONFIDENCE FORECAST IN TERMS OF
THE FINE DETAILS...HOWEVER THE GFS AND ECMWF HAVE CONVERGED ON THE
SYSTEM SLIDING BY THE AREA ON TUESDAY. THERMAL STRUCTURES ARE
SIMILAR AS WELL. DEPTH AND TRACK OF THE LOW ARE WHAT WE NEED TO
FOCUS ON NOW. THE LOW IS NOT AS DEEP AS PAST RUNS. THE ECWMF IS
STILL SHOWING A 997MB LOW PASSING THROUGH NORTHEAST INDIANA.
PRECIPITATION TOTALS ARE ON THE ORDER OF 0.30 TO 0.60 INCHES.
HEAVIER SNOW SWATH WILL LIKELY BE LOCATED ACROSS THE FORECAST
AREA...AS WILL A POTENTIAL MIX.

OVERALL A FAIRLY ACTIVE PERIOD WITH MODERATING TEMPERATURES. DEEP
ARCTIC AIR IS GONE IN THE LONG TERM AND IS REPLACED BY SOUTHWEST
FLOW AND TEMPS CLOSER TO NORMAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 713 AM EST THU FEB 26 2015

MVFR CEILINGS AND VISIBILITIES REMAIN ACROSS MOST OF THE TAF
SITES AT 12Z. SOME IFR IS INTERSPERSED FROM KGRR OFF TO THE SOUTH
AND EAST THROUGH 15Z. KMKG REMAINS VFR...WHERE THE SNOW HAS MISSED
OVERNIGHT.

THE SNOW SHOULD PEEL AWAY TO THE SOUTHEAST THROUGH THE COURSE OF
THE MORNING...ENDING BY 16Z. CONDITIONS SHOULD TURN VFR AT ALL OF
THE TAF SITES BY MIDDAY AS WELL. SOME BROKEN VFR CEILINGS WITH
BASES AROUND 3500FT MAY HANG ON FOR A GOOD DEAL OF THE AFTERNOON
ALONG I-94.

THROUGH THE COURSE OF THE AFTERNOON AND EVENING SKIES SHOULD
CLEAR. OVERNIGHT SOME VFR LAKE EFFECT CLOUDS WITH BASES AROUND
3500FT SHOULD PUSH BACK IN TO KMKG AND KGRR.

NORTHEAST WINDS AROUND 10 KNOTS THIS MORNING WILL SHIFT NORTH THIS
AFTERNOON.

&&

.HYDROLOGY...
ISSUED AT 310 PM EST WED FEB 25 2015

RIVER LEVELS ARE HOLDING STEADY WELL BELOW BANKFULL WITH ONLY MINOR
FLUCTUATIONS AT SEVERAL SITES. RIVER SURFACES ARE MOSTLY TO ENTIRELY
ICE/SNOW COVERED AND FLOW UNDERNEATH THE ICE DOES NOT APPEAR TO BE
IMPEDED BY ICE JAMS AT ANY GAUGE SITE CURRENTLY. THE RISK OF
FLOODING WILL REMAIN RATHER LIMITED UNTIL A WARM UP OR SIGNIFICANT
RAINFALL COMES AROUND.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...DUKE
AVIATION...DUKE
HYDROLOGY...CAS