Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 271915
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
314 PM EDT MON OCT 27 2014

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

.SYNOPSIS...
ISSUED AT 314 PM EDT MON OCT 27 2014

VERY MILD AIR FOR LATE OCTOBER STANDARDS WILL HOLD IN ACROSS THE
AREA THROUGH TONIGHT. A COLD FRONT WILL APPROACH THE AREA OVERNIGHT
TONIGHT AND HELP TO BRING SHOWERS AND A FEW STORMS TO THE AREA LATE
TONIGHT AND EARLY ON TUESDAY. CONDITIONS WILL DRY OUT ON TUESDAY AND
TEMPERATURES WILL BEGIN TO FALL BEHIND THE COLD FRONT.

A FEW RAIN SHOWERS WILL COME BACK FOR WEDNESDAY AS COLDER AIR MOVES
IN. TEMPERATURES WILL STRUGGLE TO GET TO 50 ON WEDNESDAY. EVEN
COLDER AIR WILL COME IN FOR THE END OF THE WEEK. A FEW SNOWFLAKES
MAY MIX IN WITH RAIN SHOWERS THURSDAY NIGHT AND FRIDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 314 PM EDT MON OCT 27 2014

TWO PERIODS OF SENSIBLE WEATHER TO DEAL WITH IN THE SHORT TERM.
FIRST ONE IS FOR THE TONIGHT INTO TUE TIME FRAME FOR PCPN/CONVECTIVE
CHCS...AND SECOND ONE IS COLD POOL AND LAKE EFFECT CHCS FOR WED.

MOST OF THE AREA IS NOW IN THE WARM SECTOR WITH TEMPS SNEAKING ABOVE
70 AT MANY LOCATIONS. ALL OF THE ELEVATED CONVECTION FROM EARLIER
HAS SHIFTED NE OF THE CWFA AS THE SFC WARM FRONT HAS REACHED A LINE
FROM ROUGHLY PENTWATER TO NORTH OF ALMA AS OF 1830Z THIS AFTERNOON.
WE ARE IN A RELATIVE MIN WITH REGARDS TO THE LLJ AND MOISTURE
TRANSPORT IN THE WAKE OF THE MAX THIS MORNING AND ANOTHER MAX THAT
IS HEADING OUR WAY FOR LATE THIS EVENING AND OVERNIGHT TONIGHT.

WE CONTINUE TO EXPECT RAIN CHCS TO INCREASE SIGNIFICANTLY DURING THE
OVERNIGHT PERIODS TONIGHT AND LAST INTO THE FIRST HALF OF TUE. SOME
SEMBLANCE OF AN UPPER WAVE ACROSS MO WILL MOVE NE INTO THE AREA
LATER THIS EVENING. ANOTHER 50+ KNOT LLJ NOSING UP INTO THE AREA
WILL STRENGTHEN THE MOISTURE TRANSPORT AND DEVELOP MORE SHOWERS AND
STORMS AHEAD OF THE FRONT. THIS MOVES IN AFTER 00Z TONIGHT...AND
EXITS BY 12Z TUE. WE WILL HAVE SHOWERS AND STORMS LAST INTO THE
FIRST PORTION OF TUE AHEAD OF THE FRONT COMING INTO THE MOIST AIR.

SEVERE THREAT LOOKS QUITE LIMITED WITH ANY STORMS THAT WILL FORM
TONIGHT. INSTABILITY IS THE BIGGEST LIMITING FACTOR WITH ALMOST NO
SFC BASED INSTABILITY AND LIMITED ELEVATED INSTABILITY. THE MAIN
THREAT WOULD BE WIND WITH THE STRONG LLJ ALOFT NEARBY WITH ANY
STRONGER SHOWER OR STORM THAT MIGHT TAP IT. INSTABILITY IN THE -10C
TO -30C LAYER IS QUITE LIMITED...SO LARGE HAIL LOOKS VERY UNLIKELY.

WE SHOULD SEE SKIES CLEAR OUT DURING THE LATE MORNING AND AFTERNOON
HOURS AS THE FRONT PASSES THROUGH THE AREA. WE WILL BECOME UNDER THE
INFLUENCE OF THE DRY SLOT AS THE JET STREAK MOVES DIRECTLY OVERHEAD
TUE AFTERNOON.

WE WILL SEE STRATOCU THEN MOVE BACK IN LATER TUE NIGHT AND FOR THE
DAY ON WED. THE UPPER COLD POOL WILL ROTATE BACK IN OVER THE AREA
ALONG WITH A SECONDARY SURGE OF LOW LEVEL COLD AIR NEAR THE SFC. THE
UPPER FLOW WILL BECOME CYCLONIC ON WED AND H850 TEMPS WILL DROP TO
AROUND -3 TO -4C OVER LAKE MICHIGAN. A FEW INSTABILITY SHOWERS WILL
BE POSSIBLE EVERYWHERE...WITH SOME LAKE ENHANCEMENT IN THE NW FLOW
AREAS WITH SUFFICIENT OVER LAKE INSTABILITY IN PLACE. RAIN SHOWERS
SHOULD END BY WED NIGHT AS THE FLOW ALOFT BECOMES ANTI-CYCLONIC AND
A SUBSIDENCE INVERSION AROUND 5K FT PER FCST SOUNDINGS SHOULD CAP
THE VERTICAL DEVELOPMENT OF THE CLOUDS.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 314 PM EDT MON OCT 27 2014

THE SUREST PART OF THE FORECAST UPDATE IS THE COLDER AIR THAT WILL
BE SINKING SOUTH THROUGH THE WEEK. THE UNCERTAINTY STILL LINGERS
WITH THE LATE WEEK SYSTEM THAT COULD BRING US SOME OF OUR FIRST
SNOWFLAKES OF THE SEASON FRIDAY.

THE PERIOD WILL START OUT SLIGHTLY BELOW NORMAL THEN TEMPERATURES
TAKE A DIVE ON FRIDAY. GUIDANCE HAS CONTINUED TO TREND IN A COOLER
DIRECTION WITH H8 TEMPS GOING FROM -2C/-4C IN THE LAST COUPLE OF
DAYS TO -7C/-10C. ONE OF THE ISSUES TO TACKLE IS THE TIMING OF THE
INTRUSION AS WE GET INTO FRIDAY MORNING. IT SEEMS THAT GFS WANTED TO
LAG BEHIND THE EURO A BIT...BRINGING COLD AIR IN LATER IN THE
MORNING AS WHERE EURO WAS SEVERAL HOURS QUICKER. THE SYSTEM THAT IS
ANTICIPATED TO MOVE INTO THE REGION IS STILL SHOWN TO REMAIN A
WEAKER SYSTEM AS IT TRACKS SOUTHEAST THROUGH THE NORTH CENTRAL
PLAINS. AS THIS SYSTEM APPROACHES THE GREAT LAKES AND UPPER LEVEL
TROUGH TAKES SHAPE ON A NORTHEAST TO SOUTHWEST AXIS THROUGH SOUTHERN
CANADA. THERE IS ANOTHER MORE PRONOUNCED SHORTWAVE ASSOCIATED WITH
THIS TROUGH THAT SLIDES SOUTHEAST...AND MAY PHASE WITH THE SYSTEM
SLIDING DOWN FROM THE NORTH CENTRAL PLAINS. GUIDANCE SEEMS TO DIFFER
NOT JUST ON TIMING BUT ALSO ON PLACEMENT OF THE JET CORE...WHICH
TRIES TO DIG THIS TROUGH A LIT DEEPER AND STRONGER AS IT HEADS
EASTWARD.

THE QUESTION TO ANSWER AS THINGS CONTINUE TO IRON THEMSELVES OUT
THROUGH THE WEEK WOULD BE HOW MUCH MOISTURE WOULD BE AVAILABLE AS
THE COLD AIR INVADES. IT STILL LOOKS AS IF SHOWERS WILL MIX WITH OR
CHANGE TO SNOW EARLY FRIDAY MORNING. THE SYSTEM QUICKLY EXITS EAST
DURING THE DAY FRIDAY WITH DRIER AIR AND MUCH COLDER TEMPERATURES.
HIGHS WILL LIKELY BE SET VERY EARLY FRIDAY WITH FALLING TEMPS
THROUGH THE DAY.

BEYOND FRIDAY...THINGS QUIET DOWN AS HIGH PRESSURE BUILDS IN AND
RIDGING SLIDES IN FROM THE WEST.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 140 PM EDT MON OCT 27 2014

I EXPECT NEARLY CLEAR SKIES MOST OF THE AFTERNOON WITH SOUTH WINDS
GUSTING TO 25 KNOTS AT TIMES. THE FRONTAL CLOUD BAND MOVES IN LATE
IN THE EVENING. AN AREA OF SHOWERS AND ISOLATED THUNDERSTORMS WILL
CROSS THE TAF SITES BETWEEN 06Z AND 12Z NEAR MKG TO 10Z TO 16Z BY
JXN. COULD BE BRIEF IFR CONDITIONS WITH MODERATE RAIN SHOWERS AND
LOW CIGS JUST AHEAD OF THE FRONT. ONCE THE FRONT COMES THROUGH THE
DRY SLOT SHOULD CLEAR OR NEARLY CLEAR THE SKY BUT IT WILL BECOME
BREEZE.

&&

.MARINE...
ISSUED AT 314 PM EDT MON OCT 27 2014

NO CHANGES TO THE MARINE HEADLINES ISSUED EARLIER TODAY. LATEST
MARINE OBS SHOW WINDS ARE JUST SHORT OF CRITERIA SO FAR THIS
AFTERNOON...BUT CLOSE ENOUGH TO MAINTAIN THE HEADLINES. WINDS WILL
PICK UP AGAIN THROUGH TONIGHT AS ANOTHER CORE OF WIND MOVES IN...AND
THEN ON TUE AS COLDER AIR SURGES IN BEHIND THE FRONT. WINDS WILL
REMAIN UP THROUGH EARLY WED BEFORE COMING DOWN LATER WED.

&&

.HYDROLOGY...
ISSUED AT 1149 AM EDT MON OCT 27 2014

THE OVERALL TREND THIS WEEKEND HAS BEEN TO GRADUALLY STEP BACK ON
PRECIP TOTALS. IT SEEMS THAT THE CHANCES FOR ANY HIGHER TOTALS
IS LOW AND WOULD BE THE OUTLIER. I SUPPOSE SOME LOCALIZED AREAS
WOULD EXCEED HALF AN INCH OR SO IF AFFECTED BY THUNDERSTORMS
TONIGHT...JUST AS THEY HAD IN NORTHERN SECTIONS OF THE FORECAST
AREA THIS MORNING. THIS SHOULD NOT LEAD TO ANY FLOODING ISSUES.
RIVERS ARE ALREADY RUNNING WELL WITHIN THEIR BANKS. WITH RECENT
DRY WEATHER ANY INCOMING PRECIP WOULD JUST BE BENEFICIAL AT THIS
POINT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EDT WEDNESDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...JAM
AVIATION...WDM
HYDROLOGY...JAM
MARINE...NJJ





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