Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 012339
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
739 PM EDT SAT AUG 1 2015

.NEAR TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 317 PM EDT SAT AUG 1 2015

HIGH IMPACT WEATHER POTENTIAL: A FEW THUNDERSTORMS THROUGH
TONIGHT...GUSTY WINDS POSSIBLE WITH ANY STORMS THAT DEVELOP.

PATTERN SYNOPSIS/EXPECTED EVOLUTION: PARADE OF SHORT WAVE TROUGHS
AROUND LARGE HUDSON BAY GYRE CONTINUES WITH ONE WAVE SLIDING EAST OF
THE AREA THIS AFTERNOON AND ANOTHER UPSTREAM WAVE PROGGED TO MOVE
NORTH OF SUPERIOR TONIGHT.  THIS SECOND WAVE WILL PLAY A KEY ROLE IN
PUSHING A COLD FRONT INTO THE NORTHERN LAKES ON SUNDAY.

PRIMARY FORECAST CHALLENGES: EVOLUTION OF LINGERING DAYTIME
CONVECTION INTO EARLY EVENING.  POTENTIAL DEVELOPMENT OF SHOWER/TSTM
AFTER MIDNIGHT OVER WESTERN PARTS OF THE AREA UNDER INCREASING
WARM ADVECTION PATTERN.

LATE AFTERNOON/TONIGHT...LINGERING DIURNAL ACTIVITY MAINLY CLOSER TO
LAKE HURON SHOULD DISSIPATE EARLY AS INSTABILITY WANES AND MESO-
SCALE LAKE CIRCULATIONS/LOW LEVEL CONVERGENCE DIMINISHES.

TONIGHT...SHORTWAVE PASSING NORTH OF SUPERIOR WILL HELP TO INDUCE
LOW LEVEL WARM AIR ADVECTION AND ISENTROPIC UPGLIDE.  BEST LOW LEVEL
JET INITIALLY WILL FOCUS CONVECTION OVER IOWA/MINNESOTA/WRN
WISCONSIN...WITH THIS ACTIVITY GRADUALLY SHIFTING EAST INTO THE
WESTERN LAKES TOWARD 12Z AS LOW LEVEL SOUTHWEST FLOW STRENGTHENS.
INCREASING ELEVATED INSTABILITY DEVELOPING AS WELL WITH INCREASING
THREAT OF SHOWERS/STORMS AFTER 08-09Z...ESPECIALLY WEST OF US-131 IN
NORTHERN LOWER.

&&

.SHORT TERM...(SUNDAY THROUGH TUESDAY)
ISSUED AT 317 PM EDT SAT AUG 1 2015

...UNSETTLED WITH A RISK FOR BENEFICIAL RAINFALL THEN TURNING
COOLER...

HIGH IMPACT WEATHER POTENTIAL:  RISK FOR SEVERE THUNDERSTORMS
ACROSS LOWER MICHIGAN SUNDAY.

PATTERN SYNOPSIS/ANTICIPATED EVOLUTION:  BROAD LOW AMPLITUDE UPPER
TROUGH OVER THE NE QUADRANT OF THE CONUS WILL SHARPEN BY EARLY IN
THE UPCOMING WORK WEEK AS A SHORT WAVE DROPS SEWD...AND A STRONGER
UPPER LOW EVENTUALLY TAKES SHAPE OVER EXTREME NRN ONTARIO. AN
ASSOCIATED SURFACE WAVE WILL BRING A RISK FOR SHOWERS AND STORMS TO
THE REGION SUNDAY AND SUNDAY NIGHT /SOME OF THESE STORMS COULD BE
SEVERE/. IN THE WAKE OF THIS SYSTEM...COOLER AIR WILL OVERSPREAD THE
GREAT LAKES MONDAY AND TUESDAY AS AFOREMENTIONED UPPER TROUGH HOLDS
FIRM. THIS WILL ALSO MAINTAIN A RISK FOR SCATTERED SHOWERS.

SUNDAY AND SUNDAY NIGHT...PREVIOUSLY REFERENCED H5 SHORT WAVE
INITIALLY OVER FAR NRN MN EARLY SUNDAY WILL DROP SEWD INTO THE WRN
GREAT LAKES DURING THE DAY. THIS WILL BE ASSOCIATED WITH DECENT
UPPER HEIGHT FALLS...AND AN IMPRESSIVE SURFACE WAVE THAT IS FORECAST
TO CROSS THE REGION BY SUNDAY NIGHT. WSW LLJ IS EXPECTED TO SUPPORT
ONGOING CONVECTION EARLY SUNDAY /POSSIBLY AN MCS/ SOMEWHERE OVER THE
WRN GREAT LAKES /WRN LOWER MI?/. THE USUAL QUESTIONS WILL THEN COME
INTO PLAY FOR THE REST OF THE DAY...NAMELY WILL CONVECTION SUSTAIN
ITSELF SUNDAY MORNING AS IT MOVES INTO THE AREA...AND WHAT IMPACT
WILL THE CONVECTION AND/OR ITS DEBRIS HAVE ON DESTABILIZATION LATER
IN THE DAY? ADDITIONALLY...MODELS NOT IN GOOD AGREEMENT REGARDING
PLACEMENT OF WARM FRONT EXPECTED TO SLOWLY LIFT NE ACROSS THE
REGION. GFS PUSHES WARM FRONT WELL NORTH TOWARD THE TIP OF THE
MITT...WHILE NAM KEEPS FRONT OVER CENTRAL LOWER. THIS WILL IMPACT
AREAS THAT DESTABILIZE...AS WELL AS LOW LEVEL SHEAR. IN SPITE OF
THESE UNCERTAINTIES...MODEL SOUNDINGS SUPPORT MLCAPES AROUND 2000
J/KG OVER SRN PARTS OF FORECAST AREA...AS H5 WINDS INCREASE TO
AROUND 50 KTS BY LATE AFTERNOON. UPSHOT...EXPECT A COUPLE ROUNDS OF
THUNDERSTORMS SUNDAY INTO SUNDAY EVENING BEFORE SURFACE FRONT
PASSES. STRONG TO LOCALLY SEVERE STORMS NOT OUT OF THE QUESTION
/SOUTH OF PETOSKEY-ALPENA LINE/ WITH DAMAGING STRAIGHT LINE WINDS
LIKELY TO BE THE MAIN THREAT.

MONDAY AND TUESDAY...LOW LEVEL CAA EXPECTED...AS UPPER TROUGH
SETTLES IN ACROSS THE REGION. IN FACT...H8 TEMPS ARE FORECAST TO
DROP TO AROUND +5C OVER THE FAR NRN GREAT LAKES BY LATE TUESDAY
/PERHAPS SUPPORTING SOME SUBTLE LAKE INFLUENCES/. WITH SAID UPPER
TROUGH...WEAK RIPPLES IN THE FLOW CONTRIBUTING TO SURFACE
TROUGHINESS/CONVERGENCE...AND DAYTIME HEATING...A SMALL RISK FOR
SHOWERS SEEMS WARRANTED BOTH DAYS FOR PARTS OF FORECAST AREA. HIGHS
EACH DAY WILL RANGE FROM THE 60S NORTH TO THE LOW-MID 70S SOUTH.

&&

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 317 PM EDT SAT AUG 1 2015

THE MAIN ISSUE FOR THE EXTENDED PERIOD WILL BE THE CHANCE FOR
WEEKEND RAIN CHANCES. RIGHT NOW...SOLUTIONS RUN THE GAMUT FROM DRY
TO A DECENT RAIN. THE PROBLEM LIES IN THE HANDLING OF THE PERSISTENT
H5 RIDGING OUT WEST. THERE SEEMS TO BE OVERALL AGREEMENT WITH A
SHORTWAVE MOVING THROUGH...OR NEAR...OUR REGION OVER THE WEEKEND.
DIFFERENCES LIE WITH THE AMPLITUDE OF RIDGING TO OUR WEST. MORE
AMPLIFIED RIDGING WILL HAVE THE BETTER FORCING FURTHER
NORTH...BRINGING RAIN TO THE CWA. LESS AMPLIFIED SOLUTIONS RESULT IN
THE SHORTWAVE TRACKING FURTHER SOUTH...AND WITH IT THE RAIN CHANCES.
CURRENT BLENDED GUIDANCE IS FAVORING CHANCE POPS OVER THE WEEKEND AS
SOME OF THE UNCERTAINTIES GET IRONED OUT. I AM NOT SOLD ON THIS JUST
YET...AS THE MORE AMPLIFIED H5 RIDGE SOLUTIONS SEEM A BIT OVERDONE.
WILL NOT REMOVE THE CHANCE POPS YET...BUT EXPECT SOLUTIONS WILL
BEGIN TO MERGE WITH THE MORE FAVORABLE FORCING TO OUR SOUTH
RESULTING IN A DRY WEEKEND FOR US. TEMPS LOOK TO BE BELOW NORMAL
THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 739 PM EDT SAT AUG 1 2015

SHRA/TSRA LIKELY SUNDAY.

COLD FRONT MOVING ACROSS THE DAKOTAS WILL MOVE INTO NORTHERN MI
LATE SUNDAY. SHRA/TSRA ARE EXPECTED TO DEVELOP AHEAD OF THE FRONT
IN THE UPPER MS VALLEY TONIGHT. THESE WILL MOVE EAST
OVERNIGHT...AND COULD REACH NORTHERN LOWER MI AT OR A BIT AFTER
DAWN. BETTER CHANCE FOR PRECIP WILL BE LATER IN THE DAY...AFTER
MORNING ACTIVITY HAS FADED OUT AND ALLOWED FOR SOME
DESTABILIZATION. DIFFICULT TO NARROW THE DOWN THE BEST RELATIVELY
NARROW WINDOW FOR TSRA CHANCES IN THE TAFS. FOR NOW...HAVE TSRA
MENTIONED FOR A 4-HR WINDOW IN THE AFTERNOON/EARLY EVENING.

LIGHT W TO SW SURFACE WINDS TONIGHT...INCREASING SUNDAY MORNING
AND VEERING W VERY LATE IN THE DAY. LLWS OVERNIGHT AT PLN...WITH
STRONGER WSW WINDS OFF THE SURFACE.

&&

.MARINE...
ISSUED AT 317 PM EDT SAT AUG 1 2015

TONIGHT/SUNDAY...TIGHTENING GRADIENT WITH INCREASING SOUTHWEST
WINDS LATE TONIGHT INTO SUNDAY IN ADVANCE OF APPROACHING COLD
FRONT NORTH OF SUPERIOR. STRONGEST WINDS LIKELY FROM GRAND
TRAVERSE LIGHT NORTHWARD TO THE STRAITS DUE TO COASTAL
CONVERGENCE. SMALL CRAFT ADVISORIES ISSUED FOR NORTHERN PARTS OF
LAKE MICHIGAN AND LAKE HURON STARTING LATE TONIGHT THROUGH SUNDAY.
WINDS SHIFT AROUND TO THE NORTHWEST SUNDAY NIGHT AFTER FROPA WITH
ADDITIONAL HEADLINES POSSIBLY NEEDED...ESPECIALLY LAKE HURON.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT SUNDAY FOR LHZ345-
     347>349.

LM...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT SUNDAY FOR LMZ323-341-
     342-344>346.

LS...NONE.
&&

$$

NEAR TERM...KEYSOR
SHORT TERM...SMITH
LONG TERM...ALM
AVIATION...JAZ
MARINE...KEYSOR



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