Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 172241
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
641 PM EDT WED SEP 17 2014

.SYNOPSIS...
ISSUED AT 355 PM EDT WED SEP 17 2014

A COLD FRONT WILL PUSH THROUGH NORTHERN MICHIGAN TONIGHT WITH COOL
CANADIAN HIGH PRESSURE BUILDING INTO THE REGION IN ITS WAKE FOR THE
DAY ON THURSDAY.  MODERATING TEMPERATURES ARE EXPECTED ON FRIDAY AS
THIS HIGH PRESSURE SYSTEM BUILDS EAST AND ALLOWS SOUTHWESTERLY FLOW
TO DEVELOP ACROSS THE REGION.  A LOW PRESSURE SYSTEM MOVING THROUGH
THE GREAT LAKES REGION WILL BRING SHOWERS AND THUNDERSTORMS TO THE
AREA BEGINNING FRIDAY NIGHT AND CONTINUING THROUGH SATURDAY BEFORE
DRIER AIR ARRIVES TO END THE WEEKEND ON SUNDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 355 PM EDT WED SEP 17 2014

BROAD TROUGHINESS AND CHILLY AIR REMAINS ACROSS EASTERN CANADA AND
DOWN INTO THE GREAT LAKES/NEW ENGLAND REGION. EVEN HAS SOME SNOW
REPORTED AT CHAPLEAU ONTARIO...ABOUT 100 MILES NORTH OF SAULT SAINT
MARIE. AT THE SFC...ILL-DEFINED EAST-WEST COLD FRONT IS NOW
STRETCHED THROUGH THE STRAITS INTO NRN WISCONSIN AND SAGGING
SOUTHWARD. QUITE A BIT OF LOW-MID CLOUD COVER BEHIND THE FRONT AND A
FEW SPRINKLES SKIRTING CHIPPEWA COUNTY. BEHIND THAT...STRONG
CANADIAN HIGH PRESSURE AND (AS MENTIONED) SOME CHILLY AIR POISED
ACROSS SOUTH-CENTRAL CANADA.

TONIGHT...HIGH PRESSURE ACROSS SOUTH-CENTRAL CANADA WILL BUILD
QUICKLY ACROSS NRN MICHIGAN TONIGHT...PUSHING COLD FRONT AND SHALLOW
COLD AIR DOWN THROUGH LOWER MICHIGAN. ATTENDING NARROW BAND OF
LOW-MID CLOUD COVER WILL FOLLOW SUITE AND WILL ALSO SAG DOWN THROUGH
THE REGION. QUESTION IS...HOW MUCH CLEARING WILL WE REALIZE
OVERNIGHT.

EASTERN UPPER MICHIGAN PROBABLY HAS THE BEST SHOT. THERE IS QUITE A
BIT OF CLOUD COVER OVER ONTARIO TODAY...BUT MUCH OF WHICH IS HEATING
INDUCED AND SHOULD THIN OUT THIS EVENING. THAT... COMBINED WITH
NORTHEASTERLY DOWNSLOPE FLOW THAT WILL DEVELOP OFF ONTARIO
TONIGHT...THINK EASTERN UPPER MICHIGAN SHOULD BE ABLE TO CLEAR OUT
FAIRLY WELL WITH TEMPS FALLING INTO THE LOWER 30S. WITH THAT IN
MIND...WILL ISSUE FROST ADVISORY FOR CHIP/MACK COUNTIES AND LINE UP
WITH THE ONGOING FROST ADVISORY FOR AREAS FURTHER WEST.

A BIT MORE NEBULOUS ACROSS NRN LOWER MICHIGAN. THERE WILL BE A
PERIOD OF LOW-MID CLOUD COVER SAGGING DOWN INTO NRN LOWER MICHIGAN
THIS EVENING. BUT GIVEN THE INCOMING SHALLOW COLD AIRMASS AND NE
FLOW DEVELOPING OFF LAKE HURON...SUSPECT LOW CLOUDS WILL REMAIN
STUCK ACROSS MUCH OF NRN LOWER MICHIGAN OVERNIGHT...PARTICULARLY NE
LOWER MICHIGAN. SO NOT AS MUCH OF A FROST THREAT DOWN THIS WAY.

.LONG TERM...(THURSDAY THROUGH WEDNESDAY)
ISSUED AT 254 PM EDT WED SEP 17 2014

...CHILLY NIGHTS GIVE WAY TO A WARMER AND UNSETTLED SATURDAY...

HIGH IMPACT WEATHER POTENTIAL:

 *FROST/FREEZE POTENTIAL THURSDAY NIGHT AND AGAIN NEXT MONDAY AND
  TUESDAY NIGHTS
 *SLIGHT CHANCE OF SEVERE THUNDERSTORM ACTIVITY THIS WEEKEND WITH
  LOCALLY HEAVY RAIN POTENTIAL

PATTERN SUMMARY/FORECAST: A STRENGTHENING PACIFIC JET IS EVIDENT
EARLY THIS AFTERNOON ACROSS THE NORTH-CENTRAL PACIFIC...WHICH IS
DESTINED TO BREAK DOWN THE CURRENT RIDGE-TROUGH PATTERN ACROSS
NOAM.  THIS WILL BRIEFLY LEAD TO A FLATTER/MORE PROGRESSIVE PATTERN
ACROSS NOAM AS THIS JET ENERGY CRASHES INTO THE WEST COAST.
HOWEVER...AS DISCUSSED YESTERDAY...SHARPENING TROUGHING OVER THE
GULF OF ALASKA WILL RESULT IN BUCKLING OF THE DOWNSTREAM FLOW WITH
AN AMPLIFIED RIDGE-TROUGH PATTERN REDEVELOPING ACROSS NOAM BY THE
END OF THIS WEEKEND INTO EARLY NEXT WEEK. BEYOND THIS...AS WE REACH
THE END OF THIS FORECAST PERIOD NEXT WEEK...THE CENTRAL PACIFIC JET
IS AGAIN PROGGED TO GET A SIGNIFICANT BOOST AS HEIGHTS LOWER OVER
THE NORTH CENTRAL PACIFIC.  THIS HAS THE POTENTIAL TO BREAK DOWN THE
DOWNSTREAM RIDGE-TROUGH /WHICH WOULD BUILD HEIGHTS OVER MUCH OF
NOAM/...BUT GIVEN THE HOW AMPLIFIED THE INITIAL RIDGE-TROUGH COUPLET
IS...WILL NOT FOLLOW TOO FAR DOWN THIS ROAD /SEE 00Z GFS WHICH
MAINTAINS THE EASTERN TROUGH MUCH LONGER THAN THE ECMWF/.

PATTERN IMPLICATIONS: THIS SUGGESTS A TYPICAL SEPTEMBER
ROLLER-COASTER PATTERN ACROSS NORTHERN MICHIGAN...WITH INITIALLY
COOL TEMPERATURES BENEATH NORTHWEST FLOW ALOFT GIVING WAY TO
MODERATING TEMPS AND INCREASING HUMIDITY AS WE REACH THE WEEKEND.
THIS WILL YIELD A PERIOD OF UNSETTLED WEATHER FRIDAY NIGHT-SATURDAY
AS THE EASTERN TROUGH RELOADS WITH LOW PRESSURE TRACKING THROUGH THE
GREAT LAKES REGION.  A RETURN TO COOL CONDITIONS CERTAINLY IN STORE
TO START NEXT WEEK...WITH SOME MODERATION POSSIBLE TO END THE PERIOD
AS OVERHEAD TROUGHING BEGINS TO DEPART EAST.

MODEL AGREEMENT/CONFIDENCE: MODEL AGREEMENT ON THE LARGE-SCALE
EVOLUTION OF THE PATTERN IS QUITE STRONG THROUGH NEXT TUESDAY...WITH
THE GFS THEN SLOWER TO BREAK DOWN EASTERN TROUGHING BEYOND THIS.
CANNOT FULLY DISCOUNT THIS GIVEN HOW PERSISTENT THE EASTERN
TROUGHING HAS BEEN THIS SUMMER AND WILL TREND TO A CONSENSUS AT THIS
RANGE WITH SOMEWHAT REDUCED CONFIDENCE.

MIDDLE RANGE /THURSDAY THROUGH SATURDAY/:

THURSDAY: QUIET...BUT CHILLY CONDITIONS WITH HIGH PRESSURE CENTERED
OVER NORTHERN MICHIGAN ALLOWING FOR LIGHT/COOL NORTHEASTERLY FLOW TO
REMAIN ENTRENCHED DURING THE DAY.  TRAJECTORIES SUGGEST A VERY DRY
LLEVEL AIRMASS WITH DEWPOINTS LIKELY FALLING THROUGH THE 30S DURING
THE DAY.  GIVEN PROXIMITY OF THE HIGH AND ASSOCIATED LARGE SCALE
SUBSIDENCE...MIXING WILL BE RATHER SHALLOW WITH MIXED LAYER LIKELY
TO REMAIN BELOW H8.  THUS...T9S 3-6C SUGGEST HIGHS REMAINING IN THE
50S CWA-WIDE.  THIS PORTENDS A CHILLY NIGHT THURSDAY NIGHT WITH THE
PRIMARY CONCERN BEING DEVELOPING LLEVEL RETURN FLOW AS HIGH PRESSURE
SLIPS EAST INTO NEW ENGLAND WITH A FAIRLY STRONG GRADIENT GETTING
GOING OVERHEAD.  EXPECT THIS TO KEEP AREAS WEST OF US131 IN THE
UPPER 30S/LOWER 40S...WITH SIGNIFICANTLY COOLER TEMPERATURES TO THE
EAST OF THIS.  CONFIDENCE RATHER HIGH FOR FROST EAST OF THIS AREA
WITH A FREEZE POSSIBLE AS WELL. DEVELOPING RETURN FLOW MAY ALSO
IMPACT TEMPS/FROST CONCERNS ACROSS WESTERN CHIP/MACK.  WILL CONTINUE
TO HIGHLIGHT FROST/FREEZE RISK IN THE AFTERNOON HWO.

FRIDAY: RETURN FLOW IN FULL FORCE FOR THE DAY ON FRIDAY BETWEEN HIGH
PRESSURE CENTERED OVER NEW ENGLAND...AND AN APPROACHING COLD FRONT
OVER THE NORTHERN PLAINS.  ANTECEDENT AIRMASS IS RATHER DRY AND WITH
SOUTHERLY LLEVEL FLOW THROUGH THE DAY...MOISTURE ADVECTION WILL BE
RATHER SLOW.  THUS...WILL RESTRICT POPS TO LATE AFTERNOON FOR
NORTHWEST LOWER AND EASTERN UPPER...WITH DRY CONDITIONS PERSISTING
EAST OF THIS.

VERTICAL MIXING WILL AGAIN BE LIMITED DUE TO RAPID WARM ADVECTION
ALOFT.  REGARDLESS...WITH T9 WARNING TO 10-13C...WE SHOULD BE ABLE
TO PUSH HIGH TEMPERATURES INTO THE MID 60S.

MOISTURE/INSTABILITY AXIS FOLDS INTO NORTHERN MICHIGAN FRIDAY NIGHT
WITH PWATS PUSHING ABOVE 1.5 INCHES AND FREEZING LEVELS RISING ABOVE
12KFT.  WHILE QG FORCING FOR ASCENT IS WEAK...MOISTURE
TRANSPORT/ISENTROPIC ASCENT IN THE PRESENCE OF ELEVATED INSTABILITY
SHOULD HAVE NO PROBLEM ALLOWING UPSTREAM SHRA/TSRA ACTIVITY TO REACH
NORTHERN MICHIGAN OVERNIGHT.  EXPECT A MUCH MILDER NIGHT WITH LOWS
IN THE 50S/LOWER 60S.

SEVERE THREAT IS PRETTY MINIMAL OVERNIGHT GIVEN ONLY MODEST ELEVATED
INSTABILITY /~500 J/KG/.  HOWEVER...FLOW AT H5 OF 40-50KTS AT LEAST
PRESENTS A CONDITIONAL THREAT FOR ROTATING UPDRAFTS...WHICH COULD
LOCALLY INCREASE THE THREAT FOR HAIL.

SATURDAY: WAVE OF LOW PRESSURE DEVELOPS ALONG SOUTHWARD SAGGING COLD
FRONT...WITH A CONSENSUS TRACK JUST NORTH OF THE CWA DURING THE
DAY.  THIS OVERALL SOLUTION IS A WEAKER ONE THAN DISCUSSED YESTERDAY
WITH THIS TREND AGREED UPON BY BOTH THE ECMWF AND GFS. THIS PLACES
NORTHERN MICHIGAN DIRECTLY WITHIN THE DEEP MOISTURE AND ELEVATED
INSTABILITY PLUME TO START THE DAY...WITH THIS GRADUALLY SHIFTING
SOUTH WITH TIME.  HAVE TO BELIEVE THERE WILL BE SOME ONGOING
SHRA/TSRA ACTIVITY MOST LIKELY OVER NORTHERN LOWER TO START THE
DAY...WITH ITS ASSOCIATED CLOUDINESS LIKELY TO KEEP SURFACE HEATING
LIMITED.  GIVEN A POSITION AHEAD OF THE SURFACE COLD FRONT THROUGH
THE DAY...HOWEVER...SEE NO REASON WHY SHRA/TSRA DEVELOPMENT WILL NOT
CONTINUE THROUGH THE DAY WITH SPECIFIC EVOLUTION IMPOSSIBLE TO PIN
DOWN AT THIS RANGE.  FEEL THAT LIKELY POPS ARE WARRANTED THROUGH THE
DAY...AND WILL HAVE TO WAIT UNTIL WE GET CLOSER TO SATURDAY TO ADD
SOME MORE TEMPORAL DETAIL.

WINDS ALOFT CONTINUE TO SUPPORT A CONDITIONAL SEVERE THREAT...WHICH
WILL PRIMARILY BE GOVERNED ON HOW MUCH INSTABILITY WE CAN REALIZE
DURING THE DAY.  GIVEN THE DISCUSSION ABOVE...FEEL THAT THE THREAT
IS LIMITED...BUT IT CONTINUES TO BEAR WATCHING.

UNIDIRECTIONAL FLOW...DEEP WARM CLOUD DEPTHS AND PWATS AROUND 1.5
INCHES SUGGESTS AT LEAST A LOCALIZED HEAVY RAIN THREAT DURING THE
DAY.

WITH AGREEMENT ON A WEAKER /AND ALSO FASTER/ SURFACE LOW...EXPECT A
QUICKER FRONTAL PASSAGE SATURDAY NIGHT...AND HAVE PULLED BACK ON
POPS /PARTICULARLY AFTER MIDNIGHT/ AS A RESULT. EXPECT ANY THUNDER
THREAT TO END DURING THE EVENING...WITH PERHAPS JUST A FEW SHRAS
UNDER MOIST CYCLONIC FLOW AFTER MIDNIGHT. COLD ADVECTION WILL BE
DEVELOPING...BUT WITH CLOUDS/PRECIP AROUND LOWS WILL STILL BE RATHER
MILD...IN THE 50S.

LONG RANGE /SUNDAY THROUGH WEDNESDAY/:

SUNDAY-MONDAY: IMPRESSIVE COLD ADVECTION REGIME CONTINUES THROUGH
THIS PERIOD...WITH PRIMARY FORECAST CONCERNS TURNING TO LAKE EFFECT
RAIN SHOWER POTENTIAL.  WE MAY SQUEAK OUT A RELATIVELY DECENT DAY
SUNDAY...AS TEMPS ALOFT REMAIN GENERALLY MILD DESPITE ONGOING COLD
ADVECTION.  CYCLONIC FLOW AND GRADUALLY INCREASING LAKE SUPPORT /DUE
TO FALLING TEMPS ALOFT/ SUGGEST A FEW SHRAS...BUT HIGHS IN THE 60S
TO EVEN LOWER 70S OVER NORTHEAST LOWER APPEAR REASONABLE.  THE
WARMTH WILL BE TEMPERED BY WHAT WILL BE A RATHER STRONG WESTERLY
GRADIENT WITH WINDS 10-20 MPH WITH HIGHER GUSTS.  BY SUNDAY NIGHT-
MONDAY...TEMPS ALOFT LOOK TO BE SIGNIFICANTLY COOLER WITH SOME
POTENTIAL LAKE EFFECT RAIN SHOWERS GIVEN T8S FALLING TO 0C UNDER
CONTINUED NORTHWEST FLOW ALOFT...WITH HIGH TEMPERATURES LIKELY 10-15
DEGREES COOLER THAN ON SUNDAY.

TUESDAY-WEDNESDAY: QUIET WEATHER TO END THE FORECAST PERIOD WITH
NEARBY HIGH PRESSURE ON TUESDAY LIKELY TO PUSH EAST OF THE REGION BY
WEDNESDAY FAVORING DRY CONDITIONS AND SLOWLY MODERATING
TEMPERATURES.  GIVEN SOMEWHAT REDUCED FORECAST CONFIDENCE AT THIS
RANGE...WILL STAY CLOSE TO CONSENSUS TEMPERATURES WHICH...DESPITE
MODERATION...WILL REMAIN BELOW NORMAL THROUGH THE END OF THE
FORECAST PERIOD.

FROST/FREEZE CONCERNS WILL CONTINUE BOTH MONDAY-TUESDAY NIGHTS GIVEN
COOL/DRY AIRMASS IN PLACE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 636 PM EDT WED SEP 17 2014

ILL-DEFINED COLD FRONT WILL CONTINUE TO SAG DOWN THROUGH THE
REGION THIS EVENING TURNING WINDS SHARPLY TO THE NORTH. SHALLOW
COLD AIR BEHIND THE FRONT STILL EXPECTED TO LEAD TO EXPANDING
LOWER STRATUS DECK (MVFR) DOWN THROUGH NRN LOWER MICHIGAN THIS
EVENING...FURTHER REINFORCED ACROSS NE LOWER MICHIGAN THROUGH THE
NIGHT (ESPECIALLY IMPACTING APN/PLN TERMINAL SITES). AT TVC/MBL...
NORTHEASTERLY DOWNSLOPING WIND COULD ULTIMATELY SCATTER-OUT LOW
STRATUS DECK LATER TONIGHT...BUT WILL CONTINUE TO HEDGE MORE
PESSIMISTIC UNTIL STRONGER SUPPORT FOR SUCH CLEARING IS REALIZED.

ON THURSDAY...ANY REMAINING LOW STRATUS WILL MIX OUT BY LATE
MORNING AS LARGE HIGH PRESSURE SYSTEM AND SUBSTANTIALLY DRIER AIR
BUILD ACROSS NRN MICHIGAN. MAINLY EASTERLY WINDS 10 KNOTS OR LESS
THROUGH THE DAY BECOMING SE LATE.

&&

.MARINE...
ISSUED AT 123 PM EDT WED SEP 17 2014

...SMALL CRAFTS UNDER NORTHERLY FLOW TONIGHT...

SUMMARY: A STRONG AREA OF CANADIAN HIGH PRESSURE WILL BUILD IN
BEHIND A DEPARTING LOW TONIGHT...WITH MODERATE WESTERLY WINDS
SHIFTING NORTHERLY AND THEN SUBSIDING BY THURSDAY MORNING.  THIS
HIGH WILL MOVE EAST OF THE REGION ON FRIDAY ALLOWING GUSTY SOUTHWEST
WINDS TO DEVELOP AHEAD OF DEVELOPING LOW PRESSURE.  WINDS WILL
WEAKEN TEMPORARILY ON SATURDAY AS A COLD FRONT SETTLES INTO THE
REGION...BUT THEN STRENGTHEN AS HIGH PRESSURE BUILDS IN BEHIND THIS
FRONT ON SUNDAY.

HEADLINES: WESTERLY WINDS REMAIN JUST BELOW SMALL CRAFT CRITERIA
THIS AFTERNOON...WITH SMALL CRAFT CONDITIONS EXPECTED TONIGHT ALONG
MUCH OF THE COASTS OF LAKES MICHIGAN AND HURON.  THESE WILL END
THURSDAY WITH THE NEXT ROUND OF SMALL CRAFTS LIKELY NEEDED ON
FRIDAY-FRIDAY NIGHT AS GUSTY SOUTHWEST WINDS DEVELOP AHEAD OF AN
APPROACHING LOW PRESSURE SYSTEM.  WIDESPREAD SMALL CRAFTS WILL AGAIN
BE NEEDED SUNDAY INTO MONDAY AS A STRONG AREA OF HIGH PRESSURE
BUILDS INTO THE REGION FROM THE NORTH AND WEST BRINGING GUSTY
NORTHWEST WINDS.

THUNDERSTORMS: THUNDER CHANCES BEGIN FRIDAY NIGHT AND CONTINUE
THROUGH SATURDAY EVENING.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT THURSDAY FOR
     MIZ008-015.
LH...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR LHZ348-349.
LM...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR LMZ323-342-
     344>346.
LS...NONE.

&&

$$

SYNOPSIS...ARNOTT
SHORT TERM...ADAM
LONG TERM...ARNOTT
AVIATION...MSB
MARINE...ARNOTT






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