Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 040730
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
330 AM EDT SAT JUL 4 2015

.NEAR TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 330 AM EDT SAT JUL 4 2015

HIGH IMPACT WEATHER POTENTIAL...SCATTERED T-STORMS MID-AFTERNOON
TO MID-EVENING SE SECTIONS.

HIGH PRESSURE HAS BEEN DISPLACED SLIGHTLY SOUTHWARD TO SOUTHERN
LOWER MI. 1005MB LOW PRESSURE IS MOVING EAST FROM THE SOUTHERN TIP
OF JAMES BAY. SEVERAL TROFS EMANATE FROM THIS LOW...ONE MOVING
ACROSS EASTERN UPPER MI AND JUST E OF GRB. THE PRIMARY THERMAL-
MOISTURE BOUNDARY EXTENDS ROUGHLY ALONG THE SOUTH SHORE OF SUPERIOR.
THE LAST OF THE DIURNAL SHRA ENDED BETWEEN MIDNIGHT AND 2
AM...THOUGH A HEALTHY AMOUNT OF MID CLOUDS REMAIN OVER NORTHERN
LOWER MI. POTENTIAL FOR DIURNAL CONVECTION IS AGAIN THE MAIN
CONCERN.

TODAY...COLD FRONT WILL GRADUALLY SLIP SOUTH ACROSS NORTHERN LOWER
MI. GOOD AGREEMENT AMONG NAM/RAP13 RUNS THAT A WAVE WILL DEVELOP
ALONG THE FRONT BY MID-AFTERNOON OVER THE SE QUARTER OF THE FORECAST
AREA. THIS WAVE FORMS THANKS TO A RIPPLE IN THE NW FLOW
ALOFT...COMBINED WITH LAND-LAKE THERMAL RESPONSES TO HEATING. BUT
WILL LOCALIZED CONVERGENCE IN THE SE RESULT IN CONVECTION? THE NAM
AND NSSL WRF AGGRESSIVELY ARGUE YES...THE RAP NO. THE NAM IS
OVERDONE WHEN IT COMES TO IT/S SURFACE PARCEL (AS IS COMMON)...78/59
IS MORE REASONABLE THAN 82/62. BUT EVEN AFTER MAKING THAT
ADJUSTMENT...21Z MLCAPE SHOULD REACH NEAR 1100J/KG. WARMER TEMPS
ABOVE 640MB RESULTS IN A FAIRLY SKINNY CAPE (LI -1/-2)...BUT NOT
WARM ENOUGH TO IMPOSE A CAP. GIVEN LAKE BREEZES WILL SERVE AS A
TRIGGER...AM REASONABLY CONFIDENT THAT SOME SPOTTY CONVECTION WILL
OCCUR IN SE SECTIONS. WILL GO WITH A SCT POP AFTER 19Z/3 PM...S OF
APN AND NEAR/E OF HTL. WIND FIELDS UP TO 700MB ARE LESS THAN
15KT...SO SHEAR AND SVR POTENTIAL IS NOT IMPRESSIVE.

ELSEWHERE...A PARTLY TO MOSTLY SUNNY 4TH IS EXPECTED. HIGHS WILL
RANGE THRU THE 70S TO NEAR 80F.

TONIGHT...SHRA/TSRA CHANCES WILL LINGER INTO MID-EVENING IN THE FAR
SE...PARTS OF IOSCO/ARENAC/STANDISH COUNTIES. HOWEVER...NW SURFACE
WINDS/COOL ADVECTION WILL BE ESTABLISHED VERY SHORTLY AFTER 00Z.
WILL KEEP THINGS DRY AFTER 02Z/10PM. SPOTTY SURFACE BASED CONVECTION
SHOULD FIRE LATE THIS AFTERNOON IN NORTHERN WI...BUT THIS ACTIVITY
WILL NOT BE ABLE TO CROSS CHILLY LAKE MI THIS EVENING. COULD SEE
SOME RESIDUAL CLOUD COVER REACH NW LOWER MI...BUT OTHERWISE SKIES
WILL CLEAR TONIGHT. MIN TEMPS WILL RANGE THRU THE 50S.

&&

.SHORT TERM...(SUNDAY THROUGH MONDAY NIGHT)
ISSUED AT 330 AM EDT SAT JUL 4 2015

HIGH IMPACT WEATHER: NONE

FORECAST CHALLENGE: FRONTAL PASSAGE MONDAY.

(7/5)SUNDAY...THE SYSTEM IN THE PLAINS BEGINS TO DEEPEN, ALLOWING
THE COLD FRONT TO STALL. THERE WERE WARNING SIGNS THE LAST FEW DAYS
THAT THIS WOULD HAPPEN. THE HIGH MOVES EAST OF THE UPPER GREAT LAKES
AND ALLOWS THE MOISTURE AND WARMTH TO BUILD S THE RETURN FLOW GET
GOING. LOOKS LIKE A GOOD PORTION, OR MAYBE EVEN MOST OF N MICHIGAN
WILL GET INTO THE LOWER 80S. OVERNIGHT, THE FRONT APPROACHES THE
UPPER GREAT LAKES, BUT THE SFC LOW BEGINS TO MOVE UP THE FRONT. SO
THAT THE FRONT LIES ON A LINE FROM THE SOUTHERN TIP OF JAMES BAY
DOWN TO KMSP. THIS HOLDS THE SYSTEM UP BY ABOUT 6-12 HOURS INTO
MONDAY.

(7/6)MONDAY...AGAIN, THE MODELS HAVE HAD TO HOLD THE SYSTEM UP AS
THE SFC LOW CONTINUES TO DEEPEN AND HEAD UP ACROSS LAKE SUPERIOR.
ONCE IT DOES, THEN THE COLD FRONT BEGINS TO RUSH INTO THE FORECAST
AREA, AROUND 00Z. OF COURSE, AS THE SFC LOW AND THE 500 MB SHORTWAVE
CONTINUE NE, THE FRONT DOES HAVE THE MOMENTUM, BUT LOOKS LIKE IT
LOSES ITS DYNAMIC LIFT. THE FRONT LOOKS TO BE THROUGH THE FORECAST
AREA OVERNIGHT, TO EARLY TUESDAY MORNING.

&&

.LONG TERM...(TUESDAY THROUGH FRIDAY)
ISSUED AT 330 AM EDT SAT JUL 4 2015

EXTENDED (TUESDAY THROUGH FRIDAY)...THINK THAT THE GFS`S FASTER
PROGRESSION WITH THE SYSTEM BY 18Z LOOKS BETTER AS THE WAVE LIFTS
OUT OF THE UPPER GREAT LAKES AND INTO QUEBEC. HIGH PRESSURE BUILDS
INTO THE REGION AND LOOKS TO KEEP THE REGION DRY THROUGH AT LEAST
THURSDAY MORNING. THURSDAY AND FRIDAY, THE MODELS ARE AT ODDS WITH
THE GFS BRINGING RAIN THROUGH THE REGION, WHILE THE ECMWF IS DRY. SO
FAR THE CONSENSUS IS FOR SLIGHT CHANCE POPS, SO REALLY, IT BEGINNING
TO LOOK DRY THROUGH THE END OF THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 129 AM EDT SAT JUL 4 2015

VFR.

A SHRA PASSING NEAR APN...WILL MOVE OFF TO THE EAST AND/OR
DISSIPATE IN THE NEXT HOUR. COLD FRONT WILL SLOWLY DROP ACROSS
NORTHERN LOWER MI TODAY...PERHAPS SPAWNING SOME SHRA/TSRA LATE
THIS AFTERNOON. HOWEVER...ANY THREAT FOR PRECIP SHOULD STAY IN NE
LOWER MI...SOUTH OF APN. SO SHOULD NOT TROUBLE THE TAF SITES. SOME
PERIODS OF MID CLOUDS AND/OR DIURNAL CU...BUT NO INTERRUPTIONS TO
VFR CONDITIONS.

LIGHT WINDS WILL GIVE WAY TO LAKE BREEZES THIS AFTERNOON.

&&

.MARINE...
ISSUED AT 330 AM EDT SAT JUL 4 2015

HIGH PRESSURE CENTERED OVER SOUTHERN LOWER MI WILL MAINTAIN WEAK
WINDS AND WAVES THRU TONIGHT. SMALL CRAFT ADVISORIES ARE NOT
ANTICIPATED. SCT PM T-STORMS ARE EXPECTED TODAY IN NE LOWER
MI...SOUTH OF ALPENA. SOME OF THESE COULD BRING BRIEF GUSTY WINDS
TO THE NEARSHORE WATERS.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...JAZ
SHORT TERM...JSL
LONG TERM...JSL
AVIATION...JAZ
MARINE...JAZ


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