Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 041531
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1131 AM EDT FRI SEP 4 2015

.UPDATE...
ISSUED AT 1107 AM EDT FRI SEP 4 2015

TODAY...DEEPER MOISTURE AXIS ROTATING NORTHWEST INTO NORTHERN
LOWER MICHIGAN THIS AFTERNOON...WHICH SHOULD KEEP THE
DRIZZLE/SHOWERS GOING. CLOUDS PRIMARILY OVER NORTHERN LOWER
/WITH SOME BREAKS CLOSER TO THE COASTS/...WITH A GOOD AMOUNT OF
SUNSHINE FOR EASTERN UPPER. SOME HINTS OF INSTABILITY THIS
AFTERNOON WITH 300-400 J/KG OF SKINNY CAPE ON FORECAST
SOUNDINGS...SO AN ISOLATED RUMBLE OF THUNDER POSSIBLE. CURRENT
FORECAST IN GOOD SHAPE AND FEW CHANGES NEEDED. SHOULD SEE A RAMP
UP IN PRECIPITATION OVER NORTHERN LOWER WITH DIURNAL HEATING.
POTENTIAL FOR HEAVY RAIN STILL THERE...GIVEN SLOW MOVEMENT OF
SHOWERS/STORMS. GIVEN THE THICK CLOUD COVER THROUGH THE I-75
CORRIDOR IN NORTHERN LOWER /CAN SEE ENHANCEMENT OF CLOUDS WITH
UPSLOPE INTO THE HIGHER TERRAIN ON SATELLITE/...WILL LOWER HIGH
TEMPS IN THIS AREA.

&&

.NEAR TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 413 AM EDT FRI SEP 4 2015

...SHOWER THREAT CONTINUE THROUGH TONIGHT...

HIGH IMPACT WEATHER POTENTIAL: LOCALLY HEAVY DOWNPOURS THROUGH
THIS EVENING.

PATTERN SYNOPSIS/FORECAST: MIDNIGHT SURFACE ANALYSIS SHOWS A 1012MB
LOW OVER SOUTHERN LOWER MICHIGAN...ALONG A FRONT THAT EXTENDS EAST
INTO THE LOWER GREAT LAKES...AND ARCS BACK AROUND SOUTHERN LAKE
MICHIGAN AND INTO THE UPPER MIDWEST.  SECONDARY BOUNDARY FROM
EASTERN LAKE SUPERIOR/FAR EASTERN UPPER MICHIGAN/NORTHERN LAKE HURON
INTO SOUTHWEST ONTARIO...WITH DRIER AIR TO THE EAST OF THIS
SECONDARY BOUNDARY WITH HIGH PRESSURE OVER QUEBEC.  UPPER LEVEL LOW
WAS SPINNING ACROSS LOWER MICHIGAN...WITH ANOTHER VORTICITY CENTER
NOTED IN WATER VAPOR IMAGERY DIGGING SOUTHEAST ACROSS SOUTHERN
WISCONSIN.  AXIS OF DEEP MOISTURE (PRECIPITABLE WATER VALUES AROUND
200 PERCENT OF NORMAL) OVER EASTERN LOWER MICHIGAN/LAKE HURON AND
ADJACENT SOUTHWEST ONTARIO...WITH DRIER AIR BORDERING LAKE SUPERIOR
TO THE WEST AND NORTH.  SPOTTY SHOWERS HAVE BEEN DEVELOPING WITHIN
THIS MOISTURE AXIS ASSOCIATED WITH LOW/MID LEVEL ISENTROPIC
ASCENT...WITH CLEARING SKIES ACROSS WESTERN/CENTRAL UPPER MICHIGAN/
NORTHERN WISCONSIN WITHIN AN AREA OF QG SUBSIDENCE.

UPPER LOW WILL CONTINUE TO SPIN ACROSS LOWER MICHIGAN THROUGH THE
NEAR TERM FORECAST PERIOD...WITH A WEAK SURFACE RESPONSE REMAINING
AS WELL.

PRIMARY FORECAST CONCERNS: OVERALL PRECIPITATION THREAT TODAY AND
TONIGHT.

TODAY...DEEP MOISTURE AXIS NOTED ABOVE IS EXPECTED TO ROTATE WEST
ACROSS NORTHERN LOWER MICHIGAN DURING THE DAY TODAY...WHICH AT THE
VERY LEAST SHOULD KEEP SCATTERED SHOWERS AND/OR SOME DRIZZLE GOING
AT THE ONSET OF THE FORECAST.  SKIES SHOULD REMAIN ON THE CLOUDY
SIDE TODAY...THOUGH SOME HINTS OF DIURNAL INSTABILITY DEVELOPING.
THIS ISN`T UNREASONABLE AS A DEEP MOIST ADIABATIC LAPSE RATE DOESN`T
TAKE MUCH HEATING TO GENERATE SOME INSTABILITY.  WHAT IS MORE
UNCERTAIN IS MAGNITUDE OF INSTABILITY...ESPECIALLY ACROSS EASTERN
UPPER WHERE NAM-WRF AND SREF PROBABILISTIC GUIDANCE (BEING OF LIKE
MIND) TRY TO CONVECT THIS AFTERNOON.  INITIAL THOUGHT IS THAT THIS
MAY BE A LITTLE OVERDONE...AND DON`T MIND KEEPING THE CURRENT
FORECAST OF DRY WEATHER ABOVE THE BRIDGE GOING FOR TODAY.  LATEST
RUN OF SPC STORM SCALE ENSEMBLE OF OPPORTUNITY ALSO LENDS SUPPORT TO
THIS IDEA.  SO WILL PLAY THE FORECAST WITH SCATTERED SHOWERS THIS
MORNING ACROSS NORTHERN LOWER AND INCREASING DIURNAL COVERAGE THIS
AFTERNOON ALONG THE POSSIBILITY OF SOME THUNDER.  GIVEN DEEP LAYER
MOISTURE AND OVERALL SLOW MOVEMENT THE POTENTIAL FOR LOCALLY HEAVY
DOWNPOURS WILL CONTINUE.  PROBABLY A DAMP DAY OVERALL WITH HIGH
TEMPERATURES IN THE 70S FOR THE MOST PART.

TONIGHT...SYSTEM STILL LINGERS ACROSS THE UPPER LAKES BUT LOOKS TO
BE OPENING UP...VEERING MID LEVEL FLOW MAY PUSH SOME LINGERING
SHOWERS INTO EASTERN UPPER THIS EVENING...BUT PRECIP THREAT MAY WIND
DOWN OVERNIGHT.  BUT THE POSSIBILITY OF MORE FOG/STRATUS WILL COME
INTO PLAY AS WELL FOR THE EARLY MORNING HOURS OF SATURDAY.

&&

.SHORT TERM...(SATURDAY THROUGH SUNDAY NIGHT)
ISSUED AT 413 AM EDT FRI SEP 4 2015

HIGH IMPACT WEATHER: SHOWERS AND THUNDERSTORMS PRODUCING HEAVY RAIN

PRIMARY FORECAST CHALLENGE: TIMING THE 500 MB LOW OUT OF THE UPPER
GREAT LAKES, AND THUS, THE RAIN SHOWER/THUNDERSTORM POTENTIAL.

(9/5)SATURDAY...MODELS CONTINUE A WEAKENED 500 MB SHORTWAVE TROUGH
OVER THE UPPER GREAT LAKES. THE GFS IS THE STRONGEST OF THE MODELS
WITH WIDESPREAD RAIN SHOWERS DURING MOST OF THE DAY, WITH LIGHT
AMOUNTS. HOWEVER, THIS MAKES IT MORE PROBLEMATIC AS THE MOISTURE IN
THE REGION REMAINS HIGH WITH THE PWAT EXPECTED TO REMAIN OVER 1.5"
THROUGH THE DAY. WIND FLOW IS WEAK IN THE 850 TO 500 MB LAYER WITH
THE 850 MB WINDS STRONGER THAN THE 500 MB WINDS (25 KNOTS VS. 10
KNOTS. THIS WILL GIVE A SLOW MOVEMENT TO THE STORMS. THE MODEL
SOUNDINGS SHOW A RELATIVELY UNSTABLE SOUNDING WITH SB CAPES OF 700
J/KG AND LITTLE CAPPING. WITH THE 500 MB TROUGH OVER THE REGION,
THEN DIURNAL HEATING, ESPECIALLY WITH LOWER 80S FOR HIGHS, WILL
EXPECT THAT SCATTERED SHOWERS AND THUNDERSTORMS WILL BEGIN WITH THE
RAIN LOCALLY HEAVY AS THE LOW WIND FLOW/HIGH MOISTURE CONTENT STORMS
DUMP OUT. HOWEVER, IT LOOKS LIKE THE TROUGH MOVES OUT AND THE NEXT
SYSTEM BEGINS TO SET UP. SO IN THE EVENING THERE WILL BE A LULL,
BEFORE THE NEXT WARM ADVECTION AREA KICKS OFF AFTER 06Z. THE GFS HAS
THIS FEATURE, WHILE THE ECMWF HOLDS THINGS OFF, SO FOR NOW HAVE SOME
LOW CHANCE POPS.

(9/6)SUNDAY...HOWEVER, IT LOOKS LIKE THAT ONCE THAT WARM FRONT IS
THROUGH THE REGION, THAT THE MORNING, AND PROBABLY THE AFTERNOON
TOO, WON`T SEE ANYTHING AS THE MODEL SOUNDINGS SHOW THAT THINGS MAY
BE CAPPED WITH NO OTHER FORCING MECHANISM TO BREAK THE CAP. IT IS
POSSIBLE THAT THERE COULD BE SOMETHING LATE IN THE AFTERNOON IN NE
LOWER, AS THE LAKE HURON LAKE BREEZE AND THE HEATING OVER THAT AREA
MAY KICK OFF A SHOWER OR TWO. HOWEVER, ONCE THE HEATING DIMINISHES
INTO THE EVENING, THEN THE FOCUS WILL BE ON THE COLD FRONT OVERNIGHT
BRINGING THE CHANCE OF THUNDERSTORMS.

&&

.LONG TERM...(MONDAY THROUGH THURSDAY)
ISSUED AT 413 AM EDT FRI SEP 4 2015

EXTENDED (MONDAY THROUGH THURSDAY)...PROBABLY ONE OF THE BIGGER
EVENTS IN NORTHERN MICHIGAN ON LABOR DAY LOOKS LIKE IT WILL BE
MARRED BY THE CHANCE OF THUNDERSTORMS AS THE COLD FRONT TAKES ITS
TIME TO MOVE THROUGH THE AREA. TUESDAY LOOKS WET AS THE ECMWF STALLS
THE FRONT OVER THE REGION, AS A SFC WAVE RIDES UP THE FRONT. THE GFS
HAS A SLOWER EVOLUTION OF THIS FEATURE DRYING THINGS OUT MONDAY
NIGHT, AND BRING RAIN IN LATE TUESDAY, INTO TUESDAY NIGHT. HOWEVER,
ONCE THE LOW MOVES NE OF THE UPPER GREAT LAKES, THE FRONT, AND THE
DRY AIR FOLLOWING IT PUSHES INTO THE REGION AND DRIES THINGS OUT FOR
WEDNESDAY, AND MAY BE THURSDAY. ALTHOUGH THERE ARE HINTS OF ANOTHER
500 MB WAVE LATE IN THE DAY ON THURSDAY ON THE ECMWF THAT COULD KICK
OFF ANOTHER ROUND OF RAIN, BUT WILL HOLD OFF ON THAT FOR NOW.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 746 AM EDT FRI SEP 4 2015

PERIODS OF MVFR/IFR CONDITIONS THIS MORNING IN LOW CLOUDS AND
FOG...MOSTLY MVFR/VFR FOR THIS AFTERNOON. FOG RETURNS TONIGHT WITH
IFR CONDITIONS.


&&

.MARINE...
ISSUED AT 413 AM EDT FRI SEP 4 2015

TODAY/TONIGHT...ONLY CONCERN FOR THE FIRST 24 HOURS OF THE FORECAST
WILL BE GUSTY EASTERLIES FUNNELING THROUGH THE STRAITS
REGION...COULD SEE SOME GUSTS OVER 20KTS AND THIS AREA MAY NEED TO
BE MONITORED FOR SMALL CRAFT CONDITIONS THROUGH THIS EVENING.

OUTLOOK...HEADLINE CONDITIONS NOT ANTICIPATED THROUGH SATURDAY
NIGHT.


&&

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

$$

UPDATE...KEYSOR
NEAR TERM...JPB
SHORT TERM...JSL
LONG TERM...JSL
MARINE...JPB



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