Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 221737
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
137 PM EDT FRI AUG 22 2014

.SYNOPSIS...
ISSUED AT 349 AM EDT FRI AUG 22 2014

AN AREA OF LOW PRESSURE OVER THE UPPER MISSISSIPPI VALLEY AND ITS
WARM FRONT ARE TRIGGERING A FEW SHOWERS OVER NORTHERN MICHIGAN
THIS MORNING. A FEW THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AS
THE HEAT AND HUMIDITY BUILD INTO THE UPPER GREAT LAKES. HIGH
PRESSURE WILL BUILD BACK INTO THE UPPER GREAT LAKES TONIGHT AND
THROUGH THE REST OF THE WEEKEND, BUT AN ISOLATED SHOWER OR
THUNDERSHOWER CAN/T BE RULED OUT FOR SATURDAY OR SUNDAY.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 349 AM EDT FRI AUG 22 2014

STALLED FRONT EXTENDS FROM CENTRAL WI TO FAR SOUTHERN LOWER MI. THIS
BOUNDARY DIVIDES VERY SOUPY AIR TO ITS SOUTH (DEW POINTS 70F OR
ABOVE...IN SOME PLACES WELL ABOVE) FROM OUR AIRMASS (DEW POINTS
MAINLY LOW/MID 60S). THIS FRONT IS ABOUT AS FAR NORTH AS IT WILL GET
IN THE NEAR-TERM...IT WILL RETREAT SOUTH THIS AFTERNOON AND CONTINUE
TO DO SO TONIGHT. IN ADDITION...ANY SOUTHERLY LOW LEVEL JET WILL
REMAIN WELL WEST OF THE MS RIVER...SO INFLOW FROM THE WARM SECTOR IS
MEAGER TO NIL. BUT THERE ARE SMALL CHANCES FOR PRECIP OVER THE NEXT
18 HOURS (ABOVE AND BEYOND THE FACT THERE ARE RETURNS ON THE RADAR
NOW).

TODAY...FOR THIS MORNING...EARLIER DEEP CONVECTION OUT IN NW/N
CENTRAL WI HAS FALLEN APART. BUT WE HAVE WEAK SOUTHERLY FLOW AT
950MB...AND WEST AT 850MB...BOTH OF WHICH ARE RESULTING IN POSITIVE
THETA-E ADVECTION. SOME SPOTTY SHRA HAVE BEEN FORMING ALONG THE
OUTER EDGE OF THE (WEAK) INSTABILITY PLUME...FROM THE WI/UPPER MI
BORDER E TOWARD BEAVER ISL. THIS ACTIVITY WAS LARGELY VIRGA A FEW
HOURS AGO...BUT HAS INTENSIFIED (AS THE MODELS HAVE BEEN
SUGGESTING). WILL OF COURSE CONTINUE TO MONITOR...FOR NOW PLANNING
ON A SCATTERED TO ISOLATED SHRA MENTION FOR MOST OF NORTHERN
LOWER AND THE STRAITS AREA THRU MID/LATE MORNING...AND NO MENTION
OF THUNDER.

THIS AFTERNOON...THERE IS A PLUME OF CIRCA-70F SURFACE DEW POINTS IN
PARTS OF SW LOWER (GRR/MKG/HOLLAND AND POINTS SOUTH). SHORT-TERM
MODELS (ESPECIALLY THE NAM) ARE INCLINED TO DRAW THIS SLOWLY
NORTHWARD...WITH NEAR-70F DEW POINTS IN THE RAW MODEL OUTPUT NEAR
TVC/CAD. COMBINED WITH LAKE BREEZE DEVELOPMENT AND WHATEVER HEATING
WE CAN MUSTER...RESULTS IN OVER 1K J/KG OF SBCAPE AND THE
DEVELOPMENT OF SPOTTY DEEP CONVECTION. THIS IS SUSPECT IN A COUPLE
OF WAYS. SURFACE WINDS WILL BE LIGHT SE-ERLY...NOT FROM THE SOUTH.
RAW NAM OUTPUT LOOKS TOO MOIST (THIS IS HARDLY A SURPRISE)...WITH
NUMERICAL MET GUIDANCE SHOWING DEW POINTS NEAR 66F AT BOTH TVC/CAD
TODAY. BUT AN 80/66 PARCEL IS STILL SPITTING OUT 900J/KG OF MLCAPE
WITH NO CAP. GOING FORECAST ALREADY HAD A CHANCE OF SHRA/TSRA IN SW
SECTIONS IN THE AFTERNOON...AND THAT STILL LOOKS REASONABLE.

CONSIDERABLE MOISTURE IN SEEN IN THE 900-700MB LAYER FOR MOST OF
NORTHERN MI...MOST OF THE DAY. THE MAIN EXCEPTION IN EASTERN UPPER
MI...PARTICULARLY IN THE AFTERNOON. OTHER THAN THAT...WE WILL SEE
MORE CLOUDS THAN SUN (BUT WILL SEE SOME SUN). THAT WILL LIMIT MAX
TEMPS TO THE UPPER 70S/NEAR 80F.

TONIGHT...CONVECTION THREAT WILL LINGER INTO MID-EVENING IN THE SW.
SURFACE-BASED INSTABILITY THEN WANES WITH LOSS OF HEATING. AND ANY
CHANCE OF ELEVATED INSTABILITY DISAPPEARS AS THE FRONT RETREATS
FURTHER SOUTH (700-500MB LAPSE RATES ARE LESS THAN 5.5 C/KM).
NUMERICAL GUIDANCE IN EASTERN UPPER (ESPECIALLY THE MET/NAM) WANTS
TO BRING IN A POP...RELATED TO LEFTOVER DIURNAL CONVECTION IN
NORTHERN ONTARIO THAT DRIFTS SOUTH. THAT IS A SCENARIO WE DON/T
TYPICALLY SEE...USUALLY ANYTHING THAT BUBBLES UP N AND NE OF THE
SAULT STAYS UP THERE. SO WILL KEEP THE REST OF THE NIGHT DRY. EVEN
PARTIAL CLEARING WILL PROVIDE A FAVORABLE SET-UP FOR FOG
FORMATION...AND WILL AMP UP WORDING FOR SAME. MIN TEMPS WILL BE
MAINLY WITHIN A FEW DEGREES OF 60F.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 349 AM EDT FRI AUG 22 2014

OVERVIEW...THE RIDGE IN THE MIDWEST WILL BEGIN TO AMPLIFY OVER THE
UPPER GREAT LAKES THROUGH THE WEEKEND. OUT IN THE WEST, THERE IS A
500 MB TROUGH THAT IS MOVING ONSHORE. THIS FEATURE WILL BEGIN TO
FLATTEN OUT THE FLOW OVER THE UPPER GREAT LAKES, ESPECIALLY ON THE
ECMWF. AM A LITTLE LESS CONFIDENT ON THE BEGINNING AND ENDING OF THE
PRECIPITATION AS THE MODELS DIFFER, NOT ONLY ON MONDAY FOR THE
BEGINNING, BUT ON WEDNESDAY NIGHT/THURSDAY FOR THE END. IT DOES LOOK
LIKE SHOWERS AND SOME THUNDERSTORMS WILL BE AROUND FOR
TUESDAY/WEDNESDAY. SO THE FORECAST WILL LOOK LIKE THIS...

(8/23)SATURDAY...ORIGINALLY, THE POPS WERE IN THE AFTERNOON, BUT IT
LOOKS LIKE THE MODELS HAVE THE BEST MOISTURE AND INSTABILITY NEAR A
FOCUSED ZONE IN THE MORNING. BY THE AFTERNOON, THE MODELS ALL DRY
THINGS OUT FOR THE AFTERNOON. SO HAVE THE 20 POPS IN NW LOWER IN THE
MORNING, AND THEN NOTHING FOR THE AFTERNOON.

SATURDAY NIGHT...THE GFS IS THE ONLY MODEL TO GET SOMETHING ANYWHERE
NEAR NW LOWER IN THE EVENING WITH MOISTURE ALONG THE LEADING EDGE OF
THE WARM ADVECTION. WILL PUT 20 POPS IN THE FOR EVENING ON THE
LEADING EDGE AS THE WARMTH FROM THE AFTERNOON, MAY LEAD TO SOMETHING
TRYING TO MOVE INTO THE REGION, BUT THINK THAT THE 500 MB RIDGE
HOLDS THINGS TO THE WEST IN WISCONSIN AS THE ECMWF/NAM SOLUTIONS
SUGGEST.

(8/24)SUNDAY...CONFIDENCE IN THE GFS IS A LITTLE LOWER THAN THE
ECMWF AS THE GFS HAS BACKED OFF THE PRECIPITATION GETTING INTO THE
FORECAST AREA ON SUNDAY. GOING FORECAST IS A 20% (SLIGHT CHC) IN THE
MORNING AS THE GFS HAS RAIN ON THE DOORSTEP OF NW LOWER (AGAIN), AND
THE NAM HAS THE SAME MOISTURE AXIS MOVING THROUGH ABOUT THE SAME
TIME, BUT WITH NO RAIN. THE ECMWF KEEPS THE PRECIPITATION WELL WEST,
AS THE UPPER AIR FEATURES ARE SHARPER FURTHER TO THE WEST. SO AGAIN
THE AFTERNOON LOOKS TO BE DRY AS THE FOCUS ON THE MODELS RETREATS
WEST WITH THE FOCUS IN WISCONSIN. OVERNIGHT, THE HAVE KEPT THE POPS
LOW AS THE GFS TRIES TO BRING THE RAIN INTO E UPPER AND NW LOWER.
THE ECMWF STILL HAS THIS FEATURE IN W UPPER, AS DOES THE NAM. SO
WILL KEEP THE POPS LOW AS WE SEE WHERE THE SYSTEM IS BY 12Z.

EXTENDED (MONDAY THROUGH THURSDAY)...(8/25)MONDAY...MODELS BEGIN TO
BRING THE COLD FRONT THROUGH THE REGION, HOWEVER, THE GFS IS REALLY
WET. SINCE THE MASS FIELDS (PRESSURE/TEMPERATURE/MOISTURE) OF THE
GFS AND THE ECMWF LOOK SIMILAR, THINK THAT THE ECMWF LOOKS MORE
REASONABLE, AND WOULD NOT BE SURPRISED BY THE LOOKS OF THIS THAT WE
GET INTO A RIP OFF ZONE AS THE SFC LOW MOVES INTO JAMES BAY AND THE
NEXT DEVELOPING SYSTEM IN THE SOUTHERN PLAINS DIVIDE THE ENERGY.
(8/26)TUESDAY...THINK THAT THE GFS IS OVERDONE WITH THE STORMS
BREAKING OUT ON THE COLD FRONT. AS MENTIONED THE ENERGY IS DIVIDED
BETWEEN THE TWO SYSTEMS, AND THINK THAT THE CHANCES ARE LOW. THINK
THAT THE NOTHING HAPPENS. WILL KEEP THE LOW CHANCES, UNTIL THE GFS
PULLS THIS FEATURE OUT. (8/27)WEDNESDAY...THE FLAT JET OF THE ECMWF
OR THE SLOWLY MOVING 500 MB TROUGH? EITHER WAY, IT WILL PROBABLY
RAIN. WILL KEEP THE THUNDER IN THE FORECAST FOR NOW, BUT IF THE
ECMWF IS RIGHT WE WILL BE ON THE NORTHERN SIDE OF THE RAIN SHIELD,
WITH NO THUNDER. OVERNIGHT, IT LOOKS LIKE THE THUNDER SHOULD STOP AS
THE MAIN SYSTEM IS EAST OF US. (8/28)THURSDAY...GFS SHOWS ISOLATED
INSTABILITY SHOWERS, THE ECMWF DRY. WILL GO DRY AS THINK THAT THE
500 MB TROUGH IS TOO AMPLIFIED, AND THINK THAT THE THE ECMWF DRY
SOLUTION IS MORE LIKELY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 134 PM EDT FRI AUG 22 2014

SIMPLE PERSISTENCE WILL DO FOR THIS TAF CYCLE. SHOWERS WILL PASS BY
TO OUR SOUTH OVER THE NEXT 24 HOURS AND BEYOND...WITH CURRENT
MVFR/IFR CLOUD DECK STEADILY MIXING THE REMAINDER OF THIS
AFTERNOON. LIGHT WINDS AND AMPLE LOW LEVEL MOISTURE WILL ONCE
AGAIN LEAD TO FOG/STRATUS DEVELOPMENT TONIGHT...EXPECTED TO BE
MOST WIDESPREAD AT KAPN WHERE LIGHT WINDS WILL REMAIN OFF THE COOL
LAKE WATERS. IMPROVING CONDITIONS SATURDAY MORNING.

&&

.MARINE...
ISSUED AT 349 AM EDT FRI AUG 22 2014

A LIGHT EAST WIND WILL PREVAIL OVER THE NEXT COUPLE OF
DAYS...NORTH OF A FRONT IN THE SOUTHERN LAKES AND NORTHERN OHIO
VALLEY. WINDS/WAVES WILL REMAIN COMFORTABLY BELOW SMALL CRAFT
CRITERIA. HOWEVER...THE AIRMASS REMAINS HUMID...AND FOG WILL BE A
CONCERN...ESPECIALLY IN THE NIGHTS/MORNINGS.


&&

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

&&

$$

SYNOPSIS...JL
SHORT TERM...JZ
LONG TERM...JL
AVIATION...MSB
MARINE...JZ





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