Area Forecast Discussion
Issued by NWS Gaylord, MI

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918
FXUS63 KAPX 171447
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1047 AM EDT SUN MAY 17 2015

.UPDATE...
ISSUED AT 1047 AM EDT SUN MAY 17 2015

...SOME SEVERE THUNDERSTORM POTENTIAL THIS AFTERNOON AND EVENING...

LOW LEVELS CONTINUE TO TURN OVER...AND SHOULD CONTINUE TO DO SO
THROUGH THE REMAINDER OF THIS MORNING AND EARLY AFTERNOON. THIS WILL
RESULT IN AT LEAST SOME POCKETS OF SUN...HELPING TEMPERATURES WARM
WELL UP INTO THE 70S/NEAR 80 DEGREES. THIS...ALONG WITH INCREASING
MOISTURE...WILL HELP DESTABILIZE THE ATMOSPHERE THIS AFTERNOON AND
EVENING...SETTING THE STAGE FOR THUNDERSTORM DEVELOPMENT. QUESTION
REALLY BECOMES ONE OF FORCING WITH REGARDS TO COVERAGE AND SEVERE
WEATHER POTENTIAL. DEFINITELY NOT A CLEAR CUT ANSWER TO THE
ABOVE...WITH ALL REAL DEEP LAYER FORCING EXPECTED TO REMAIN WEST OF
THE AREA CLOSER TO STRONG SHORTWAVE ROTATING THROUGH THE CENTRAL
PLAINS. OVERHEAD HEIGHTS BEGIN TO FALL LATE...AND WHEN COMBINED WITH
LEAD VORT LOBE ROTATING OUT OF MISSISSIPPI VALLEY/POSSIBLE LAKE
MICHIGAN FORCED VEERING OF LOW LEVEL WIND FIELDS...SHOULD BE ENOUGH
TO ENTICE SHOWER/STORM DEVELOPMENT LATER THIS AFTERNOON ACROSS THE
FAR SOUTHWEST. INSTABILITY NOT OVERWHELMING...WITH MODIFIED
SOUNDINGS SHOWING UPWARDS OF ONLY 800 J/KG OF MEAN LAYER CAPE...
STILL ENOUGH HOWEVER TO PROMOTE CONVECTION AND HELP MAINTAIN IT AS
IT PROPAGATES EAST ACROSS THE AREA THIS EVENING.

AS FOR SEVERE WEATHER POSSIBILITIES: LATEST SPC DAY HAS EXPANDED
SLIGHT RISK EAST INTO OUR FAR SOUTHWEST AREAS (TVC AND POINTS
SOUTH)...WHILE ALSO NUDGING MARGINAL PROGS A TOUCH EAST. CANNOT
ARGUE WITH SUCH...ESPECIALLY WITH MARGINAL SHEAR PROFILES EXPECTED
AS CONVECTION BEGINS. MAIN THREAT WOULD BE SEVERE WIND GUSTS AND
HAIL TO ONE INCH IN DIAMETER. THESE IMPACTS SHOULD REMAIN SCATTERED
AT BEST. HAVE ALREADY UPDATED ALL OUR HAZARDOUS WEATHER PRODUCTS TO
HEIGHTEN AWARENESS OF THIS POTENTIAL.

&&

.NEAR TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 330 AM EDT SUN MAY 17 2015

DEEP LOW PRESSURE WILL LIFT N/NE OUT OF THE PLAINS TODAY AND INTO
THE ARROWHEAD OF MINNESOTA BY LATE TONIGHT. WARM/MOIST AIR WILL RIDE
NORTHWARD INTO MICHIGAN IN ADVANCE OF THIS SYSTEM...WITH SURFACE
DWPTS SURGING INTO THE UPPER 50S IN ERN UPR MICHIGAN AND INTO THE
LOW TO MID 60S IN NRN LWR MICHIGAN. 850 MB THETA E RIDGE AND THE ERN
EDGE OF THE 850 MB LOW LEVEL JET LEANS INTO MICHIGAN LATER THIS
AFTERNOON AND ESPECIALLY THIS EVENING. DYNAMICS STRENGTHEN AS WELL
DURING THIS TIME IN RESPONSE TO THE ERN EDGE OF A 55 KT 500 MB JET
MAX NOSING INTO MICHIGAN. MUCAPE WILL APPROACH 2000 J/KG BY LATE
AFTERNOON...BUT WILL DIMINISH DURING THE EVENING AS THE SUN SETS AND
DIURNAL HEATING/INSTABILITY BEGINS TO WANE. CERTAINLY BETTER
DYNAMICS...INSTABILITY AND MOISTURE REMAIN WEST AND SOUTH OF OUR
CWA. HOWEVER...THE ERN EDGE OF ALL SVR WX INGREDIENTS MENTION ABOVE
POKES INTO OUR WRN CWA. THUS...CERTAINLY CANNOT RULE OUT THE
POSSIBILITY OF A FEW STORMS REACHING SVR LIMITS LATE THIS AFTERNOON
AND TONIGHT. THIS SCENARIO IS IN AGREEMENT WITH THE LATEST DAY 2 SPC
OUTLOOK WHERE WE HAVE A MARGINAL CHANCE OF SVR STORMS FOR LOCATIONS
ALONG AND WEST OF I-75 IN NRN LWR MICHIGAN.

HAVE MADE SOME MINOR UPWARD ADJUSTMENTS TO POPS FOR TODAY AND
TONIGHT...BUT OVERALL FLAVOR OF THE FORECAST WILL GO UNCHANGED. BEST
CHANCE FOR STORMS AND POSSIBLY A FEW STRONG/MARGINALLY SEVERE STORMS
WILL BE THIS EVENING WHEN ALL OF THE ABOVE INGREDIENTS COME
TOGETHER. WILL CONTINUE TO MENTION THIS WITHIN THE HWO. UNTIL
THEN...WE MAY SEE A FEW SCATTERED SHOWERS OR STORMS...BUT OVERALL
CONDITIONS WILL BE PARTLY TO MOSTLY CLOUDY AND WARM. AFTERNOON HIGHS
WILL WARM INTO THE 70S ACROSS UPPER MICHIGAN AND INTO THE UPPER 70S
AND LOWER 80S ACROSS LWR MICHIGAN. LOW TEMPS TONIGHT WILL DROP BACK
INTO THE 50S IN UPPER MICHIGAN AND INTO THE 60S FOR LWR MICHIGAN.

&&

.SHORT TERM...(MONDAY THROUGH TUESDAY NIGHT)
ISSUED AT 330 AM EDT SUN MAY 17 2015

HIGH IMPACT WEATHER: TUESDAY NIGHT LOW TEMPERATURES/FROST POTENTIAL
FOR N LOWER.

FORECAST CHALLENGE: HOW FAR WILL THE TEMPERATURES FALL TUESDAY
NIGHT.

(05/18)MONDAY...THE GFS/NAM STILL SHOWING A STRONG DRY SLOT MOVING
OVER THE REGION IN THE WARM SECTOR AT 850 MB, WHILE AT THE 700-500
MB LAYER ALL THE MODELS SHOW SIGNIFICANT DRYING LEADING THE 500 MB
LOW INTO THE REGION. THE QUESTION IS THEN, HOW MUCH MIXING FROM
ALOFT AND INTO THE BOUNDARY LAYER WILL THERE BE? BECAUSE IF THE
MIXING IS SIGNIFICANT ENOUGH AS THE GFS LETS ON, THEN THERE WILL BE
NO PRECIPITATION. NOW THAT THE 00Z ECMWF IS IN, AND IT TOO HAS
ELIMINATED THE RAIN FROM THE FORECAST AREA, SO WILL PULL WHAT POPS
THERE ARE AS THE MOISTURE WILL BE MINUSCULE FOR THE FRONT TO PRODUCE
ANYTHING. THEN AS THE COLDER AIR MOVES INTO THE REGION BY THE
EVENING, THE MOISTURE DEPTH WILL BE FAIRLY SHALLOW, AND AS THE 850
MB TEMPERATURES FALL DURING THE NIGHT, WILL EXPECT THAT THE
INSTABILITY WILL BE MINIMAL.

(05/19)TUESDAY...AS THE 500 MB LOW MOVES NORTH OF ANJ, WILL EXPECT
THAT SOME OF THE MOISTURE ASSOCIATED WITH IT WILL DROP INTO E UPPER.
THIS WILL KICK OFF SOME SHOWERS ESPECIALLY DURING THE AFTERNOON.
STARTING TO THINK THAT THE 850 MB TEMPERATURES ARE TOO COLD ON THE
ECMWF WITH THE -8C TEMPERATURES BY 00Z. IT SEEMS THAT WHILE IT CAN
BE COOL DURING THIS TIME OF YEAR, SOMETHING THIS COOL IS USUALLY
MORE ASSOCIATED WITH THE 500 MB LOW FARTHER NORTH IN CANADA, SO WILL
LEAN TOWARD THE GFS  WITH THE -4C TEMPERATURES AND MIX SOME SO OF
THE RAIN IN THE EVENING WITH SNOW. OVERNIGHT, THE SKY WILL CLEAR AS
THE MOISTURE PULLS OUT OF THE UPPER GREAT LAKES, AND WITH THE PATCHY
FROST AS MORE ISOLATED LOCATIONS CAN GET FROST IN N LOWER. HOWEVER,
IF THE WINDS THAT THE MODELS ARE SHOWING ARE RIGHT, THEN WE MAY BE
TOO "MIXY" FOR FROST FORMATION, BUT TEMPERATURES COULD GET INTO THE
LOWER 30S.

&&

.LONG TERM...(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 330 AM EDT SUN MAY 17 2015

EXTENDED (WEDNESDAY THROUGH SATURDAY)...WITH THE 500 MB LOW HAVING
MOVED TO THE EAST THE HEIGHTS AT 500 MB RISE A BIT, AND THEN HOLD
STEADY, AND SFC HIGH PRESSURE SITS OVER THE UPPER GREAT LAKES
THROUGH SATURDAY. TEMPERATURES BEGIN TO MODERATE HIGHS GETTING BACK
TO THE UPPER 60S, AND WOULDN`T BE SURPRISED IF THEY GET CLOSER TO
LOWER 70S CLOSER TO CLIMO.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY)
ISSUED AT 650 AM EDT SUN MAY 17 2015

RESIDUAL FOG/LOW STRATUS WILL MIX OUT THIS MORNING AS DAYTIME
HEATING CONTINUES TO RAMP UP. CHANCES OF SHOWERS AND
THUNDERSTORMS WILL STEADILY INCREASE THROUGHOUT THE DAY AND
ESPECIALLY TOWARD LATE AFTERNOON AND EVENING AS STRONG WAA AND
MOISTURE ADVECTION TAKE PLACE IN ADVANCE OF DEEP LOW PRESSURE
LIFTING TOWARD THE WRN GREAT LAKES REGION. CONDITIONS SHOULD BE
MAINLY VFR THRU THE DAY...BUT WILL DIMINISH TO MVFR TONIGHT AS
SHOWERS AND STORMS BECOME MORE NUMEROUS. LIGHT E/SE WINDS THIS
MORNING WILL STRENGTHEN A BIT TO AROUND 10 KTS DURING THE DAY AND
WILL THEN SHIFT TO THE SOUTH TONIGHT.


&&

.MARINE...
ISSUED AT 330 AM EDT SUN MAY 17 2015

CHANCES OF SHOWERS AND STORMS WILL STEADILY INCREASE TODAY INTO THIS
EVENING AHEAD OF DEVELOPING LOW PRESSURE LIFTING NE OUT OF THE
PLAINS TO THE ARROWHEAD OF MINNESOTA. WINDS AND WAVES WILL REMAIN
BELOW SCA CRITERIA THRU TONIGHT...BUT MAY APPROACH CRITERIA ON
MONDAY IN RESPONSE TO A TIGHTENING OF THE GRADIENT AS DEEP LOW
PRESSURE TRACKS THRU NRN MICHIGAN. AREAS OF FOG WILL CONTINUE TO BE
AN ISSUE FOR OUR NEARSHORE AREAS THRU TONIGHT. VSBYS SHOULD BEGIN TO
IMPROVE ON MONDAY AS DRIER AIR BEGINS TO PUSH INTO THE REGION...WITH
NOTICEABLY COOLER AIR ARRIVING MONDAY NIGHT AND TUESDAY.


&&

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

$$

UPDATE...MSB
NEAR TERM...MLR
SHORT TERM...JSL
LONG TERM...JSL
AVIATION...MLR
MARINE...MLR



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