Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 192004
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
404 PM EDT SUN APR 19 2015

.NEAR TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 402 PM EDT SUN APR 19 2015

HIGH IMPACT WEATHER: MINIMAL

FORECAST CHALLENGE: TIMING OF THE RAIN TONIGHT.

OVERVIEW...WHILE THE MOISTURE HAS BEEN INCREASING ALONG THE LAKE
HURON SHORE AND INLAND OF NE LOWER, NW LOWER HAS BEEN DRYING OUT
WITH A GOOD PORTION OF THE AREA WEST OF I-75 HAVING FALLEN BELOW
25%. IN E UPPER, THE RH HAS BEEN BETWEEN 40% AND 45%. WHAT THIS IS
DOING IS DELAYING THE RAIN SHIELD`S TRAVEL NORTH, WHICH HAD JUST
MADE IT TO THE MICHIGAN/INDIANA BORDER AROUND 19Z. USING THE TIMING
TOOL ON AWIPS, IT LOOKS LIKE THE RAIN SHOULD GET TO THE M-55
CORRIDOR AROUND 23Z, M-72 AROUND 00Z, M-32 AROUND 01Z, AND THE
STRAIT BETWEEN 02Z AND 03Z.

DETAILS FOR TONIGHT...AS WAS MENTIONED, TRYING TO TIME THIS SYSTEM
WITH THE DRY AIR IN THE LOWER LEVELS IS MADDENING. THE QUESTION
ISN`T IF THE AIR WILL LEAVE, BUT WHEN AS THE SFC LOW WILL, AS IT
MOVES UP FROM THE MID-MISSISSIPPI VALLEY, OVERWHELM WITH DRY AIR
WITH ITS MOISTURE, AND ALLOW THE RAIN TO FALL ALL THE WAY TO THE
SFC. HOWEVER, ONCE THE RAIN STARTS, IT WILL FALL THROUGH THE NIGHT
AS THE SFC NORTH OVER THE WESTERN PART OF THE STATE BETWEEN 06Z AND
12Z. THIS SFC LOW AND ASSOCIATED 500 MB SHORTWAVE TROUGH AND 50 KNOT
SPEED MAX THAT MOVES OVER THE STATE, OVER THE WARM FRONT. WITH THE
PWAT AROUND 1.0" OVERNIGHT OVER THE FORECAST AREA, WILL EXPECT
THAT A DECENT STEADY RAIN WILL RESULT.

&&

.SHORT TERM...(MONDAY THROUGH WEDNESDAY)
ISSUED AT 402 PM EDT SUN APR 19 2015

...SHOWERY/COOL/UNSETTLED THROUGH MIDWEEK...

HIGH IMPACT WEATHER POTENTIAL: MINIMAL.

PATTERN SYNOPSIS/FORECAST: WELL-DEFINED SPLIT FLOW PATTERN FROM THE
END OF LAST WEEK NOW CONSOLIDATING AS NORTHERN BRANCH SHORT WAVE
TROUGH DIGS SOUTHEAST FROM WESTERN CANADA AND SCOOPS UP PESKY
SOUTHERN BRANCH VORTEX THAT HAS BEEN SPINNING ACROSS THE GREAT
BASIN/SOUTHERN ROCKIES SINCE THE MIDDLE OF LAST WEEK.  POSITIVE
PACIFIC TELECONNECTIONS LEADING TO A MORE AMPLIFIED PATTERN (BIG
TROUGH EAST OF THE DATELINE WITH +PNA RIDGING ALONG THE WEST COAST
OF NORTH AMERICA.  THIS CONSOLIDATING CENTRAL NORTH AMERICAN TROUGH
WILL BECOME THE PREDOMINANT WEATHER FEATURE THIS WEEK AS IT TAKES UP
RESIDENCE WITH REX BLOCKING ALONG THE WEST COAST...WITH AN UPPER LOW
EVENTUALLY PARKING ITSELF OVER THE GREAT LAKES BY MIDWEEK.

SOUTHERN BRANCH DISTURBANCE LOOKS TO COME OUT IN TWO PIECES
MONDAY...WHILE CLOSED CIRCULATION ALOFT DEVELOPS OVER NORTHWEST
ONTARIO/UPPER MIDWEST.  UPPER LOW THEN SETTLES OVER LAKE SUPERIOR
TUESDAY AND HANGS IN THROUGH MIDWEEK.  AT THE SURFACE...LEAD
SOUTHERN BRANCH SHORT WAVE TROUGH HAS AN ASSOCIATED SURFACE LOW OVER
THE MID MISSISSIPPI VALLEY THAT IS FORECAST TO DEEPEN AND LIFT NORTH
INTO LOWER MICHIGAN BY MONDAY MORNING...PROBABLY BELOW 990MB WHICH
IS PRETTY SIGNIFICANT BY MID-APRIL STANDARDS.  THIS LOW WILL PULL
COOLER AIR INTO MICHIGAN STARTING MONDAY NIGHT...CYCLONIC FLOW
LINGERS INTO MIDWEEK.

PRIMARY FORECAST CONCERNS: VARYING PRECIPITATION CHANCES THROUGH
MIDWEEK...AS WELL AS PRECIPITATION TYPE.

MONDAY...12Z SOUNDINGS AND GOES SOUNDER IMAGERY SHOWS A NICE SURGE
OF MOISTURE COMING UP ACROSS THE SOUTHEASTERN STATES (1.00-1.50 INCH
PRECIPITABLE WATER) WHICH IS PUSHING A LARGE ARE OF RAIN NORTHWARD
ACROSS THE OHIO VALLEY...AND EVENTUALLY INTO MICHIGAN TONIGHT/MONDAY
MORNING.  THIS WILL PUSH THROUGH THE FORECAST AREA MONDAY MORNING
(PERHAPS FAIRLY QUICKLY) WITH MID LEVEL DRYING (POSSIBLY TAPERING
OFF TO A PERIOD OF DRIZZLE).  SURFACE LOW TRACKS ACROSS NORTHERN
LOWER MONDAY MORNING...BEHIND THAT A LINGERING BAND OF DEFORMATION/
FRONTOGENETIC PRECIPITATION WILL ROTATE IN FROM THE WEST DURING THE
AFTERNOON HOURS.  IN ADDITION...COULD SEE SOME CONVECTIVE PRECIP
CLOSE TO THE SOUTHEAST PORTION OF THE FORECAST AREA DURING THE LATE
MORNING/AFTERNOON WITH SOME ELEVATED INSTABILITY (TQ INDICES
POTENTIALLY IN THE 16-20C RANGE NEAR LOW LEVEL THETA-E RIDGE) AND
SECOND PIECE OF SOUTHERN BRANCH ENERGY SWINGING NORTHEAST ACROSS THE
LOWER PENINSULA.  MORE LIKELY THIS ACTIVITY WOULD OCCUR ACROSS THE
THUMB INTO LAKE HURON...BUT MAY BE CLOSE.  WILL NOT TRY AND VARY
PRECIP PROBABILITIES IN THE FORECAST GRIDS TO ACCOUNT FOR TIMING OF
VARIOUS WAVES OF PRECIPITATION (AS IT WILL BE WRONG ANYHOW)...WITH A
GENERIC HIGH LIKELY/CATEGORICAL POP THROUGH THE DAY SUFFICIENT FOR
NOW. AS LONG AS INITIAL AREA OF RAIN SCOOTS NORTH QUICKLY MONDAY
MORNING... NOT EXPECT A LOT OF RAINFALL IN THE 12Z-00Z TIME FRAME
(UNLESS CONVECTION CAN CLIP FAR EASTERN ZONES DURING THE AFTERNOON)
WITH FORECAST 12H QPF UNDER 0.25 INCH THOUGH COULD BE HIGHER ACROSS
EASTERN UPPER/FAR NORTHEAST LOWER GIVEN THE ABOVE CAVEATS.  TRACK OF
THE LOW RIGHT ACROSS LOWER MICHIGAN WILL LEAD TO SOME TRICKY
TEMPERATURE FORECASTS...IN GENERAL COOLER WEST AND WARMER EAST WITH
FALLING TEMPERATURES DURING THE MID/LATE AFTERNOON AS WINDS SWITCH
AROUND TO A MORE WESTERLY COMPONENT.

WHAT REMAINS OF DEFORMATION PRECIP BAND EXPECTED TO LIFT NORTHEAST
ACROSS NORTHERN MICHIGAN MONDAY EVENING...AFTER THAT MAY BE ON THE
QUIET SIDE OVERNIGHT AND WILL CONFINE POPS TO THE EVENING HOURS.
PRECIP TYPE MAY BE IN QUESTION ACROSS EASTERN UPPER AS DEPTH OF
SURFACE BASED WARM LAYER SHRINKS.  AS NORTHERN BRANCH SHORT WAVE
TROUGHS START GETTING INVOLVED IN THE FORECAST SCENARIO CAN`T RULE
OUT SOME ADDITIONAL SHOWERS DEVELOPING OVERNIGHT INTO TUESDAY
MORNING BUT NOT CONVINCED THE PROBABILITY RISES TO A SUFFICIENT
LEVEL TO INCLUDE IN THE FORECAST...WILL LEAVE IT OUT AND MAINTAIN
CONTINUITY.

TUESDAY...DEEP LAYER CYCLONIC FLOW ACROSS THE UPPER LAKES SPELLS
UNSETTLED AND NOT WARM WEATHER FOR TUESDAY.  DEEP MOISTURE WILL
ROTATE AROUND THE SOUTH SIDE OF THE UPPER LOW...AND COOL
TEMPERATURES ALOFT (AT OR BELOW -30C/500MB) WILL ADD A DIURNAL
COMPONENT TO SUPPORT SHOWERS...AND GIVEN COOL TEMPERATURES PRECIP
COULD FALL AS RAIN/SNOW/GRAUPEL.  GUSTY SOUTHWEST WINDS (20-30MPH
GUSTS PROBABLE NORTHERN LOWER) WON`T MAKE IT FEEL ANY WARMER...WITH
AFTERNOON HIGHS AROUND 40-MID 40S (10-15 DEGREES BELOW NORMAL).
SHOWERS WILL CONTINUE INTO TUESDAY NIGHT...COVERAGE MAY DECREASE
WITH ON DOWNWARD SIDE OF DIURNAL HEATING CYCLE BUT THEY WILL STILL
BE AROUND.  COOLING TEMPERATURES ALSO WILL TREND PRECIPITATION TO
ALL SNOW SHOWERS TUESDAY EVENING.

WEDNESDAY...MORE OF THE SAME FOR WEDNESDAY WITH CONTINUED COOL
CYCLONIC FLOW AND VARIOUS DISTURBANCES ROTATING AROUND THE PARENT
VORTEX.  HIGH TEMPERATURES PROBABLY A FEW DEGREES COOLER WEDNESDAY
AFTERNOON...WITH MORE TEMPERATURES STUCK BELOW 40 DEGREES LIKELY.

&&

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 402 PM EDT SUN APR 19 2015

THE PERIOD PICKS UP JUST AS THE PREVIOUS LEFT OFF WITH UPPER LEVEL
TROUGHING OVERHEAD AND MULTIPLE WEAK WAVES ROTATING THROUGH THE BASE
OF THE TROUGH...BRINGING RAIN/SNOW SHOWER CHANCES WEDNESDAY NIGHT
AND INTO THE DAY THURSDAY. AS MENTIONED BY PRIOR SHIFT...THE
MOVEMENT OF THE OVERALL PATTERN LOOKS MINIMAL THROUGH THE WEEKEND
WITH TROUGHING CLOSE ENOUGH WHERE ANY SUBTLE WAVE COULD KICK OFF
ADDITIONAL SHOWER ACTIVITY. HAVE GONE AHEAD AND ADDED LOW END CHANCE
POPS FOR THURSDAY NIGHT (MAINLY DIRECTLY DOWNWIND OF LAKE MICHIGAN
AND FOR THE EASTERN U.P.)...BUT WILL KEEP A MAINLY DRY FORECAST FROM
FRIDAY THROUGH SUNDAY AS THE MAJORITY OF THE TIME LOOKS TO REMAIN
PRECIPITATION FREE.

NO DOUBT THE OVERALL PATTERN WILL BE A RATHER CHILLY ONE...WITH H8
TEMPS APPROACHING -8C THROUGHOUT THE PERIOD. A BLENDED MODEL
GUIDANCE APPROACH WOULD SUGGEST HIGH TEMPERATURES STUCK IN THE UPPER
30S AND 40S (A SOLID 10-15 DEGREES BELOW NORMAL) AND LOWS MAINLY IN
THE 20S TO LOWER 30S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 142 PM EDT SUN APR 19 2015

MOISTURE HAS BEEN SLOW TO MOVE INTO THE REGION THIS AFTERNOON, AND
THUS, HAVE BEEN SLOWING DOWN THE TIMING OF THE RAIN. BEST GUESS AT
THIS POINT IN THE AFTERNOON, IS THAT IT SHOWS UP AROUND 23Z AT
MBL/TVC AREA, AND ABOUT 00Z AT APN/PLN. AFTER THAT THE VSBY LOOKS
TO FALL INTO THE MVFR CATEGORY, BUT THE CIGS BY 12Z/MON FALL TO
IFR AS THE LOW MOVES OVER US AND BRINGS MORE MOISTURE OVER THE
REGION.

&&

.MARINE...
ISSUED AT 402 PM EDT SUN APR 19 2015

TONIGHT THROUGH TUESDAY...EAST WINDS AHEAD OF THE SFC LOW WILL
CONTINUE TO INCREASE ACROSS THE UPPER GREAT LAKES AS THE PRESSURE
GRADIENT TIGHTENS UP ESPECIALLY OVER LAKE HURON AND E UPPER. THE SFC
LOW MOVES OVER N LAKE MICHIGAN AND IT LOOKS LIKE THE GRADIENT SHOULD
JUST BE SLACK ENOUGH FOR THE WINDS TO REMAIN BELOW MOST OF THE SMALL
CRAFT CRITERIA IN THE NEARSHORE WATERS. ONCE THE SFC LOW MOVES NORTH
OF THE UPPER MICHIGAN, THE PRESSURE GRADIENT WILL TIGHTEN BRIEFLY
OVER THE UPPER GREAT LAKES BRINGING SMALL CRAFT CRITERIA TO MOST, IF
NOT ALL OF THE NEARSHORES MONDAY AFTERNOON AND MONDAY NIGHT.
TUESDAY, AS THE SFC LOW STALLS NORTH OF LAKE SUPERIOR, THE WINDS
WILL INCREASE AS THE GRADIENT AGAIN TIGHTENS, AND THEN RELAXES BY
THE AFTERNOON.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY UNTIL 2 PM EDT MONDAY FOR LHZ345>349.

LM...SMALL CRAFT ADVISORY UNTIL 9 AM EDT MONDAY FOR LMZ341-342.

LS...SMALL CRAFT ADVISORY UNTIL 2 PM EDT MONDAY FOR LSZ321-322.

&&

$$

NEAR TERM...JSL
SHORT TERM...JPB
LONG TERM...GILLEN
AVIATION...JSL
MARINE...JSL


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