823
FXUS64 KHUN 131046
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
546 AM CDT SUN APR 13 2025
..NEW AVIATION
NEAR TERM
(THIS EVENING THROUGH SUNDAY)
ISSUED AT 1021 PM CDT SAT APR 12 2025
STRONG NNW FLOW ALOFT WILL CONTINUE ACROSS THE TN VALLEY
OVERNIGHT, BUT WILL WEAKEN AND BACK TO THE NW TOMORROW AS A
SHORTWAVE TROUGH LIFTS NORTHEASTWARD OFF THE MID-ATLANTIC COAST
AND A MID- LEVEL RIDGE SHIFTS EASTWARD IN ADVANCE OF AN AMPLIFYING
WAVE DIGGING EAST-SOUTHEASTWARD INTO THE NORTHERN PLAINS. AT THE
SURFACE, HIGH PRESSURE (INITIALLY CENTERED ACROSS THE MID-SOUTH
REGION) WILL SPREAD INTO EASTERN PORTIONS OF KY/TN BY 12Z,
INDUCING CALM WINDS ACROSS THE FORECAST AREA OVERNIGHT. ALTHOUGH
DEWPOINT DEPRESSIONS REMAIN FAIRLY LARGE (EVEN AT THIS HOUR), A
PATCHY-AREAL COVERAGE OF FROST STILL APPEARS LIKELY ACROSS
PORTIONS OF NORTHEAST AL (WHERE TEMPERATURES MAY REACH THE 34-36F
RANGE BY SUNRISE), AND WE WILL LEAVE THE CURRENT FROST ADVISORY
INTACT FOR JACKSON/DEKALB COUNTIES. HOWEVER, A FAIR COVERAGE OF
CIRROFORM CLOUD COVER IS SPREADING SOUTH-SOUTHEASTWARD TOWARD THE
TN VALLEY IN THE FLOW BETWEEN THE 500-MB RIDGE TO OUR NW AND
TROUGH TO OUR NE, AND THIS MAY ULTIMATELY HAVE AN IMPACT ON THE
SPATIAL COVERAGE OF FROST (EVEN WITHIN THE ADVISORY AREA).
A MODEST INCREASE IN SSE FLOW AT THE SURFACE IS EXPECTED SHORTLY
AFTER SUNRISE TOMORROW, AS THE LOCAL PRESSURE GRADIENT CONTRACTS
BETWEEN A RIDGE EXTENDING FROM THE NORTHEASTERN GULF INTO THE
SOUTHWESTERN NORTH ATLANTIC AND AN AREA OF LOW PRESSURE THAT WILL
TRACK NORTHEASTWARD FROM CENTRAL KS INTO SOUTHERN IA/NORTHERN MO.
WITH HIGH CLOUDS EXPECTED TO DISSIPATE THROUGHOUT THE DAY AND WSW
FLOW AT THE 850-MB LEVEL PREDICTED TO STRENGTHEN TO 25-35 KNOTS, A
SUNNY AND WARMER DAY IS EXPECTED WITH HIGHS RANGING FROM THE M-U
60S IN ELEVATED TERRAIN TO THE L-M 70S IN THE VALLEY.
SHORT TERM
(SUNDAY NIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 1021 PM CDT SAT APR 12 2025
SHORT RANGE MODEL CONSENSUS SUGGESTS THAT LIGHT-MODERATE SSW FLOW
IN THE LOW-LEVELS WILL CONTINUE ACROSS THE REGION ON SUNDAY
NIGHT, AS A DEEPENING MID-LEVEL TROUGH (ACROSS THE NORTHERN
PLAINS) INDUCES SURFACE CYCLOGENESIS IN THE NORTHWESTERN GREAT
LAKES VICINITY. THIS, ALONG WITH A GRADUAL INCREASE IN BOUNDARY
LAYER MOISTURE, WILL YIELD WARMER OVERNIGHT LOWS (U40S NE TO U50S
NW), AND MAY ALSO CONTRIBUTE TO A GREATER COVERAGE OF PATCHY FOG
IF WINDS TEMPORARILY SUBSIDE.
DURING THE DAY ON MONDAY, THE MID-LEVEL TROUGH WILL SHIFT
EASTWARD ACROSS SOUTHERN ONTARIO, WITH THE NORTHERN PORTION OF THE
SURFACE LOW'S TRAILING COLD FRONT EXPECTED TO ACCELERATE
EASTWARD, FOCUSING THE GREATEST COVERAGE OF WARM SECTOR CONVECTION
FROM NORTHERN KY NORTHWARD INTO THE LOWER GREAT LAKES. HOWEVER,
DURING THE AFTERNOON HOURS (AS TEMPS WARM INTO THE L80S AND
DEWPOINTS RISE INTO THE U50S-L60S), A NARROW BAND OF WEAKER
CONVECTION WILL LIKELY EVOLVE ACROSS WESTERN PORTIONS OF KY/TN
ALONG THE SLOWER- MOVING SOUTHERN PORTION OF THE COLD FRONT. AS
THE COLD FRONT SHIFTS SOUTHEASTWARD ACROSS OUR FORECAST AREA
MONDAY EVENING/EARLY TUESDAY MORNING, DEEP-LAYER LIFT WILL
STRENGTHEN AS A VORT MAX (PERIPHERAL TO THE DOMINANT MID-LEVEL
TROUGH) DIGS SOUTHEASTWARD INTO THE MID-MS VALLEY, RESULTING IN
AMPLIFICATION OF THE HEIGHT FIELD ALOFT. ALTHOUGH THIS MAY LEAD TO
AN INCREASE IN THE COVERAGE/INTENSITY OF THE BAND OF SHOWERS AS
IT TRACKS ACROSS OUR REGION, CHANCES FOR THUNDERSTORMS APPEAR
RATHER LOW AS FORECAST SOUNDINGS DEPICT A STRONG MID-LEVEL
INVERSION WITH ONLY SMALL AMOUNTS OF ELEVATED CAPE (ABOVE THE
INVERSION).
SURFACE WINDS WILL VEER SHARPLY TO NW IN THE WAKE OF THE COLD
FRONT, ADVECTING A COOLER, MODIFIED NORTH PACIFIC AIRMASS INTO THE
REGION TO END THE SHORT TERM PERIOD. REGARDLESS, WITH ABUNDANT
SUNSHINE EXPECTED ON TUESDAY, TEMPS WILL STILL MANAGE TO REACH THE
M-U 60S. WINDS WILL BEGIN TO DIMINISH LATE TUESDAY AFTERNOON AS
THE CENTER OF A SURFACE HIGH BUILDS EASTWARD INTO THE REGION, WITH
LOWS IN THE U30S-L40S TUESDAY NIGHT AS CONDITIONS WILL BE
FAVORABLE FOR RADIATIONAL COOLING ONCE AGAIN.
LONG TERM
(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 1021 PM CDT SAT APR 12 2025
SURFACE HIGH PRESSURE WILL CONTINUE TO TRACK SLOWLY EASTWARD
ACROSS THE TN VALLEY ON WEDNESDAY AND INTO THE CENTRAL/SOUTHERN
APPALACHIANS ON WEDNESDAY NIGHT, MAINTAINING LIGHT/VARIABLE WINDS
ACROSS THE LOCAL FORECAST AREA. HOWEVER, SSE FLOW IS EXPECTED TO
RETURN ON THURSDAY AS THE ANTICYCLONE SHIFTS EASTWARD OFF THE
SOUTHERN MID-ATLANTIC COAST. LOW-LEVEL FLOW WILL THEN VEER TO SSW
ON THURSDAY NIGHT AS A SUBTLE MID-LEVEL WAVE AND RELATED SURFACE
LOW EJECT NORTHEASTWARD ACROSS THE CENTRAL PLAINS IN ADVANCE OF A
DEVELOPING CUTOFF UPPER LOW (WHICH WILL DROP SOUTH-SOUTHEASTWARD
ACROSS THE WESTERN CONUS AND INTO THE FOUR CORNERS VICINITY BY THE
END OF THE FORECAST PERIOD).
PRESENT INDICATIONS ARE THAT THE SSW FLOW REGIME IN THE LOW-
LEVELS WILL PERSIST FROM THURSDAY-SATURDAY, WITH A GRADUAL
INCREASE IN BOUNDARY LAYER MOISTURE EXPECTED WITH TIME AS
DEWPOINTS RISE BACK INTO THE U50S-L60S BY SATURDAY. ALTHOUGH AN
INCREASE IN CLOUDS AND PERHAPS EVEN A FEW LIGHT SHOWERS CAN BE
EXPECTED WITHIN THE STRENGTHENING DEEP-LAYER WARM/MOIST ADVECTION
REGIME, THE GREATEST SPATIAL COVERAGE OF SHOWERS AND THUNDERSTORMS
WILL OCCUR IN THE VICINITY OF THE SURFACE LOW'S TRAILING COLD
FRONT, WHICH (IN SIMILAR FASHION TO THE EARLIER COLD FRONT THIS
WEEK) WILL DRIFT SLOWLY SOUTHEASTWARD ACROSS THE MID-MS VALLEY AS
THE PARENT LOW RACES NORTHEASTWARD THROUGH THE LOWER GREAT LAKES
AND INTO NEW ENGLAND. THE COLD FRONT MAY MAKE IT AS FAR
SOUTHEASTWARD AS SOUTHWESTERN KY/NORTHWESTERN TN ON SATURDAY
BEFORE STALLING AS A NEW SURFACE LOW DEVELOPS ACROSS THE SOUTHERN
HIGH PLAINS, AND FOR THIS REASON, A LOW (10-30%) POP HAS BEEN
INTRODUCED ON FRIDAY NIGHT/SATURDAY WITH HIGHEST VALUES NORTH OF
THE TN RIVER. AFTERNOON HIGHS WILL WARM PROGRESSIVELY BACK INTO
THE L80S FOR MOST OF THE REGION ON FRIDAY/SATURDAY, WITH OVERNIGHT
LOWS RISING INTO THE U50S-L60S.
AVIATION
(12Z TAFS)
ISSUED AT 546 AM CDT SUN APR 13 2025
VFR CONDITIONS ARE FORECAST THROUGH THE TAF PERIOD. LIGHT WINDS
WILL GRADUALLY INCREASE THROUGH THE DAY OUT OF THE SOUTH. BY THIS
EVENING EXPECT GUSTS 15-18 KNOTS. LLWS IS FORECAST OVERNIGHT AS
THE LOW LEVEL JET INCREASES.
HUN WATCHES/WARNINGS/ADVISORIES
AL...FROST ADVISORY UNTIL 8 AM CDT THIS MORNING FOR ALZ009-010.
TN...NONE.
NEAR TERM...70
SHORT TERM....70
LONG TERM....70
AVIATION...GH
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