FXUS64 KBMX 301142
AFDBMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
530 AM CST MON NOV 30 2009
.UPDATE...AVIATION DISCUSSION.
&&
.SHORT TERM...TODAY THRU TUESDAY.
A SOLID AREA OF RAIN HAS MOVED INTO NW ALABAMA THIS MORNING AHEAD
OF A SURFACE COLD FRONT. THE FRONT WAS NEAR TUPELO MISSISSIPPI AT
3 AM...AND SHOULD REACH WESTERN MARION COUNTY AROUND 5 AM. THE
AREA OF RAIN HAS BEEN HOLDING TOGETHER NICELY AND WENT AHEAD AND
RAISED POPS TO CATEGORICAL VALUES FOR MUCH OF CENTRAL ALABAMA.
RAINFALL AMOUNTS HAVE BEEN AVERAGING CLOSE TO ONE INCH ACROSS
NORTHERN MISSISSIPPI WITH THIS SYSTEM...BUT INTENSITY HAS BEEN
DECREASING...AND EXPECT RAINFALL AMOUNTS ACROSS AREAS ALONG AND
NORTH OF I-20 TO AVERAGE AROUND ONE-HALF INCH... WITH LESSER
AMOUNTS SOUTH OF I-20.
RAIN BAND IS MOVING STEADILY SOUTHEAST...AND RAIN SHOULD END FOR
AREAS NORTH OF I-20 BY NOONTIME WITH RAIN ENDING ACROSS SOUTHERN
AREAS BY SUNSET. CLOUD COVER AND COLD AIR ADVECTION ON NORTH SIDE OF
FRONT WILL KEEP TEMPERATURES IN THE 50S TODAY FOR NORTHERN
AREAS...AND WITH TEMPERATURES FALLING INTO THE 40S BY LATE
AFTERNOON. CLEARING SKIES TONIGHT AS A VERY DRY AIR MOVES IN BEHIND
FRONT.
TUESDAY SHAPING UP TO THE NICEST WEATHER DAY THIS WEEK WITH PLENTY
OF SUNSHINE AND HIGHS CLIMBING TO NEAR 60 DEGREES AREA WIDE.
.LONG TERM...WEDNESDAY THROUGH SUNDAY.
A VERY ACTIVE WEATHER PERIOD SHAPING UP FOR LATE TUESDAY NIGHT
THROUGH WEDNESDAY NIGHT. MODELS CONTINUE TO ADVERTISE A STRONG
UPPER LOW MOVING OUT OF THE SOUTHWEST STATES ON TUESDAY. A SURFACE
LOW IS FORECAST TO DEVELOP OFF THE LOUISIANA COAST TUESDAY NIGHT
AND DEEPEN WHILE IT TRACKS NORTHEAST. EASTERLY WINDS WILL INCREASE
TUESDAY NIGHT WITH SUSTAINED WINDS OF 15-20 MPH WITH HIGHER GUSTS
LIKELY ACROSS SOUTH ALABAMA. THE TRACK OF THE SURFACE LOW WILL
HAVE A BIG IMPACT ON THE AMOUNT OF GULF AIR THAT ADVECTS
INLAND...DAYTIME TEMPERATURES...AND AXIS OF HEAVIEST RAINFALL.
MODELS ARE STARTING TO COME TO A BETTER CONSENSUS REGARDING
SURFACE LOW TRACK WITH GFS SHIFTING FARTHER WESTWARD WITH EACH
RUN...AND MORE IN LINE WITH NAM AND ECMWF. SURFACE LOW SHOULD
TRACK NEAR TO NEAR BIRMINGHAM WHICH WILL LIKELY PULL 60-65 SURFACE
DEWPOINTS NORTHWARD TO MONTGOMERY. THE STORM PREDICTION CENTER
HAS OUTLOOKED SOUTHEAST ALABAMA FOR SLIGHT RISK OF SEVERE
STORMS...WHICH SEEMS REASONABLE BASED ON THE STRONG DYNAMICS OF
THIS SYSTEM. THIS WILL BE A HIGH SHEAR/LOW CAPE ENVIRONMENT...AND
ALSO MARKED BY A NEARLY SATURATED AIR MASS. ANOTHER FEATURE WHICH
COULD ENHANCE SEVERE THREAT IS 130 KNOT JET STREAK FORECAST BY NAM
MODEL TO MOVE NORTHWARD ALONG THE ALABAMA AND MISSISSIPPI STATE
LINE.
THE OTHER HAZARD WHICH NEEDS TO BE ADDRESSED IS THE POTENTIAL FOR
HEAVY RAINFALL. THE GFS AND ECMWF MODELS HAVE BEEN VERY AGGRESSIVE
WITH RAINFALL AMOUNTS ACROSS SOUTHEAST ALABAMA...WITH STORM TOTALS
OF 3-5 INCHES. GIVEN THE HIGH RAINFALL RATES THIS TYPE OF SYSTEM
CAN PRODUCE...FLASH FLOODING COULD BE AN ISSUE. SURFACE LOW IS
FORECAST TO EXIT EAST ALABAMA BY LATE WEDNESDAY AFTERNOON...WHICH
SHOULD BRING AN END TO THE HEAVY RAINFALL AND SEVERE THREAT.
GUSTY SURFACE WINDS WILL LIKELY CONTINUE INTO WEDNESDAY NIGHT DUE
TO TIGHT PRESSURE GRADIENT ON BACK SIDE OF SURFACE LOW. STRONG COLD
AIR ADVECTION WILL PUSH TEMPERATURES DOWN INTO THE 30S BY THURSDAY
MORNING. THERE WILL ALSO BE SOME LIGHT RAIN ASSOCIATED WITH SHORT
WAVE TROF AS IT MOVES ACROSS NORTH ALABAMA WEDNESDAY NIGHT...AND
HIGH RAIN CHANCES KEPT IN FOR WEDNESDAY NIGHT.
THE COLDEST AIR OF THE SEASON WILL INVADE ALABAMA THURSDAY AND
FRIDAY WILL HIGHS NOT LIKELY TO GET OUT OF THE 40S ACROSS NORTH
ALABAMA. 1000-850MB THICKNESS FORECASTS SUGGEST DAYTIME
TEMPERATURES WILL BE COLDER THAN CURRENTLY FORECAST. A GRADUAL
WARM-UP INTO THE WEEKEND AS THE NEXT COLD FRONT APPROACHES THE
AREA. RAIN COULD RETURN TO THE AREA ON SUNDAY AND WILL INTRODUCE
CHANCE OF RAIN.
58/ROSE
&&
.AVIATION...12Z TAF DISCUSSION.
RAIN AHEAD OF AN APPROACHING COLD FRONT WILL IMPACT ALL TAF SITES
DURING THE DAY TODAY. PREVAILING CONDITIONS WILL INCLUDE RAIN FOR
AROUND 6 HOURS TODAY...ENDING AS THE COLD FRONT PASSES. VISIBILITY
MAY TEMPORARILY DROP TO AROUND 3SM WITH THE HEAVIER SHOWERS BUT
PREVAILING CONDITIONS WILL BE AROUND 5 MILES OR GREATER. WILL HANDEL
ANY ANTICIPATED IFR VISIBILITY RESTRICTIONS BASED ON RADAR TRENDS
AND AMEND AS NEEDED. SOUTHWESTERLY WIND WILL BE SUSTAINED AROUND 10
KNOTS BY 16Z...SHIFTING NORTHWESTERLY BEHIND THE FRONT. CEILINGS
WILL DROP TO BETWEEN 1000 AND 2000 FEET JUST AHEAD OF THE
FRONT...BUT REBOUND AFTER ITS PASSAGE. SIGNIFICANT CLEARING IS
EXPECTED AT TCL BHM AND EET BY 2200 OR 2300...AND BY 0000 AT
ANB...010400 NEAR MGM AND TOI.
&&
.BMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
