FXUS64 KBMX 232117
AFDBMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
317 PM CST WED DEC 23 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY.
PRETTY QUIET ACROSS THE STATE THIS AFTERNOON WITH PARTLY TO MOSTLY
CLOUDY SKIES AND SOME LIGHT SHOWERS ENTERING OUR NORTHWEST COUNTIES
FROM MISSISSIPPI. THESE SHOWERS ARE ASSOCIATED WITH A UPPER LEVEL
SHORTWAVE WHICH IS OUT AHEAD OF THE MAIN SURFACE LOW THAT WE WILL BE
DEALING WITH TOMORROW.
SPEAKING OF OUR SURFACE LOW...PLENTY OF CONVECTION IS BEING CREATED
BY THIS SYSTEM...WITH THUNDERSTORMS BEING SEEN AS FAR NORTH AS NW
MISSOURI. THIS SYSTEM IS NOT JUST A STRONG WEATHER MAKER...ITS ALSO
A WINTER WEATHER MAKER AS WINTER WEATHER ADVISORIES AND WARNINGS ARE
POSTED FROM NEW MEXICO TO WISCONSIN.
CLOSER TO HOME...THE ONLY THING THAT HAS CHANGED FORECAST-WISE IS
CONFIDENCE...IN THAT IT HAS INCREASED. MODELS CONTINUE TO SHOW
FURTHER CYCLOGENESIS AS THE UPPER LEVEL TROUGH TILTS NEGATIVELY OVER
THE SOUTHERN PLAINS. THIS WILL IN TURN TIGHTEN THE SURFACE PRESSURE
GRADIENT OVER THE THE NORTHERN GULF STATES...INCLUDING CENTRAL
ALABAMA. BECAUSE OF THIS WE HAVE ISSUED A WIND ADVISORY THAT WILL
BE VALID BEGINNING AT 6 AM THURSDAY AND LIKELY LAST THROUGH MIDNIGHT
FRIDAY. PLEASE VIEW THESE PRODUCTS FOR MORE INFORMATION.
THESE GRADIENT WINDS ARE GOING TO BE ONE CONCERN...THE OTHER CONCERN
IS GOING TO BE A SQUALL LINE THAT IS EXPECTED TO DEVELOP THURSDAY
MORNING OVER LOUISIANA AND ARKANSAS. THIS SQUALL LINE...WITH THE
OUTSIDE CHANCE OF A FEW DISCRETE CELLS AHEAD OF IT...IS THE REASON
SPC HAS PUT MUCH OF THE LOWER MISSISSIPPI VALLEY IN A SLIGHT RISK OF
SEVERE WEATHER. OUR SAVING GRACE IN CENTRAL ALABAMA WILL BE TWO
THINGS...A LACK OF ANY SIGNIFICANT INSTABILITY AND A PLETHORA OF
0-3KM HELICITIES...SOME OF WHICH COULD BE IN THE NEIGHBORHOOD OF
800-1000 M^2/S^2. THIS IS ENOUGH TO SHEAR APART ANY KIND OF
CONVECTION THAT MAY FORM.
SO FOR CENTRAL ALABAMA AND THE SQUALL LINE...WE COULD SEE THIS LINE
OF SHOWERS AND ISOLATED THUNDERSTORMS ENTER THE WESTERN PORTIONS OF
THE STATE BY 5 PM. AT THAT POINT...THERE WILL BE JUST ENOUGH
INSTABILITY TO PRESENT AN OUTSIDE CHANCE OF ONE OR TWO SEVERE WIND
GUSTS ACROSS SUMTER AND MARENGO COUNTIES. THIS THREAT IS EXPECTED
TO DISSIPATE THROUGH THE EVENING AS THIS LINE MOVES EASTWARD INTO
MUCH MORE STABLE AIR. DEW POINTS ARE STILL ONLY EXPECTED AROUND
60-62 DEGREES IN THE SOUTHWEST AND WITH THE WEDGE STILL IN PLACE
ACROSS THE EASTERN TWO THIRDS OF THE STATE...IT IS NOT LIKELY THERE
WILL BE A STRONG ENOUGH SURGE OF MOISTURE INTO THE REST OF THE CWA
TO SUSTAIN THIS LINE OF STORMS. EXPECT TO SEE ANY THUNDERSTORMS
THAT DO DEVELOP TO DISSIPATE...AND TURN INTO MODERATE SHOWERS...
EXITING THE EAST SIDE OF THE STATE AROUND MIDNIGHT.
QPF IS EXPECTED TO BE IN THE 1-3 INCH RANGE FOR THIS SYSTEM AND
LOCAL RIVERS AND STREAMS HAVE HAD ENOUGH TIME SINCE THE LAST SYSTEM
TO RECOVER...THEY SHOULD BE ABLE TO HANDLE THIS AMOUNT OF RAIN.
.LONG TERM...CHRISTMAS DAY THROUGH WEDNESDAY.
THE REMAINDER OF THE FORECAST IS FAIRLY QUIET. DAYTIME TEMPERATURES
ARE EXPECTED TO BE THE NEIGHBORHOOD OF THE LOW 40S AND UPPER
50S...BUT OVERNIGHT LOWS SUN-TUE WILL BE IN THE MIDDLE 20S FOR A
MAJORITY OF THE CWA.
MODELS ARE ALL OVER THE PLACE IN REGARDS TO NEXT WEEKS SYSTEM...SO
WILL REFRAIN FROM MUCH TALK ABOUT IT. LOOKS TO BE SOMETHING IN THE
TUE-THU TIME FRAME.
27
&&
.AVIATION...18Z TAF DISCUSSION.
VFR CONDITIONS ARE EXPECTED TO PERSIST THRU 06Z. RAIN OVER NORTHERN
MISSISSIPPI WILL TRACK NORTHEAST AND STAY NORTH OF TAF SITES THROUGH
AT LEAST 12Z. 5000 FOOT CLOUDS WILL CONTINUE TO STREAM ACROSS
CENTRAL ALABAMA FROM THE WEST KEEPING SKIES BROKEN THROUGH THE DAY.
LOWER CLOUDS WITH CIGS 1500-2500 FEET WILL LIKELY FORM AFTER 06Z DUE
TO INCREASING MOISTURE.
SOUTHEAST WINDS WILL INCREASE OVERNIGHT AS A LOW PRESSURE SYSTEM
WEST OF THE MISSISSIPPI RIVER RAPIDLY DEEPENS. SUSTAINED SPEEDS
BETWEEN 10 AND 15 KNOTS ARE EXPECTED BY SUNRISE AND AROUND 15 KNOTS
BY 18Z. GUSTS WILL LIKELY REACH 25 KNOTS BY 18Z. WITH SUCH STRONG
SURFACE WINDS LLWS THRESHOLDS WILL BE HARD TO REALIZE DESPITE 30 TO
40 KNOT 2000 FOOT WINDS.
12/SIRMON
&&
.PRELIMINARY POINT TEMPS/POPS...
GADSDEN 43 56 44 50 28 / 20 80 100 20 10
ANNISTON 46 56 47 52 28 / 20 80 100 20 10
BIRMINGHAM 51 56 42 50 28 / 30 90 100 20 10
TUSCALOOSA 52 61 40 52 28 / 40 100 90 10 10
CALERA 51 59 44 51 31 / 30 90 100 20 10
AUBURN 45 56 47 53 30 / 20 80 100 10 10
MONTGOMERY 51 63 46 55 32 / 20 90 100 10 10
TROY 50 63 46 55 30 / 20 80 100 10 10
&&
.BMX WATCHES/WARNINGS/ADVISORIES...WIND ADVISORY FOR ALL OF
CENTRAL ALABAMA FROM 6 AM THURSDAY UNTIL MIDNIGHT FRIDAY.
&&
$$
27/12
