Red Flag Warning 9, NWS Birmingham, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
520 AM CST SAT FEB 21 2009

.UPDATE...AVIATION DISCUSSION.

&&

.SHORT TERM...TODAY AND TONIGHT.

VIGOROUS AND RATHER SHARP SHORTWAVE TROUGH
FORECAST TO SWING ACROSS THE GREAT LAKES AND OHIO VALLEY STATES
OVER THE NEXT 24 HOURS. ASSOCIATED SURFACE LOW WILL PASS TO
ALABAMAS NORTH...BUT DRAG A FAST MOVING COLD FRONT THROUGH HERE
LATER TODAY. ALTHOUGH GULF INFLOW INTO THIS SYSTEM IS FAIRLY
WEAK...THERE IS ENOUGH LARGE SCALE LIFT ASSOCIATED WITH THE
SHORTWAVE ALONG WITH FRONTAL CONVERGENCE IN THE LOW LEVELS TO FORM
A RELATIVELY NARROW BAND OF RAIN. THIS RAIN BAND SHOULD QUICKLY
MOVE THROUGH CENTRAL ALABAMA THIS AFTERNOON AND EARLY
EVENING...CAUSING NO MORE THAN 3-4 HOURS OF RAIN AT ANY PARTICULAR
LOCATION.

OF COURSE...WITH CONDITIONS PRETTY COLD INITIALLY THIS MORNING...AND
WITH ANOTHER GOOD SURGE OF COLD AIR COMING IN WITH THE FRONT...WE
HAVE TO BE MINDFULL OF THE WINTRY PRECIP POTENTIAL. AND AFTER GIVING
THE MODEL SOUNDINGS AND OTHER TEMPERATURE AND MOISTURE CHARTS A
THOROUGH GOING-OVER...HAVE DETERMINED THAT THAT POTENTIAL IS STILL
VERY LOW. WHILE CONDITIONS WILL QUICKLY CHILL DUE TO WETBULBING AT
THE ONSET OF THE PRECIPITATION...THAT SHOULD BRING SURFACE TEMPS
DOWN TO THE UPPER 30S AT THE LOWEST THROUGH THE DURATION OF THE
PRECIPITATION. IF I SQUINT MY EYES JUST RIGHT...AND DO A LITTLE
INTERPOLATION...I MIGHT COULD IMAGINE A 15-30 MINUTE WINDOW OF
OPPORTUNITY FOR SNOW RIGHT AS THE PRECIP ENDS. THATS NOT A BIG
ENOUGH CHANCE OR A BIG ENOUGH WINDOW TO WARRANT INCLUSION OF ANY
WINTER PRECIP AT THIS TIME.

ALL PRECIPITATION SHOULD END SHORTLY AFTER MIDNIGHT TONIGHT...IF NOT
SOONER. NORTHWEST WINDS RETURN BEHIND THE FRONT...AND THE COLD
ADVECTION KICKS IN YET AGAIN.

/61/

.LONG TERM...SUNDAY THROUGH FRIDAY.

A HIGHLY AMPLIFIED UPPER AIR PATTERN ON SUNDAY WILL PUSH COLD AIR
DEEP INTO THE SOUTHERN STATES. THE VERY PROGRESSIVE SYSTEM WILL ALSO
PUSH THE RAIN OUT OF SOUTHEAST ALABAMA BY SUNRISE SUNDAY. SUNDAY
WILL BE RATHER COLD AND BLUSTERY WITH NORTH WINDS OF 10 TO 15
MPH...BUT GOOD NEWS IS THAT THERE WILL BE PLENTY OF SUNSHINE. SURFACE
DEWPOINTS EXPECTED TO FALL INTO THE TEENS MONDAY AND TUESDAY. WITH
LIGHT WINDS AT NIGHT...SUB-FREEZING TEMPERATURES EXPECTED MONDAY AND
TUESDAY MORNINGS. THE NORMALLY COLDER VALLEYS COULD SEE MIDDLE TO
UPPER TEENS MONDAY MORNING.

MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE TUESDAY THRU FRIDAY
TIME FRAME. UPPER FLOW WILL EVOLVE INTO A ZONAL FLOW PATTERN BY
MID WEEK. WITH UPPER HEIGHTS RISING AND SURFACE RIDGE MOVING OFF
TO THE EAST OF ALABAMA...SURFACE TEMPERATURES WILL REBOUND ON
TUESDAY WITH HIGHS NEAR AVERAGE. LOW LEVEL GULF MOISTURE WILL
INCREASE TO THE WEST OF ALABAMA ON TUESDAY ON BACK SIDE OF EXITING
SURFACE HIGH. THIS MOISTURE WILL WORK ITS WAY EASTWARD BY
WEDNESDAY AND THURSDAY...BUT WITH STABLE CONDITIONS ALOFT AND
LITTLE OR NO FORCING...RAIN CHANCES WILL BE CONFINED TO AREAS
NORTH OF I-20. A DIGGING SHORT WAVE TROF WILL PUSH ACROSS THE OHIO
VALLEY STATES ON FRIDAY AND PUSH A COLD FRONT INTO ALABAMA.
MOISTURE AND INSTABILITY LOOKS LIMITED WITH THIS SYSTEM AND KEPT
POPS IN THE CHANCE CATEGORY.

58/ROSE

&&

.AVIATION...12Z TAF DISCUSSION.

VFR CONDITIONS ARE EXPECTED UNTIL AT LEAST 00Z.  FAST MOVING COLD
FRONT WILL BRING A 3-4 HOUR LONG PERIOD OF AT LEAST MVFR
CONDITIONS...STARTING AROUND 02Z IN THE WEST AND LASTING AS LATE AS
11Z IN THE EAST. RAIN DOESNT LOOK TO BE PARTICULARLY HEAVY.
HOWEVER...IT COULD BE HEAVY ENOUGH TO BRIEFLY DROP CEILINGS BELOW
2000 FEET.

/61/

&&

.FIRE WEATHER...SURFACE DEWPOINT RECOVERY WILL BE SLOWER OVER
EAST ALABAMA TODAY...AND FORECAST RELATIVE HUMIDITY VALUES WILL
FALL BELOW 25 PERCENT FOR SEVERAL HOURS THIS AFTERNOON. A RED
FLAG WARNING WILL BE ISSUED FOR EAST ALABAMA.

&&

.BMX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING THIS AFTERNOON EAST ALABAMA.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BIRMINGHAM AL
541 AM CST SAT FEB 21 2009

ALZ011>015-017>050-221130-
AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE-
CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE-
JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY-
PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA-
TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON-
541 AM CST SAT FEB 21 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE COUNTIES SERVED BY THE
NATIONAL WEATHER SERVICE OFFICE IN BIRMINGHAM.

.DAY ONE...TODAY AND TONIGHT.

LOW RELATIVE HUMIDITIES IN THE AFTERNOON WILL RESULT IN A HIGH FIRE
DANGER...ESPECIALLY EAST OF INTERSTATE 65 TODAY.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

AFTERNOON RELATIVE HUMIDITIES WILL DROP BELOW 25 PERCENT FOR SEVERAL
HOURS ON BOTH SUNDAY AND MONDAY...RESULTING IN A HIGH FIRE DANGER
BOTH DAYS.

NO OTHER HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT IS NOT
EXPECTED AT THIS TIME.

61