River Flood Warning 4, NWS Huntsville, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
449 PM CST SUN JAN 13 2013

.DISCUSSION...
AS OF 3PM...A STRONG COLD FRONT IS JUST ENTERING THE CWA AND EXTENDS
FROM CENTRAL KENTUCKY TO NEAR NASHVILLE...JUST EAST OF MUSCLE SHOALS
AND SOUTHWEST TOWARD JACKSON MS. TEMPS EAST OF THE FRONT ARE SITTING
IN THE UPPER 60S TO MID 70S WHILE VALUES QUICKLY FALL OFF INTO THE
40S BY CENTRAL MS. LOCATIONS CLOSE TO THE MS RIVER HAVE BEEN SEEING
30 DEGREE TEMPS AND A FEW SITES HAVE REPORTED UNKNOWN PRECIP TYPE ON
THE BACK EDGE OF THE PRECIP SHIELD. LARGE AMOUNTS OF RAIN HAVE FALLEN
TODAY FROM THE ARK-LA-MISS TOWARD WEST/CENTRAL TN...LEADING TO
WIDESPREAD FLOODING PROBLEMS TO OUR WEST/NORTHWEST.

THE FRONT WILL CONTINUE TO PUSH ACROSS THE CWA THROUGH THE EVENING
HOURS...AND BRING A BRIEF ROUND OF CONVECTION. THE WARM AND MOIST
ATMOSPHERE WE HAVE ENJOYED TODAY HAS PROVIDED FUEL FOR SOME OF THE
STORMS ALONG THE FRONT TO BECOME STRONG TO SEVERE...BUT THE POTENTIAL
FOR SEVERE WEATHER SHOULD DIMINISH THROUGH THE EVENING HOURS. AREAS
OF RAIN WILL CONTINUE BEHIND THE FRONT THROUGH THE OVERNIGHT
PERIOD...WITH DRIER AIR POSSIBLY GIVING THE SHOALS AREA A BRIEF BREAK
IN POPS BTWN 09-15Z. THE BIGGER CONCERN FOR THE EARLY MORNING PERIOD
IS THE POTENTIAL FOR FREEZING/FROZEN PRECIP.

MODEL SOUNDINGS SHOW THE SURGE OF LOW LEVEL COLD AIR...WHILE WARM AND
MOIST AIR CONTINUE TO RISE OVER THE REGION BTWN 850-700MB. THE
STRONG WARM NOSE WILL PREVENT CONCERNS FOR SNOW POTENTIAL ACROSS THE
CWA BUT THE MOISTURE COMBINED WITH STRONG LL COLD ADVECTION COULD
PROVIDE A SETUP FOR SLEET OR FREEZING RAIN...PRIMARILY IN NW AL
(ALONG AND W OF A LINE FROM MOULTON TO WINCHESTER TN). TEMPERATURES
IN THIS AREA WILL DROP INTO THE 30S DURING THE EARLY MORNING HRS
(NEAR 30 AT WATERLOO...TO UPPER 30S ALONG THE LINE MENTIONED JUST
ABOVE) WHILE DEWPOINTS WILL FALL BELOW FREEZING. WITH THE WET BULB
TEMPS BELOW FZG AND INCREASING DEPTH OF COLD AIR AS WE MOVE
NW...SLEET OR FZG RAIN WILL BE POSSIBLE. THE GOOD NEWS IS THAT
UNSEASONABLY WARM TEMPS THE PAST SEVERAL DAYS SHOULD KEEP ROADS AND
OTHER SFCS WARM ENOUGH TO PREVENT ACCUMULATION IF SLEET OR FZG RAIN
DEVELOPS (UNLESS PRECIP RATES INCREASE SIGNIFICANTLY DURING PERIODS
OF STRONG COLD ADVECTION). ANOTHER LIMITING FACTOR TO WINTERY PRECIP
WILL BE THAT WITH TEMPS/TDS SO CLOSE TO FZG...LATENT HEAT RELEASE
WITH ANY FREEZING OF HYDROMETEORS WILL HELP PUSH TEMPS BACK TOWARD
AND ABV FZG. CONTINUED STRONG COLD ADVECTION COULD COMBAT THIS...BUT
CONFIDENCE IS LOW IN THIS POTENTIAL.

OTHERWISE...RAIN INTENSITY AND COVERAGE SHOULD INCREASE AGAIN DURING
THE AFTERNOON HOURS...PRIMARILY OVER SE PORTIONS OF THE CWA.
CONSIDERING THAT THAT PORTION OF THE CWA HAS REMAINED FAIRLY DRY OVER
THE PAST SEVERAL DAYS...FF GUIDANCE IS HIGHER AND SHOULD THEREFORE
TAKE LONGER FOR ANY POTENTIAL FLOODING PROBLEMS TO DEVELOP. FOR THAT
REASON HAVE OPTED TO NOT ISSUE ANY HYDRO WATCHES ATTM.
YET...CONTINUED ROUNDS OF RAIN SHOULD PERSIST ACROSS THIS REGION
THROUGH WEDNESDAY AND MAY EVENTUALLY LEAD TO MORE AREAL FLOODING
CONCERNS IN ADDITION TO RIVER RISES. THEREFORE...DEPENDING ON HOW
RAIN RATES EVOLVE OVERNIGHT INTO TOMORROW MORNING...A WATCH MAY BE
NEEDED FOR MUCH OF THE EASTERN HALF OF THE CWA.

TUESDAY MORNING COULD BRING ANOTHER CHANCE FOR SOME FREEZING RAIN OR
SLEET...BUT THE LINE BETWEEN RAIN AND WINTERY PRECIP WILL BE VERY
FINE. AGAIN NW AL WILL HAVE THE HIGHER POTENTIAL FOR SEEING FREEZING
OR FROZEN PRECIP...BUT THE LACK OF CONFIDENCE IN THE DEPTH OF THE SFC
COLD AIR HAS PRECLUDED INCLUDING THE MENTION OF ANY OTHER P-TYPE
THAN RAIN IN THE FCST ATTM.

THE PRECIP WILL BE SLOW TO MOVE OUT...WITH THE POTENTIAL FOR
ADDITIONAL ROUNDS OF RAIN THROUGH THURSDAY NIGHT. MODELS HAVE BEEN
SHOWING SIGNIFICANT VARIATION IN THEIR HANDLING OF THE LINGERING
MIDLEVEL SHORTWAVE AS IT PROGRESSES EASTWARD...BUT ARE SLOWLY COMING
INTO MORE AGREEMENT. ATTM HAVE TRENDED TOWARD THE ECWMF SOLN SINCE IT
HAS BEEN SHOWING BETTER RUN-TO-RUN CONTINUITY. THIS WOULD CLEAR OUT
THE CWA BY EARLY MORNING FRIDAY.

CCC

&&

.AVIATION...
/ISSUED 1156 AM CST SUN JAN 13 2013/
FOR 18Z TAFS...HAVE CONTINUED BASICALLY WITH IFR CONDITIONS THROUGH
MOST OF THE FORECAST AS LOW CLOUDS AND RAIN SHOULD SPREAD ACROSS THE
AREA. HAVE IMPROVED CONDITIONS AT MSL AFTER 10Z...AS EXPECT SOME
BREAKS IN THE LOWER CLOUDS BETWEEN 10Z TO 14Z.

TT

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    36  38  37  43 / 100  80  80  90
SHOALS        33  37  33  39 / 100  80  60  70
VINEMONT      37  39  36  43 / 100 100  90  90
FAYETTEVILLE  34  37  35  40 / 100  80  70  80
ALBERTVILLE   42  46  41  46 / 100 100  90  90
FORT PAYNE    45  49  43  46 / 100 100 100  90

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR ALZ001>005.

TN...NONE.
&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.