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000
FXUS64 KHUN 161132 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
632 AM CDT SUN JUN 16 2013

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 401 AM CDT SUN JUN 16 2013/
AN ANALYSIS OF 16/0000Z 500MB UPPER AIR PLOTS AND THE WATER VAPOR
SATELLITE VIEW CONFIRMS REX-STYLE BLOCKING SITUATED FROM ALASKA TO
WEST OF VANCOUVER. EAST OF THIS BLOCK...A STORMY FLOW CONTINUE OVER
THE US/CANADA BORDER...WITH WEAK LOWS OVER SASKATCHEWAN/MANITOBA AND
NEWFOUNDLAND. ALSO...A WEAK FLOW MOVING NORTHWARD FROM MEXICO AND
THE GULF OF MEXICO (INTO A FLATTENING RIDGE OVER THE SOUTHERN
STATES)...ALONG WITH PASSING UPPER AIR DISTURBANCES WAS SPAWNING
CONVECTION FROM THE SOUTHERN ROCKIES AND HIGH PLAINS TO THE SOUTHERN
GREAT LAKES. REGIONALLY...NO WEATHER OF CONSEQUENCE WAS OCCURRING.
HOWEVER...CLOUDS WERE ON THE INCREASE FROM THE NW...AS BLOW-OFF MID/
HIGH CLOUDS FROM CONVECTION NW OF HERE NEARS.

WITH THE MOISTURE/INSTABILITY ON THE INCREASE...THE DRY SPELL OF THE
PAST COUPLE OF DAYS WILL COME TO AN END BEGINNING THIS AFTERNOON. THE
NAM HAD A SERIES OF UPPER LEVEL DISTURBANCES TO OUR NW (ASSOCIATED
WITH THE INCREASING CLOUDS) MOVING THIS DIRECTION. HAVE STAYED ON A
DRY PATH FOR THIS MORNING. EVEN THOUGH IT IS DRY... THINK ENOUGH
MOISTURE/INSTABILITY WILL BE REALIZED FOR SCATTERED RAIN CHANCES AS
OPPOSED TO A SLIGHT CHANCE. A CHANCE FOR RAIN CONTINUES TONIGHT AS
ADDITIONAL UPPER LEVEL SUPPORT/MOISTURE MOVE IN. THE HIGHER
RESOLUTION/SHORTER RANGE MODELS (HRRR/NSSL WRF AND OUR WRF RUN FROM
YESTERDAY) WERE IN GOOD AGREEMENT STARTING THE SHOWER ACTIVITY
AROUND NOON.

TO KEEP THE FORECAST FROM FLIP FLOPPING...WILL STAY WITH LOWER END
LIKELY RAIN CHANCES FOR MON/MON NIGHT...AND RAISED THEM TO SIMILAR
ODDS FOR TUE. OUTPUT FROM THE VARIOUS MODEL RUNS...INCLUDING THE SREF
WERE NOTING QPF ACROSS THE REGION DURING THIS PERIOD. BUFFR
SOUNDINGS FROM THE NAM...SIMILAR TO YESTERDAY WAS FORECASTING PRECIP
WATER AMOUNTS AT OR ABOVE 2 INCHES FROM LATE MON NIGHT INTO TUE. THUS
LOCALLY HEAVY RAINFALL IS A POSSIBILITY IN THE HEAVIER SHOWERS ALONG
WITH THE USUAL GUSTY WINDS. ELECTRICALLY ACTIVE STORMS ARE ALSO
POSSIBLE...AS HAVE SEEN LOTS OF LIGHTNING IN SIMILAR SITUATIONS
BEFORE. UNFORTUNATELY THE 00Z GFS APPEARS TO BE SUFFERING FROM
CONVECTIVE AND/OR GRID SCALE FEEDBACK AGAIN. ONE OF THE STRONGER
IMPULSES MOVING EAST OF THE ROCKIES ON MON...THE GFS HAS FORMED INTO
A CLOSED SURFACE LOW THAT TRACKS FROM THE FRONT RANGE TO THE
CAROLINAS. NONE OF THE OTHER MODELS SHOW THIS FEATURE. A RESULT OF
THIS HAS THE GFS ENDING THE SHOWER ACTIVITY ON WED...AS IT PUSHES A
COLD FRONT SOUTHWARD ACROSS THIS REGION. THINK THAT A FRONTAL
BOUNDARY WILL BE NEAR THE AREA BUT SHOULD NOT PUSH AS STRONGLY TO THE
SOUTH. IN ANY CASE...SHOWER ACTIVITY SHOULD WIND DOWN A LITTLE
LATER...WED NIGHT...WITH A BRIEF DRY PERIOD WED NIGHT THROUGH THU
NIGHT.

THE MEDIUM MODELS AS IS USUALLY THE CASE IN THE WARMER MONTHS ARE
NOT IN TOO GOOD AGREEMENT WITH ONE ANOTHER. BUT THEY DO INDICATE
ENOUGH INSTABILITY/MOISTURE RETURNING TO BRING A SLIGHT CHANCE OF
SHOWERS/THUNDERSTORMS TO END THE SPRING SEASON AND START SUMMER. FOR
THOSE CURIOUS...SUMMER 2013 STARTS AROUND 1204 AM FRI MORNING.

RSB

&&

.AVIATION...
FOR 12Z TAFS...EVEN WITH MID/HIGH CLOUDS STREAMING INTO THE AREA FROM
THE W...VFR CONDS ARE GENERALLY XPCTED THROUGH THE TAF PERIOD. SCT
SHRA/TSRA ARE EXPECTED TO GRADUALLY OVERSPREAD THE AREA FROM NW TO SE
DURING THE AFTERNOON HRS...AS A SERIES OF UPPER DISTURBANCE BEGIN TO
TRAVERSE EWD ACROSS THE REGION. CONDS COULD EASILY DROP INTO THE MVFR
CAT DUE TO REDUCED VIS/LOWER CIGS IN AND NEAR HEAVIER PRECIP...BUT
CONFIDENCE ON EXACT PLACEMENT/TIMING REMAINS TOO LOW TO INCLUDE IN
THE PREVAILING FORECAST ATTM.

09

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

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