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Area Forecast Discussion

499
FXUS64 KOHX 221137
AFDOHX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
537 AM CST SAT NOV 22 2014

.UPDATE...FOR 12Z AVIATION FORECASTS.

&&

.AVIATION...
A FEW MORNING SPRINKLES IN NORTHWEST COUNTIES/CKV...OTHERWISE NO
PRECIPITATION TODAY. EXTENSIVE MID AND HIGH CLOUDS WILL CONTINUE
STREAMING ACROSS MIDDLE TN AHEAD OF A UPPER LEVEL STORM SYSTEM
THAT WILL APPROACH LATE TONIGHT AND SUNDAY. SFC WINDS WILL PICK UP
A LITTLE TODAY AS GRADIENTS TIGHTEN.

INCREASING MOISTURE WILL HELP DEVELOP LOW CLOUDS AFTER 00Z TONIGHT.
MVFR CIGS POSSIBLE AT BNA AND CKV TOWARD 12Z SUNDAY. HIGH CHANCE OF
RAIN AND MVFR/IFR CIGS SHORTLY AFTER THIS FORECAST CYCLE ENDS AT
12Z SUNDAY.

&&

.PREV DISCUSSION... /ISSUED 416 AM CST SAT NOV 22 2014/

DISCUSSION...

THE SURFACE RIDGE THAT HAS KEPT US DRY ACROSS THE MID-STATE THE LAST
COUPLE OF DAYS HAS MOVED OFF TO THE EAST.  NOW SITTING OVER THE
MID-ATLANTIC STATES...IT HAS PUT THE SOUTHEAST U.S. INTO A
SOUTHEASTERLY BOUNDARY LAYER FLOW.  COUPLED WITH A WEAK MID-LEVEL
DISTURBANCE MOVING ENE THROUGH THE MID-MISSISSIPPI/TN/OHIO
VALLEYS...THERE ARE A FEW SHOWERS ON THE RADAR.  THE CATCH IS...IT`S
BEEN SO DRY AND THE ATMOSPHERE IS TAKING SO LONG TO SATURATE THAT
NOT MUCH OF THIS RAIN IS REACHING THE GROUND.  KCKV SHOWED LIGHT
RAIN A COUPLE OF HOURS AGO...BUT THEY ONLY MEASURED A TRACE.  THESE
RADAR REFLECTIVITIES SHOULD MOVE OFF TO THE NE THROUGH THE MORNING
HOURS...LEAVING PARTLY TO MOSTLY CLOUDY CONDITIONS ACROSS THE
STATE.  THE MOST INTERESTING PART OF THE DAY WILL BE THE WINDS AS
THE PRESSURE GRADIENT TIGHTENS ACROSS MIDDLE TN.  IT WILL BE BREEZY
AND MOST EVERYONE WILL WARM INTO THE 60S TODAY WITH MIDDLE TO UPPER
50S ON THE PLATEAU.

ALREADY IN ITS BEGINNING STAGES...AN INTENSE SHORTWAVE TROUGH IS
EXPECTED TO DEVELOP OVER THE DESERT SOUTHWEST TODAY.  THIS SYSTEM
WILL BE OUR WEATHER MAKER ON SUNDAY.  IN RESPONSE TO THIS SYSTEM
ROUNDING THE BASE OF THE LONGWAVE PATTERN...A SURFACE LOW WILL
DEVELOP OVER E TEXAS TONIGHT...MOVING NEWD...AND PASSING JUST TO THE
WEST OF US.  UNFORTUNATELY...THIS PUTS US IN A PRECARIOUS POSITION.
THE UPPER LEVEL TROUGH SWINGS INTO A NEGATIVE TILT SUNDAY MORNING
AND BECAUSE OF THIS...THE SURFACE LOW DEEPENS PRETTY RAPIDLY.  THIS
WILL RESULT IN A COUPLE OF THINGS...FIRST...IT WILL BE WINDY
SUNDAY.  WHILE TODAY`S BREEZY CONDITIONS WILL RELAX A BIT TONIGHT...
THE SURFACE PRESSURE GRADIENT TIGHTENS BACK UP SIGNIFICANTLY AND WE
COULD SEE SUSTAINED WINDS OF 15-25 MPH WITH GUSTS TO 35 OR 40 MPH
ON SUNDAY. THIS WILL PUT US ON THE BRINK OF A WIND ADVISORY...
BUT THIS LIKELY WON`T BE ISSUED UNTIL LATER TODAY OR EVEN TONIGHT.
A SECOND RESULT OF THE QUICK INTENSIFICATION OF THIS SYSTEM IS THE
AMOUNT OF WIND SHEAR THAT WILL ENSUE. DEEP LAYER SHEAR OF 50-70
KTS IS LIKELY AND 0-3KM SRH VALUES OF 800-1000 M^2/S^2 MAY ALSO
OCCUR. THIS AMOUNT OF WIND SHEAR MIGHT ACTUALLY BE OUR SAVING
GRACE. BECAUSE OF THE SOUTHEAST BOUNDARY LAYER FLOW OVER THE NEXT
24-36 HOURS...RETURN MOISTURE SHOULD BE FAIRLY MODERATE AHEAD OF
THIS SYSTEM THIS FAR NORTH. IN FACT...THE 60 DEGREE DEW POINT LINE
SHOULD REMAIN SOUTH OF US. WITH SO MUCH WIND SHEAR AND RELATIVELY
LITTLE INSTABILITY...WE SHOULD REMAIN NORTH OF ANY WIDESPREAD
SEVERE WEATHER THREAT. WHAT WILL BE OF CONCERN IS THE 850MB JET
THAT IS PROGGED TO DEVELOP SUNDAY MORNING THAT COULD BE AS STRONG
AS 50 TO 75 KTS. THIS MEANS WE CAN`T RULE OUT THE POTENTIAL FOR AN
ISOLATED STRAIGHT LINE WIND THREAT WITH ANY THUNDERSTORMS THAT
DEVELOP. I WILL GO AHEAD AND HIGHLIGHT THIS ISOLATED WIND THREAT
IN THE HAZARDOUS WEATHER OUTLOOK THIS MORNING FOR SUNDAY...BUT
THIS SHOULD NOT BE A WIDESPREAD SEVERE WEATHER EVENT.

FROPA WILL BE A LITTLE DELAYED WITH THIS SYSTEM...OCCURRING THROUGH
THE MORNING HOURS ON MONDAY.  SOME LIGHT RAIN MAY RESULT...BUT THE
BULK OF THE ACTIVITY SHOULD BE ON SUNDAY.

BELOW NORMAL TEMPERATURES WILL RETURN FOR THE REMAINDER OF THE
WEEK.  DAYTIME HIGHS IN THE 40S ARE EXPECTED BY TUESDAY...WITH
OVERNIGHT LOWS IN THE 20S AND 30S...BUT WE SHOULD REMAIN DRY
THROUGHOUT THE WEEK.

UNGER


&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

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