Area Forecast Discussion
Issued by NWS Mobile, AL

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000
FXUS64 KMOB 132342 AAA
AFDMOB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MOBILE AL
642 PM CDT SUN JUL 13 2014

.AVIATION [14.00Z KMOB/KBFM/KPNS TAF ISSUANCE]...VFR CONDITIONS
FORECAST TO PERSIST IN THE NEAR TERM. LIGHT SOUTH WINDS AROUND 5
KNOTS OVERNIGHT WILL INCREASE TO 8 TO 12 KNOTS BY NOON MONDAY.
VCTS AND BROKEN 4000 FOOT CEILINGS RETURN BY 14.21Z. /22

&&

.PREV DISCUSSION... /ISSUED 256 PM CDT SUN JUL 13 2014/

SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)...FOR TONIGHT THROUGH
MONDAY...UPPER RIDGING OVER THE REGION WEAKENS THROUGH MONDAY AS A
LONG-WAVE TROF BEGINS TO ADVANCE INTO THE EASTERN STATES. A SURFACE
RIDGE REMAINS OVER THE NORTHERN GULF AND PROMOTES A SOUTHERLY FLOW
OVER THE FORECAST AREA. DEEP LAYER MOISTURE INCREASES SOMEWHAT
THROUGH THE PERIOD FROM 1.5-1.9 INCHES TO 1.7-1.9 INCHES WITH THE
LOWER VALUES OVER THE INTERIOR PORTION OF THE FORECAST AREA. A POORLY
DEFINED DEFORMATION ZONE CURRENTLY EXISTS ACROSS THE NORTHEASTERN AND
NORTH CENTRAL GULF...EAST OF AN UPPER LOW OFF SOUTHWEST LOUISIANA.
THE UPPER LOW CONTINUES FURTHER WESTWARD OVERNIGHT WITH A POORLY
DEFINED AXIS OF DILATATION SHIFTING SLOWLY NORTHWARD TO OVER NORTH
CENTRAL GULF COAST AREA BY MONDAY. WHILE THE SEA BREEZE AND WEAK
BOUNDARIES LEFT OVER FROM PREVIOUS CONVECTION ARE EXPECTED TO BE THE
MAIN INITIATING MECHANISMS FOR CONVECTION...THE WEAK DEFORMATION ZONE
IS EXPECTED TO ALSO CONTRIBUTE SOMEWHAT TO COVERAGE OF CONVECTION.
WILL HAVE SLIGHT CHANCE POPS THIS EVENING FOR LINGERING CONVECTION
THEN CHANCE POPS FOLLOW ACROSS THE AREA ON MONDAY...SLIGHTLY HIGHER
OVER THE SOUTHERN PORTION OF THE AREA. SURFACE BASED CAPES WILL
INCREASE TO 1500-2000 J/KG ON MONDAY AND WHILE SHEAR VALUES REMAIN
LOW IN AN OTHERWISE FAIRLY MOIST ATMOSPHERE...MAY SEE SOME STRONG
STORMS WITH STRONG WIND GUSTS AND HEAVY RAIN. DAYTIME HIGHS WILL BE
SLIGHTLY ABOVE NORMAL WITH NEAR NORMAL OVERNIGHT LOWS. /29

MONDAY NIGHT THROUGH TUESDAY NIGHT...AS AN UPPER LOW MOVES EAST
ACROSS THE GREAT LAKES...A STRONG VORT LOVE SWEEPS SOUTH AROUND THE
BACK SIDE OF THE UPPER TROUGH STRETCHING SOUTH ACROSS THE EASTERN
CONUS. THIS PUSHES A FRONT ACROSS THE FA TUESDAY INTO TUESDAY NIGHT
BEFORE LAYING IT UP ALONG THE NORTHERN GULF COAST WEDNESDAY. THIS
FRONT IS A BIT SLOWER THAN PREVIOUS RUNS AND IS ADVERTISED STRETCHING
ACROSS THE FA AT 00Z WED.

FOR MONDAY NIGHT INTO TUESDAY...HAVE WENT WITH INCREASING CHANCES FOR
RAIN. WITH THE UPPER SYSTEM NOT BEING ADVERTISED AS DEEPENING AS IT
CROSSES THE GREAT LAKES...THIS COMBINED WITH DISTANCE WILL KEEP THE
ONSHORE FLOW AHEAD OF THE FRONT ON THE LIGHTER SIDE...LIMITING THE
MOISTURE INFLUX AND INSTABILITY OVER THE FA AHEAD OF THE FRONT.

THE FRONT ITSELF IS EXPECTED TO BE ON THE WEAK SIDE...LIMITING THE
CHANCE OF SEVERE WEATHER. ANY SIGNIFICANT UPPER SUPPORT REMAINS NORTH
OF THE FA...SO AT MOST...AN ISOLATED STORM MAY BECOME STRONG TO
SEVERE...BUT ORGANIZED SEVERE WEATHER IS NOT EXPECTED WITH THIS FROPA.

FOR THE FORECAST TEMPS AND POPS...WENT A BIT BELOW SEASONAL WITH
TEMPS MONDAY NIGHT WITH AN INCREASING CHANCE OF PRECIP...TO ABOVE
SEASONAL BY SUNRISE TUESDAY. TUESDAY...WITH THE CHANCE OF RAIN
EXPECTED TO BE ABOVE SEASONAL AS A FRONT MOVES ACROSS THE FA...AM
EXPECTING TEMPS TO BE BELOW SEASONAL DUE TO THE RAIN AND INCREASED
CLOUD COVER FROM CONVECTION. TUESDAY NIGHT...TEMPS AROUND SEASONAL
SOUTH...A BIT BELOW NORTH AS THE FRONT SAGS TO THE COAST. POPS
ABOVE DUE TO THE FRONT.

LONG TERM...(WEDNESDAY ON)...GFS PROGNOSES SHOW A TROUGH AT 500 MB
HAVING A SLIGHT POSITIVE TILT LOCATED OVER THE TENNESSEE AND OHIO
VALLEYS. IT BECOMES SLIGHTLY MORE POSITIVELY TILTED AS IT STALLS
WHILE ITS PARENT LOW MOVES FROM SOUTHERN QUEBEC MOVING INTO CENTRAL
LABRADOR. AT THE SAME TIME AT 500 MB...A RIDGE WITH A CLOSED
GEOPOTENTIAL HEIGHT OF 5940 WILL COLLAPSE AND REMAIN OVER THE
SOUTHWEST STATES BY TUESDAY. THE OUTPUTS NOW AGREE ON A COLD FRONT
REACHING MUCH FURTHER SOUTH OVER OUR AREA BUT THE GFS DOES NOT PUSH
IT AS STRONGLY AS THE EURO WHICH PICKED THAT UP WITH THE EURO MOS
SHOWING COLDER TEMPERATURES THURSDAY MORNING ALONG WITH OUR
NEIGHBORS. THIS IS DUE TO THE ALIGNMENT OF THE FEATURE WITH THE DEEP
WAVENUMBER 5 TROUGH TO OUR NORTH WHICH WILL BRING A NORTHWEST FLOW
ALOFT OVER OUR REGION AROUND MIDWEEK. WE EXPECT MID LEVEL
PERTURBATIONS IN THE 500 MB FLOW ALONG THE FRONT...AND WITH CAPES
2500 TO 3500 J/KG BOTH DAYS...LIFTED INDEX GENERALLY AROUND -4 DURING
THAT PERIOD...AND PRECIPITABLE WATER AROUND 2 INCHES BOTH DAYS. WE
THEREFORE EXPECT NUMEROUS SHOWERS AND THUNDERSTORMS TUESDAY THROUGH
POSSIBLY WEDNESDAY. IN THAT 48 HOUR PERIOD BASIN AVERAGE RAINFALL OF
AN INCH TO AN INCH AND A QUARTER IS POSSIBLE WITH HIGHER TOTALS
POSSIBLE WHERE SHOWER/THUNDERSTORM TRAINS SET UP. THURSDAY SHOULD BE
CLOUD AND RAIN FREE FOLLOWING PASSAGE OF A ROBUST FRONT BUT WHEN IT
GETS TO THE BEACH THURSDAY EVENING WE EXPECT IT WILL START BACKING UP
AND DISSIPATING.

WE CONTINUE TO SEE MODEL OUTPUTS PLUNGING POST-FRONTAL TEMPERATURE
INTO THE LOW 60S THURSDAY MORNING. CLOSE COORDINATION AND DISCUSSION
WITH OUR COLLEAGUES AT BMX AND JAN HAS RESULTED IN CONCURRENCE THAT
ADDING 3 TO 4 FAHRENHEIT DEGREES TO THE EURO GUIDANCE IS A PRUDENT WAY
TO GO AT LEAST AT THIS POINT...WHILE WATCHING THE OUTPUTS. THE GFS
MOS IS STARTING TO COME AROUND BUT WE STILL BELIEVE IT IS BEHIND.
AS MENTIONED YESTERDAY...WE HAD A BIG RIDGE ALOFT THAT SHIELDED US
FROM COOLING TRENDS IN THE NORTHERN PLAINS BUT THAT RIDGE HAS ERODED
EVEN FURTHER AS INDICATED BY PHYSICAL MODEL OUTPUT.  WILL KEEP
WATCHING THESE MODEL CALCULATIONS IN FUTURE RUNS

MARINE...A RIDGE OF HIGH PRESSURE OVER THE NORTHERN GULF SHIFTS
INTO THE CENTRAL GULF THROUGH TUESDAY.  A COLD FRONT MEANWHILE
APPROACHES FROM THE NORTH AND MOVES INTO THE COASTAL WATERS TUESDAY
NIGHT BEFORE STALLING NEAR THE COAST ON WEDNESDAY.  LIGHT SOUTHERLY
WINDS BECOME WESTERLY TO NORTHWESTERLY TUESDAY NIGHT THEN RETURN TO
A SOUTHWEST FLOW ON WEDNESDAY.  THE FRONT GRADUALLY DISSIPATES
THROUGH FRIDAY WITH A SOUTHERLY FLOW PREVAILING OVER THE MARINE
AREA. /29

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      73  91  71  87  71 /  20  40  30  60  40
PENSACOLA   74  90  74  87  73 /  20  40  40  60  50
DESTIN      76  89  78  86  77 /  20  40  40  60  50
EVERGREEN   70  93  72  87  71 /  20  30  30  60  30
WAYNESBORO  69  93  71  86  67 /  20  30  40  70  30
CAMDEN      69  93  71  86  68 /  20  20  40  70  30
CRESTVIEW   70  91  71  89  71 /  20  40  40  60  50

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
FL...NONE.
MS...NONE.
GM...NONE.
&&

$$








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