Interesting OHX Discussion concerning POPs this week

[servocrow]

Mods, I wasn't sure the BEST place to put this...

000
FXUS64 KOHX 260914
AFDOHX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
350 AM CDT WED JUL 26 2006

.DISCUSSION...
SFC RIDGE CONTINUES OVER THE EXTREME SERN US AND MID ATLANTIC STATES. TO THE WEST A DEVELOPING LOW PRESSURE SYSTEM IS LOCATED OVER THE WRN GREAT LAKES AND CNTRL PLAINS.

AT MID LEVELS...AN H5 TROUGH AXIS EXTENDS FROM CNTRL CANADA SWWD THROUGH MINNESOTA TO NEBRASKA. THE UPPER PORTION OF THE TROUGH IS MOVING EWD THROUGH THE GREAT LAKES...ATTEMPTING TO STRETCH THE ASSOCD FRONTAL ZONE OUT NE-SW. TO THE SW...A WEAKLY DEFINED H5 LOW IS NOTED OVER THE S TEXAS COAST WITH EXTENSIVE ASSOCD MID LVL MOISTURE PLUME OVER THE LOWER MISS VALLEY AND DEEP SOUTH.

THE FCST TICKS ALONG PRETTY GOOD FOR THE 1ST TWO PERIODS...THEN THINGS START TO DIVERGE. DRAMATIC DIFFERENCES ARE NOTED BETWEEN  THE GFS AND THE NAM(ETA) BY FRIDAY. THE MODEL SOUNDINGS FOR THE GFS MODEL SHOWS PRECIPITABLE MOISTURE AMOUNTS OF 2.16 INCHES FOR FRI AM...WHILE THE NAM INDICATES ONLY 1.13 INCHES FOR THE SAME TIME.  FURTHER...THE GFS FIGURE MAXES OUT AT AN ASTOUNDING 2.41 INCHES FOR FRI EVE.

THESE DRAMATIC DIFFERENCES IN MODEL MOISTURE PRODUCE THE EXPECTED RESULTS...A WET AND COOL GFS AND A DRY AND WARM NAM. TEN DEGREES DIFFERENCE IN HIGH TEMPS AND 60 PERCENTAGE POINTS DIFFERENCE IN POPS. WELL...WHAT TO DO...WHAT TO DO?

WITH A SOUTH FLOW DIRECTLY OFF THE GULF OF MEXICO...PRUDENCE
DICTATES KEEPING SHOWERS AND THUNDERSTORMS IN THE FORECAST.
WHILE LARGE BLOBS OF DRY AIR IN THE 850-500MB LEVEL HAVE BEEN
KNOW TO ROTATE NWD OFF THE GULF INTO THE MID SOUTH...I`M NOT
GOING TO PUT ALL MY EGGS IN THAT BASKET(NAM). SO A CONSENSUS MOS POSITION WAS ADOPTED FOR PERIODS 3-5. HISTORY INDICATES THAT THAT IS ALMOST ALWAYS THE MOST ACCURATE FORECAST.
&&

.PRELIMINARY POINT TEMPS/POPS...
NASHVILLE    92  73  89  72 /  20  30  50  40
CLARKSVILLE  91  71  88  71 /  20  30  50  40
CROSSVILLE   85  68  83  68 /  20  30  50  40

Am I reading correctly that there is a low developing in the Great Lakes Region that could ENHANCE the moisture from this Tropical Low? :?:

It sounds like the models are all over the board with the precip amounts...

[msdawg911]

It's fine right here.

I love reading the AFDs. It shows you a specific forecaster's thoughts and his thought processes. Sometimes, they are humorous, just as this one is.

[kailynleto | Nightwolf]

000
FXUS64 KOHX 272000
AFDOHX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
300 PM CDT THU JUL 27 2006

.SHORT TERM...ISOLATED STORMS HAVE STARTED TO BREAK OUT NEAR THE KENTUCKY STATE LINE, ALTHOUGH NEARLY ALL OF MIDDLE TENNESSEE REMAINS RAIN-FREE THIS HOUR. SKIES ARE GENERALLY BROKEN, ALTHOUGH THIS HASN`T STOPPED TEMPERATURES FROM REACHING 90 DEGREES MOST PLACES WEST OF THE PLATEAU.

SURFACE ANALYSIS AT 19Z SHOWS A RIDGE OF HIGH PRESSURE ALONG THE APPALACHIANS, WITH A 1008 MB LOW CENTERED OVER SOUTHWEST
WISCONSIN, AND A 1007 MB LOW CENTERED OVER NORTH-CENTRAL TEXAS, WITH A FRONTAL BOUNDARY RUNNING BETWEEN THE TWO. THIS MEANS AN STRONGER PRESSURE GRADIENT OVER MIDDLE TENNESSEE, INCREASING THE SOUTHERLY FLOW AND ADVECTING ADDITIONAL MOISTURE INTO THE MID STATE.

.LONG TERM...ATMOSPHERIC MODELS SHOW THE 500 MB SHORTWAVE
ADVANCING EASTWARD OVERNIGHT, BRINGING A WIDE BAND OF HIGH 1000- 500 MB RELATIVE HUMIDITIES CLOSER TO THE MID STATE, THEREBY INCREASING OUR POP`S LATER TONIGHT AND TOMORROW. LOOK FOR THE FRONT TO STALL OUT OVER MIDDLE TENNESSEE DURING THE WEEKEND, AS THE UPPER MIDWEST LOW ACCELERATES EASTWARD, AND CAUSING THE FRONT TO BECOME MORE LATITUDINAL.

UPPER RIDGE WILL BEGIN TO BUILD OVER THE MID STATE THE FIRST OF
NEXT WEEK, LOWERING OUR RAIN CHANCES, ALTHOUGH TEMPERATURES THE COMING WEEK WILL BE VERY CONSISTENT, GIVEN NO FRONTAL PASSAGES OR AIR MASS CHANGES. ISOLATED POP`S WILL REMAIN IN THE FORECAST NEXT WEEK GIVEN THE HUMID AIR MASS, SEASONAL TEMPERATURES, AND AFTERNOON/EVENING HEAT-DRIVEN CONVECTION THAT COMBINATION USUALLY BRINGS.