Oak Ridge Weather

000
FXUS61 KPBZ 310050 AAB
AFDPBZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PITTSBURGH PA
850 PM EDT FRI JUL 30 2010

.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL CROSS THE REGION DURING THE
WEEKEND... BRINGING THE CHANCE OF SHOWERS SATURDAY WITH SHOWERS
AND THUNDERSTORMS POSSIBLE ON SUNDAY. THE TROUGH WILL PASS EAST OF
THE AREA BY MONDAY...WITH DRY A START TO NEXT WEEK ACROSS MOST OF
THE UPPER OHIO VALLEY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
THE LATEST RUC 500 MB ANALYSIS INDICATES THE UPPER OHIO VALLEY IN
A MID-LEVEL NORTHWESTERLY FLOW. AT THE SURFACE...A 1018 MB HIGH IS
CENTERED NORTH OF LAKE HURON AND SLOWLY SLIDING SOUTHEASTWARD INTO
THE EASTERN GREAT LAKES. AN INVERTED TROUGH IS LOCATED ACROSS THE
CENTRAL PLAINS. MOISTURE FILTERING INTO THE AREA FROM CONVECTION
IN THE CENTRAL PLAINS AND MORE STRATIFORM PRECIP IN THE MIDWEST
ALONG WITH DIURNAL CUMULUS HAS ALLOWED FOR PARTLY CLOUDY SKIES THIS
AFTERNOON.

TONIGHT...HAVE INCREASED CLOUD COVER OVERNIGHT AS LATEST MODEL
DATA SHOWING A SLOW INCREASE IN MID AND HIGH LEVEL CLOUDS
OVERNIGHT. THE ADDITIONAL CLOUD COVER IS MOVE SOUTHEAST WITH AN UL
WAVE IN NW FLOW ALOFT. THE INCREASE IN THE MOISTURE FIELDS IS
LINING UP WELL WITH CURRENT SAT PICS. WITH THE INCREASE IN CLOUD
COVER...HAVE NUDGE OVERNIGHT LOWS UP.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
THE NAM/GFS SOLUTIONS ARE IN AGREEMENT THAT A BROAD MID-LEVEL
TROUGH AXIS WILL CROSS THE GREAT LAKES ON SATURDAY WITH AN
INVERTED SURFACE TROUGH APPROACHING FROM THE LOWER OHIO VALLEY.
ISENTROPIC LIFT ASSOCIATED WITH THIS SYSTEM WILL ADVECT INTO THE
AREA BY LATE DAY...PROVIDING A SOURCE FOR THE LIFE WITH THE CHANCE OF
SHOWERS ON SATURDAY. THUNDER HAS BEEN REMOVED FROM THE GRIDS WITH
LITTLE INSTABILITY IN THE FORECAST. WITH TDS IN THE 50S AND A
RELATIVELY DRY AIR MASS TO START THE DAY...BELIEVE PRECIP WILL
INITIALLY HAVE A DIFFICULT TIME TO REACHING THE SURFACE BEFORE
EVAPORATING. AS THE COLUMN MOISTENS UP A LITTLE BIT AND BETTER
LIFT GETS INTO THE AREA LATE IN THE DAY...ISOLATED TO SCATTERED
SHOWERS CANNOT BE RULED OUT INTO SUNDAY MORNING. TEMPS SATURDAY
INTO SUNDAY MORNING ARE CLOSEST TO A MAV/MET BLEND...A FEW DEGREES
BELOW NORMAL SEASONAL VALUES.

SUNDAY AND MONDAY...AS THE MID-LEVEL TROUGH AXIS AND INVERTED TROUGH CROSS
THE AREA ON SUNDAY...INCREASED INSTABILITY IS MORE SUPPORTIVE OF THE
POSSIBILITY OF THUNDERSTORMS IN THE AFTERNOON. OVERALL COVERAGE
OF PRECIPITATION APPEARS TO STILL BE LIMITED WITH THIS
SYSTEM...WITH ONLY LIGHT AMOUNTS OF PRECIP EXPECTED. THE MID-LEVEL
TROUGH AXIS WILL DEEPEN AND SLOW AS IT MOVES INTO THE MID-
ATLANTIC. THE MOISTURE WITH THIS SYSTEM WILL LINGER ALONG THE
EASTERN RIDGES INTO MONDAY...SO A CHANCE OF SHOWERS AND
THUNDERSTORMS REMAINS THERE. FORECAST TEMPS SUNDAY AND MONDAY ARE
CLOSEST TO THE WARMER MAV GUIDANCE...WITH TEMPS NEAR NORMAL
VALUES.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
GFSE/ECMWF/NAEFS ARE IN CONSIDERABLE AGREEMENT FOR THE MAJORITY OF
THIS PERIOD WITH A MID-LEVEL TROUGH AXIS NEAR THE NEW ENGLAND COAST
AND DEEP RIDGING CENTERED ACROSS THE ARKLATEX REGION EARLY NEXT
WEEK. BETWEEN THE TWO FEATURES...THE UPPER OHIO VALLEY REMAINS IN A
NORTHWESTERLY FLOW. BY MID-WEEK THE TROUGH AXIS WILL FLATTEN WITH
MORE OF A ZONAL PATTERN ACROSS THE AREA. WITH MODEL AGREEMENT...THE
TIMING OF COLD FRONT ON WEDNESDAY IS CLOSEST TO THE OPERATIONAL GFS
WITH GUIDANCE FROM HPC.

ANY ISOLATED CONVECTION FOCUSED CLOSER TO THE TROUGH AXIS ACROSS THE
MID-ATLANTIC WILL DIMINISH MONDAY NIGHT. WITH THE FLOW TRANSITIONING
TO MORE ZONAL ON TUESDAY...SCHC POPS ARE FORECASTED...WITH STILL
SOME UNCERTAINTY IN TIMING THE PASSAGE OF ANY MID-LEVEL WAVES.
HOWEVER...MODELS ARE MORE FAVORABLE TO A DRY TUESDAY AS A SOUTHERLY
FLOW BEGINS TO INCREASE AHEAD OF THE COLD FRONT. THE FRONT WILL
APPROACH FROM THE NORTHWEST TUESDAY NIGHT AND CROSS THE AREA ON
WEDNESDAY. THE BEST CHANCE FOR CONVECTION SEEMS TO BE WEDNESDAY
AFTERNOON WITH THE FRONTAL BOUNDARY IN THE VICINITY OF THE UPPER
OHIO VALLEY. CHANCES DIMINISH BY EARLY THURSDAY WHEN THE BOUNDARY
DROPS SOUTH OF THE AREA AND HIGH PRESSURE BUILDS IN FROM THE
NORTHWEST. WITH HIGH PRESSURE BUILD IN FOR THE LATE WEEK AND A
WNWRLY FLOW...FORECAST IS DRY THURSDAY AND FRIDAY. TEMPS THROUGH
THIS PERIOD WILL BE A FEW DEGREES ABOVE NORMAL.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
LATEST MODEL SOLUTIONS INDICATING MORE MID AND UPPER LEVEL CLOUDS
MOVING OVER THE AREA TONIGHT. DUE TO THIS...HAVE SCALED BACK ON
MENTION OF FOG EARLY SAT MORNING. WILL MONITOR CONDITIONS AND MAKE
ANY NEEDED UPDATES IF VIS BEGIN TO DECREASE.

RECENT SREF MODEL OUTPUT SHOWS THAT AS THE HIGH PRESSURE CENTER
EXITS EAST...SOUTHERLY WINDS WILL BRING A RETURN FLOW OF GULF
MOISTURE AND HIGHER DEW POINTS INTO THE UPPER OHIO VALLEY STARTING
LATE SATURDAY OR SUNDAY. PREVALENT VFR CONDITIONS ARE EXPECTED TO
CONTINUE INTO TUESDAY...BUT THERE MAY BE SHORT PERIODS OF
RESTRICTIONS DUE TO EARLY MORNING FOG AND SCATTERED LATE DAY
THUNDERSTORMS...PARTICULARLY WHEN AN UPPER LEVEL DISTURBANCE PASSES
THROUGH THE REGION SUNDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$

NWS PBZ Office Area Forecast Discussion