National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 170634
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
234 AM EDT FRI MAY 17 2013

.SYNOPSIS...
STALLED FRONT WILL REMAIN SOUTH OF THE AREA THROUGH MOST OF
SATURDAY. FRONT WILL SHIFT NORTHWARD SUNDAY.

&&

.NEAR TERM /THROUGH TODAY/...
SURFACE FRONT OVER MID-ATLANTIC IS DRIFTING SOUTHWARD IN RESPONSE
TO HIGH PRESSURE MOVING ACROSS GREAT LAKES. SUBSIDENCE FROM HIGH
HAS ALLOWED SKIES TO CLEAR. LATEST OBS ARE INDICATING THAT A TD
BOUNDARY IS STRETCHING ACROSS THE REGION...PRETTY MUCH CUTTING
THE AREA IN HALF. TO THE NORTH OF THE BOUNDARY...TDS ARE IN THE
30S TO LOWER 40S...WHILE SOUTH OF THE BOUNDARY...TDS ARE RANGING
FROM THE MID 50S TO LOWER 60S. PAST THE OBVIOUS DIFFERENCE IN
HUMIDITY LEVELS...THIS WILL ALSO MEAN FOG WILL DEVELOP AND THICKEN
OVER THE SOUTH AS THE NIGHT PROGRESSES. WILL INCLUDE FOG IN THE
SOUTH WITH DENSE POSSIBLE IN RIVER VALLEYS.

HIGH PRESSURE WILL REMAIN PARKED OVER THE GREAT LAKES...WHILE THE
PRESSURE FRONT SITS OVER THE MID ATLANTIC. THE AFOREMENTIONED TD
BOUNDARY...SHOULD SLIDE A BIT FURTHER SOUTH WITH A PUSH OF DRIER
AIR FROM THE NORTH. WITH NO REAL WAVES OF ENERGY TO PIN CONVECTION
ON...THINK THAT ANY ACTIVITY WOULD DEVELOP OVER THE FAR SOUTH IN
THE AREA OF HIGH TDS.

TEMPS WILL CONTINUE TO BE WARM.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
FOR TONIGHT INTO SUNDAY...GENERAL AGREEMENT THAT BOUNDARY WILL
PUSH NORTHWARD BUT AGAIN DISAGREE ON TIMING AND STRENGTH OF
POSSIBLE SHORTWAVES. CONTINUE THE PREVIOUS TRENDED TOWARD NAM
SOLUTION WITH HIGHEST SHOWER CHANCES ACROSS THE SOUTH AND RIDGES
THROUGH THE WEEKEND UNTIL SUNDAY.

TEMPERATURES A COMPROMISE BETWEEN 21Z SREF AND GFS MOS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MODEL AGREEMENT ON THE OVERALL UPPER LEVEL PATTERN IS BEGINNING TO
IMPROVE...AT LEAST THROUGH DAY 6 BEFORE THERE ARE GLARING
DIFFERENCES. IN GENERAL...UPPER LEVEL RIDGING WILL CONTINUE TO
AMPLIFY OVER THE EASTERN HALF OF THE CONUS AS A CUTOFF LOW DEVELOPS
OVER THE NORTHERN PLAINS. THIS LOW WILL SLOWLY MAKE IT`S APPROACH
THROUGH THE PERIOD...HELPING TO SWING AN ASSOCIATED FRONT ACROSS THE
REGION BY LATE WEDNESDAY/EARLY THURSDAY. HOWEVER...DIFFERENCES STILL
REMAIN IN THE AMOUNT OF CONVECTIVE ACTIVITY THERE WILL BE IN THE
WARM SECTOR SUNDAY THROUGH WEDNESDAY AS DIFFERENT SHORTWAVES MOVING
THROUGH THE UPPER LEVEL FLOW ARE TIMED DIFFERENTLY FROM RUN TO RUN.
TO TAKE INTO ACCOUNT THESE DIFFERENCES...OPTED TO REMAIN
CONSERVATIVE WITH POPS UNTIL LATE TUESDAY BEFORE INCREASING CHANCES
IMMEDIATELY AHEAD OF THE COLD FRONT. TEMPERATURES WERE ALSO KEPT
BELOW MOS GUIDANCE...ESPECIALLY ON TUESDAY AND WEDNESDAY AS AMPLE
MOISTURE AND CLOUD COVER WILL LIKELY KEEP TEMPERATURES FROM REACHING
THE MID 80`S SUGGESTED.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
A FAIRLY ABRUPT DEWPOINT DISCONTINUITY SNAKES THROUGH NORTHEASTERN
OHIO TO JUST SOUTH OF KBTP AND JUST NORTH OF KIDI. ALL OF THIS
SITES SOUTH OF THIS ARE LIKELY TO EXPERIENCE AT LEAST SOME FOG
THROUGH THE EARLY MORNING HOURS. IN PARTICULAR...LIFR CONDITIONS
IN FOG/STRATUS ARE LIKELY AT KZZV...KHLG...AND KMGW THROUGH
MORNING. BECAUSE SURFACE MOISTURE IS SLIGHTLY LOWER AROUND
KPIT...JUST MVFR VIS WAS CARRIED. BY ROUGHLY 13Z...DIURNAL MIXING
SHOULD INCREASE AND MIX OUT FOG EVERYWHERE...WITH VFR CONDITIONS
EXPECTED AT ALL TERMINALS AFTER THAT TIME. FRIES

.OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/...
GENERAL VFR SHOULD CONTINUE UNTIL SATURDAY AFTERNOON WHEN INCRSG
MSTR AND INSTABILITY SPPRT PCPN CHCS AND RESTRICTIONS...WHICH ARE
EXPECTED TO PERIODICALLY CONT THROUGH TUESDAY.
-- End Changed Discussion --

&&

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

&&

$$