Area Forecast Discussion
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000
FXUS61 KPBZ 050834
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
434 AM EDT TUE MAY 5 2015

.SYNOPSIS...
A SLOW MOVING FRONTAL BOUNDARY WILL KEEP RAIN CHANCES IN THE
FORECAST THROUGH WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
CURRENT RADAR IMAGERY SHOWS ISOLATED TO SCATTERED SHOWERS
STRETCHING FROM WEAK ECHOES OVER FAYETTE COUNTY PA WEST TO
STRONGER RETURNS NEAR DAYTON OH. THIS ACTIVITY IS LOCATED ALONG
AND JUST SOUTH OF THE CURRENT WEAK SURFACE FRONT...ORIENTED WITH
HIGHER MOISTURE CONTENT. EXPECTING CURRENT TRENDS OF DECAYING
CONVECTION TO FURTHER WEAKEN AS IT MOVES INTO THE FORECAST AREA
DURING THE PRE-DAWN HOURS.

BROAD FRONTAL ZONE AND DEEPER MOISTURE WILL SHIFT NORTH SOME
THROUGH MIDDAY AS A WAVE CURRENTLY PRODUCING STRONG CONVECTION
OVER EASTERN IOWA TRACKS ACROSS THE SOUTHERN GREAT LAKES. THIS
WILL SHIFT THE FOCUS OF ANY AFTERNOON SHOWER OR THUNDERSTORM
ACTIVITY NORTH AS WELL. HI-RES MODELS THAT ARE HANDLING THE
CURRENT TRENDS WITH SOME SUCCESS...ARE BEARISH WHEN IT COMES TO
CONVECTIVE DEVELOPMENT THIS AFTERNOON...TO THE POINT OF VERY
LITTLE PRECIPITATION ACROSS THE FORECAST AREA. DONT THINK THIS IS
NECESSARILY PRUDENT...GIVEN THE AVAILABILITY OF MOISTURE AND THE
AT LEAST MARGINAL INSTABILITY NOTED IN THE AFTERNOON SOUNDINGS.
WILL MAINTAIN CHANCE TO LIKELY POPS NORTH OF PITTSBURGH.

MODEL GUIDANCE HAS TRENDED FURTHER NORTH WITH THE TRACK OF THE
UPPER-LEVEL WAVE TONIGHT...AS THE RIDGE OF HIGH PRESSURE RE-BUILDS
IN THE MID-WEST. MODIFICATIONS WERE MADE TO PUSH TONIGHTS RAIN
CHANCES WELL NORTH OF PREVIOUS FORECAST. SOME OF OUR SOUTHERN AND
WESTERN ZONES SHOULD EVEN GET SOME CLEARING HEADING INTO TONIGHT
WITH THE FOCUS OF DEEPER MOISTURE SHIFTING NORTH.
TAX

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
RIDGING STARTS TO BUILD OVER THE OHIO VALLEY DURING THE DAY ON
WEDNESDAY. THIS WILL DROP H500 HEIGHTS ACROSS THE CWA IN RESPONSE
AND HELP TO SAG THE FRONTAL BOUNDARY A BIT FURTHER SOUTH DURING
THE DAY. FOCUSED HIGHER POPS IN SOUTHERN PORTIONS OF CWA DURING
THE AFTERNOON. ENOUGH INSTABILITY IS PRESENT FOR THE CONTINUED
CHANCE OF THUNDER AS WELL. KEPT POPS IN CHANCE CATEGORY WITH
CONTINUED UNCERTAINTY AS TO FRONTAL EVOLUTION. AS RIDGE STARTS TO
BUILD EASTWARD...FRONTAL BOUNDARY WILL BECOME MORE DIFFUSE WITH
TIME. ALLOW POPS TO FALL OFF DURING THE EVENING HOURS WITH LOSS OF
HEATING.

H500 RIDGE IS IN CONTROL FOR THE REMAINDER OF THIS PERIOD...WITH
THE RIDGE AXIS PASSING BY AROUND 00Z FRIDAY. GFS/ECMWF BOTH PAINT
SOME DIURNAL QPF ACROSS THE AREA THURSDAY AND FRIDAY AFTERNOONS.
THINK THAT THIS IS OVERDONE FOR THE MOST PART AS AT LEAST MODEST
CAPPING SHOULD BE PRESENT UNDER THE RIDGE. EXCEPTION COULD BE
ALONG THE EASTERN RIDGES WITH MODEST UPSLOPE FLOW...AND KEPT AN
AFTERNOON/EVENING SLIGHT CHANCE BOTH AFTERNOONS IN THIS AREA.
OTHERWISE...DRY AND WARM CONDITIONS WILL PERSIST. A SLOW WARMING
TREND WILL SEE TEMPERATURES RISE BACK INTO THE LOWER AND MID 80S
FOR MOST AREAS BY FRIDAY.  CL

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
UPPER RIDGE GETS SLOWLY DISLODGED WITH TIME AS ENERGY EJECTS FROM
WESTERN U.S. TROUGH AND TOWARDS THE UPPER MISSISSIPPI VALLEY BY
00Z MONDAY. RESULTING SURFACE LOW AND FRONTAL SYSTEM WILL ADVANCE
EASTWARD WITH TIME...PERHAPS ARRIVING MONDAY NIGHT OR TUESDAY.
AHEAD OF THIS...MAINLY DIURNAL POPS GET A BIT HIGHER EACH DAY
WITH THE DEPARTURE OF THE RIDGE. RIPPLES ALONG THE BACK SIDE OF
THE RIDGE MAY PROVIDE LOCALIZED ENHANCEMENT...WHICH OF COURSE ARE
TOUGH TO TIME AT THIS DISTANCE. THE FRONT BRINGS MORE GENERALIZED
PRECIPITATION CHANCES MONDAY INTO TUESDAY.

FAIRLY STATIC ABOVE NORMAL TEMPERATURES ARE FORECAST FRIDAY NIGHT
THROUGH MONDAY NIGHT...WITH HIGHS IN THE 80S AND LOWS ON EITHER
SIDE OF 60. COOLER TEMPERATURES MAY ARRIVE TUESDAY WITH THE FRONT.
CL

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
A COMPLICATED NEAR-TERM FORECAST EARLY THIS MORNING AS A BROAD
FRONTAL ZONE IS HOLDING HIGHER MOISTURE CONTENT ACROSS THE
FORECAST AREA. THIS HAS RESULTED IN VERY SELECT REGIONAL TERMINALS
DROPPING DOWN TO VERY LOW VISIBILITIES...ALTHOUGH MOST OF OUR
MAJOR TERMINALS HAVE BEEN IMMUNE THUS FAR. HAVE CURRENT VFR
CONDITIONS GIVING WAY TO MVFR IN THE PRE-DAWN HOURS WITH
VISIBILITY REDUCTIONS. THIS IS BY FAR THE AREA OF LEAST
CONFIDENCE.

ADDITIONALLY A LINE OF RESIDUAL SCATTERED SHOWERS STRETCHES FROM
ZZV TO JUST SOUTH OF HLG. NOT EXPECTING MUCH FURTHER EXPANSION OR
STRENGTHENING OF THESE SHOWERS...BUT IF ONE DRIFTS OVER
ZZV/HLG...IT COULD LEAD TO TEMPORARY RESTRICTIONS.

LATER TODAY...HAVE THIS LINE OF SHOWERS LIFTING NORTH WITH THE
BROAD FRONTAL ZONE WHERE INSTABILITY THIS AFTERNOON COULD DRIVE
ADDITIONAL SHOWERS/THUNDERSTORMS. HAVE INCLUDED VCTS FOR MOST TAF
SITES...BUT SPATIAL EXTENT OF THUNDERSTORM ACTIVITY SHOULD BE
FAIRLY LIMITED.
TAX

.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
SCATTERED RESTRICTIONS IS A POSSIBILITY EARLY WEDNESDAY AS
FRONTAL BOUNDARY SLOWLY DECAYS.

&&

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

&&

$$



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