782
FXUS61 KPBZ 091351
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
951 AM EDT SUN AUG 9 2020
SYNOPSIS
WARM AND MOSTLY DRY WEATHER WILL CONTINUE THROUGH MONDAY UNDER HIGH
PRESSURE. A WEAK FRONT WILL APPROACH ON TUESDAY AND BRING THE NEXT
CHANCE OF RAIN TO THE AREA.
NEAR TERM /UNTIL 6 PM THIS EVENING/
GOES EAST VISIBLE IMAGERY SHOWS RIVER VALLEY FOG DISSIPATING ACROSS
THE AREA NOW THAT THE SUN HAS RISEN AND DIURNAL MIXING HAS BEGUN.
WATER VAPOR IMAGERY AND MODEL ANALYSIS INDICATES A VERY SUBTLE
SHORTWAVE TROUGH MOVING OVERHEAD IN AN OTHERWISE LARGE-SCALE RIDGING
PATTERN ACROSS MUCH OF EASTERN NORTH AMERICA. THIS TROUGH IS HELPING
TO BRING A FEW MID/UPPER-LEVEL CLOUDS TO THE REGION, BUT OTHERWISE
WILL HAVE LITTLE IMPACT ON THE SENSIBLE WEATHER W/ SUBSIDENCE AND
SURFACE HIGH PRESSURE PREVAILING.
12Z PIT SOUNDING SAMPLED A RATHER STRONG CAPPING INVERSION BETWEEN
ROUGHLY 840 AND 810 MB. THIS WILL HELP SLOW THE TEMPERATURE RISE
TODAY, AND MAY ACTUALLY RESULT IN A SLIGHTLY LOWER MAX TEMPERATURE
THAN INITIALLY FORECAST. ONCE THE T REACHES ~84 AT PIT BY 1 OR 2PM,
THE TEMPERATURE WILL ONLY SLOWLY RISE THEREAFTER AS TURBULENT MIXING
AT THE TOP OF THE BOUNDARY LAYER ERODES THAT CAP.
GIVEN THE CAPPING INVERSION ABOVE 850MB, DIURNALLY-DRIVEN CUMULUS
FIELD MAY BE SLOW TO OCCUR TODAY, IF OCCUR AT ALL. TEMPERATURES WILL
GENERALLY MAX OUT IN THE MID 80S, POSSIBLY UPPER 80S IF ALL THAT
ABUNDANT AND STRONG AUGUST SUNSHINE AND BOUNDARY LAYER MIXING
SUFFICIENTLY ERODES THAT CAP.
SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/
THE SURFACE HIGH WILL DRIFT EASTWARD TONIGHT AND MONDAY, AIDED BY
WEAK QUASI-ZONAL FLOW ALOFT. LOW-LEVEL FLOW WILL TURN SOUTHERLY WITH
TIME, WHICH WILL HELP TO KEEP WARMTH AND HUMIDITY ON AN UPWARD TREND.
AFTER A MOSTLY CLEAR NIGHT, MONDAY WILL ONCE AGAIN FEATURE ONLY
SCATTERED CUMULUS FOR THE MOST PART, AS THE MOISTURE INCREASE WILL BE
MAINLY LIMITED TO THE LOWER LEVELS. STILL, WITH 850MB TEMPERATURES
PUSHING 19C DURING THE AFTERNOON, HIGHS NEAR OR JUST ABOVE 90 APPEAR
LIKELY FOR MANY AREAS. GOING TO CONTINUE WITH A DRY FORECAST FOR NOW
GIVEN THE LACK OF UPPER MOISTURE, ALTHOUGH THE EASTERN RIDGES COULD
CONCEIVABLY SEE SOME ISOLATED DEVELOPMENT.
BY TUESDAY, A FAIRLY WEAK MID-LEVEL TROUGH WILL ARRIVE IN THE OHIO
VALLEY, WHICH WILL HELP TO PUSH A FRONTAL BOUNDARY OUR WAY FROM THE
NORTHWEST. INCREASING MOISTURE/PWAT ASSOCIATED WITH THE SYSTEM WILL
FINALLY ALLOW SUFFICIENT INSTABILITY FOR SCATTERED SHOWERS AND
STORMS, PARTICULARLY DURING THE AFTERNOON HOURS. ABOVE-NORMAL
TEMPERATURES WILL CONTINUE, WITH 90 DEGREE READINGS AGAIN POSSIBLE.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
ALTHOUGH MODEL DETAILS DIFFER, CURRENT THINKING IS THAT THE FRONTAL
BOUNDARY WILL SLOW TO A CRAWL OVER OUR REGION WEDNESDAY, AND THEN
STALL IN THE GENERAL VICINITY OF THE MIDDLE OHIO VALLEY INTO NEXT
WEEKEND. OVERALL MOISTURE EXPECTED TO REMAIN ELEVATED, AND SEVERAL
SHORTWAVES ARE EXPECTED DURING THE WEDNESDAY-SATURDAY PERIOD. THUS,
PRECIPITATION CHANCES WILL BE INCLUDED FOR EACH DAY, WITH DIURNAL
FACTORS LEADING TO THE HIGHEST POPS DURING THE AFTERNOON AND EVENING
PERIODS. LOCALIZED HEAVY RAINFALL MAY BE A CONCERN, ESPECIALLY IN
AREAS NEAR THE QUASI-STATIONARY FRONT. TEMPERATURES WILL REMAIN ABOVE
NORMAL, ALTHOUGH THE FRONT AND PRECIPITATION WILL LIKELY KEEP 90
DEGREE READINGS IN CHECK.
AVIATION /14Z SUNDAY THROUGH THURSDAY/
BUILDING HIGH PRESSURE WILL CONTINUE TO ENSURE VFR WITH LIGHT WIND
THROUGH THE TAF PERIOD. THE EXCEPTION WILL BE POSSIBLE MORNING VALLEY
FOG, MAINLY AT ZZV, WHERE CROSSOVER TEMPERATURES ARE MOST LIKELY TO
BE REACHED. DRY LOWER LEVELS SHOULD INHIBIT MOST FOG FORMATION
ELSEWHERE DESPITE EFFECTIVE RADIATIONAL COOLING.
OUTLOOK
PERIODIC RESTRICTION POTENTIAL RETURNS TUE THROUGH THU WITH A SLOW
MOVING SFC FRONT.
PBZ WATCHES/WARNINGS/ADVISORIES
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
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