285
FXUS61 KPBZ 181809
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
209 PM EDT SAT APR 18 2026
WHAT HAS CHANGED
THE SEVERE THREAT TODAY HAS DIMINISHED SOME BUT A LOW END DAMAGING
WIND THREAT STILL EXISTS. FROST AND FREEZE THREATS ARE INCREASING
FOR SUNDAY NIGHT NORTH OF PITTSBURGH AND ESPECIALLY MONDAY NIGHT
ACROSS MOST OF OUR AREA. A FREEZE WATCH HAS BEEN ISSUED NORTH OF
PITTSBURGH FOR SUNDAY NIGHT WITH A MORE WIDESPREAD WATCH LIKELY
MONDAY NIGHT. THE MIDDLE TO LATTER HALF OF NEXT WEEK FAVORS WARMER
THAN AVERAGE TEMPERATURES WITH LOW, BUT NOT ZERO, RAIN CHANCES.
KEY MESSAGES
1) A COLD FRONT SATURDAY AFTERNOON AND EVENING WILL BRING ANOTHER
ROUND OF STRONG THUNDERSTORMS. DAMAGING WIND WILL BE THE MOST LIKELY
THREAT WITH HAIL AND TORNADO VERY LOW PROBABILITY.
2) TEMPERATURES CRASH TO BELOW NORMAL SUNDAY AND MONDAY WITH
FROST/FREEZE CONCERNS EACH NIGHT AND EVEN A FEW SNOWFLAKES.
3) THE MIDDLE TO END OF NEXT WEEK LOOKS TO FEATURE ABOVE-NORMAL
TEMPERATURES WITH LOW, BUT NOT ZERO, RAIN CHANCES.
DISCUSSION
KEY MESSAGE 1...
SATURDAY MORNING SATELLITE AND RADAR IMAGERY SHOWS THE REMNANTS OF A
STRONG CLUSTER OF CONVECTION OFF TO OUR WEST IN INDIANA LINGERING AS
MOSTLY A SHIELD OF RAIN WITH CONVECTIVE DEBRIS CLOUDS THROWN OFF TO
THE EAST. LATEST SPC MESOANALYSIS IS DEPICTING THE EXPECTED PRE-
FRONTAL TROUGH AND SOME SCATTERED LIGHT SHOWERS ALONG IT AHEAD OF
THE MAIN RAIN SHIELD, AND THIS FEATURE IS LIKELY WHAT RE-DEVELOPMENT
OF THUNDERSTORMS WILL FOCUS ALONG THIS AFTERNOON AND EVENING.
THERE REMAINS DOUBT TO THE SETUP OVERALL TODAY THAT COULD LIMIT
SEVERE POTENTIAL. ONE UNCERTAINTY IS HOW MUCH DESTABILIZATION
WE'RE GOING TO GET LOCALLY WITH A COUPLE FACTORS AT PLAY.
AFOREMENTIONED DEBRIS CLOUDS ARE ALREADY MOVING OVERHEAD THIS
MORNING POTENTIALLY LIMITING HEATING AND NOT FULLY REALIZING OUR
CAPE POTENTIAL WITH ENOUGH BREAKS AND FILTERED SUN RATHER
TOPPING OUT MLCAPE AROUND 500-700 J/KG. NOTED WARMER MID-LEVEL
AIR IN OUR 12Z BALLOON AND RECENT PIT ACARS SOUNDINGS WITH
LITTLE ROOM TO WET-BULB IT OUT WILL NOT LEND MUCH CREDENCE TO
CONFIDENCE IN DESTABILIZATION EITHER. ANOTHER CONCERN IS HOW
MUCH LOW-LEVEL DRY AIR WE HAVE IN PLACE. WHILE MORNING T/TD
SPREADS WERE LOW, JUST A FEW THOUSAND FEET OFF OF THE SURFACE
LIES A GOOD BIT OF DRY AIR. DESPITE GOOD SOUTHWEST FLOW, DEW
POINTS AREN'T MUCH HIGHER IN THAT DIRECTION, AND IT'S SEEMING
MORE LIKELY THAT MIXING COUNTERACTS MOISTURE ADVECTION PROVIDING
HIGH CLOUD BASES AND AN INVERTED V TYPE SOUNDING. EVEN THE
USUALLY MOISTURE-EXCITED NAM3K IS FALLING CLOSER IN LINE WITH
OTHER CAMS. MID-LEVEL FLOW WILL STILL BE SUFFICIENT FOR A LOW
CAPE/MODERATE SHEAR ENVIRONMENT WITH A BELT OF 50-60 KNOT
SOUTHWESTERLIES AT 500 MB RESULTING IN 40-45 KNOT EBWD VALUES.
WHAT THIS MEANS IMPACT-WISE TODAY IS THAT A LOW-END WIND THREAT
IS WHAT WE'RE FACED WITH TODAY, PRIMARILY IF/WHERE STORMS CAN
CONGEAL AND SURGE ALONG OUTFLOWS OR COLD POOLS, WITH TORNADO AND
HAIL VERY LOW. 12Z CAMS SUGGEST BROKEN CONVECTIVE CLUSTERS
ENTERING EASTERN OHIO AROUND OR JUST AFTER 18Z, WESTERN PA 20Z,
AND THROUGH THE RIDGES AROUND 00Z. AFTER SUNSET, THE SEVERE
THREAT WILL QUICKLY DIMINISH, BUT ADDITIONAL SHOWERS ARE LIKELY
TO CONTINUE INTO THE OVERNIGHT HOURS AS A TRAILING COLD FRONT
PASSES WITH LIFT ENHANCED ALONG A MID-LEVEL WAVE.
KEY MESSAGE 2...
LOW LEVEL COLD ADVECTION ENSUES BEHIND SATURDAY NIGHT'S FRONT AS A
DEEP UPPER LEVEL TROUGH SETTLES IN. NORTHWEST FLOW AS SURFACE
HIGH PRESSURE ESTABLISHES WILL ALLOW FOR THE COLDEST AIR SINCE
EARLY APRIL TO ARRIVE BACK LOCALLY SUNDAY AND MONDAY. TEMPERATURES
WILL DIP CLOSE TO OR BELOW FREEZING SUNDAY AND, ESPECIALLY,
MONDAY NIGHT. MONDAY NIGHT WILL BE THE COLDER ONE WITH LIGHTER
WIND AND LOWER DEW POINTS BENEATH THE CORE OF THE HIGH. A
FROST/FREEZE THREAT WILL CROP UP BOTH NIGHTS. SUNDAY NIGHT, THE
MAJORITY OF THE AREA SHOULD SEE LOWS DIP BELOW 36F BUT HOVER
RIGHT AROUND OR ABOVE FREEZING SAVE NORTH OF PITTSBURGH AND IN
THE RIDGES WHERE HIGHER CONFIDENCE IN SUB-FREEZING TEMPERATURES
LIES. THERE, CONFIDENCE AT THIS TIME IS HIGH ENOUGH TO WARRANT
ISSUANCE OF A FREEZE WATCH. ELSEWHERE, ELEVATED WIND SUNDAY
NIGHT IS LIKELY TO PREVENT WIDESPREAD FROST DEVELOPMENT, SO IT
LOOKS LIKE A FREEZE OR NOTHING SETUP SAVE SOME LOCALIZED
SHELTERED AREAS. MONDAY NIGHT BRINGS A MUCH HIGHER PROBABILITY
FOR AN AREAWIDE FREEZE WITH THE CHANCE FOR LOWS <32F AT 70-90+%,
AND FROST/FREEZE HEADLINES WILL VERY LIKELY BE NEEDED AGAIN.
LIGHT PRECIP ALSO RETURNS EXPECTED SUNDAY AFTERNOON AND NIGHT
AS WEAK VORTICITY LOBES ROUND THE COLD UPPER TROUGH.
THERMODYNAMIC PROFILES WILL LIKELY SUPPORT SOME WIDELY SCATTERED
LIGHT SNOW SHOWERS AMONG THE RAIN SHOWERS, ESPECIALLY AFTER
DARK SUNDAY NIGHT, BUT ACCUMULATION POTENTIAL IS LOW WITH
PERHAPS A DUSTING ON ELEVATED SURFACES IN THE COLDEST AREAS
(RIDGES AND I-80 CORRIDOR).
KEY MESSAGE 3...
ALBEIT WITH SOME TIMING, AMPLITUDE, AND ORIENTATION DISCREPANCY
AMONG LONGER RANGE ENSEMBLES, MID-LEVEL RIDGING IS EXPECTED TO BUILD
ACROSS THE CENTRAL CONUS AND SLIDE EAST INTO OUR AREA FOR THE LATTER
HALF OF THE WEEK ULTIMATELY PROVIDING OVERALL DRIER AND WARMER
WEATHER. WE STILL LOOK TO BE FAVORING A NORTHWEST FLOW REGIME ON
WEDNESDAY AS A WEAK SURFACE LOW DIVES THROUGH LAKE ERIE TO LAKE
ONTARIO. THIS, AND AN ASSOCIATED SHORTWAVE, COULD BRING SOME PRECIP
BACK ON WEDNESDAY WITH A DEEPER MID-LEVEL WAVE FAVORING THE "WET"
SOLUTION WHICH STILL IS <0.5" OF QPF IN A SCATTERED NATURE ON THE
HIGH END. ALL TOLD, WEDNESDAY DOES NOT LOOK TO FEATURE A NOTABLE
AMOUNT OR COVERAGE OF RAIN, AND MACHINE LEARNING SUGGESTS LOW TO
ZERO SEVERE WEATHER PROBABILITY.
THURSDAY FAVORS DRIER AND WARMER AS THE RIDGE AXIS TRANSLATES
OVERHEAD, BUT THAT PERIOD OF HIGHER CONFIDENCE DRY WEATHER ENDS
QUICKLY AS THE RIDGE BREAKS DOWN FRIDAY INTO SATURDAY AND PRECIP
CHANCES LIKELY RETURN. TIMING DETAILS REMAIN QUITE UNCERTAIN WITH
ARRIVAL TIMES RANGING FROM LATE FRIDAY AFTERNOON TO EARLY SATURDAY
MORNING. PROBABILITY TO EXCEED 80F FOR HIGHS ON THURSDAY CREEPS UP
TO AROUND 35% FOR PITTSBURGH (HIGHER SOUTH AND WEST), AND MUCH
HIGHER ON FRIDAY TO 50-75% ACROSS MOST OF THE AREA. MOISTURE
SHOULDN'T REBOUND A WHOLE LOT FROM THE MUCH LOWER DEW POINTS THROUGH
MID-WEEK, BUT, THE HEAT RISK MAP DOES DEPICT SOME MINOR CATEGORY
ARRIVING LOCALLY FOR BOTH DAYS. WHILE MOST SHOULD NOT BE AFFECTED,
ANY WHO ARE ESPECIALLY SUSCEPTIBLE TO THE HEAT SHOULD TAKE
PRECAUTION IF SPENDING PROLONGED PERIODS OUTDOORS.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
VFR REMAINS IN PLACE AT THE VERY START OF THE TAF PERIOD, BUT
IMPACTS ARE EXPECTED THIS AFTERNOON AND TONIGHT WITH THE
APPROACH AND PASSAGE OF A COLD FRONT. ONGOING SHOWERS AND
THUNDERSTORMS WILL CONTINUE TO SLOWLY APPROACH FROM THE WEST.
INSTABILITY IS NOT OVERLY IMPRESSIVE AND DO NOT FORESEE A
WIDESPREAD THREAT OF STRONG WIND GUSTS. NEVERTHELESS, HAVE
MAINTAINED TWO-HOUR TEMPO GROUPS FOR THE MOST-LIKELY TIMING FOR
THUNDERSTORMS...GENERALLY BETWEEN 19Z AND 23Z FROM WEST TO EAST.
CANNOT RULE OUT 35 TO 40 KNOT GUSTS IN THE STRONGEST STORMS, BUT
THINK CHANCES ARE LOW ENOUGH TO LEAVE OUT EXPLICIT GUST MENTIONS
FROM THE TAFS. OUTSIDE OF STORMS, EXPECT S-SW WIND WITH GUSTS
FROM 25-30KT THROUGH THE AFTERNOON.
WIDESPREAD MVFR IS EXPECTED IN A POST-FRONTAL LOW-LEVEL COLD
ADVECTION REGIME WITH SHOWERS CONTINUING AS A MID-LEVEL TROUGH
COMPLETES ITS PASSAGE. THUNDER AND ESPECIALLY SEVERE CHANCE
BOTH DIMINISH GREATLY AFTER SUNSET. A WIND SHIFT TO THE WNW IS
ALSO EXPECTED AFTER FROPA, THOUGH GUSTS SHOULD GRADUALLY
DIMINISH THROUGH THE EVENING. CEILINGS ARE LIKELY TO IMPROVE TO
VFR DURING THE POST-SUNRISE HOURS, WITH WIND GUSTS CONTINUING
FROM THE WNW.
OUTLOOK...
AREAS OF MVFR CIGS ARE EXPECTED TO REDEVELOP SUNDAY AFTERNOON
INTO MONDAY UNDER A CROSSING UPPER TROUGH AND COLD W-NW FLOW.
SCATTERED RAIN AND SNOW SHOWERS ARE ALSO EXPECTED AT TIMES. VFR
RETURNS LATER MONDAY AND TUESDAY UNDER HIGH PRESSURE. ANOTHER
COLD FRONT WILL BRING SHOWER AND RESTRICTION POTENTIAL ON
WEDNESDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...FREEZE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY MORNING FOR
PAZ007>009-013>016-020-022-074-076>078.
OH...FREEZE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY MORNING FOR
OHZ039>041-048>050-057-058.
WV...FREEZE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY MORNING FOR
WVZ001-510>514.
DISCUSSION...MLB
AVIATION...CL
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