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Pittsburgh, PA Thread: Winter 2015-2016


meatwad

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The coastal hasn't taken over yet,  We can assume then that "bombogenesis" hasn't occurred, which should reinforce the precip shield.  Obviously the dynamics of that have yet to play out so we don't really know what will happen - does the low get captured and pulled?  Does it not close off and move more progressively?  Based on what the NAM is spitting out I have to assume it shows a capture event.

 

Interesting to look at the water vapor and see just how deep of a trough has formed in the East.

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586
FXUS61 KPBZ 230310
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1010 PM EST FRI JAN 22 2016

.SYNOPSIS...
LOW PRESSURE WILL YIELD WIDESPREAD SNOW OVER THE MID ATLANTIC. THE
HEAVIEST SNOW IS EXPECTED SOUTH AND EAST OF PITTSBURGH. THE SYSTEM
WILL PULL OFF TO THE EAST LATE SATURDAY...WITH HIGH PRESSURE
BUILDING OVERHEAD ON SUNDAY. WARMER WEATHER IS FORECAST MONDAY AND
TUESDAY WITH TEMPERATURES REACHING INTO THE 40S.

&&

.NEAR TERM /THROUGH SATURDAY/...
FORECAST PLAYING OUT AS FIGURED WITH ROUNDS OF HEAVY SNOW OVER
NORTHERN WV AND WESTERN MD. BAND OF SNOW THAT CAMPED OUT OVER
PARTS OF CENTRAL ALLEGHENY COUNTY HAS WEAKENED...BUT STILL A GOOD
DISCREPANCY FROM US 422 CORRIDOR TO I-70. STRONG ISENTROPIC
UPGLIDE AT 290K CONTINUES TO GENERATE PRECIP OVER THE REGION. IR
SATELLITE ILLUSTRATES CLOUD TOPS CONTINUING TO COOL ACROSS THE
NORTHERN HALF OF WV ABOVE THE WARM CONVEYER BELT...WHICH WILL
KEEP SNOW ACCUMULATIONS OVER SERN PART OF CWA GOING THROUGH THE
NIGHT TIME. SNOWFALL RATES OF 1-2" PER HOUR ARE LIKELY. MIGHT HAVE
TO ADD INDIANA COUNTY TO THE WARNING GIVEN EXTRAPOLATION OF RADAR.

WITH STRONG WINDS IT WILL BE TOUGH TO GET ACCURATE MEASUREMENTS.
WE ARE ALREADY GETTING REPORTS OF 5-6 FOOT SNOW DRIFTS IN THE
HIGHER ELEVATIONS OF PRESTON COUNTY IN WV. PREVIOUS DISCUSSION
BELOW...

MODEL TRENDS CONTINUE TO SUGGEST A SLIGHTLY NORTHERN TRACK WITH
THE UPPER LOW...AND THUS THE TRACK AND DEVELOPMENT OF THE COASTAL
LOW OVERNIGHT. THIS HAS BEEN REFLECTED IN THE CURRENT
FORECAST...WITH A SLIGHT UPTICK IN AMOUNTS ACROSS THE REGION BUT
MOST NOTABLY TO THE AREAS SOUTH OF I-70. THE NAM STILL SEEMS TO
BE THE MOST BULLISH WITH SNOW AMOUNTS ACROSS THE REGION BUT DOES A
GREAT JOB OF PORTRAYING THE DEFORMATION ZONE THAT IS ANTICIPATED
TO DEVELOP ACROSS A PORTION OF THE REGION TONIGHT/SATURDAY
MORNING. WHERE THIS EVENTUAL BAND OF SNOW/TROWAL WILL SET UP AND
PRODUCE THE BEST SNOW FALL RATES/AMOUNTS...STILL REMAINS IN
QUESTION BUT....GENERALLY ANTICIPATE OVER A FOOT OF SNOW FROM
WETZEL-GREENE-FAYETTE-WESTMO RIDGES AND ALMOST 2 FEET (OR MORE) IN
THE PRESTON...TUCKER...AND GARRETT.

ALL IN ALL VERY MINUTE CHANGES TO THE FORECAST...WITH ENHANCEMENTS
MADE BASED ON THE LATEST QPF FORECAST FROM WPC. AS WAS MENTIONED
PREVIOUSLY...SNOW RATIOS SHOULD REMAIN AT OR BELOW CLIMATOLOGY IN
THE 10-12:1 RANGE THROUGH THE EVENT...IT WILL BE THE MESOSCALE
BANDS OF SNOW THAT WILL ENHANCE THE SNOW TOTALS ACROSS THE REGION.

IN REGARD TO THE WIND...GUSTS TO 30MPH MAY BE POSSIBLE IN THE
HIGHER TERRAIN...ESPECIALLY AS THE LOW LEVEL JET RAMPS UP THIS
EVENING. THIS COULD CAUSE BLOWING SNOW AND VISIBILITY CONCERNS IN
THOSE LOCATIONS.

AS THE COASTAL LOW MOVES OFF TO THE EAST...SNOW WILL LINGER WHERE
THE DEFORMATION BAND/TROWAL REMAINS...BUT SHOULD END FROM WEST TO
EAST BY LATE SATURDAY AFTERNOON. THE HRRR HAS SNOW ENDING FOR
MOST OF ALLEGHENY COUNTY AND THE AREAS FROM ZZV-PIT-DUJ BY EARLY
MORNING...BUT WILL LEAVE THE CURRENT PRODUCT END TIMES AS IS FOR
NOW.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE WILL START TO BUILD OVERHEAD SATURDAY NIGHT AS THE
SYSTEM MOVES NORTHEASTWARD. UPPER LEVEL FLOW WILL BE BACKING TO
THE NORTHEAST AND WITH SATURATION IN THE DENDRITIC GROWTH
ZONES...SOME LIGHT SNOW MAY BE POSSIBLE UNTIL SUNDAY MORNING IN
THE RIDGES. ELSEWHERE...IT APPEARS SKIES WILL CLEAR OUT.
TEMPERATURES WERE KEPT NEAR A BLEND OF GUIDANCE FOR LOWS...BUT
COULD BE COLDER IF WE FULLY DECOUPLE.

FLATTENING RIDGE ALONG AND SURFACE HIGH PRESSURE ARE IN CONTROL
ON SUNDAY...WITH DRY WEATHER AND A SLIGHT MODERATION IN
TEMPERATURES. SOME MID/HI CLOUDS WILL RETURN DURING THE AFTERNOON.
THIS SLOW CLOUD INCREASE WILL CONTINUE THROUGH SUNDAY NIGHT AND
MONDAY AS FLOW TURNS SOUTHWEST AHEAD OF THE NEXT FRONTAL SYSTEM. A
FEW RAIN OR SNOW SHOWERS MAY ARRIVE IN OUR WESTERN COUNTIES BY 00Z
TUESDAY...BUT MOST WILL REMAIN DRY THROUGH THAT TIME. THE
SOUTHWEST FLOW WILL HELP TO PUSH TEMPERATURES TO NEAR OR EVEN
SLIGHTLY ABOVE NORMAL BY MONDAY.

NO MAJOR CHANGES TO THE GRIDDED FORECAST DURING THIS PERIOD.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
FRONTAL BOUNDARY PEGGED TO MOVE THROUGH DURING THE DAY TUESDAY.
PRECIPITATION MAY BEGIN AS LIGHT SNOW SUNDAY NIGHT...BUT SHOULD
CHANGE TO RAIN WITH TIME. CANNOT RULE OUT ISOLATED POCKETS OF FZRA
BUT CHANCES ARE TOO LOW TO INCLUDE AT THIS TIME. MOST AREAS SHOULD
BE ABLE TO CHANGE TO RAIN TUESDAY...BEFORE TURNING BACK TO SNOW
BEHIND THE FRONT. PRECIPITATION OVERALL SHOULD BE REASONABLY LIGHT.
A BRIEF DRY INTERLUDE WEDNESDAY NIGHT INTO THURSDAY WILL BE FOLLOWED
BY ANOTHER SYSTEM TO CLOSE OUT THE WORK WEEK.

THE GRIDS DURING THIS PERIOD WERE MOSTLY CONSTRUCTED BY USING THE
SUPERBLEND GUIDANCE.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
WHILE BVI/FKL/DUJ SHOULD REMAIN TO THE NORTH OF HEAVIER SNOW AND
WILL EVENTUALLY DROP TO MVFR CONDITIONS...REST OF TERMINALS SHOULD
DROP TO IFR AND LOWER CONDITIONS. LIFR IS EXPECTED TO CONTINUE
THROUGHOUT THE NIGHT UNTIL CONDITIONS START TO IMPROVE SLOWLY FROM
WEST TO EAST ON SATURDAY. CERTAINLY CANNOT RULE OUT VLIFR
VISIBILITIES IN THE HEAVIEST SNOW BANDS. NE WIND GUSTS OF 15 TO
25 KNOTS WILL BECOME COMMON TONIGHT...WHICH MAY LEAD TO SOME
BLOWING AND DRIFTING SNOW IN PORTIONS OF SW PA AND NORTHERN WV.
IMPROVEMENT WILL BEGIN TOWARDS THE VERY END OF THE TAF
PERIOD.

.OUTLOOK.../SATURDAY AFTERNOON THROUGH WEDNESDAY/...
RESTRICTIONS WILL CONTINUE TO WANE THROUGH SATURDAY NIGHT AS THE
SYSTEM PULLS AWAY...WITH VFR RETURNING ON SUNDAY. COLD FRONT WILL
BRING POSSIBLE RESTRICTIONS TUESDAY.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WARNING UNTIL 1 AM EST SUNDAY FOR MDZ001.
OH...WINTER WEATHER ADVISORY UNTIL 7 PM EST SATURDAY FOR OHZ049-050-
057>059-068.
WINTER STORM WARNING UNTIL 7 PM EST SATURDAY FOR OHZ069.
PA...WINTER WEATHER ADVISORY UNTIL 7 PM EST SATURDAY FOR PAZ021-023.
WINTER STORM WARNING UNTIL 1 AM EST SUNDAY FOR PAZ031-074>076.
WINTER STORM WARNING UNTIL 7 PM EST SATURDAY FOR PAZ029-073.
WV...WINTER WEATHER ADVISORY UNTIL 7 PM EST SATURDAY FOR WVZ002-003.
WINTER STORM WARNING UNTIL 1 AM EST SUNDAY FOR WVZ012-021-
509>514.
WINTER STORM WARNING UNTIL 7 PM EST SATURDAY FOR WVZ004.

&&

$
 

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BOOM

 

Winter Storm Warning
URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE PITTSBURGH PA1034 PM EST FRI JAN 22 2016PAZ021-023-231145-/O.UPG.KPBZ.WW.Y.0004.000000T0000Z-160124T0000Z//O.EXA.KPBZ.WS.W.0001.000000T0000Z-160124T0000Z/ALLEGHENY-INDIANA-INCLUDING THE CITIES OF...PITTSBURGH METRO AREA...INDIANA1034 PM EST FRI JAN 22 2016...WINTER STORM WARNING IN EFFECT UNTIL 7 PM EST SATURDAY...THE NATIONAL WEATHER SERVICE IN PITTSBURGH HAS ISSUED A WINTERSTORM WARNING FOR HEAVY SNOW...WHICH IS IN EFFECT UNTIL 7 PM ESTSATURDAY. THE WINTER WEATHER ADVISORY IS NO LONGER IN EFFECT.* SNOW ACCUMULATION...2 TO 5 INCHES NORTH...6 TO 10 INCHES SOUTH.* PERIOD OF MOST INTENSE SNOW...THROUGH 3AM.* SNOW ENDING...LATE SATURDAY AFTERNOON.* IMPACT...HAZARDOUS TRAVEL CONDITIONS ARE EXPECTED DUE TO SNOW.  SOME DRIFTING OF SNOW WILL ALSO BE POSSIBLE.* WIND...NORTHEAST AROUND 10 MPH WITH GUSTS UP TO 25 MPH.* IMPACTS...HAZARDOUS TRAVEL CONDITIONS ARE EXPECTED DUE TO  REDUCED VISIBILITY AND SNOW ACCUMULATION.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHERCONDITIONS ARE EXPECTED OR OCCURRING.  SIGNIFICANT AMOUNTS OFSNOW ARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL INAN EMERGENCY. IF YOU MUST TRAVEL...KEEP AN EXTRA FLASHLIGHT...FOOD...AND WATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY.&&$$
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Verszyla is one of the worst on camera fakes in the nation.

 

http://www.crh.noaa.gov/Image/lmk/pdf/deformation_zones.pdf

 

The deformation zone seems to be setting up on the AGC/WSH border.  Watch the movement of the returns of the radar.."airstreams flowing toward each other and then fanning out as they meet"

 

We have a long way to go.  Hope you all enjoy it. 

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This was on their facebook page an hour ago lol

 

US National Weather Service Pittsburgh PA We've expected the entire time that there will be a wide spread in snowfall totals across Allegheny County. A realistic range is 2" along the Allegheny-Butler county line all the way to 8" in the southern tip. Since our advisories and warnings are county-based averages, we don't expect to issue a warning for Allegheny County.

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The coastal hasn't taken over yet,  We can assume then that "bombogenesis" hasn't occurred, which should reinforce the precip shield.  Obviously the dynamics of that have yet to play out so we don't really know what will happen - does the low get captured and pulled?  Does it not close off and move more progressively?  Based on what the NAM is spitting out I have to assume it shows a capture event.

 

Interesting to look at the water vapor and see just how deep of a trough has formed in the East.

You're right, it's such a close call as to what happens in part II of this system overnight.

How far does that 850 mb fetch make it back.

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What is the difference between base and composite reflectivity?
The main difference is composite reflectivity shows the highest dBZ (strongest reflected energy) at all elevation scans, not just the reflected energy at a single elevation scan. This can be seen in the images below from the Salt Lake City radar.
 

  Base Reflectivity   Composite Reflectivity refl.gifcomp.gif

Notice the additional reflectivity that is visible in the composite reflectivity (far right). It is most readily seen around the name 'Wendover'. Also notice the composite view displays a slightly larger area of heavy rain (orange-red area to the west of Wendover).

Why the difference? Base reflectivity only shows reflected energy at a single elevation scan of the radar. Composite reflectivity displays the highest reflectivity of ALLelevations scans. So, if heavier precipitation is higher in the atmosphere over an area of lighter precipitation (the heavier rain that has yet to reach the ground), the composite reflectivity image will display the stronger dBZ level.

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