[CALV-AUXCOMM] [New post] Update on weekend weather

[Calvert County Auxiliary Communications Services]

Post       : Update on weekend weather
URL        : https://auxcomm.k3cal.org/2016/06/04/update-on-weekend-weather/
Posted     : June 4, 2016 at 10:48 am
Author     : Eric Christensen
Categories : Weather

This weekend is shaping up to be potentially stormy. While I'm not expecting an AUXCOMM activation I am expecting a SKYWARN activation (a mission that we do support).  Severe weather reports can be relayed on the local SKYWARN repeater (145.350MHz), over our 146.985MHz repeater (if someone is guarding for such messages), or directly to the National Weather Service office in Sterling.  Please review the reporting criteria ( http://www.weather.gov/lwx/skywarn_svr-reports )  now. The latest Hazardous Weather Outlook from Sterling notes:
SPOTTER ACTIVATION WILL BE POSSIBLE THIS AFTERNOON..AND LIKELY ON SUNDAY.
With that in mind, everyone should monitor the 146.985MHz repeater as much as possible. I will try to pass along any watches and warnings on that repeater, APRS, and by email. Because my messages aren't automatic (I'm trying to work on a solution for that) it is important that you monitor NOAA All-Hazards Radio ( http://www.weather.gov/lwx/nwr )  (you do have one, correct?) for real-time warnings.
Today
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A slight risk of severe weather exists for today over much of Maryland. The highest threat will be from damaging winds although hail and an isolated tornado cannot be ruled out.   Below is the forecast discussion ( http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=AFD&format=CI&version=1&glossary=1&highlight=on )  and an edited version of the Day 1 Convective Outlook ( http://www.spc.noaa.gov ) .  These products are not static and it's important to review the latest information available.

 
Forecast area within a saturated airmass this morning. Any synoptic
features are subtle. Therefore, the bigger concern in the immediate
term is the fog potential. In light of Friday`s rainfall, there is
definitely room for areas of fog to develop. The uncertainty is with
regard to how dense it will be, and for how long. The current cloud
cover would be a mitigating factor. Am seeing that evolve as low
clouds instead along I-95. Therefore, am not planning on a Dense Fog
Advisory at this time.  Of course, we will continue to monitor.

It may take a little while for the low clouds and fog to burn off
after sunrise. Once it does, the approaching trough axis and deep
southwest flow around mid-level subtropical ridge will allow for
moisture advection into area...on top of the already humid air mass.
The column will be saturated, with building instability (MUCAPE
greater than 1000 j/kg) within an approaching theta-e ridge axis.
That will result in an atmosphere that will be conducive for
thunderstorms to develop. Then, to top it off, there are indications
that a zone of 30-40 kt bulk shear in the 0-3 km layer will advance
into the mountains late in the day. Therefore, am concerned with
local damaging winds from wet microbursts as well as heavy rainfall.

Precipitable waters will be running near the daily max. Recent
rainfall in the Potomac Highlands and neighboring valleys have left
those areas saturated. Have opted to raise a Flash Flood Watch for
counties between the Appalachians to the Blue Ridge, as well as the
central foothills. Guidance lowest and PoPs highest here.  There are
also metro DC area concerns, but thunderstorm coverage, forward
motion, and not quite the risk of training cells preclude a watch at
this time.

Thunderstorm development will focus on the mountains late in the
day, and will migrate east during the evening. Most of the
instability will wane during the course of the evening hours.
However, shear will be increasing, and area will be pegged at the
heart of the isentropic ridge. Therefore, am keeping PoPs somewhat
high through the night.
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT SAT JUN 04 2016

VALID 041300Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE OH/TN RIVER VALLEYS
TO MID-ATLANTIC STATES...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MIDWEST/TN VALLEY TO
THE MID-ATLANTIC STATES...

...SUMMARY...
THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF THE OHIO AND TENNESSEE
VALLEYS TO THE MID-ATLANTIC STATES TODAY...ACCOMPANIED BY A RISK FOR
SOME SEVERE STORMS WITH DAMAGING WIND GUSTS AND HAIL.

...SYNOPSIS...
AN AMPLIFIED LARGE-SCALE PATTERN WILL DOMINATE THE CONUS AND
ADJACENT CANADA/MEXICO THROUGH EARLY SUNDAY. A SHORTWAVE TROUGH WILL
CONTINUE TO AMPLIFY/SPREAD SOUTHEASTWARD OVER THE UPPER
MIDWEST/UPPER GREAT LAKES...WHILE A PERSISTENT UPPER LOW OVER TX
GENERALLY SHIFTS SLOWLY SOUTHWARD. IN THE WEST...AN UPPER LOW
CURRENTLY OFF THE CA COAST IS EXPECTED TO REACH NORTHERN/CENTRAL CA
TONIGHT WHILE AN UPPER RIDGE OTHERWISE PERSISTS OVER THE GREAT BASIN
AND ROCKIES.

...OH/TN VALLEYS TO MID-ATLANTIC STATES...
60S F SURFACE DEWPOINTS WILL BE PREVALENT WITHIN A RELATIVELY BROAD
WARM/MOIST SECTOR ACROSS THE REGION...WITH EARLY-MORNING
SATELLITE/RADAR IMAGERY IMPLYING THAT THE STRONGEST
INSOLATION/DESTABILIZATION WILL OCCUR IN AREAS SOUTH OF THE OH RIVER
LATER TODAY. WEAKENING INHIBITION WITH 1000-1500 J/KG MLCAPE IS
EXPECTED BY EARLY/MID-AFTERNOON PARTICULARLY FROM PARTS OF
TN/EASTERN KY INTO WV/VA AND FAR SOUTHERN PORTIONS OF OH AND PA. AS
INCREASING THUNDERSTORM DEVELOPMENT OCCURS LATER
TODAY...SOUTHWESTERLY LOW/MID-TROPOSPHERIC WINDS ARE EXPECTED TO
STRENGTHEN ACROSS THE OH VALLEY AND ADJACENT PARTS OF THE TN
VALLEY/APPALACHIANS THROUGH THE AFTERNOON/EVENING...WITH 40+ KT
MID-LEVEL WINDS CONTRIBUTING TO INCREASINGLY FAVORABLE WIND PROFILES
FOR ORGANIZED STORMS INCLUDING SUSTAINED MULTICELLS AND POTENTIALLY
SOME SUPERCELLS. ASIDE FROM AN INCREASING COVERAGE/INTENSITY OF THE
THUNDERSTORMS ACROSS THE OH/TN VALLEYS THIS AFTERNOON...A SOMEWHAT
SEPARATE CORRIDOR OF THUNDERSTORMS IS EXPECTED TO DEVELOP OVER THE
WV/VA MOUNTAINS AND INTENSIFY/MOVE EAST-SOUTHEASTWARD PRIMARILY
ACROSS PARTS OF VA/MD. DAMAGING WINDS/SOME SEVERE HAIL WILL BE
POSSIBLE ACROSS THESE REGIONS THIS AFTERNOON AND EVENING.

..GUYER/DEAN.. 06/04/2016

Sunday
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Sunday contains our greatest threat for severe weather starting around 2PM (EDT). There is a moderate risk of severe weather with the greatest threat coming from severe winds and hail. Below is the forecast discussion ( http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=AFD&format=CI&version=1&glossary=1&highlight=on )  and an edited version of the Day 1 Convective Outlook ( http://www.spc.noaa.gov ) .  Again, these products are not static and it's important to review the latest information available.
Like today, Sunday will start off with a lot of low level residual
moisture.  It may be more in the way of lingering showers. Then, the
500 mb trough axis pivots into area and tilts negatively, which in
turn will provide added lift. The almost 50 knot shear max will be
positioned across the area. Dewpoints will still be in the upper 60s
to near 70f. Therefore, we will be in an environment favorable for
thunderstorm development.  The wild card remains the extent of
daytime heating. Given any insolation, numerous strong to severe
thunderstorms appear likely. Damaging winds would be the primary
concern.  Lapse rates not as impressive as Saturday, which makes
hail not as likely. However, its still possible in any supercell.
Hodographs do not look to favor tornadoes, but like the dayshift
yesterday said, the threat is non-zero. Finally, rainfall should
still be heavy as precipitable waters will remain near 2 inches.
given the threat for multiple rounds, that suggests that there will
be another round of potential flash flooding, which this time would
extend into the urban/suburban corridor. Will maintain the mention
in the Hazardous Weather Outlook.

The cold front will cross the area Sunday evening, which should
rapidly push thunderstorms toward the eastern shore. Am holding onto
a few lingering showers east of I-95 after midnight. The rest of the
area should have a dry overnight.
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 AM CDT SAT JUN 04 2016

VALID 051200Z - 061200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS ERN VA...NERN
NC...MD...DE...SRN NJ...SERN PA...

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN GA ACROSS THE MID
ATLANTIC AND INTO PA/NJ...

...THERE IS A MRGL RISK OF SVR TSTMS OVER MUCH OF THE ERN STATES
EXCEPT FOR NEW ENGLAND AND SRN FL...

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS APPEAR LIKELY ACROSS PARTS OF THE MID
ATLANTIC REGION SUNDAY AFTERNOON AND EVENING. DAMAGING WINDS...A
TORNADO OR TWO AND MARGINALLY SEVERE HAIL ARE POSSIBLE. MORE
ISOLATED AND MARGINAL SEVERE STORMS ARE ALSO POSSIBLE MAINLY DURING
THE AFTERNOON ACROSS PARTS OF THE SOUTHEASTERN STATES...AND AS FAR
NORTH AS SOUTHERN NEW YORK.

...SYNOPSIS...
A NEGATIVELY-TILTED SHORTWAVE TROUGH WILL MOVE FROM THE OH VALLEY
INTO THE MID ATLANTIC WITH 50 KT MIDLEVEL SPEED MAX ACROSS VA AND MD
BY 00Z. LOW PRESSURE WILL DEEPEN OVER SRN ONTARIO AND QUEBEC WITH
SFC TROUGH EXTENDING SEWD ACROSS ERN PA...VA...AND INTO THE CNTRL
CAROLINAS. AHEAD OF THE LOW PRESSURE TROUGH...MID TO UPPER 60S F
DEWPOINTS WILL EXIST AND COMBINE WITH AREAS OF HEATING TO CREATE A
MARGINALLY UNSTABLE ATMOSPHERE SUFFICIENT FOR SCATTERED SEVERE
STORMS MAINLY FROM NC INTO ERN VA...THE DELMARVA...SRN NJ AND SERN
PA DURING THE AFTERNOON. FARTHER N INTO NY AND SRN NEW
ENGLAND...PRECIPITATION WILL OCCUR BUT INSTABILITY WILL LIKELY BE
TOO WEAK FOR ANYTHING MORE THAN ISOLATED SEVERE STORMS.

TO THE S...A VERY MOIST AIR MASS WILL ALSO EXIST ACROSS THE GULF
COAST STATES...WITH WEAK CONVERGENCE ASSOCIATED WITH THE TAIL END OF
THE MID ATLANTIC SHORTWAVE TROUGH CREATING ENOUGH LIFT FOR ISOLATED
MARGINAL WIND.

...MID ATLANTIC REGION...
SCATTERED NON-SEVERE STORMS MAY BE ONGOING SUNDAY MORNING ACROSS
MUCH OF THE APPALACHIANS NEWD ACROSS PA AND INTO SRN NEW ENGLAND IN
ASSOCIATION WITH WARM ADVECTION COURTESY OF 25-30 KT SWLY 850 FLOW.
AN EFFECTIVE WARM FRONT WILL EXIST ACROSS SRN NY INTO SRN NEW
ENGLAND...POSSIBLY REINFORCED BY PRECIPITATION. TO THE
S...RELATIVELY WARM TEMPERATURES ALOFT WILL EXIST BUT HEATING AND A
VERY MOIST AIR MASS WILL RESULT IN AROUND 1000-1500 J/KG MUCAPE BY
AFTERNOON.

WIND FIELDS WILL INCREASE DURING THE DAY...WITH HODOGRAPHS BECOMING
MARGINALLY FAVORABLE FOR SUPERCELLS. ANY LOCALIZED LOW-LEVEL BACKING
OF THE SFC WINDS NEAR THE WARM FRONT AND/OR ACROSS THE DELMARVA MAY
SUPPORT A LOCALIZED TORNADO THREAT. STORMS ARE EXPECTED TO FORM IN
THE 18-21Z TIME FRAME ACROSS SERN PA INTO CNTRL VA AND WRN NC AS
CONVERGENCE INCREASES...WITH STORMS MATURING EWD TOWARD THE COAST BY
EVENING. DAMAGING WINDS APPEAR LIKELY AS MEAN WIND FIELDS
INCREASE...BUT ANY SUPERCELLS WILL ALSO BE CAPABLE OF HAIL DESPITE
WARM TEMPERATURES ALOFT.

NRN EXTENT OF THE SLIGHT RISK MAY BE MODULATED IN LATER OUTLOOKS DUE
TO POSITIONING OF THE WARM FRONT.

..JEWELL.. 06/04/2016

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