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FXUS61 KRNK 231330

Area Forecast Discussion
National Weather Service Blacksburg VA
930 AM EDT Sat Jun 23 2018

A weak wedge of cool air will linger across the region this
morning, then drift northeast of the area during the afternoon 
and evening. Low pressure aloft over the Ohio Valley will also
lift northeast today through Monday. High pressure aloft will
build over the eastern U.S. during the later half of the week.
Much of the upcoming week will feature warm and humid conditions
with just isolated to scattered mainly afternoon and evening
showers and thunderstorms.


As of 930 AM EDT Saturday...

Modified temperatures utilizing the latest surface obs, their
trends and shaped towards GLAMP for late morning into this
afternoon. Adjusted pops and weather with current radar trends 
and tweak toward HRRR for late morning. More changes later
this morning...

As of 445 AM EDT Saturday...

In the wake of yesterday's widespread convection largely
supported by a notable short wave associated with the Ohio
Valley upper trough, a weak in-situ wedge has developed across
much of the forecast area. As of early this morning, the wedge
boundary was near a BLF-HLX line. East of the wedge boundary,
low ceilings, generally AOB 010 have settled in along with MVFR
BR in many areas. Scattered -RA or -DZ lingers in associated
with the southwest flow aloft and minor ripples a top the wedge
air mass. The better lift remains northeast in association with
the northeastward moving upper low from the Ohio Valley, the
vestiges of which are noted with showers across Bath county the
last few hours.

The wedge will persist pretty much in place through mid-late
morning, then erode and lift northeast during the afternoon. The
general theme aloft for the next several days well into next
week will be rising heights aloft. The upper low over the Ohio
Valley will lift out across the northeast U.S. by Monday, so
that upper support will be dwindling with time. HIRES mesoscale
(RAP, HRR, NamNest) models do not support any organized
convection today compared to Saturday. While SPC has left our
eastern areas in a Marginal Risk for severe with a slight risk
just to our east over AKQ/LWX CWAs, organization with 
convective today across our region is lacking in the HIRES as 
well as the synoptic-scale models. The best instability will be 
pooled across the coastal plain. For most of the CWA only chance
pops are warrantied, with the highest pops across the north and
eastern areas, tapering to slight chance across south 
central/southwest areas outside orographic influences. Bottom 
line, convection should be far less numerous and widespread than
what was observed Saturday in association with the upper trough
and southward moving cool air wedge.

Temperatures today will be on par with Saturday levels thanks to
the wedge in the morning and decreasing clouds in the afternoon.
Look for highs mainly in the 80s ranging downward to the upper
70s in the mountains. Far south central/southeastern areas will
be near 90F. Lows both this morning and Monday morning will be
mostly in the 60s to near 70 across the Piedmont with dewpoints
failing to drop much below 60 anywhere, especially Monday

/Confidence Levels/
Precipitation Chances...Low to medium
Thunderstorm Chances...Low to medium


Quasi-zonal mid-level height regime will govern conditions aloft 
across the eastern two-thirds of CONUS to begin the period. Zonal 
pattern begins to buckle somewhat in response to strong digging 
upper trough across New England into Monday. An expectation that 
northerly-northeast flow will develop as surface ridging begins to 
wedge down the Blue Ridge/central Appalachians. Northwest-southeast 
oriented frontal zone, separating hot, humid air building 
across the Deep South/southern Plains from cooler air in New 
England, is forecast to move little into Tuesday. 

Considerable uncertainty exists for Sunday with regard to timing any 
convective threat. Air mass should again become moderately unstable 
and seasonably strong belt of mid-level westerlies are elements that 
would lend themselves to at least loosely organized thunderstorms. 
Sunday isn't a washout with periods of dryness at times. But threat 
of thunderstorms still will exist with PoP chances being on the high 
side of Chance. Any subtle shortwave troughs that may reside early 
Sunday will significantly influence when/if and how strong 
thunderstorms may develop. Poor consensus exists regarding that 
important detail. SPC does have the far western portion of the CWA 
in a 5%/Marginal Risk of severe weather, which seems reasonable 
attm. As zonal patterns are notoriously difficult to time 
disturbances, it's not out of the realm of possibility that this 
outlook may shrink or expand. Flow becomes northwest Sunday night 
with passage of a frontal zone, with somewhat lower dewpoints for 
Sunday night. 

Front from the previous day then lingers around the central 
Carolinas northwestward across the central Appalachians into the 
Ohio Valley. Kept PoP chances for showers/storms confined to a 
roughly Danville to Bluefield line. Weaker flow aloft should mute 
any organized strong/severe storms Monday. Northerly more stable 
flow across the northern/eastern counties should also trend things 
drier. Any thunderstorm threat should end by midnight as wedging 
becomes enhanced and shifts the front further south. Tuesday on the 
whole looks dry, though enough easterly convergence against the 
southern Blue Ridge to support limited chances for scattered showers 
and thunderstorms from the Blue Ridge south of Roanoke, the Mountain 
Empire/Grayson Highlands, mountains of NW North Carolina into the 

Temperatures generally similar to prior days for Sunday, highs into 
the 80s/spot 90. A cooler/drier trend into Monday and Tuesday with 
temperatures being more seasonal by Tuesday. 

Forecast confidence Sunday is below average, with poor consensus and 
low predictability regarding thunderstorm timing. Confidence then is 
average for Monday and Tuesday.


As of 500 AM EDT Saturday...

Northern jet stream remains progressive the first part of the
week with the models in decent agreement bringing the next,
albeit weak, trough through the northeast United States on 
Wednesday and Thursday. 

Surface high pressure over the northeast and Mid Atlantic on Tuesday 
will move offshore by Wednesday. This will mean a return of moisture 
and a daily thunderstorm threat each afternoon and evening. 
Potential for west to northwest surface to 850MB winds on Thursday 
and Friday as seen on the ECMWF may limit areal coverage of 
precipitation. Temperatures will be slightly above normal through 
the period. 

During the later part of the week, high pressure aloft building
over much of the eastern U.S. will be the main story with 596dm
heights projected by the end of the week. This will result in
less convection and above normal temperatures for the most part.
Heat and humidity will be the main weather story as we move 
into the weekend.

/Confidence Levels/
Temperatures - Medium to High
Precipitation Chances - Low to Medium
Thunderstorm Chances - Low to Medium


As of 750 AM EDT Saturday...

A weak wedge remains across the mid Atlantic this morning,
promoting widespread ceilings in the MVFR/IFR range with some 
locations reporting 1SM-3SM in BR conditions. The wedge will 
hold in place until around 14Z at which point it will lift back 
to the northeast as a warm front. By late morning to early 
afternoon, the entire forecast area is expected to be back in 
the warm sector as winds shift south-southwesterly. With the 
wind shift, ceilings and visibilities are expected to improve to
VFR in the 14Z-16Z time frame at all TAF sites.

Broad upper low over the Ohio Valley will continue to shift
northeast today with the best upper support from this low also
shifting north and east. Would not expect as much thunderstorm 
activity as there was Friday afternoon, but still feel that 
spotty & unorganized pulse showers and a few storms will 
develop given any weak disturbances tracking around the upper 
low in the northwest flow and the moist, warm, unstable air mass
in place across the region. Any convection that passes across an
airport is expected to remain moving, with a brief period of
heavy rain producing IFR conditions. 

With no real change in airmass, expect MVFR/IFR ceilings and
patchy fog to redevelop early Sunday morning across the region.

/Confidence Levels/
Wind...Medium to High
Thunderstorm Chances...Low to Medium

.Extended Aviation Discussion...

A cold front will finally sweep through the region Sunday with 
improving mostly VFR conditions Monday and Tuesday. Isolated to
scattered MVFR showers and thunderstorms are possible 
by Wednesday.


As of 200 PM EDT Friday...

The NOAA weather radio transmitter in Hinton, West Virginia that
is WXM72 and broadcasting at a frequency of 162.425 MHz is off 
the air. Parts are on order to repair the transmitter, but there
is no known time of restoration. We apologize for any 





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