-- Discussion containing changed information from previous version are highlighted. --
144
FXUS61 KRNK 010708
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
308 AM EDT Wed May 1 2024

.SYNOPSIS...
-- Changed Discussion --
Dry, high pressure will cover the region today into Thursday with
continued above normal temperatures. Another cold front brings wet
weather to the region for the weekend. Unseasonably warm
temperatures and a daily threat of late day showers and
thunderstorms continues early next week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 255 AM EDT Wednesday...

Key message:

 - Patchy dense fog this morning

Winds have turned to the west to northwest and isolated showers have
moved out of the piedmont. Satellite Fog Product images showed
stratus expanding over the mountains and fog in the river valleys
west of the Appalachians.

Low clouds will continue to spread toward the Virginia and North
Carolina foothills early this morning. Fog will develop where there
was rain Tuesday afternoon. There will be patches of dense fog
through 12Z/8AM. The stratus and fog will be shallow, as seen on
the Bufkit forecast soundings, and will quickly dissipate in
most locations by 14Z/10AM.

Some of the Hi-Res guidance had a low probability of showers this
afternoon in the piedmont, others kept that area dry. Will stay with
a probability of precipitation less than 15 percent.

No reason to vary much from the NBM for both maximum temperatures
today and lows tonight.
-- End Changed Discussion --


&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
As of 230 AM EDT Wednesday...

Key Points:

1. Above normal temperatures with Thursday the warmest day.
2. Dry Thursday.
3. Afternoon showers and few storms across the mountains Friday.
4. Showers and storms increase in coverage and from west to east
   later Friday night and Saturday.
5. Locally heavy rain possible on Saturday.

A look at the 30 April 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows an upper ridge centered from the Lower Ohio Valley to
the Southeast US Coast on Thursday. A closed low will be centered
near the ND/Canadian border. On Friday, the center of the ridge
shifts a bit east while the upper low does likewise. By Saturday,
the ridge axis continues its eastward shift, placing it over New
England, south to to along the coasts of the Carolinas. The upper
low is expected to be over central Ontario with a trough axis
extending south into the Great Lakes region. At the surface, surface
low pressure tracks from southern Ontario on Thursday to northern
Quebec on Saturday. Anchored off the US East Coast will be a ridge
of high pressure. The ensemble blend washes out a lot of the details
the various members offer, but on average the primary cold front
associated with the surface low is expected to make gradually
progression towards our region, arriving Sunday.

Output from the 30 Apr 12Z Ensemble Situational Awareness Table
shows 850mb temperatures on Thursday around +16C across the region,
or values that would be within the 90 to 99 percentile of the thirty-
year climatology. For Friday, values are expected to be only
slightly lower, averaging +14C to +16C across the area. On Saturday,
values will be slightly lower still, averaging around +12C.
Precipitable Water values on Thursday will be around 0.75 inch, for
Friday about 1.00 to 1.25 inches, and on Saturday around 1.25 to
1.50 inches, or values that are with in the 90 to 97.5 percentile of
the thirty-year climatology.

The above weather scenario offers a dry but very warm day for
Thursday with high pressure over the area and well above normal
850mb temps. For Friday, while the ensembles washout this feature, a
number of deterministic model offer a weak front crossing the area,
with primarily afternoon convection across the mountains. On
Saturday, the surface ridge shifts far enough east for better
Atlantic onshore flow into the Carolinas, that curve northward into
our region. With good daytime heating and increased moisture,
showers and storms are expected to be more numerous on Saturday as
compared to Friday. Above normal PW values on Saturday suggest some
locally heavy rain could be possible if there is any training of
cells. For Sunday, the main front associated with the Canadian low
moves into the region. Specific timing is still questionable, along
with its duration over the area. The result will be another day with
showers and storms in the forecast. After Thursday`s very mild
conditions, Friday and Saturday will be a bit cooler, but still at
levels above normal for this time of year.

Confidence in the above conditions is moderate to high.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
-- Changed Discussion --
As of 210 AM EDT Wednesday...

Key Points:

1. Slightly cooler temperatures but still a bit above normal Sunday
   and Monday.
2. Very mild conditions possible Tuesday.
3. Chance of showers and storms each day with Sunday having the
   greatest probability.

A look at the 30 April 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows an upper ridge centered near the Canadian Maritimes.
Additionally, a flattened trough will be crossing Quebec and the mid-
Atlantic states. Another upper low will developing over NV. On
Monday, the Quebec trough continues on an eastern progression to the
Canadian Maritimes while zonal flow develops our region. The low
across western CONUS shifts east as a trough into the Rockies. By
Tuesday, a se-nw oriented ridge is starting to develop from SC to
MI. The trough over the Rockies makes small headway eastward. At the
surface, ensemble averaging is washing out some of the details the
various members offer, but in general there is question as to the
fate of the cold front which arrives on Sunday. Averaging suggests
this feature may meander around the region for a while, perhaps
heading north again as a warm front Monday into Tuesday as a result
of a deepening low over central CONUS.

Output from the 30 Apr 12Z Ensemble Situational Awareness Table
shows 850mb temperatures on Sunday and Monday are expected to
average around +12C to +13C across the area. For Tuesday, values
increase to around +14C to +16C, or values that are with in the 90
to 97.5 percentile of the thirty-year climatology. Precipitable
Water values for Sunday are expected to be around 1.00 to 1.25
inches, for Monday around 1.00 inch, and Tuesday 1.00 to 1.25 inches.

The above weather scenario offers a period of unsettled weather with
each day potentially having rounds of showers and few storms as a
front remains over or very close to our region. Of the three days,
Sunday has the greatest probability of precipitation. Temperatures
will be slightly warmer than normal on Sunday and Monday, but
potentially on Tuesday could be as mild as values expected Thursday,
or what recently happened across the area on Tuesday April 29.

Confidence in the above weather conditions is low to moderate with
the greatest uncertainty fueling a lot of the forecast parameters
being the position of the cold front after Sunday.
-- End Changed Discussion --

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
As of 150 AM EDT Wednesday...

Winds have turned to the west to northwest at less than 10 mph.
Isolated showers have moved out of the area. Satellite Fog
product images showed stratus expanding over the mountains and
fog in the river valleys west of the Appalachians.

IFR stratus will continue to spread toward the Virginia and
North Carolina foothills early this morning. Fog will develop
where there was rain Tuesday afternoon. A majority of the fog
will produce MVFR visibilities, but there will be patches of
LIFR conditions. KLWB, KBCB, and KLYH are expected to have
occasional LIFR ceilings and visibilities before 12Z/8AM. The
stratus and fog will be shallow and quickly dissipate in most
locations by 14Z/10AM.

VFR flight conditions are then expected for the rest of the day
and into the evening with winds remaining less than 10 kts.

Average confidence for ceiling and visibility.
Above average confidence for wind.

Extended Aviation Outlook...

Thursday is forecast to be VFR and dry.

The next cold front and probability of precipitation arrive in
the area on Friday. This will bring a chance of showers and
thunderstorms to the mountains Friday afternoon and evening.

The potential for showers and thunderstorms with MVFR ceilings
and visibilities increases Saturday into Sunday.
-- End Changed Discussion --

&&

.CLIMATE...
-- Changed Discussion --
As of 300 AM EDT Wednesday...

Record high temperatures for May 2

Bluefield, WV....89 in 2010
Danville, VA.....93 in 1942
Lynchburg, VA....91 in 1942
Roanoke, VA......92 in 1959
Blacksburg, VA...87 in 1942
-- End Changed Discussion --

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$

SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...DS
LONG TERM...DS
AVIATION...AB/AMS
CLIMATE...AMS