Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/17/20
Area Forecast Discussion
National Weather Service Bismarck ND
918 PM CDT Tue Jun 16 2020
Issued at 917 PM CDT Tue Jun 16 2020
Forgot to remove the Wind advisory...this corrects that.
UPDATE Issued at 910 PM CDT Tue Jun 16 2020
Thunderstorms continue to try and break through the CAP this
evening, but so far none have been successful. As the cold front
in western North Dakota moves a little more east this evening we
should see more convection, as a single storm or several clusters
of storms,from just west of Bismarck north into central North
In the meantime, we will cancel teh wind advisory as winds have
diminished below advisory criteria.
UPDATE Issued at 756 PM CDT Tue Jun 16 2020
We will cancel the wind advisory for south central North Dakota,
and keep the advisory for the James River Valley going until 10
UPDATE Issued at 612 PM CDT Tue Jun 16 2020
Current radars show convective initiation over northeast Bowman
county, at least one cell at this time. This is very close to the
HRR timing and location, so we have some confidence the HRR CAM
model is probably on track. Current forecast looks good.
.SHORT TERM...(This evening through Wednesday)
Issued at 332 PM CDT Tue Jun 16 2020
Severe thunderstorm potential late this afternoon through tonight
west and central, and late Wednesday afternoon and evening across
the James River valley, is the focus of the short term forecast.
As of 20 UTC, surface pressure falls on the order of 2-3 mb/3 hrs
are centered on northwest and north central ND with related mass-
field responses of thermal and moisture advection ongoing. RAP-
based objective analyses show strong MLCIN at this hour, which is
consistent with the warm elevated mixed layer sampled by the 12
UTC RAOBs. Forecast soundings from multiple model cores including
the 12 UTC CAMs suggest weakening MLCIN by late afternoon as low-
level theta-e advection continues, though residual capping still
remains in most profiles, casting uncertainty on the probability
of surface-based convective initiation through early evening. It
does, however, appear that the window of opportunity for surface-
based convection will be focused in west central ND roughly along
and ~75 miles east of the Highway 22 corridor, northward to about
Stanley and across the western end of Lake Sakakawea. It`s along
that corridor where a low-level wind shift is forecast to reach
by 00 UTC. The length of the wind shift will have a non-zero risk
of convective initiation. However, two mesoscale areas of focus
could be around the western end of Lake Sakakawea, where the low-
level thermal ridge axis may overlap the moist axis closer to a
surface low in northwest and north central ND, and around the
Dickinson area where low-level warm air advection may be most
focused the next few hours.
The CAPE-shear setting through early evening for any surface-based
parcels will be characterized by MLCAPE on the order of 2000 J/kg,
effective shear magnitudes of 40-50 kt, and very steep low- and
midlevel lapse rates. Given at least a modest orthogonal component
of deep-layer wind fields to the surface wind shift, and the large
amount of capping present, discrete modes -- and supercells -- are
favored. This setting favors the possibility of very large hail up
to baseball size along with damaging gusts, though again this is a
very conditional risk. CAMs through the 19 UTC HRRR are relatively
consistent in this scenario though, with modest probabilities and
clustering of UH >150 m2/s2 from the 12 UTC HREF centered on west
central ND. Low-level hodographs enlarge with time toward sunset,
but the relatively modest boundary layer moisture with dewpoints
generally in the 60 F range will contribute to MLLCL heights close
to 2000 m AGL, which will constrain the tornado risk.
Otherwise, from late evening through about 09 UTC, convection will
likely increase in coverage toward a scattered nature as heights
aloft fall more steadily as an upper-level trough shifts eastward.
Forecast soundings support related cooling of the warm elevated
mixed layer, while a strong low-level wind maximum on the order of
50-60 kt as low as 2000 ft AGL continues moisture transport along
and ahead of an eastward-shifting cool frontal boundary. This may
allow for clusters of elevated strong to severe convection, when
and where moisture profiles are deep enough for elevated parcels
to have reduced MUCIN while MUCAPE remains in the 2000-3000 J/kg
range. Given the elevated nature of the effective inflow layers
after dark in this setting, as supported by forecast soundings,
hodographs will become shorter and thus effective shear overnight
will decrease closer to 40 kt. As a result, we are messaging hail
up to golf ball size with overnight storms along with a continued
risk of damaging gusts.
On Wednesday, the surface front will shift eastward and may again
result in surface-based convective initiation in the James River
valley by late day. However, there is spread among 12 UTC models
with how far east the front will be by the time initiation occurs,
and deep-layer shear vectors will be oriented parallel to the
front. Thus, messy convective modes are expected, which may limit
the ceiling of the severe risk, but large CAPE will be present to
compensate to some extent.
Finally, the Wind Advisory through this evening is on target,
with forecast soundings in the Ashley, Oakes, and Jamestown areas
all supporting peak winds at the top of the mixed layer in the 45
to 50 kt range from 21 to 00 UTC, suggesting near high wind
criteria south winds. We`ve increased messaging in the advisory
for gusts to 55 mph, though confidence in more than isolated gusts
nearing warning criteria within the low-level warm air advection
regime was too low to upgrade any counties to a warning.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 332 PM CDT Tue Jun 16 2020
Cooler, but seasonable temperatures and periodic shower and storm
chances will highlight the long term, including the weekend.
The consensus of the 00 through 12 UTC global deterministic and
ensemble suites calls for a middle- and upper-level low to evolve
over south central Canada by Thursday as the initial trough aloft
lifts northeastward. The middle- and upper-level low is forecast
to only slowly shift eastward through in the succeeding days, with
cyclonic flow and lower heights on its southern flank in place in
the northern Plains. Some spread exists in the 850 mb temperatures
forecast by individual GEFS members, but the coldest air is likely
to arrive late this week with NBM-driven forecast highs only in
the 60s in the west and north Thursday, and forecast lows Thursday
night in the 40s in most areas. Confidence in temperature trends
is above average through the weekend -- with forecast highs mainly
in the 70s F, but with a slow warming trend -- given a relatively
small one standard deviation in NBM membership forecasts. We have
a chance of showers and thunderstorms in the forecast many times
and places, but it won`t be a washout; predictability of impulses
embedded in the flow is low, and activity will likely be diurnally
driven. By early next week, it appears midlevel heights will begin
to rise, leading to a drying and warming trend, though the exact
timing of that transition is somewhat uncertain.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 612 PM CDT Tue Jun 16 2020
VFR expected through the forecast.
Hazards to aviation include scattered thunderstorms over west and
central North Dakota this evening. Also low level wind shear
will develop over the James River Valley when strong southerly
low level winds develop between 1 to 2 thousand agl across this
area after midnight, and surface winds diminish at KJMS.
Otherwise, initial thunderstorm development will be across KDIK
by 01-02z spreading north and east to KMOT-KBIS between 03 and
06z. Storms expected to diminish in intensity after 06z-08z.
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
633 PM CDT Tue Jun 16 2020
Issued at 312 PM CDT Tue Jun 16 2020
A high amplitude H5 pattern continues across the CONUS
today. Low pressure was noted over South Carolina with a trough
extending south into southern Florida. West of this feature, a
positive tilted ridge of high pressure extended from Texas, north
northeast into the upper Mississippi valley and the western Great
Lakes. West of this feature, closed low pressure was located over
western Washington state. A trough of low pressure extended south of
this feature into northern California and northern Nevada.
Downstream of this trough, a strong shortwave was noted from eastern
Idaho into southwestern Montana. HT. falls of 60 to 90 meters were
noted from northeastern Nevada, to southern Idaho and northern Utah
this morning. At the surface, low pressure was located over far
southeastern Montana. A warm front extended east northeast from the
low into northeastern North Dakota, while a cold front extended to
the southwest into west central Wyoming. A surface trough extended
south from the low from eastern Wyoming into eastern Colorado. Winds
were southerly this afternoon and were gusting up to 48 MPH at North
Platte at 2 PM CT. Temperatures at 2 PM CT ranged from 88 at
Ainsworth to 96 at North Platte and Imperial.
.SHORT TERM...(This evening through Wednesday night)
Issued at 312 PM CDT Tue Jun 16 2020
Temperatures and a
small threat for thunderstorms tonight, then temperatures and the
threat for thunderstorms Wednesday afternoon and Wednesday night are
the main forecast challenges. For tonight, the latest NAM12 and GFS
solns indicate a rather strong low level jet tonight with speeds
ranging from 50 to 60 KTS generally east of the Panhandle. A nice
surface pressure gradient sets up tonight with a deepening surface
trough of low pressure noted over the western Panhandle. That being
said, for locations east of the panhandle, lows tonight will be very
mild with readings in the upper 60s to around 70. In the eastern
panhandle where winds will be lighter, lows will be in the lower to
middle 60s. As for the thunderstorm threat this evening, it will be
confined to the far western forecast area. The latest NAM 12
solution indicates a weakening in the cap across northeastern
Colorado and the southern Nebraska Panhandle later this afternoon.
This could be enough for initiation in these areas. Steering winds
will carry this activity to the north northeast into the evening
hours. With only 15 to 20 KTS of deep layer shear available, not
expecting much in the way of severe storms across the western
forecast area this evening. Storms however, will be high based and
may produce some gusty winds given the current strong surface winds.
A cold front will approach the northwestern forecast area Wednesday
morning, stalling across the panhandle for the remainder of the day.
Temps in advance of this feature will surge well into the 90s once
again, with some readings possible around 100 in the far
southwestern forecast area. The latest NAM12 soln develops a dryline
bulge which noses into Keith, Arthur and McPherson counties around
21z Wednesday. This would be a favored area for storm initiation
late Wednesday afternoon given a weakening cap as depicted in the
NAM12 soln as well as the 12z HRRR which develops convection around
22z Weds to the northwest of North Platte. Any activity which does
develop in west central Nebraska, will quickly track north
northeasterly given the H5 steering winds. As this activity lifts
north, it will encounter CAPES of 2500 to 4000 J/KG in north central
Nebraska Wednesday evening. Deep layer shear will increase into the
evening hours as well with 30 to 40 KTS of deep layer shear noted.
This will favor strong to severe storms with the main threat being
strong winds (inverted V type soundings) and some marginally large
hail given the decent mid level lapse rates. By late evening, the
front will begin to progress east across the forecast area with a
more generalized threat for showers and thunderstorms overnight.
ATTM, the highest pops will be over northern and northeastern
portions of the forecast area, where mid level support is strongest.
.LONG TERM...(Thursday through Tuesday)
Issued at 312 PM CDT Tue Jun 16 2020
The before mentioned front,
will push into eastern Nebraska Thursday morning taking with it the
primary threat for thunderstorms. For the bulk of the forecast area,
cooler and dry conditions are expected with highs mainly in the mid
to upper 70s. By Friday, the front will lift north into southern and
southwestern Nebraska. At the same time a decent mid level
disturbance will lift across the area Friday night. This appears to
be the best chance for precipitation across the forecast area over
the next 7 days. A second northern stream trough of low pressure may
bring some showers to the forecast area Saturday night into Sunday,
but forecast confidence is low as there are some decent differences
between the EC and GFS solns. Beyond Sunday forecast confidence
slips further as the GFS has an active northern stream across the
northern CONUS while this pattern is depicted over southern Canada
in the latest EC soln. The latter would favor warmer temps and
ridging across the western CONUS. With the latter solution favored,
highs will rebound back into the upper 80s to lower 90s early next
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 633 PM CDT Tue Jun 16 2020
VFR is expected across western and north central Nebraska tonight
and Wednesday. Isolated thunderstorms are possible west of highway
61 this evening and again Wednesday afternoon 21z-00z affecting
the Sandhills and northern Nebraska.
LLWS tonight is expected to produce occasional SFC G40-45KT through
09z Wednesday morning.
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1044 PM EDT Tue Jun 16 2020
Low pressure will cross the area tonight, weakening inland Wednesday
into Thursday. High pressure builds back into the area later this
week into the weekend.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 10 PM Tues...Surface low pressure east of Cape Fear continues
to very slowly move northward, with deep moisture advection
continuing across eastern North Carolina. scattered to
widespread showers continue late this evening, with areas of
heaviest rainfall focused along the coast where an inverted
trough axis and greater instability offshore is providing for
more convective elements and higher rainfall rates. Primary
changes to the forecast for the late evening update were to
more aggressively bring drying in from the southwest as mid-to-
upper level subsidence begins to move in in the wake of the low
Flash Flood Watch remains in effect for all CWA counties along
and east of US Hwy 17. An additional 1 to 3 inches of rainfall
are locally possible, especially along the Crystal Coast and
Previous Discussion...Hi-res guidance shows pockets of heavy
showers enveloping eastern NC into the evening. SPC
mesoanalysis shows a wide area of strong deep moisture
convergence along our southern counties south into Onslow Bay.
RAP analysis also shows a broad area of 35-45 kts of 0-6km bulk
shear across the CWA overlapped by an area of 500-1500 J/kg of
CAPE west of Hwy 17. As a result, storms are expected to
continue developing over Onslow Bay and the Gulf Stream and move
NNE ashore. With marginal severe parameters in place, any
strong to severe storms that form offshore could maintain
strength moving inland. The possibility for waterspouts
continues with the risk of a few moving ashore. The bulk of the
heavy rain and thunderstorms will begin lifting north over the
northern OBX and NE counties as the upper low lifts NW towards
central NC with the sfc low following suit.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
As of 415 PM Tuesday...Upper-level low crawls across central NC
during the day on Wednesday with low-level flow turning
southerly. A bulk of the precip will stay towards our northern
tier into VA, but scattered showers and storms will be possible
during the day. Latest HRRR guidance shows MLCAPE values around
1500-2000 J/kg during the day, providing ample fuel for storms.
Hi-res guidance disagrees on storm coverage, but overall, expect
scattered showers and thunderstorms through Wednesday. Daytime
heating will be more efficient tomorrow with partly sunny skies
across the SE portions of the CWA, which may promote convective
activity. Along with Srly flow, we can expect high temps to
move closer to 80.
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
As of 255 PM Tue...Unsettled weather will continue across
Eastern NC through late week. Lingering stationary front along
with a stacked low will continue to produce scattered to
numerous mainly diurnal showers and thunderstorms through
Friday. We should finally begin to dry out some over the weekend
into early next week, with a return to warm and humid
Wednesday night through Thursday...Low continues to become
vertically stacked across the Carolinas, slowly weakening and
lifting northward Wed night and Thu. Rainfall should taper off
Wed night and Thu will still have the potential to be locally
heavy but coverage should be less, as the upper/surface lows
begin to weaken and lift north. The precipitation then becomes
more tied to diurnal cycle.
Friday through Tuesday...The upper low weakens late in the
week, however upper troughing will continue along the eastern
seaboard which will continue to allow for a decent coverage of
showers and thunderstorms, especially inland during peak heating
when instability is maximized. The upper trough axis slowly
shifts eastward through the period and coverage of storms
expected to gradually diminish each day. Temps will also be on
a warming trend with above normal temps returning by the weekend
with highs potentially in the lower 90s inland locations
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term /Through Wednesday/...
As of 730 PM Tuesday...Low pressure off Cape Fear will lift
across the area tonight into Tuesday, bringing deep moisture
convection and widespread flight restrictions. IFR will
generally prevail through the morning, though brief improvement
is possible, depending on how precip coverage trends. Then, by
mid to late morning, ceilings will begin to improve, first to
MVFR, then potentially VFR by afternoon. Visibility
restrictions will be limited to those resulting from pockets to
rainfall, which could be heavy, brining IFR visibilities at
times, especially this evening and overnight.
Long Term /Wednesday Night through Sunday/...
As of 150 PM Tuesday...Sub-VFR conditions possible into
Thursday, with scattered to scattered showers and tstms.
Conditions then expected to improve to VFR by Thurs night.
Coverage of storms expected diminish late in the week as the
upper low lifts north of the area, however an upper trough will
remain over the area with shower and thunderstorm chances
continuing, especially during peak heating each afternoon.
Short Term /through Wednesday/...
As of 8 PM Tuesday...Gusty northeast winds funneling down the
mouth of the Neuse River necessitates the addition of the Neuse
to the SCAs.
Previous Discussion...Small Craft Advisories remain in effect
for most area waterways as low pressure lifting toward the area
have NE winds 20-30 kt persisting. Seas will be 4-6 ft for the
southern waters with 5-7 ft waves in the central and northern
waters through the night.
Winds will begin to subside tomorrow morning and gradually shift SE
during the day. Expect 4-6 ft waves along the central and
northern waters calming to 3-5 ft by Wed night.
Long Term /Wednesday night through Sunday/...
As of 255 PM Tue...An weak area of low pressure will lift north
of the region Wednesday night into Thursday, then the waters
will be under the influence of Atlantic high pressure and a lee
trough with decent boating conditions expected during this
period. The flow will mainly be S/SW 5-15 kt through Sunday with
the strongest winds in the afternoons and evenings with seas
2-4 ft, highest during the periods of stronger flow.
Record rainfall amounts for 6/16 (Tuesday)
New Bern 2.51/2010 (KEWN ASOS)
Cape Hatteras 2.46/1893 (KHSE ASOS)
Morehead City 3.55/1965 (COOP - Not KMRH ASOS)
NC...Flash Flood Watch until 10 AM EDT Wednesday for NCZ045>047-080-
Beach Hazards Statement through Wednesday evening for NCZ196-
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for AMZ131-135-
Small Craft Advisory until 8 PM EDT Wednesday for AMZ150-152-
Small Craft Advisory until 11 AM EDT Wednesday for AMZ156-158.
Area Forecast Discussion
National Weather Service New York NY
855 PM EDT Tue Jun 16 2020
High pressure over New England remains in control through
Wednesday and then gradually shifts offshore Wednesday night
into Friday. A cutoff low drifts north into the forecast area
over the weekend. A frontal system approaching from the west
merges with the low early next week.
.NEAR TERM /THROUGH WEDNESDAY/...
Minor adjustments to the forecast to account for latest
observations and trends.
High pressure will continue to be in control bringing tranquil
conditions to the Tri-State through Wednesday. The upper level
low across the southeast will only make slow progress
northwestward with ridging in place aloft over the region.
The ridging should keep most clouds away from the area, but
there may be just a scattering of high clouds at times tonight,
especially near the coast. Will also have to watch for some
low cloud development across far SE CT and eastern Long Island.
Dry air and ridging should hold much if any low clouds
offshore. The NAM profiles seem most aggressive, but even the
HRRR and RAP hint that some low clouds could develop briefly
around day break. Overall, mostly clear to partly cloudy
conditions tonight with lows ranging from the low 50s inland to
the middle and upper 50s most elsewhere.
The core of the high begins to shift towards the coast on Wednesday,
but otherwise similar conditions are anticipated as observed in
previous days. Some high clouds are likely with fair weather
flat cumulus possible in the afternoon. Sea breezes are likely
which will keep temperatures in the middle and upper 70s, but
locations furthest inland may be able to reach 80 degrees as the
onshore flow will take longest to reach those locations.
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
The high begins moving offshore Wednesday night with ridging
aloft remaining in place across New England. With the high
moving offshore, low level moisture begins to increase. There is
greater potential for a deck of low stratus to develop Wednesday
night, especially near the coast. Low clouds should diminish
Thursday morning with daytime heating leading to another partly
cloudy day on Thursday. The high pressure will continue shifting
offshore with surface ridging across the region remaining in
place. The upper level low will only slowly lift north-
northwestward. Any moisture and lift associated with the upper
low is likely to remain well to our south and west, so have
continued with a dry forecast for Thursday. High temperatures
will be closer to seasonable averages in the upper 70s to low
80s. Immediate shoreline locations will see temperatures in the
lower to middle 70s.
There is a moderate rip current risk on Wednesday at the Atlantic
facing beaches due to a continued 3 to 4 ft easterly swell.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Upper level cut off low drifts north Thursday evening into Friday
bringing with it remnants of subtropical moisture. For the
majority of the day Friday the additional moisture is only
visible through an increase in cloudiness. However by the late
afternoon and into the evening we could see a few showers and
isolated thunderstorms develop. These showers become more likely
over northeastern New Jersey and the Lower Hudson Valley. Areas
not impacted by showers should reach the low 80s.
Diurnal afternoon showers are expected over the weekend owing to the
moist airmass overhead. Precipitable water values around 1.75 inches
coupled with some elevated instability should be sufficient for
late afternoon convection. There is a fairly sharp west to east
gradient of CAPE with the highest values over northeast New
Jersey and the Lower Hudson valley. Meaning that thunderstorms
should be confined to those areas and a passing shower over the
NYC metro can`t be ruled out. Temperatures should be slightly
warmer over the weekend with afternoon highs in the mid 80s and
overnight lows in the mid to upper 60s.
Monday into the early part of next week a longwave trough over the
Great Lakes will have to be monitored. Models are depicting an
embedded shortwave north of Lake Ontario shifting into Quebec
through the day. As this happens the associated front boundary
shifts moisture eastward over southern New York. It is possible that
the lift from the shortwave and the boundary will initiate more
storms late Monday. Then Tuesday the main longwave trough axis moves
into central New York which again should promote showers and
isolated thunderstorms Tuesday evening.
There is a moderate rip current risk on Thursday at the
Atlantic facing beaches due to gradually subsiding easterly
swell. The rip risk may decrease in the afternoon.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
High pressure will remain anchored across the northeast through the
middle of the week.
VFR through the period, although there is low chance for
MVFR/IFR stratus formation late tonight into early Wednesday
morning for KGON/KISP.
E/SE early this evening will once again back around to the E/NE
overnight at 5 kt or less. A familiar but weaker wind flow on
Wed, with E/NE winds 5-10 kt in the morning, becoming ESE/SE in
.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.Wed Night-Thu...MVFR/IFR cigs possible for coastal terminals late
Wed Night into Thu morning, likely for eastern terminals. E winds
AM, S/SE winds PM.
.Thu Night-Sun...MVFR/IFR conds possible at night/early morning.
Chance of aft/eve shower or thunderstorm on Fri-Sun for NYC/NJ and
western terminals. S winds.
High pressure will remain in control over the waters through
Friday leading to a weak pressure gradient and Sub-SCA
South winds dominate over the weekend ranging 10-15 kts over the
ocean waters with gusts less than 20kts. Wave highs hover around 3
feet over the ocean waters and 1 foot over the Long Island sound.
Winds become southwesterly Monday into Tuesday and increase slightly
13-18kts over the ocean as a frontal system approaches from the
No hydrologic impacts are forecast through this week.
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is undergoing
its final stages of testing, and is operating at full power.
Area Forecast Discussion
National Weather Service Blacksburg VA
718 PM EDT Tue Jun 16 2020
The region was between low pressure off the North Carolina coast
and high pressure over New England. Little change in this
weather pattern is expected through Thursday so the wet and
unseasonably cool weather will persist. Over the weekend a cold
front coming out of the central United States will cross the
Great Lakes and bring a chance of showers and thunderstorms to
the Mid Atlantic area.
.NEAR TERM /THROUGH WEDNESDAY/...
As of 700 PM EDT Tuesday...
No significant change in the forecast rationale and details.
The slow-moving upper low and surface wedge maintains an
impressive blanket of clouds and scattered rainfall across the
region this evening. No hydrologic impacts to this point with
few more details discussed in hydro section below.
Previous valid discussion...
As of 155 PM EDT Tuesday...
Closed upper low drifts back north to the Virginia/North Carolina
border tonight and Wednesday. This will prolong the very deep flow
off the Atlantic. 3km NAM was showing to areas of enhanced low
level convergence tracking across southern Virginia and northern
North Carolina this afternoon and evening. Also little change
in the weather pattern expected at the surface with a low along
the North Carolina coast and high pressure wedges down the
central and southern Appalachians.
While there will be some upslope tonight and Wednesday, the wind
direction was mainly east to northeast so not expecting a big
enhancement in rainfall amounts along and into the foothills. Expect
the air mass to become unstable under the core of the upper low and
over the Virginia and North Carolina piedmont by Wednesday
afternoon. Cloud cover may limit heating but temperatures aloft will
still be cool and provide larger lapse rates. Will keep probability
of precipitation high tonight and Wednesday with favorable synoptic
and isentropic lift and good inflow of high axis of precipitable
water. Have added a chance of thunder Wednesday afternoon
around the periphery of the wedge.
Combination of persistence and NBM used for lows tonight. Expect
highs on Wednesday to be a couple of degrees warmer than today.
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 200 PM EDT Tuesday...
The ever-present cutoff low remains the dominant feature through
this period, keeping us in anomalously cool, wet conditions. The
closed low continues its slow retrograde from the Carolinas towards
the OH Valley. Widespread light rain will persist during this
process, even as the low rejoins the northern stream late on Friday
and begins to open up. The center of the low will rotate our flow
from easterly to southwesterly and some instability will be
introduced into the atmosphere, bringing some chance for storms
Thursday and Friday PM.
This period will see our region undergo a slight warm up, getting
closer to normal values (but still below), with highs in the 60s and
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 200 PM EDT Tuesday...
The cutoff low will become a shortwave and be swept off towards New
England over the weekend. Some ridging over us should clear the
skies a bit and let some peeks of sunshine through, helping warm us
back to normal temperatures for mid-June. Persistent rain coverage
will be replaced by afternoon convection, especially along the
mountains. By Monday, areal coverage of precipitation will expand
again, as the next upper trough approaches bringing showers and
storms to the region.
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 720 PM EDT Tuesday...
Flight categories across the forecast area currently range from
VFR to IFR at observing sites this evening but a general
deterioration in CIGs is expected overnight. VSBYs will
fluctuate with passing showers of variable intensity, but
predominantly 3-5SM expected. KDAN may see the most intense
rainfall later this evening with some lower CIGs/VSBys if the
stronger convective activity over the NC coastal areas
maintains coherence and remains on track. A TEMPO group will
cover that possibility.
Winds are generally east to northeast under 10 kts with
occasional higher gusts and this also will be slow to change
during the entire valid TAF period.
Extended Aviation Discussion...
The closed upper low will continue to meander about the central
and southern Appalachians through Friday, finally beginning to
lift to the north by the weekend. As the low weakens, the threat
for prevailing IFR conditions and persistent -RA will begin to
Showers and thunderstorms, with MVFR ceilings and visibilities
are expected Saturday and Sunday, mainly each afternoon and
As of 715 PM EDT Tuesday...
Rainfall amounts are really sort of all over the map to this
point (23Z/7PM), with storm totals ranging from less than 0.25
inches over parts of the southside and the far western basins
to pockets of 3+ inches in several areas. Hard to even discern a
generalized pattern but 1 to 2 inches are fairly widespread per
radar and ran gages, with slight underestimation by radar
compared to gages. With another 1 to 2 inches of rain forecast
(QPF) and isolated higher (and lower) amounts there may still be
some hydrologic issues but they will be limited in scope and
magnitude unless some sustained higher rain rates can move
across a basin. No RFC river forecast points are currently
forecast to reach Flood stage, though a few are progged to hit
Action stage but it will depend on how this variable QPF works
out. Of note, the National Water Model (NWM) experimental
products based HRRR short-range (0-18 hr) and GFS ensemble QPFs
(18-hr to 10-days) are showing low probabilities for bankfull
stages to be reached in any of the Blacksburg WFO rivers and