Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/06/20
Area Forecast Discussion
National Weather Service Lincoln IL
531 AM CST Thu Mar 5 2020
Issued at 254 AM CST Thu Mar 5 2020
Windy but otherwise mild conditions expected today. Temperatures
will warm into the mid to upper 50s across central Illinois, but
be accompanied by winds gusting 30 to 45 mph. Briefly cooler, more
seasonable, temperatures return on Friday with highs in the 40s,
but winds will gradually subside through the day. Breezy and warm
temperatures return this weekend with highs in the 50s and 60s.
.SHORT TERM...(Today through Friday)
ISSUED AT 254 AM CST Thu Mar 5 2020
Early this morning, ridge of high pressure stretches from the
eastern Great Lakes across the mid Mississippi Valley while low
pressure is located over the Upper Midwest with a cold front
stretching south across Iowa. This front is progged to shift east
to the Illinois River by late morning/early afternoon, then across
the remainder of the state through the afternoon. Breezy
southwest winds will occur ahead of the front, but stronger winds
are expected behind the front as cold advection drives steep low
level lapse rates tapping into 30 to nearly 50 kt winds aloft.
Momentum transfer algorithms in forecast soundings from the GFS
and RAP suggest that wind gusts may flirt with advisory criteria
of 39 kt (45 mph). Guidance shows a 900mb wind speed max wrapping
into portions of west central Illinois towards the Illinois River
Valley this afternoon and early evening. Counties under this speed
max will have the best chance for reaching advisory criteria
winds, so will be hoisting an advisory for Schuyler, Fulton, and
Knox counties, though cannot rule out needing some eastward
expansion later today.
Winds will remain gusty overnight as cold advection and mixing
prevents any strong decoupling overnight, and continue into the
day Friday. A corridor of 2-4mb/3hr pressure rises is progged to
move across portions of east central Illinois early on Friday,
which coupled with the continued tight gradient may result in near
but sub-advisory criteria winds across east central Illinois
early Friday. Farther west, the gradient will begin to relax ahead
of a broad ridge of high pressure building across the Great
Plains. 850mb thermal trough will shift across central Illinois
very early on Friday with morning lows dipping below freezing many
areas. Temperatures are expected to rebound into the low to mid
40s Friday afternoon under sunny skies.
.LONG TERM...(Friday night through Wednesday)
ISSUED AT 254 AM CST Thu Mar 5 2020
A strong upper ridge will build across the Great Plains late this
week, then begin to shift east across the Midwest over the
weekend. Meanwhile, at the surface, an expansive ridge of high
pressure centered over the Midwest early Saturday will shift to
the mid Atlantic coast over the weekend allowing return flow to
overspread the Mississippi Valley. Warm advection into the region
coupled with sunny skies Saturday and partly cloudy to mostly
sunny on Sunday will allow temperatures to warm well above normal
this weekend. Models are in good agreement suggesting low to mid
50s for high temps on Saturday and upper 50s to lower 60s on
Sunday. Cloud cover will be a bit of a wild card on Sunday. Mid
level isentropic ascent may allow for some higher based clouds to
overspread the area on Sunday, but should remain fairly low in
coverage. More widespread, lower cloud cover is not progged to
arrive until after sunset Sunday night.
Synoptic scale ascent ramps up on Sunday with a number of factors
lining up for widespread precip to occur. Low and mid level
southwest flow will increase ahead of an approaching shortwave
trough Monday while surface ridge axis moving off the east coast
allows gulf moisture to flow freely north along the Mississippi
Valley. Strengthening isentropic ascent across the 290-305K
surfaces and PWats increasing to just over an inch will set the
stage for a rainy Monday. A moderately strong low level jet
focused over the area may help overcome meager mid level lapse
rates for a few embedded thunderstorm to occur, but for now the
better signal for thunder stays south of the forecast area where
weak MUCAPE is expected.
Precip chances will diminish Monday night into Tuesday, but a
zonal pattern sets up in its wake with the baroclinic zone
lingering over the region. There will be additional chances for
precip as we head to midweek. Temperatures will moderate some in
the zonal flow, but near to slightly above normal temperatures are
favored Tuesday into Wednesday.
.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 527 AM CST Thu Mar 5 2020
Main forecast concern today will be the developing strong and
gusty winds. This morning a cold front is pushing east across
eastern Iowa allowing south to southwesterly flow to increase
ahead of the front this morning. Winds will veer to the west
northwest and further increase this afternoon and evening with
passage of the front. There may be a brief window of MVFR stratus
that moves across the region tonight, but should only last a few
hours before clearing out.
Issued at 527 AM CST Thu Mar 5 2020
A cold front will sweep across central Illinois today.
Unseasonably warm temperatures are expected ahead of the front,
then deep mixing will develop behind the front with dew points
falling into the 20s and resulting in afternoon RH values in the
25 to 35 percent range. Meanwhile, strong northwest winds gusting
30 to 45 mph are expected much of the day once the front passes
through. This combination of factors may result in erratic fire
behavior today, though early morning projections are that
afternoon minimum RH values will fall just shy of reaching red
flag warning criteria. Caution is still warranted today given the
strong winds expected.
Wind Advisory from 9 AM this morning to 6 PM CST this evening
AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1013 PM EST Thu Mar 5 2020
Cold front crosses overnight. Moisture fetch off the Great
Lakes sets up Friday with rain/snow in the lowlands and
significant high elevation snow. High pressure this weekend.
.NEAR TERM /THROUGH FRIDAY/...
As of 1010 PM Thursday...
Delayed onset of precipitation until overnight, mainly with the
cold front, per latest near term guidance. An out-ahead cloud
band was finally staring to form over the southwest portion of
the forecast area, as the mid level short wave trough
approached. The HRRR does pick up on this moving northeast, so
allowed this to be realized up toward the northern mountains
during the overnight.
Warnings and advisories for mountain snow Friday remain as are.
As of 705 PM Thursday...
Nixed some early evening showers over the middle Ohio Valley,
and temperatures were again running high ahead of the
approaching cold front. Otherwise, the forecast is on track.
As of 200 PM Thursday...
Cold front with clipper system currently transiting the Upper Great
Lakes will bring a chance of rain showers and a northwesterly wind
shift late this evening. Rain accumulations across the Lowlands are
expected to be minimal given initially rather dry low levels, with
perhaps a tenth of an inch of liquid equivalent in the mountains
with some light snow across the highest ridges prior to daybreak.
The aforementioned northern stream system will phase positively with
a southern stream system over the Florida Panhandle at this hour and
combined with building high pressure over the central US will set up
a decent moisture fetch off Lake Erie/Huron and Michigan with
terrain forcing as well as the parent upper level low of the
northern system providing forcing for ascent. Not currently
anticipating much in the way of accumulation over the Lowlands with
a combination of marginal surface temperatures, marginal cloud top
temperatures for ice crystal growth, marginal cold air aloft
limiting overall surface based instability, and early March Sun
angles. The previously mentioned dry low level conditions will help
out some with wet-bulbing, especially Friday morning, but think
grassy surfaces and elevated surfaces will be the only chance to see
anything sticking for most lowlanders.
Significantly more liquid equivalent is expected in the mountains of
WV, and despite snow ratios much more muted than the last couple
events, should be able to pile up 5 to 10 inches of heavy wet snow
above 3000 feet with locally higher amounts possible in the most
upslope favored northwest facing slopes and/or most persistent lake
enhanced snow bands. Have opted to upgrade our Winter Storm Watch to
a Winter Storm Warning for Northwest Pocahontas, Southeast Randolph,
and Eastern Webster County. Winds will also gust 35 to 40 mph across
these locations at least some blowing and drifting expected despite
the heavy wet nature of the snow. Have also added Winter Weather
Advisories further south across eastern Nicholas and Fayette County
where lesser accumulations of 3 to 5 inches can be expected. Given
the previously mentioned Sun angles and squally nature of lake
enhanced snow bands, will likely see significant melt back on well
traveled surfaces during any breaks in the snow during the daylight
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 150 PM Thursday...
Upslope event will be ongoing Friday evening with H85 streamlines
pointing to Erie/Huron moisture contributions on 40 kts of
flow. This combined with the aforementioned instability will
allow for some hefty totals in the northern mountains. Snow
showers will be noted in the lowlands as well, but any skiffs
should be primarily confined to the hilltops. The upper trof
axis shifts east late Friday night with low level WAA
effectively shutting off the upslope event after midnight.
Models and WPC continue to suggest 6 to 12 inches by the time
the event winds down late Friday night with highest amounts on
the northwest facing slopes.
Upper level heights quickly build into the MS Valley Saturday
with continued low level WAA into our area leading to seasonable
temps amid a sunny sky. Ridge/valley split likely for temps
Saturday night, though maybe not as pronounced in the northern
mountains given snowpack.
Transient ridge shifts into the eastern half of the country
Sunday as temps climb above normal even as cirrus works in from
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 155 PM Thursday...
Quasi-zonal flow will develop across the country early
next week with a progressive upper level disturbance sending
rain chances our way Monday nigh and/or Tuesday. This will be
followed by another rain maker late week. Temperatures will
remain a bit above normal.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
As of 705 PM Thursday...
Widespread MVFR to IFR conditions are expected in low clouds,
rain and snow showers Friday.
After a VFR evening, a cold front will cross overnight tonight,
resulting in stratocu and a few rain showers, but no flight
West to northwest flow follows the cold front for Friday,
setting up a good moisture feed off the Great Lakes, as a deep
upper level trough slowly crosses. This will bring MVFR stratocu
across the area quickly, from 12-13Z along the Ohio valley, to
14-15Z in the mountains. The onset of these MVFR ceilings will
be followed closely behind by MVFR visibility in rain and snow
This will be a very elevation dependent system in terms of rain
versus snow, as colder air continues to move in aloft, while the
strengthening early March sun tries to heat the ground. Thus,
during Friday afternoon, IFR conditions are likely to develop in
the mountains on visibility and ceilings, in snow. The lowlands
will have a mix of rain and wet snow, with conditions remaining
mostly MVFR, although brief IFR periods and VFR breaks are also
Light, mostly southerly flow ahead of the cold front tonight,
will shift to light west behind the cold front overnight, and
then become gusty from the west to northwest on Friday. Peak
gusts are expected to be in the 15-20 kt range Friday morning,
then up to 20-25 kts in the afternoon, even close to 30 kts at
BKW and 35 kts over the higher ridges. Light to moderate south
to southwest flow aloft tonight will become moderate west to
northwest overnight, and then moderate northwest on Friday.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Conditions are likely to be highly
variable in rain and snow showers on Friday. Gusty winds on
Friday will also fluctuate.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE FRI 03/06/20
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H L H
BKW CONSISTENCY H H H H H H H H H H H H
EKN CONSISTENCY H H H H H H H H H H H H
PKB CONSISTENCY H H H H H H H H H M M H
CKB CONSISTENCY H H H H H H H H H H H M
AFTER 00Z SATURDAY...
IFR possible in snow into Friday night in the mountains.
WV...Winter Weather Advisory from 7 AM Friday to 1 AM EST Saturday
Winter Storm Warning from 4 AM Friday to 1 AM EST Saturday for