Tools used in the drought outlook included: the official CPC long-lead precipitation outlook for
FMA, El Niño soil moisture composites, warm ENSO composites for
FMA, the Palmer Drought Index probability projections for April, and various medium and short-range forecasts and models such as the 6-10
day and 8-14 day forecasts. For this outlook, an in-house modified version of the Palmer Drought Projections applied to historical El
Niño's was given considerable weight.
The forecast for persisting or expanding drought in the Great Lakes region and Ohio Valley is
consistent with the below-normal precipitation pattern expected for FMA during El Niños or
positive PDO occurrences. The dry signal is especially strong during periods with negative AO,
and that is the way this winter is shaping up so far. The forecast is also consistent with last
month's drought outlook and recent precipitation trends. Locally heavy lake-effect snows will
significantly boost moisture conditions in favored downwind areas, but no attempt was made to
account for such local impacts on the national map.
Confidence in the outlook is much less for the Plains states. There is an El Niño or PDO signal
for above-normal precipitation in the southern and central Plains, but forecast signals are much
weaker or absent to the north in the Dakotas and to the east in Missouri. Past Palmer Drought
Index changes during El Niños for this time of year show a tendency for improvement into South
Dakota and southern Iowa, and the forecast map reflects this. Somewhat less improvement is
shown this month than last month due to recent trends toward dryness, but the mid-January
snowfall and the recent shift of the upper level ridge westward are consistent with a wetter
pattern.
The outlook for the western states is again largely driven by the FMA precipitation outlook
and Palmer drought projections based on previous years with El Niño conditions and similar initial
drought indices. The latter tools show a tendency for the drought indices to improve by April
across the Southwest. Confidence for improvement is less this month, given the lack of an influx
of El Niño-related tropical moisture into the Arizona area so far this season. Also, the SST
anomalies for the ENSO 1+2 region off the South American coast are small relative to those near
the dateline, and this could reduce the odds of heavy precipitation. Some numerical models also
point to below-normal precipitation for the Southwest. A wet pattern is still the best bet, but it is
by no means assured. To the north, the forecast for persisting drought across the northern
Rockies and interior Northwest is consistent with last month's outlook and recent trends toward
below-normal snowfall. The depiction also considered the January 1 spring and summer
streamflow forecasts produced by USDA/NRCS.
In the Northeast, the outlook continues to call for improvement in Maine, based largely on
past El Niño composites. Palmer indices tend to improve during El Niño periods in Maine.
In Hawaii, a tendency toward El Niño-related dryness during the February-April period results in
a continued forecast of drought development. This is also consistent with recent trends toward
expanding dryness.
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